Unhed States EPA-600/R-92-159
Environmental Protection
August 1992
>EPA Research and
Development
SURFACE- COATING-FREE
MATERIALS WORKSHOP
SUMMARY REPORT
Prepared for
Office of Policy, Planning and Evaluation
Prepared by
Air and Energy Engineering Research
Laboratory
Research Triangle Park NC 27711
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EPA REVIEW NOTICE
This report has been reviewed by the U.S. Environmental Protection Agency, and
approved for publication. Approval does not signify that the contents necessarily
reflect the views and policy of the Agency, nor does mention of trade names or
commercial products constitute endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/R-92-159
August 1992
SURFACE-COATING-FREE MATERIALS WORKSHOP
SUMMARY REPORT
by
Coleen M. Northeim
Mary W. Moore, and
John L Warren
Center for Environmental Analysis
Research Triangle Institute
P.O. Box 12194
Research Triangle Park, North Carolina 27709
EPA Cooperative Agreement CR815169-02
EPA Project Officer Michael Kosusko
U. S. Environmental Protection Agency
Air and Energy Engineering Research Laboratory
Research Triangle Park, North Carolina 27711
Prepared for:
U.S. Environmental Protection Agency
Office of Research and Development
Washington, DC 20460
EPA Headquarters Library
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ABSTRACT
Surface coating operations release approximately 15 percent of stationary area volatile
organic compound (VOC) emissions as estimated by the 1985 National Acid Precipitation
Assessment Program (NAPAP) emissions inventory. Emissions occur during the initial coating,
as well as each time that a surface is recoated during the life of the object or structure. If
materials or products could be developed that do not need coating during either manufacture or
use (surface-coating-free materials) significant reduction in VOC and air toxic emissions could be
achieved.
The U.S. Environmental Protection Agency, with the assistance of the Research Triangle
Institute, sponsored a pollution prevention workshop exploring the concept of surface-coating-free
materials and the potential impact of these types of materials on VOC and air toxic emissions
from surface coating operations. The purpose of this report is to summarize the background and
methodology used in planning the workshop, discussions that took place in the brainstorming
sessions, and recommendations from the workshop. Included with the report are the technical
papers that were presented as part of the workshop.
The workshop consisted of two parts; technical paper presentations and brainstorming
sessions. Technical papers were presented by representatives of a varied group of industries that
currently use or are developing surface-coating-free materials. The focus of the small group
brainstorming sessions was to discuss specific topics related to the use of surface-coating-free
materials. A major objective of these sessions was to identify and develop pollution prevention
research concepts and recommendations for consideration by EPA that could expand the use of
surface-coating-free materials. The brainstorming session topics were:
-regulatory and economic incentives and barriers to technology innovations,
-methods for enhancing the appearance and marketability of surface-coating-free
materials, and
-potential pollution prevention research, development, and demonstration projects.
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CONTENTS
Abstract ii
Acknowledgments v
1.0 Background 1
2.0 Introduction 3
3.0 Methodology 5
4.0 Workshop Discussion 9
4.1 Research, Development, and Demonstration Opportunities 9
4.1.1 Potential SCFM Research, Development, and
Demonstration Projects 9
4.1.2 Low- and No-VOC Coatings Research Needs 10
4.1.3 Project Selection Criteria 10
4.2 Methods for Enhancing Appearance and Marketability
of Surface-Coating-Free Materials 11
4.3 Barriers and Incentives 14
4.3.1 Perceived Barriers 14
4.3.1.1 High Development Costs 14
4.3.1.2 New Product Uncertainty 15
4.3.1.3 Regulatory Uncertainty 15
4.3.1.4 Corporate Bureaucracies 15
4.3.1.5 Technology Transfer 15
4.3.1.6 Environmental Life-Cycle Costs 16
in
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4.3.1.7 Military Specifications 16
4.3.2 Regulatory and Economic Incentives 16
4.3.2.1 Tax Incentives 17
4.3.2.2 User Tax 17
4.3.2.3 Enhanced Regulatory Environment 17
4.3.2.4 Improved Communications, EPA Public Relations,
and Technology Transfer 18
5.0 Conclusions and Recommendations 18
Appendix A. Surface-Coating-Free Materials
Workshop Participants A-1
Appendix B. Paper Presentations B-1
Surface-Coating-Free Materials for the Reduction of
VOC Emission (P. Bierman-Lytte) B-3
Applications for Puttruded Products (R. Dillner) B-12
The Use of Uncoated Aluminum as the Major
Component of American Airlines Aircraft (J. L Katopodis) B-17
Uncoated Titanium - Compatible with the Environment (E. E. Mild) B-23
Uncoated Weathering Steel For Bridges and Other Structures (B. R. Appleman) B-50
Painting Thermoplastics with a Rim (C. H. Fridtoy and V. H. Rampelberg) B-59
Tedlar PVF Rim Coating Applications (J. H. Rogers) B-67
Materials Related to the National Aero-Space Plane (T. M. F. Ronald) B-71
Appendix C. Conversion Factors C-1
rv
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ACKNOWLEDGMENTS
The authors would like to acknowledge all those who participated in, and presented papers at the
workshop and helped to make it a success. The authors would also like to acknowledge the
contributions of the following individuals who contributed their time and energy by facilitating the
brainstorming sessions:
Lynn Vendinello - U.S. EPA, Office of Pollution Prevention
Paul Randall - U.S. EPA, Risk Reduction Engineering Laboratory
Linda Pratt - San Diego County Health Department
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1.0 Background
The national ambient air quality standard for ozone (0.12 ppm) is exceeded in over 100
geographic areas throughout the United States. Extensive reduction of volatile organic compound
(VOC) emissions is required for attainment. The difficulty of dealing with stationary area sources
has been a major obstacle to attaining these reductions.
Surface coating operations release approximately 15 percent of stationary area VOC emission
as estimated by the 1985 National Acid Precipitation Assessment Program (NAPAP) emissions
inventory. Many of the VOC and other emissions from surface coating operations are also air
toxics having additional impacts on human health and the environment. Emissions occur during
the initial coating, as well as each time that a surface is recoated during the life of the object or
structure. If materials or products could be developed that do not need coating during either
manufacture or use (surface-coating-free materials), it is anticipated that increased use of these
products could result in reduction of VOC emissions. These emissions would be reduced not only
from the applied coating but from other products required to use surface coatings such as
solvents, surface preparation formulations, and paint removers. Some examples of commonly
used surface-coating-free materials include vinyl siding, various forms of aluminum and other
metals, many types of plastic parts ranging from computer casings to toys to military applications,
and nonmetallic inorganic building materials such as brick and stone.
The U.S. Environmental Protection Agency's (EPA) Air and Energy Engineering Research
Laboratory (AEERL) is responsible for a research program entitled, "Demonstration of Emerging
Area Source Prevention Options for Volatile Organics." The program's goal is to reduce
emissions from stationary area sources by developing, evaluating, and/or demonstrating pollution
prevention options. The program has two project areas: (1) Alternative Coating Materials and
Processes, and (2) Consumer Product Prevention Options. Each of the two project areas has
several specific tasks. One of the tasks under the Alternative Coating Materials and Processes
project area is the investigation of surface-coating-free materials.
The U.S. EPA, with the assistance of the Research Triangle Institute (RTI), sponsored a workshop
exploring the concept of surface-coating-free materials, the potential impact of these types of
materials on VOC and air toxic emissions from surface coating operations, and the means for
promoting the surface-coating-free materials ethic.
This report summarizes the discussions and recommendations from the workshop. The
discussion section is a result of notes that were taken during the brainstorming sessions. The
individuals that participated in these sessions were from a wide variety of backgrounds and
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Surface-Coating-Free Materials Workshop
sponsoring organizations. As a result, a wide variety of viewpoints and priorities were expressed.
The purpose of this report is to summarize and present the information as it was discussed and
should not be construed to represent Agency policy.
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Summary Report
2.0 Introduction
The workshop, entitled "Workshop on the Use of Surface-Coating-Free Materials for the
Reduction of VOC Emissions From Surface Coating Operations," was held July 17-19, 1991, in
San Diego, California. The purpose of the workshop was to explore the concept of surface-
coating-free materials and discuss their use as a means of reducing VOC and air toxic emissions
from surface coating operations. A main objective of the workshop was to identify research and
development (R&D) opportunities for the further development of surface-coating-free materials
(SCFM) currently being used by some industries and to recommend ways for increasing the use
of such materials by other industries. In addition, the workshop offered a forum for the exchange
and development of innovative concepts related to SCFM and technology innovation. A list of
the workshop participants is contained in Appendix A.
There are a large number of materials (e.g., many metals and plastics) that are suitable for use
uncoated. On the first day of the workshop, technical papers were presented by representatives
of a varied group of industries that currently use or are developing some of these types of
surface-coating-free materials. The papers were grouped into the following sessions:
* Architectural Products,
* Applications for Uncoated Metals,
* Plastic Materials and Films,
4 Development of Materials for High Temperature Applications, and
+ Regulatory Perspective.
A list of the speakers and copies of their papers are included in Appendix B.
The second day of the workshop consisted of a series of small group sessions. The focus of
these sessions was identifying and developing research concepts that could expand the use of
surface-coating-free materials. Each session lasted 2 hours, and the maximum number of
participants per session was 12. The objective of each session was to discuss issues related to
one specific topic and to develop a series of recommendations for consideration by EPA. The
specific topics discussed were:
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Surface-Coating-Free Materials Workshop
* Potential Demonstration Projects to be Considered by the EPA/AEERL
Pollution Prevention Program,
* Methods for Enhancing the Appearance and Marketability of Surface-
Coating-Free Materials,
+ Regulatory and Economic Incentives to Encourage the Use of Surface-
Coating-Free Materials and Barriers to Technology Innovation,
At the end of the second day, the facilitators from each of the sessions summarized the highlights
and recommendations from each of their sessions. Section 4 of this report is based on their
summaries and notes taken throughout the day.
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3.0 Methodology
The concept of using uncoated materials for various applications is not new. For example, many
plastics, metals, glass, and nonmetallic inorganic materials are regularly used uncoated in a wide
variety of applications. The concept of encouraging their use as a means of reducing VOC and
toxic emissions from coating operations is, however, a new way of thinking. This may involve the
substitution of materials that can be used uncoated for those that routinely require coatings. A
common example of this is the use of vinyl siding as a replacement for wood siding in building
construction. There are many corrosion- and ultra violet(UV)-resistant uncoated materials on the
market and additional materials are emerging rapidly in the marketplace. Identification,
discussion, and transfer of these materials to other applications as a replacement for materials
that require coatings was a main goal of this workshop.
Because this is a new concept, the initial approach was to contact potential workshop speakers
and participants by telephone. This provided us the opportunity to explain EPA's program, the
concept of surface-coating-free materials, and the plans for the workshop. Representatives from
the following industries were contacted.:
• Automotive,
• Aerospace,
• Plastics and composite materials,
• Specialty metals,
• Aluminum and steel,
• Building and architectural,
• Paint and coatings,
• Wood furniture and wood products,
• Government agencies (Defense Department, National Aeronautics and
Space Administration (NASA), and EPA),
• Pollution prevention and environmental groups, and
• Trade associations.
Out of these contacts, the workshop speakers were identified and interest in and support for the
workshop were established. In addition, approximately 2 months prior to the workshop, an
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Surface-Coating-Free Materials Workshop
announcement/registration flier was mailed to 750 potential participants.
Several of the individuals contacted expressed a concern that it appeared that EPA was
promoting one industry (surface-coating-free materials) at the expense of another (paint and
coatings). EPA understands the importance of paints and coatings in many applications and
acknowledges that many recent improvements have been made within this industry in response
to a growing concern over VOC emissions. However, there may be opportunities for material
substitutions that result in a further reduction of VOC and air toxic emissions and pollution
prevention in general. The purpose of this workshop was to introduce a new way of thinking and
explore these opportunities with the final goal of improving the environment and reducing risks
to human health.
The technical paper presentations served the purpose of introducing the concept of surface-
coating-free materials by discussing some of the currently available materials and applications
for their use. The papers were also useful for stimulating discussions and research concepts
ideas on the second day of the workshop. The materials that were discussed covered a wide
range of product types and applications.
The first paper was presented by Paul Bierman-Lytle of The Masters Corporation and included
discussions on several different types of commercially available building products that do not
require surface coatings. The first product discussed, autoclaved cellular concrete (ACC) has
been used throughout the world for all types of construction ranging from single-family homes to
large industrial, institutional, or commercial projects for over 70 years. It is a strong, lightweight,
and versatile material that requires no surface coating. Currently it is not manufactured within the
United States and must therefore be imported for use. An additional potential consideration with
the use of this material is that it is produced from fly-ash which is known to contain low-levels of
toxic metals. The safety of the use of fly ash as a component in building materials is currently
being debated. A decision concerning this safety issue likely will have an effect on the
widespread use of this product and other potential applications for fly ash within the United
States.
The second product discussed during this pres -ntation was cement-bonded particle boards that
are manufactured in Finland from 30% wood chips and 70% Portland cement. The uses for these
particle boards include wall and ceiling panels, acoustic panels, special boards, drywall systems,
and floor panels. The panels have a wood-veneered surface that does not require any type of
surface coating. An additional type of surface-coating-free building panel that was discussed was
a nonasbestos-containing roofing material similar in appearance to slate.
Pultruded products made from fiberglass reinforced plastic were discussed by Robert Dillner of
Creative Pultrusions, Inc. Pultrusion is a continuous process of pulling fiberglass reinforcements
(or other reinforcing materials) through a bath of thermosetting resin and into a heated forming
and curing die. The curing process takes place within the die and is initiated by precise
temperature control. The material solidifies in the exact shape of the die cavity as it is
continuously pulled by the pultrusion machine. Specific strength, corrosion resistance, thermal,
and other properties can be engineered for custom applications. Color is uniform throughout the
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cross section of the product, thereby eliminating the need for many painting requirements. The
resulting product is light weight, high strength, and relatively maintenance free. Application for
plutruded products include the electric, building/construction, and transportation industries.
Jim Katopodis from American Airlines discussed his company's history of flying and maintaining
basically uncoated aluminum airplanes. Various types of aluminum alloys are available for a wide
variety of applications. For the aircraft industry, the primary material property of importance is
the ability to withstand many types of loads without being damaged. Additionally, the material
must withstand cyclic fatiguing and be corrosion resistant. American Airlines has selected
aluminum alloys that meet these necessary requirements. Included with this paper is a
comparison of environmental and cost implications of painted versus nonpainted aircraft.
Another metal, titanium, can be used uncoated in a wide variety of applications and was the
subject of a paper by Edward Mild of TIMET. Titanium is a generic term used to describe the
entire list of commercially available grades of the metal and its alloys. In all its chemical
compositions, titanium is resistant to corrosion by the atmospheric environment, seawater, and
fresh water. Applications for uncoated titanium exist in many areas including: architecture, power
plant flue gas desulfurization systems, and seawater applications. The initial cost of titanium
products is higher than that of other metals such as aluminum or stainless steel however, its
corrosion resistance is much greater and therefore will last longer, require less maintenance, and
ultimately could result in lower costs over the entire life of a product. An additional factor to
consider in the selection of titanium (and other metals as well) is the energy requirements (and
resulting pollution) associated with production.
Bernard Appleman from the Steel Structures Painting Council presented data on successful and
unsuccessful case histories of the use of weathering steel. Weathering steel is a high strength
steel containing low amounts of chromium and other alloys. Under certain circumstances these
alloys promote the formation of a tightly adhering dense oxide layer which precludes the need for
any surface coating. This property provides distinct advantages over conventional carbon steel
which requires a coating system for corrosion protection in virtually all exterior atmospheric
environments. Applications where weathering steel has been used include rail cars, buildings,
bridges, and utility poles. There have been some problems with use of this material in some of
these applications and therefore caution should be exercised in the selection of this material.
This paper discusses the advantages and disadvantages of this material as well as recommended
applications and use procedures.
The next two papers, presented by Victor Rampelberg of Avery Dennison and John Rogers from
DuPont, both discussed the use of polymer film coatings that can be applied to a wide variety of
materials under controlled conditions. The films provide a weather and stain resistant surface for
both interior and exterior applications. Some of the current uses for these films include
automotive parts, residential siding material surfaces, decals for vehicle decorations, and aircraft
interior surfaces. While these products technically stretch the definition of surface-coating-free
materials (they in fact are coatings), their long life and controlled manufacture and application are
likely to result in fewer VOC emissions than would result from the repeated and uncontrolled
application of traditional coatings to the same products.
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Surface-Coating-Free Materials WorksrnD
The final technical paper was presented by Lawrence Hjelm from the United States Air Force
Materials Laboratory. The topic of this paper was materials that are being developed for the
National Aero-Space Plane Program. The goal of this program is the construction and flight
testing of an experimental, fully reusable hypersonic aerospace plane. To meet this goal a variety
of new materials are being developed and tested. Because one of the goals of the SCFM
Workshop was to assist in the transfer of material technologies, it was anticipated that some of
the materials being developed for this program would be applicable to other industries. The
materials that were discussed included titanium alloys, titanium-based metal-matrix composites,
carbon-carbon composites, ceramic-matrix composites, and copper-matrix composites. In all
cases these materials are designed for very high temperature applications and are very
expensive. Therefore their applicability is limited to other situations where material cost is not a
prime consideration.
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4.0 Workshop Discussion
Workshop participants were divided into small groups for the discussion sessions that took place
on the final day of the workshop. The individuals that participated in these sessions were from
a wide variety of backgrounds and industries. As a result, varying viewpoints and priorities were
expressed. The following sections summarize these sessions and present the participatants
recommendations.
4.1 Research. Development, and Demonstration Opportunities
One of the primary goals of this workshop was to identify potential research projects related to
the use of surface-coating-free materials. Identified projects would then be incorporated with the
list of potential demonstration projects to be considered for funding by AEERL In addition to the
identification of potential use of SCFM research projects, a significant amount of time was spent
discussing potential research projects related to low- and no-VOC coatings. One of the
discussion groups focused part of their time on the identification of important project selection
criterion. These discussions are summarized in the following sections.
4.1.1 Potential SCFM Research. Development, and Demonstration Projects
The ideas that were generated in these discussion groups range from very general to very
material- and project-specific. A recurring concept was that many materials currently exist that
could be, and sometimes are, used without coatings. The group's recommendation for EPA
research was to further expand the uses for existing materials rather than to develop new ones.
Many other research organizations invest heavily in materials development. As these new
material technologies become available, EPA could become involved in demonstration testing for
different applications. In no particular order, the specific SCFM research projects identified during
the brainstorming sessions were:
1. Environmental life cycle analysis of existing surface-coating-free materials.
2. Investigation of opportunities for expanding the markets of currently available surface-
coating-free materials.
3. Material-specific focus groups.
4. Improved accelerated aging tests for materials.
5. Investigation of specific surface-coating-free building materials.
6. Research to identify opportunities for the increased use of SCFM in the construction
industry.
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Surface-Coating-Free Materials Workshop
7. Increased development and technology transfer of composite materials used in the
aerospace'industry.
8. Investigation and demonstration of the use of uncoated aluminum, and potentially other
metals, in the transportation industry (i.e., work with the U.S. Postal Service to develop
and test SCFM for postal vehicles).
9. Investigation of the process involved in producing and applying plastic film coatings.
10. Investigation of the use of weathering steel.
11. Conduct R&D on basic chemistry and physics of wood, plastic, etc.
4.1.2 Low- and No-VOC Coatings Research Needs
Although discussions of low- and no-VOC coatings were not a primary goal of this workshop,
many of the participants felt that EPA should be conducting research in this area. Their thinking
was that coatings are always going to be required in some applications; therefore focusing
resources on improving coating technologies would be valuable. The following research areas
were suggested:
1. Improvements in powder coating application technologies.
2. Demonstrations of UV-cured coatings and characterization of generated wastes.
3. Improvements in water-based coatings.
4. Demonstration of the plastic flame coat technology in various applications.
5. Evaluation of methods for improving the transfer efficiency in coating operations.
6. Investigation of surface preparation/priming requirements and opportunities for in-factory
coating.
7. Organization of a workshop/conference on the topic of low- and no-VOC coatings.
8. Work with the U.S. Navy to test different coatings (and SCFM) on Navy vessels.
4.1.3 Project Selection Criteria
One of the groups felt that identification of project selection criteria was as valuable as the
selection of actual projects. This group came up with a list of criteria that may be useful for EPA
not only in the selection of projects for SCFM research but for other research areas as well. The
criteria are the following:
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1. Consideration of the total volume of VOC that can be reduced.
2. The opportunity for impacting multimedia problems.
3. Transferability of the technology.
4. Risk (success potential) versus benefits.
5. The need for sustainable development strategies.
6. Potential for outside co-funding.
7. Cost-effectiveness for utilization by small businesses and general public.
8. Time frame for implementation/completion of project.
4.2 Methods for Enhancing Appearance and Marketability of Surface-Coatlnq-Free
Materials
A large number of materials or material types are currently available and are used surface-
coating-free. Expanded use of these materials in new applications involves more than
overcoming technical barriers. Consumer acceptance may be difficult to gain for products that
appear different from the norm.
These sessions focused on issues related to developing surface-coating-free materials with
appearances and quality similar to traditional materials requiring surface coating. The three
discussion groups covered a wide range of issues, often only tangentially related to the topic.
This is partly due to the fact that manufacturers are very sensitive to appearance and
marketability issues. In many cases, how the product looks is the critical element in the purchase
decision, whether it is a $15,000 automobile or a $50 dinette chair. Consequently, any change
in the appearance of the surface is viewed with skepticism by manufacturers.
The discussion groups raised questions rather than provided any answers. The key topics that
emerged from the discussion groups included:
• Life-time of product
• Quality of final product
• Differences among markets
• Improved communications, EPA public relations, and technology transfer.
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• Appearance/marketability issues
• Management issues, and
* Regulatory environment.
Why is the coating needed? The answer to this simple question has complex ramifications.
Often the answer is based on past experience or the "we've always done it this way" syndrome.
However, it is critical to understand whether the purpose of the coating is appearance, marketing,
customer demand, corrosion protection, chip resistance, or some other factor. In evaluating the
use of materials, it is often important to look at the use of coatings and ask the following
questions:
* Why is the coating needed?
+ Given these reasons, what approaches to eliminating the use of the
coating are possible? Is elimination feasible for this use?
+ Would changing the substrate be feasible?
+ Could the uses be modified to not require a coating?
+ Are there other components of the coating/application/
substrate/use system that could be modified to allow for a SCFM
approach?
Trade-offs between SCFM and those with coatings have to be evaluated considering the useful
lifetime of the product In many cases, the coating provides a longer useful product life. For
example, coating air conditioners in a beach environment prevents or at least reduces the effects
of corrosion from salt spray. An alternative would be a reinforced plastic casing that required no
coating and would be immune to salt water problems. If the product design dictates a short life,
then a manufacturer may be unwilling to invest in a long-life component that may be more
expensive. In the case of a product with a long design life, would it be appropriate to allow
"more" VOC emissions to be released during the products production and/or use? Consumers
may not be willing to pay the additional initial expense for longer-lived products.
Participants expressed serious concern about the extent, real or perceived, that product quality
might be affected by moving to a SCFM. In many cases (e.g., automobiles), the coating is critical
to the marketing and actual sale. The DeLorean, with its stainless steel body, was a car with a
SCFM skin; however, consumers may prefer a shiny and lustrous red to a duller stainless steel.
Issues discussed included how to determine when a quality finish is critical to the sale or, more
importantly, the effective use of the product. Coating is critical to the performance of a non-stick
frying pan yet is not critical to the performance of the exterior of a commercial aircraft fuselage.
Even more challenging, is how to define product quality so that it can be evaluated with and
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without SCFM. The groups concluded that quality is difficult to measure and assess objectively
and can vary with the type of use.
A critical element related to coating issues is the cost of being wrong -- what if the SCFM doesn't
work. For example, in developing alternative non-VOC finishes for wood or paper products,
manufacturers have had problems producing a product with similar finish and "quality."
Alternatively, essentially all products inside an airplane are coated, primarily for corrosion
resistance because interiors of a plane are very susceptible to moisture buildup. Many of these
parts are not readily visible making inspections more difficult. Consequently, manufacturers are
reluctant to move to a SCFM product until it can be unequivocally demonstrated that it will be as
resistant as the coated product. The consequences of a defective part are too serious.
SCFM marketability will vary depending on whether the market is consumer, industrial,
government (nonmilitary), or military. Each market has different expectations of the same product
based on how they plan to use it. Any program for promoting SCFM must recognize that different
strategies should be employed for different market sectors.
In addition, there are several factors affecting appearance and marketability of SCFM. First,
where is the coating applied: at the factory or in the field at the point of use of the product? The
location of application may affect the extent to which a SCFM product could be developed or
substituted for a coated product. Second, the type of substrate affects the need for coatings.
Certain steels can be designed so as not to require coating while others would always require
some coating for specific uses. Third, the point where most of the VOC releases occur needs
to be identified. If there are low VOC emissions because of the type of application, etc., it may
be appropriate to select other products for SCFM development. Finally, specifications set by
large purchasers, such as the military and the automobile industry, have a significant impact on
what their numerous small suppliers do. By working with the specification writers, regulators
could facilitate the incorporation of SCFM alternatives into the specifications.
Two nontechnical areas were the source of much discussion: resistance to change and the effect
of the regulatory environment on the choice of coating. All participants agreed that management
attention and support were critical to considering SCFM as part of pollution prevention. Like
everyone, managers and workers are resistant to change. This resistance needs to be addressed
in developing innovative SCFM approaches. Otherwise, adoption of the new technologies may
be slow in coming.
The discussion groups came up with the following series of recommendations related to the use
of SCFM and low VOC coatings.
1. Establish regional technical innovation centers to promote and market surface-
coating-free materials.
2. Improve education of professionals and the general public on alternatives to
coatings.
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Surface-Coating-Free Materials Workshop
3. Standardize and accelerate coating testing and methodologies.
4. Develop systems approach to use/nonuse of coatings.
5. Conduct conferences and workshops for actual users, etc.
6. Conduct industry-specific focus groups.
7. Establish center for low-VOC products similar to the Southern California Edison
energy conservation center.
8. Conduct research and development (R&D) to find non-VOC coatings approaches
for coating needs.
9. Determine factors that influence marketability related to coatings and use them to
guide R&D needs.
10. Develop an on-line reference for products and coatings with reduced or low-VOC
releases.
4.3 Barriers and Incentives
The purpose of this session was to focus first on barriers to technology innovation and then on
potential regulatory and economic incentives that could break down these barriers and encourage
the use of surface-coating-free materials. Three groups of participants had the opportunity to take
part in this discussion. Although these groups met separately, several common themes and/or
concerns were expressed by all three.
4.3.1 Perceived Barriers
In no particular order, the major barriers identified are discussed in the following sections.
4.3.1.1 High development costs
Industry wants to do what is best for the environment but is reluctant to invest
heavily in new product development unless the potential for profit is great. The
expense associated with the development and marketing of a new product can
be very high. The lack of revenue during the development stage makes it
particularly difficult for smaller companies, without large research budgets, to
invest the time and effort required to develop a new technology. In today's
uncertain economic and regulatory climate, many companies are not interested
in taking such risks.
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4.3.1.2 New product uncertainty
Consumer acceptance is also a critical issue in the development of a new product
or technology. A product has to be more than just environmentally friendly. It
should also retain the same (or better) performance characteristics (at a
competitive price) than the less environmentally friendly product that it is
attempting to replace. In some cases, a new product may require users to
modify their use patterns to get the best product performance. This may require
some form of consumer education. Several workshop participants pointed out
that this process can be very difficult - resistance to change can be very great.
Changing consumer attitudes often involves expensive marketing efforts.
4.3.1.3 Regulatory uncertainty
Regulatory uncertainty was a topic that received a great deal of attention in all
of the discussion groups. Many participants expressed their frustration at
attempting to develop new technologies with the ever-changing environmental
regulations. Regional regulatory variations were stated by many workshop
participants to also have a significant impact on the ability of a company to
pursue technology advancements. Companies also have to consider the
regulatory variations that exist from country to country. It was stated by several
workshop participants that less stringent environmental regulations have resulted
in businesses moving from the United States.
A similar type of barrier that was mentioned by the workshop participants is a
perceived (or real?) non-uniformity of enforcement of environmental regulations,
specifically with regard to small businesses. Some of the workshop participants
expressed the opinion that enforcement personnel target large facilities and
corporations and allow small firms to operate more freely.
4.3.1.4 Corporate bureaucracies
Red tape and bureaucracy exist in most institutions. Although many corporations
are sincerely committed to reducing pollution and protecting the environment,
making improvements in large operating systems can require perseverance and
patience. Some workshop participants indicated that new and innovative
concepts are sometimes stifled by corporate bureaucracy.
4.3.1.5 Technology transfer
Technology transfer is an issue critical to the advancement of the use of surface-
coating-free materials. As stated, there are many materials (e.g. plastics,
aluminum products and other metals) that traditionally have been used uncoated
in a variety of applications. In addition, new materials are routinely developed.
Often these materials are designed for one purpose and little effort goes into
15
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Surface-Coating-Free Materials Workshop
expanding their applicability. Educating the producers and developers of these
materials on the concept and potential benefits of surface-coating-free materials
would likely be a very effective way to expand their use. Along with the transfer
of materials technologies, there must be trust and cooperation between parties.
Several of the workshop participants expressed the concern that competition
between companies and the desire to have a competitive edge would have a
negative effect on building the trust necessary for an effective technology transfer
program.
4.3.1.6 Environmental life-cycle costs
The importance of performing environmental life cycle analysis was stressed
many times throughout this workshop. A particular material or product may
appear to have fewer adverse environmental impacts than another, but a detailed
life cycle analysis may indicate the reverse to be true.
One primary issue in a life cycle analysis is the service life of the product.
Several of the workshop participants indicated that a barrier to the use of certain
uncoated materials is that no value is given to life cycle costs. In other words,
a product that does not require repeated coatings may be more expensive
initially. However, when the costs associated with the required recoating over the
life of the product are factored into the equation, total costs may be competitive.
It may be difficult to convince consumers to buy the initially more expensive
product.
4.3.1.7 Military specifications
The aerospace industry was well represented at the workshop and identified the
issue of military specifications for materials and coatings as a major barrier to
innovation. All Defense Department contracts contain detailed specifications for
all materials and coatings that are to be used as part of the project. The process
required to modify these specifications is very expensive and time consuming,
and therefore military specifications are very slow to change-even when a better
(with regard to performance or environmental impacts) product is identified.
Fears of many defense contractors are that if they would recommend a coating
that was not part of the contract specifications, they would be labeled as being
noncompliant, and they would endanger their existing or future Defense
Department projects.
4.3.2 Regulatory and Economic Incentives
Regulatory and economic incentives that were discussed during the brainstorming sessions are
briefly described in the following sections. No attempt has been made to prioritize or rank the
incentives.
16
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Summary Report
4.3.2.1 Tax Incentives
The use of tax incentives for research and development was considered by many
of the participants to be one of the greatest incentives to encourage industry to
develop new surface-coating-free materials. Many specific types of incentives
were discussed such as tax credits based on a percentage of a company's R&D
budget, tax credits for materials or VOC-related research only, and tax credits for
pollution prevention technology implementations. An additional type of incentive
discussed, without direct tax savings, is the use of other types of awards that
could result in good public relations for a company.
4.3.2.2 User tax
The concept of a user tax or fee that is based on the actual costs (both
production and environmental) of an item was recommended. Such a tax could
be based on the VOC or air toxic content of a product and/or the amount of
VOCs/toxics emitted during the production of a product. Such a tax or fee would
give consumers a better understanding of what they are paying for and allow
them to compare products and make decisions based on environmental impacts.
A good example of the use of this kind of fee can be found in the auto industry.
A quality appearance and finish is critical to the sale of automobiles and other
coated products. There is a great deal of competition between various
manufacturers to develop better finishes that are environmentally compliant
Many of the finishes that have the most consumer appeal are the least
environmentally friendly. An example of user fees could be a charge added to
the sticker price of automobiles that are manufactured with these types of
coatings. This fee should appear as a Rne item on the window sticker of each
automobile. The window sticker would also indicate whether a low- or no-VOC
coating had been used. This would allow consumers to compare finish types and
appearances and make decisions based on a coatings' environmental costs.
4.3.2.3 Enhanced regulatory environment
Many of the workshop participants expressed the opinion that there is a need for
improvements in the U.S. environmental regulatory system. Suggested
improvements ranged from establishment of a import tariff on noncompliant
foreign products (or products manufactured in countries that do not meet U.S.
environmental regulations) to a reduction of the regulatory burden associated with
making minor process changes at existing facilities. As mentioned in Section
4.3.1, many of the participants expressed the need for a "level playing field" with
respect to environmental regulations. This issue was raised again pertaining to
enforcement and regional regulatory variations.
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Surface-Coating-Free Materials Workshop
4.3.2.4 Improved communications, EPA public relations, and technology
transfer
A final incentive discussed at the workshop involved communication. Industry
would like to be informed of and be involved in EPA programs and research.
They are interested in the development of partnerships and co-funded research.
Industry would also like to be included up-front on more policy development
issues. It was suggested that EPA develop (or possibly improve and better
publicize) information transfer programs. This could include information on
research projects and results, opportunities for industrial participation,
training/assistance, and public relations for the EPA concerning ways that they
can help industry and vice versa.
5.0 Conclusions and Recommendations
The EPA/RTI workshop on surface coating-free materials provided an opportunity for discussion
of a new pollution prevention concept that could result in reduced VOC and air-toxic emissions
from coating operations. As can be seen from the list of participants (Appendix A), a wide variety
of organizations/industries were represented. This diversity resulted in a unique forum for the
exchange of informatoin and differing viewpoints. The purpose of this document is to summarize
the information from the meeting as it was discussed.
Although there are a wide variety of materials that are currently (and have been for a long time)
used uncoated, the concept of increasing and encouraging their use as a means for helping to
reduce VOC and air toxic emissions from surface coating operations is new. In the early stages
of this project a great deal of effort was devoted to explaining this concept to potential workshop
participants. Generally speaking most have agreed that it is a good concept however, it is going
to take persistence and time for it to be understood and adopted on a wide basis. It was
recommended that EPA continue to advance the concept through the use of workshops, meetings
and briefings with potentially involved industries and trade associations, and paper presentations
at appropriate meetings and conferences.
In conjunction with the further development of the concept of surface-coating-free materials, there
needs to be an investigation of the life-cycle environmental impacts of the use of specific
materials. On the surface, it may appear that one material is less polluting than a similar product.
However, a complete investigation of the product's entire life cycle needs to be performed to
ensure that adverse environmental or health impacts are not associated with different stages of
a material's production, use, disposal, etc. A recommendation from the workshop was that EPA
perforr q life-cycle analysis on several currently used, coated materials and alternative surface-
coatin ee materials. The results from these analyses could then be compared to determine
which r.oduct is less polluting.
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Summary Report
Coatings serve many very important functions and will continue to do so in the future. Therefore,
EPA should focus attention on the development and demonstration of low- and no-VOC coatings
in addition to surface-coating-free materials. Many of the workshop participants recommended
that EPA conduct additional workshops in these areas. Specific recommendations concerning
content of additional workshops varied. Some indicated that a large broadly defined conference
encompassing coating technologies and surface-coating-free materials would be the most
appealing. Others indicated that small specifically focussed industrial group meetings might result
in the best exchange of information.
Additional specific research projects were recommended by the workshop participants. These
projects were discussed in Section 4.1.
19
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Appendix A
Surface-Coating-Free Materials Workshop Participants
A-1
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Attendees List
Surface-Coating-Free Materials Workshop
July 17-19, 1991
San Diego, California
Dr. Ronald Ambrose
PPG Industries, Inc.
P. O. Box 9, Research Center
Allison Park, PA 15101
Dr. Bernard Apple man
Steel Structures Painting Council
4400 Fifth Avenue
Pittsburgh, PA 15213-2683
Ms. Elaine Chang
South Coast Air Quality Management District
21865 East Copley Dr.
Diamond Bar, CA91731
Mr. Howard Collingwood
Allied Signal, Inc.
Box 1053
Morristown, NJ 07962
Mr. Paul Bierman-Lytle
The Masters Corporation and
Environmental Outfitters
P. O. Box 514
New Canaan, CT 06516
Ms. Linda Collins
Caspian, Inc.
4951 Ruff in Road
San Diego, CA 92123
Mr. John Bunnell
Southern California Edison
2244 Walnut Grove Avenue
Rosemead, CA 91770
Mr. Patrick Connors
Mobay Corporation
15631 Lake Lodge Drive
Houston, TX 77062
Mr. David Carey
McDonald Douglas
Space Systems
Dept 242, MS-22-2
5301 Bolsa Avenue
Hunting Beach, CA 92647
Ms. Linda Causey
CH2M Hill
2510 Red Hill Avenue
Santa Ana, CA 92705
Mr. Charles Darvin
U.S. EPA
Air & Energy Engineering Research Lab.
MD-61
Research Triangle Park, NC 27711
Mr. Dean DelCamp
National Steel & Shipbuilding
265 Quintard Street, B94
Chula Vista, CA 91911
A-2
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Mr. Bob Dillner
Creative Pultrusions, Inc.
Pleasantville Industrial Park
Alum Bank, PA 15521
Mr. Jim Katopodis
American Airlines
3800 N. Mingo, MD#10
Tulsa, OK 74151
Mr. Fred Drake
Reynolds Metals Company
1941 Raymet Road
Richmond, VA 23237
Mr. Michael Kosusko
U. S. EPA
Air & Energy Engineering Research Laboratory
MD-61
Research Triangle Park, NC 27711
Mr. Clark Fessler
Horizon Architectural Coatings, Inc.
1463 Fayette Street
El Cajon, CA 92020
Ms. Thuy Le
San Diego Air Pollution Control Division
9150 Chesapeake Drive
San Diego, CA 92123
Mr. Lawrence Hjelm
U. S. Air Force Materials Lab
WL-MLL
Wright-Patterson AFB. OH 45433-6523
Dr. James Lents
South Coast Air Quality Management District
21865 East Copley Dr.
Diamond Bar, CA 91765
Mr. Kevin Jameson
ENSR Consulting & Engineering
35 Nagog Park
Acton, MA 01720
Mr. Bob Manseill
Energy, Environment & Resource Center
327 S. Stadium Hall
Knoxville, TN 37996-0710
Mr. George Jung
Lockheed Advanced Development Company
P. O. Box 250
Sunland, CA 91041-3731
Mr. Alexander Marr
Southern California Edison
2244 Walnut Grove Avenue
Rosemead, CA 91770
Mr. Vishnu Katari
U.S. EPA
401 M Street, SW EN-341
Washington, DC 20460
Ms. Cindy McComas
University of Minnesota - MNTAP
1313 5th Street, SE #207
Minneapolis, MN 55414
A-3
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Mr. Ron Meier
Northrop Corporation
8562 Bermuda Avenue
Westminster, CA 92683
Ms. Linda Pratt
San Diego County Health Department
San Diego Hazardous Materials Mgmt. Div.
P. O. Box 85261
San Diego, CA 90024
Mr. Ed Mild
TIMET
W. Lakemead Drive at Atlantic
P O. Box 2128
Henderson, NV 89015
Mr. Victor Rampelberg
Avery Dennison/Decorative Films
650 West 67th Place
Schererville, IN 46375
Ms. Mary Moore
Research Triangle Institute
P. O. Box 12194
Research Triangle Park, NC 27709
Mr. Paul Randall
U. S. EPA - Risk Reduction Engineering Lab
26 W Martin Luther King Drive
Cincinnati, OH 45140
Mr. Glenn Morris
General Dynamics Convair
P. O. Box 85357
San Diego, CA 92186 M-43-6310
Mr. Paul Murray
Herman Miller, Inc.
8500 Byron Road
Zeeland, Ml 49464
Mr. James Reimer
Vice President Research & Technology
Plastic Flamecoat Systems
1613 Highway 3
League City, TX 77575
Mr. John Rogers, Jr.
DuPont Polymers
P. O. Box 80712
Wilmington, DE 19880-0712
Ms. Coleen M. Northeim
Research Triangle Institute
P. O. Box 12194
Research Triangle Park, NC 27709
Mr. Jim Ronsse
PPG Industries, Inc.
465 Crenshaw Boulevard
Torrance, CA 90509
Dr. Connie Oldham
U.S. EPA
Office of Air Quality Planning & Standards
MD-12
Research Triangle Park, NC 27711
Mr. Jordan Rosengard
Hughes Aircraft
EDSG, BkJg. E-1.MSF-157
P. O. Box 902
El Segundo, CA 90245
A-4
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Mr. Mike Stamatelatos
SCIENTECH, Inc.
3314 Lone Jack Road
Encinitas. CA 92024
Mr. John Warren
Research Triangle Institute
P. O. Box 12194
Research Triangle Park, NC 27709
Dr. Roger Sung
Southern California Edison
2244 Walnut Grove Avenue
Rosemead, CA 91770
Mr. Larry Watkins
South Coast Air Quality Management Division
Technology Advancement Office
2165 East Copley Dr.
Diamond Bar, CA 91765
Mr. Laki Tisopulos
South Coast Air Quality Management District
21865 East Copley Dr.
Diamond Bar, CA 91765
Mr. Sam Williams
Forest Products Laboratory
One Gifford Pinchot Drive
Madison, Wl 53705
Mr. Gerry Topp
Santa Barbara County APCD
26Castilian, B-23
Goleta, CA 93117
Mr. Donald Willis
San Diego Air Pollution Control Division
9150 Chesapeake Drive
San Diego, CA 92133
Mr. Khiet Trankiem
DuPont Company
DuPont Building Room D-12082
Wilmington, DE 19898
Mr. Fonda Wu
Hughes Aircraft
RE/R7/406
P. O. Box 902
ElSegundo, CA 90245
Ms. Lynn Vendinelto
U. S. EPA Office of Pollution Prevention
401 M Street SW
Washington, DC 20460
Ms. Mildred Yamada
Northrop Corporation
One Northrop Avenue, 5791/23
Hawthorne, CA 90250
Mr. Stephen Walata, III
Alliance Technologies Corporation
100 Europa Drive, Suite 150
Chapel Hill, NC 27514
Ms. Azita Yazdani
Pollution Prevention International
4221 Wilshire Boulevard, Suite 240
Los Angeles, CA 90010
A-5
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Appendix B
Paper Presentations
The following Is a list of the speakers at the workshop. Page numbers for each of the papers
are Included In parentheses after the title.
SESSION 1
Architectural Products
Dr. James M. Lents, Executive Officer Keynote Address
South Coast Air Quality Management District Use of Surface-Coating-Free
Materials
Mr. Paul Blerman-Lytle Surface-Coating-Free Materials for
The Masters Corporation and the Reduction of VOC Emissions
Environmental Outfitters (B-3 through B-l 1)
Mr. Robert Dlllner AppScations for Pultruded Products
Creative Pultruslons, Inc. (B-12 through B-16)
SESSION 2
Applications for Uncoated Me/ate
Mr. Jim L Katopodls The Use of Uncoated Aluminum as
American Airlines Ihe Major Component of American
AHnes Aircraft (B-l7 through B-22)
Mr. Edward E. Mild WarVum-Compcrttote wf/n the
TIMET Environment (B-23 through B-49)
Dr. Bernard R. Appleman Uncoated Weathering Steel for
Steel Structures Painting Council Bridges and Other Structures
(B-50 through B-58)
B-l
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SESSION 3
Plastic Materials and Films
Mr. Victor H. Rampelberg (Speaker)
Avery Dennbon
Mr. Charles H. Frldley (Co-Author)
Avery Dennteon
Painting Thermoplastics with a Rim
(B-59 through B-66)
Mr. John H. Rogers, Jr.
DuPont Company
TEDLAR PVF Film Coating
Applications (B-67 through B-70)
SESSION 4
Development of Materials for High Temperature Applications
Mr. Lawrence J. HJelm (Speaker)
U. S. Air Force Materials Laboratory
Mr. Terence M. F. Ronald (Co-Author)
U. S. Air Force Materials Laboratory
Materials Related to the National
Aero-Space Plane (NASP)
(B-71 through B-78)
SESSIONS
Regulatory Perspective
Mr. Charles H. Darvln
U. S. Environmental F»rotectton Agency
Air and Energy Engineering Research Laboratory
The Pollution Prevention Challenge
to Scientists and Engineers
B-2
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SURFACE-COATING-FREE MATERIALS
FOR THE
REDUCTION OF VOC EMISSIONS
Author
PAUL BIERMAN-LYTLE
President
The Masters Corporation
P. O. Box 514
New Canaan, Connecticut 06516
I. AUTOCLAVED CELLULAR CONCRETE (ACC)
ACC is a building material developed by a Swedish architect, Johan Axel Erikkson, and patented
in 1928. It is a superior, fine-grained, porous concrete material that is suitable for all types of
construction, ranging from single-family homes to large industrial, institutional, or commercial
projects.
ACC is manufactured and used for housing and commercial/industrial buildings in many countries
throughout the world. YTONG, of West Germany, began manufacturing ACC in 1929 and
presently has 40 plants in various countries. SIPOREX, of Sweden, has plants in 23 countries around
the world. HEBEL. of West Germany, has 32 plants in 12 countries. H & H. of Denmark, has 6 plants
in Europe. THERMALJTE has 7 plants in the U. K. Currently, several of the European companies are
exploring the U.S. market. WEYERHAEUSER is actively involved in developing the ACC industry in
the United States.
The Department of Technology Education. West Virginia University, is involved in a
diffusion/adoption project to promote the establishment of an ACC manufacturing plant in West
Virginia. Under the direction of Professor Edward Pytlik, several papers have been prepared for
the introduction of ACC into the U.S. market. These papers include: ACC, The Building Material
For The 21st Century, and ACC, A Useful Shelter Technology For Developing Countries. According
to HEBEL, of West Germany, ACC has met and complied with U. S. building codes and has several
test projects under way in Florida. HEBEL is planning on opening manufacture of ACC by 1993 in
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Surface-Coating-Free Materials for
the Reduction of VOC Emissions
the United States. However, currently, the closest manufacturing plant of ACC is located in
Mexico.
MANUFACTURE OF ACC
The raw materials required for ACC are finely ground sand or fly-ash, lime, water and a small
amount of aluminum paste or powder. Research and development in the manufacture of ACC
have led to the replacement of sand with fly-ash (pulverized fuel-ash) by as much as 100% in some
cases. Fly-ash is a by-product from coal-fired electric generating stations. In 1985, more than 48
million tons of fly-ash was produced in the United States of which only 5.1% was used in concrete
products.
The raw materials are mixed into a slurry and tapped into greased molds up to two-thirds of their
depth. For large reinforced units, rust-protected reinforcement nets are positioned into the molds
before casting. The aluminum paste or powder creates a chemical reaction releasing hydrogen
gas, which aerates the mixture producing millions of microscopic nonconnecting cells. Depending
on the process used, it takes from 20 minutes to 2 hours for the mixture to harden enough to be
cut and shaped.
This mixture is then cured in an autoclave for 10 to 12 hours and the finished product, ACC, is 80%
to 90% air by volume.
PROPERTIES OF ACC
LIGHTWEIGHT: Because of its porous structure, ACC weighs less than one quarter of the weight
of traditional concrete. This reduces transportation costs, worker injuries, and installation time.
COMPRESSIVE STRENGTH: ACC has twice the compressive strength of air-cured concrete of
identical composition and density.
THERMAL INSULATION: Because of the totally enclosed air cells distributed evenly throughout its
structure. ACC provides Its own thermal insulation and can substantially reduce heating and air-
conditioning costs.
WORKABILITY: ACC can be easily drilled, sawn, chased, or nailed with ordinary woodworking tools.
SOUND ABSORPTION: ACC provides quiet interiors for housing and protects against production
noise in industrial settings.
FIRE RESISTANCE: ACC is purely mineral in composition, and thus it is noncombustible. It provides
twice the fire resistance of traditional concrete.
EARTHQUAKE RESISTANCE: Tests have proven that ACC performs excellently in seismically active
areas.
B-4
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Paul Bierman-Lytle
VERSATILITY: ACC can be manufactured in various forms: large precision blocks, lightweight
partition panels, load bearing and non-load bearing lintels, reinforced units for floors, roof slabs
and wall units, profiled blocks or units with tongue and groove joint faces.
INSECT RESISTANCE: ACC is inorganic and therefore 100% termite resistant and free from insect
problems.
COST COMPETITIVE: ACC has proven to be cost competitive with traditional concrete when
access to ACC is regional as with traditional concrete.
HEALTH HAZARDS: ACC emits no VOCs. contains no formaldehyde. It can pose a "dust hazard"
when it is being worked, similar to wood dust, sheetrock dust, or other concrete dust products.
SURFACE COATING FREE: ACC requires no surface coating and is manufactured in cement grey
or white. However, it can accept most surface coatings, such as plaster, stucco, wood or
masonry veneer, or paints (such as white-wash).
APPLICATIONS OF ACC
Although ACC has been in production for over 70 years, and worldwide production exceeds 24
million cubic meters, it is not currently manufactured in the United States.
However, in the United States, there are more than 2 dozen buildings made from imported ACC.
These include a 750.000ft2 building in Rhode Island in 1964; a 40.000 ft2 building in Orlando, Florida.
in 1986; and test facilities in Florida and at West Virginia University. ACC has been approved as
a building material by HUD and BOCA.
The Masters Corporation, of New Canaan. Connecticut, is planning to utilize ACC in ECO-tourist
hotels in Costa Rica and in southern California, as well as in seven 21st Century environmental
buildings in Michigan beginning in 1992.
Environmental Outfitters, of Connecticut and California, specializing in catalog, retail, and
wholesale of 21st Century, environmental building materials, is investigating ACC to include in Its
inventory for sales in the United States and Canada.
LIMFTATIONS OF ACC
Currently ACC is not available in the United States unless one imports it from Europe. Once
available, the product will have to gain acceptance among the conventional concrete industry,
installers, engineers, building inspectors, and architects. Given Its track record in Europe for over
70 years, and its good environmental report card, acceptance in the United States could be
earlier than later.
II. ELAM OY CEMENTIOUS BUILDING PANELS
ELAM OY products are ready-surfaced fire-retardant wall and ceiling panels used mainly for public
interiors. Cement and gypsum-bonded particleboards are used as core material, but for the
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Surface-Coating-Free Materials for
the Reduction of VOC Emissions
purpose of this workshop, I will focus on the ready surfaced wood veneer particleboards.
MANUFACTURE OF ELAM BOARDS
ELAM cement-bonded particleboards are manufactured in Kuusankoski, Finland. Their products
have been approved in Finland. Sweden, Denmark, Norway, Iceland, UK, Germany, France,
Netherlands, Spain, and the Soviet Union. Projects have included:
Sports Center in Nakkila, Finland
Church of Maria, Helsinki, Finland
Sheraton Hotel. Gothenburg. Sweden
Concert Hall, Mikkeli. Finland
Culture Centre, Espoo, Finland
Office of Haka Oy. Helsinki, Finland
Ikvik-Finnsauna, Stockholm, Sweden
Ministry of Gas, Soviet Union
Music Conservatory, Madrid, Spain
Over 20 Hotels in Soviet Union
The products are currently not available in the United States or Canada, except through import.
Environmental Outfitters is currently establishing a distribution of the products via its retail centers
in Santa Monica, California, and New York City.
COMPOSITION OF ELAM PANELS
ELAM cement-bonded particleboard consists of wood chips (30% dry weight) and Portland
cement (70% dry weight). The boards are sanded and thickness calibrated suitable for requested
use or for surface coatings. The boards can be installed as they are from the mill, or they can be
covered with decorative melamine, wallpaper, high-pressure laminate or paint, either at the mill
or on site.
Edges can be grooved at the mill for appropriate fixing methods. Installation brackets and joiner
hardware is also available from ELAM.
The products are autoclaved and emit no toxic fumes or VOCs. They are formaldehyde-free
unless surface coatings which contain formaldehyde are requested.
PROPERTIES OF ELAM PANELS
Density: 1,250kg/m3
Thickness Swelling: 1% 2 hr in water
Sound Reduction: Good
Thermal Conductivity: 0.35 W/m°K
Resistant to Fungi and Termites
B-6
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Paul Bierman-Lyrle
Alkalescence: 12 pH value
Weather Resistant
Moisture Resistant
USES OF ELAM PANELS
The uses of ELAM cement-bonded particleboards include wall and ceiling panels, acoustic panels,
special boards, drywall systems, and floor panels.
The Masters Corporation currently is only specifying the use of wood-veneered cement-bonded
particleboards for interior wall and ceiling panels, as well as acoustic panels.
LIMITATIONS OF ELAM PANELS
The boards are currently not available in the United States, although efforts by ELAM OY are under
way to introduce the panels to North America.
The boards are heavy because they are comprised of wood chips and Portland cement and thus
have installation concerns; however, because they are designed to be fitted into each other or
into specially designed hardware, installation is expedited. Also, since surface coatings are not
required, several steps are avoided that reduce cost and maintenance.
Pricing is expected to be competitive since the product offers many one-step features. Boards
can be made to meet U. S. customary dimensions and are offered with a variety of thicknesses.
The wood-veneered panels are very handsome, easy to maintain, require no coatings, satisfy most
fire requirements, and are good sound barriers. These features make up for the premium in initial
cost and newness to the market.
III. ETERNtT CEMENTIOUS BUILDING PRODUCTS
ETERNIT produces a family of nonasbestos panel products used in building construction and for
industrial components. These include:
• Roofing Slates
• Glasweld
• Eterspan
• Eflex
* Eterboard.
• Profile 6
• Substrate 500
* Facad.
For the purpose of this workshop on surface-coating-free materials which contribute to the
reduction of VOC emissions, I will focus on ETERNIT roofing slates. Profile 6. Facad and Glasweld.
However, I will briefly describe the other products as well.
B-7
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Surface-Coating-Free Materials for
the Reduction of VOC Emissions
ETERSPAN is a medium-density calcium silicate panel which is used as a substrate for the direct
application of synthetic and cementitious coatings, ceramic tile and thin brick. It is widely used
as a component in prefabricated wall panels and in on-site studwall assemblies.
EFLEX, the uncoated substrate for GLASWELD, is the highest auality, high-density, nonasbestos, fiber
reinforced cement panel available. Uses include substrate for architectural metals, ceramic tile,
stone and stone aggregate. Industrial uses include laboratory fume hood linings and electrical
components.
ETERBOARD is a medium-high-density calcium silicate panel developed as a direct replacement
for commodity asbestos cement panels. Its applications range from residential to commercial and
industrial uses. It is often used as a component panel facing and as a core for laminated panels.
SUBSTRATE 500 is a ceramic tile backer board, strong, light weight and highly water resistant. It
eliminates the problem of gypsum board or gypsum plaster breakdown in shower and tub
locations.
GLASWELD. an architectural facing panel is used for facades, curtainwall cladding, fascias and
interior applications. It is an opaaue mineral fiber reinforced cement panel available in a
spectrum of permanent designer colors.
FACAD is a slate-textured cladding panel fiber-cement with a GLASWELD surface or uncoated.
Uses include fascias. facades and interior walls.
ROOFING SLATES are fiber-reinforced cement shingles. Available with an authentically textured
surface, they are supplied in blue-black, grey-green, and rose grey in two sizes. They can be used
for high-quality roofing, fascias. facades and mansards.
PROFILE 6 is a corrugated, fiber-reinforced cement sheet used for roofing, siding and partitions in
industrial, commercial and institutional buildings. It is also a major component in cooling tower
construction.
MANUFACTURE OF ETERNIT PRODUCTS
ETERNfT. headquartered in Brussels. Belgium, is one of the world's largest producers of building
materials. The company is a leader in fiber-reinforced cement products and inorganic color
systems and has plants and sales offices in over 50 countries. ETERNIT has recently developed
technologies which enable rt to produce nonasbestos cement products which retain the superior
physical characteristics of asbestos but do not contain that hazardous material.
ETERNfT. INC.. located in Reading. Pennsylvania, was initially organized to market GLASWELD. The
company has recently established the Standard Products Division to market a line of commodity
and specialized mineral-fiber-reinforced panels: Elfex, Eterspan and Eterboard.
B-8
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Paul Bierman-Lytle
The U. S. Etemrt company has established a nationwide network of distributors and representatives.
Etemit has in-house technical support and is backed by the resources of the parent company in
Belgium.
FEATURES OF ETERNIT ROOFING SLATES
PERFORMANCE: Etemit Slates meet the requirements for Class A usage in accordance with ASTM
E-108 (83) when installed over 5/8-inch sheathing. A test report by an independent laboratory is
available upon request.
WATERPROOF: Prolonged soaking does not affect the slates. The stone-like product provides 100%
integrity to properly designed and prepared roofs.
PERMANENCE: Etemit slates stand up to generations of freeze-thaw, hail and standing snow.
Industrial effluents, salt spray, termites, vermin or fungus have no effect on the slates.
NONASBESTOS, NON-VOC EMITTING: Eternlt's unique formulation of fiber-reinforced cement does
not present a health hazard to consumers or installers.
WARRANTY: Protected by a 30-year nonprorated warranty.
IV. AIR KRETE INSULATION
AIR KRETE is an ultralight cementitious foam insulation that is being marketed, following 10 years
of intense research and development, as a viable alternative to urea formaldehyde and other
foamed-in-place insulation products. Headquartered in Weedsport, New York. AIR KRETE is
distributed exclusively in the United States via a network of licensed manufacturers. Efforts are
being made to export the product to Europe and Canada. Patents for AIR KRETE have been
issued.
COMPOSITION OF AIR KRETE INSULATION
AIR KRETE is a formulation of two proprietary components, water, calcium chloride, and magnesite,
which when expanded with compressed air, produce a foam primarily designed for installation
in cavity fill applications. It can be installed in any cavity through a 5/8 to 2 1/8' diameter hole,
and its flow properties ensure confidence in filling all voids. Bulgy or cracked walls, due to
produce expansion, are eliminated because AIR KRETE does not expand after leaving the
application equipment.
AIR KRETE has successfully been installed in noncavity applications.
MANUFACTURE OF AIR KRETE INSULATION
AIR KRETE insulation is made on site by trained installers. The various components are shipped to
the nearest distributor, who. in turn, delivers it to the contractor/installer.
B-9
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Surface-Coating-Free Materials for
the Reduction of VOC Emissions
AIR KRETE has enjoyed quick compliance with local code authorities due to its unique features.
It has been installed in HUD buildings, U.S. Army projects. Union Carbide, Safeway Foods, high
schools across the United States, and many hundreds of residences.
FEATURES OF AIR KRETE INSULATION
Chemical Analysis:
inorganic
nontoxic
no asbestos
no irritative fibers
no VOCs during or after installation
minimizes corrosion
pest resistant
ozone safe
no formaldehyde
no fluorocarbons
moisture resistant
Fire Characteristics:
Thermal Conductivity
Acoustical
firewall test (El 19)
no toxic fumes
noncombustible
no smoldering
ASTM-84-81A
flamespread 0
fuel contributed 0
smoke density 0
firestopping approved
R-value 3.9 per inch
zero shrinkage ASTM C951
no expansion
total fill characteristics
nonsettling
8 to 9 decibel improvement (50%)
LIMfTATIONS OF AIR KRETE INSULATION
Cost:
Installation:
Resilience:
approximately 280 to 50C/bf
requires available technician
requires trained technician
friable at the density of 2 Ib/ft3
B-10
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Paul Biemnan-Lytle
Moisture: will absorb moisture even though it doesn't affect structure
it does not hydrolyze as a result of vapor flow transmission,
high heat or humidity
B-ll
-------
APPLICATIONS FOR PULTRUDED PRODUCTS
Author
ROBERT DILLNER
Creative Puttrusions, Inc.
Pleasantville Industrial Park
Alum Bank, Pennsylvania 15521
Pultrusion is a continuous manufacturing process utilizing glass or fibrous reinforcement in a
polyester or other thermosetting resin matrices. Pre-selected reinforcement materials like fiberglass
roving, mat or cloth are drawn through a resin bath where all the materials are thoroughly
impregnated with a liquid thermosetting resin. The wet-out fibrous laminate is formed to the
desired geometric shape and pulled into the heated steel die. Once in the die, the resin cure is
initiated by controlling precise elevated temperatures. The laminate solidifies in the exact shape
of the die cavity as it is being continuously pulled by the pultrusion machine. Specific strength
characteristics can be designed into the composite optimizing laminate performance for a
particular application by strategic placement of high performance reinforcements. Color is
uniform throughout the cross section of the part, eliminating the need for many painting
requirements.
The puftrusion process produces parts with constant cross-section shapes. Many forms of
reinforcing material (examples: rovings. continuous strand mats, woven and nonwoven fabrics.
and a variety of surfacing veils) plus a wide selection of resin systems allow the designer versatility
in engineering the pultruded structural composite to meet the end-use requirements in the most
cost-effective way. Cost of the product is also minimized by low tooling cost and the low labor
content of the pultrusion process. Because the reinforcing materials are processed in continuous
forms, product properties are very consistent. Last, the length of the pultruded part is limited only
by shipping considerations.
Pultrusion is a continuous process making constant cross-section profiles. The process is designed
to pull flexible reinforcements through a liquid resin bath into a heated die. A pultrusion process
line is long and narrow with lengths from 40' to over 80' with the width being 5' to over 20'. The
overall space requirement depends primqrily on the size and number of the creels used to hold
the reinforcements.
A typical pultrusion line consists of six basic stations:
&-12
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Robert Dillner
* Reinforcement dispensing
* Resin impregnation
* Performing
* Heated die curing
+ Oamp/puller
* Cut-off.
For reinforcement dispensing background, in the first station, continuous fiberglass roving is
dispensed from center-pull packages that sit on shelves called creels. The roving is guided
through porcelain eyelets that eliminate static buildup and fuzzing. The roving then passes through
a carding index that orients the fibers prior to entering the resin bath. Other reinforcements such
as mat. veils, carbon fiber tows, etc., are routinely used and are dispensed on the rolls.
Resin impregnation is a reinforcement package that passes through the wet-out tank. Pan guides
function within the resin bath to keep the roving separate and to maintain tension on the strands
to permit the resin to wet-out each fiber. The resin bath can be of the standard dip tank design
or the straight-through resin pan as for hollow sections or complex profiles. Pressure impregnation
is a third method used for unique application. In this method, the resin polymerization all occurs
inside a closed die. This area is the main concern for VOC release in the form of fugitive styrene
vapors. However, because of the closed die, processing/pultrusion is typically lower than spray
up or winding processes (with the profile chops having releases of 3% to 5% and rod producers
approaching 0.8%).
When the reinforcement package exits the resin bath, it then passes through a series of bushings
or forming guides that are designed to strip off excess resin and guide the uncured composite into
the final composite shape. This is called the performing section.
The heart of the pultrusion process is the curing die. After the resin-impregnated reinforcement
package leaves the final pre-shaping section. It enters a heated steel die or dies that are in the
shape of the finished composite. The dies range in length from 30 to 60 inches and are heated
either by electric strip heaters or plates on the top and bottom of the die surfaces. The interior
die surfaces are generally chrome plated for increased die life and improved surface finish.
The term "pultrusion' comes from the fact that the composite is pulled through the entire process
by a gripper/puller system. There are two different types of gripper/pull systems used, the
reciprocating clamp design and the opposed tread caterpillar-tractor type. The former method
utilizes two identical pullers that operate in tandem to alternately grip and continuously pull the
profile through the process. The puller process is mainly used for mat/roving composites in which
urethane cleats grip the part and pull It through the mold.
The final station is the cut-off station of the pultrusion process. This station consists of a diamond
abrasive cut-off saw. This saw is synchronized with the movement of the pullers and is activated
by a preset cut-to-length limit switch.
The raw materials that make up the bulk of pultruded products consist mainly of reinforcement
and matrix. The reinforcements include glass fibers in the form of continuous roving, continuous
strand mats, knitted and woven fabrics, tapes and cloths. More exotic reinforcements include
B-13
-------
Applications for Pultruded Products
carbon fiber, aramid. boron and several new thermoplastic fibers and veils.
Fibers are formed from several glass compositions, the most common of which are A (alkaline),
C (chemical). E (electrical), and S (strength). Continuous roving of the E-glass type comprises the
bulk of the reinforcement used in pultrusion. Continuous roving is a collection of filaments coated
with a sizing that is compatible with the resin system and brought together into a single strand
called an end.
Bulk roving is also used in pultrusion. This product form is designed to improve the transverse
properties in localized areas of pultruded composites where mat cannot be formed.
C-glass, A-glass and thermoplastic are some of the surfacing materials used in pultrusion. Polyester
veils are the most commonly used surfacing fabrics and provide an 8- to 11-mil resin-rich barrier
that improves corrosion resistance, reduces fiber exposure on the surface, and improves resistance
to UV attack. Surface veils have been processed which withstood 4,000 hours accelerated
weathering with only a slight loss of gloss.
The two major families of resin matrices are thermoset and thermoplastic. Today the majority of
resin matrices used in pultrusion are thermoset. Several thermoset resin types are used in pultrusion
with standard polyester and flame-retardant polyester resins being the most widely used.
However, new applications and processing technologies are increasing the demands for
vinylesters, epoxies. flame-retardant vinylesters, low shrink systems and even thermoplastic resins.
The choice of the resin will determine the degree of corrosion resistance, the upper operating
temperature limit, performance in fatigue applications, and to a limited degree, the mechanical
properties of the pultruded laminate. The reinforcement primarily determines the strength and
electrical properties of the pultruded laminate. Fillers may be added to improve flame retardancy
and processabilrty and to reduce cost.
Pultruded composites are generally divided into two parts. One being all unidirectional roving
parts (rod and bar stock), and two being continuous strand mat/unidirectional roving parts
(shapes and flat sheet). Typically, all unidirectional roving parts have superior mechanical
properties in the longitudinal direction, where glass contents range from 65% to 85% by weight.
These values for shapes, flat sheet and rod/bar stock are taken from ASCE's Structural Plastic
Design Manual and tell you the range of properties one might expect with fiberglass polyester
pultrusions.
The reinforcements in flat sheet are mat and roving. Flat sheet is commonly produced in thickness
up to 1" and widths up to 56", with 48" being standard.
Pultrusions are used in a variety of markets, the first being the electrical industry. This is one of the
largest markets for pultruded composites because of their high strength-to-weight ratio and
excellent dielectric insulation properties. The use of pultruded side rails have almost completely
antiquated the wooden ladder and the electrical nonconductivity of fiberglass has allowed almost
complete replacement of the aluminum ladder by electrical utilities. The color in the ladder
channel is molded through the laminate. Orange and yellow are safety colors and can be seen
on almost any utility truck today. Usage of pultruded products are found in pole line hardware
B-14
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Robert Dillner
where pultruded tubes and rods are used for tools for work on high power lines because of the
added benefit of being electrically nonconductive.
Also, the puftrusion process is used to manufacture structural components which will withstand
severe corrosive environments. All fiberglass products can be considered to be corrosion resistant
with the choice of the resin determining the degree of corrosion resistance. Grating
manufactured with puttruded components is also the strongest fiberglass grating on the market.
The method of construction of the pultruded shapes ensures excellent corrosion resistance.
Bearing bars and cross rods are pultruded and fabricated into grating for many industries such as
electroplating, water and waste, marine, offshore and others.
Another example of the use of pultruded products for corrosion resistance is mist eliminators.
Louver blades separate vapors and solid particles from stack emissions such as in coal burning
utilities. Pultruded blades are replacing wood, stainless steel and thermoplastics giving an
increased usable life.
In the construction industry pultruded products are viable materials because of their strength, light
weight, corrosion resistance, mblded-in color and thermal and electrical insulation. For example,
pultruded components make nonmetallic window frame and sash lineals the ultimate in
performance. These components are quickly replacing aluminum and other competitive materials
with a new generation of thermally efficient, dimensionally stable window frames.
Another example for the construction industry is roof supports. Roofing systems with a four-to-one
safety factor for wind and snow loads and the added benefit of corrosion resistance have been
installed for pole enclosures.
Pultrusions have long been accepted in the transportation market. Pultruded panels run the entire
length of the Intercity Transit Bus and provide insulation and dent resistance as well as long-term
improved appearance. Automotive Class A surface is attainable with pultruded parts. Part
consolidation and a lock together design of two puttruded parts cut production line time by
replacing 22 roll-formed aluminum parts.
The pultrusion process, because of its many benefits, lends itself to a variety of other applications,
the most popular being standard structural shapes. From 1 /8" rod to 48" wide flat sheet, pultruded
components are stocked by manufacturers, distributors and fabricators in all major cities in the
United States and throughout the world for corrosion, electrical and construction applications.
In conclusion, although the pultrusion process is almost 40 years old, it is still basically in its infancy.
New products and processing techniques are being developed every day. Carbon and
thermoplastic fibers and cloths provide an even wider range of properties to the pultruded
product line for custom applications.
New thermosetting resins and puttrudable phenolic and the work currently being done in
thermoplastic resins offer a potential for an unlimited combination of fibers and resin matrices. The
pultrusion industry has been growing steadily and new ideas and process development are
making pultruded products the system of choice for many current and potential applications.
B-15
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Applications for Purtruded Products
ACKNOWLEDGMENT
I would like to thank the Pultrusion Industry Council of SPI for their contributions.
B-16
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THE USE OF UNCOATED ALUMINUM AS THE MAJOR
COMPONENT OF
AMERICAN AIRLINES AIRCRAFT
Author
JIM L. KATOPODIS
Specialist, Engineering Lab
Materials and Process Engineering
American Airlines
3800 N. Mingo, MD#10
Tulsa, Oklahoma 74151
Abstract
The author presents the history of American Airlines flying and maintaining basically uncoated
airplanes, the types of materials used that do not require coating, why and how these materials
were selected, manufacturing techniques used to allow them to be used, and their chemical and
physical properties. Maintenance practices and procedures will be reviewed and cost
implications versus coated surfaces will be compared. Case studies within the airline industry will
be discussed along with potential applications to other industries.
BACKGROUND HISTORY OF AMERICAN AIRLINES FLYING UNCOATED AIRCRAFT
American Airlines has always taken pride in flying and maintaining uncoated fleets of aircraft.
Today I would like to share with all of you how this has been accomplished over the years.
Dating back to the very early thirties, American Airlines has flown basically uncoated airplanes.
What decorative trim, identification markings and logos on the aircraft were decals. Originally the
aircraft were not painted because it was American Airlines Corporate image. Today, however,
not only is it our Corporate image but also one of enhanced inspectability, costs associated with
paint stripping, waste disposal, primers/paints, and masking materials. Also, weight savings is an
important consideration. With today's aging aircraft and environmental problems, it is to our
advantage to fly and maintain unpointed aircraft.
Originally on single engine and tri-motor aircraft the exterior skins were made from corrugated
galvanized steel. Over the years these galvanized skins were replaced with aluminum. American
B-17
-------
The Use of Uncooted Aluminum as the Major
Component of American Airlines Aircraft
Airlines took delivery of its first DC-2 in 1934. This aircraft had aluminum skins which were not
painted but maintained externally by polishing. In 1936 American Airlines took delivery of DC-3
aircraft, also with aluminum skins maintained externally by polishing. DC-4's were added in 1946
and DC-6 aircraft in 1947. The first aircraft in American's fleet with non-stop coast to coast service
was the DC-7. This plane was placed in service in November of 1953. The first jet-powered aircraft
to enter American's fleet was the 707 in January of 1959. 707's were followed by the Convair 990
March of 1962 and the 727 in April of 1964. American inaugurated its first 747 jumbojet wide body
service in March of 1970 followed by DC-10 wide body service in August of 1971. MD-80,767 and
757 aircraft have also joined American over the years.
TYPES OF MATERIALS USED IN EARLY YEARS COMPARED WITH TODAY'S
As one can see, American Airlines has been successful over the years in flying and maintaining
uncoated aircraft. There are several reasons that can be attributed to this success. One is
maintenance practices and procedures, which will be discussed later. The most important,
however, is the type of materials used on aircraft since DC-2 aircraft were placed in service.
Major commercial jet aircraft are primarily constructed of aluminum. Alclad 2014 was the first alloy
used on the fuselage surfaces of older model aircraft. This alloy was eventually replaced by
Alclad 2024. It is an aluminum-copper-magnesium alloy that is generally used in the naturally
aged temper of T-3. Other alloys used on the exterior of aircraft include Alclad 2219 and Alclad
7075.
WHY AND HOW THESE MATERIALS WERE SELECTED
Throughout this presentation on the various aluminum alloys, the term alclad was used. Alclad is
pure aluminum. Alcladding is a process of metallurgically bonding a thin layer of this pure
aluminum to the core alloy. The alclad liner is used to improve the corrosion resistance of the core
alloy by providing electrochemical protection. The pure aluminum alloy, which has higher
electrochemical potential than the core alloy, will serve as a sacrificial anode protecting this inner
metal. The alclad can also throw its power of protection over areas that have no alcladding.
such as around rivet holes and exposed edges of the metal.
Aluminum alloys are used in commercial aircraft because their weight-to-strength ratios allow
construction of an aircraft that can be flown economically. The alloys primarily used in the
Aerospace Industry are known as wrought heat-treated aluminum alloys. Wrought alloys are
materials that are produced in worked forms such as sheet, foil, plate, extrusions, tubes, forgings.
etc. Working operations such as rolling, extruding, and forging combined with thermal practices
such as heat treating, annealing, aging, and quenching change the cast ingot structure to
wrought structure.
The primary need for aircraft material is to take many types of loads without permanently
deforming or breaking. Loads such as gust, shear, acceleration, emergency, etc., must all be
designed for. Also the material must withstand cyclic fatiguing and be resistant to corrosion to be
used for the primary structure on aircraft.
B-18
-------
MANUFACTURING TECHNIQUES THAT ALLOW THESE MATERIALS TO BE USED
The complexity of producing an entire fuselage with aesthetically pleasing and uniform
appearance is enormous. Airframe fabrication ranges from severely stretch-formed to substantial
chem-milled parts, requiring special mill fabrication. Tailormade practices for the exterior
aluminum skins allow for consistent manufacturing results while maintaining an extremely constant
finish for the fuselage.
The initial shipment of raw stock utilizes special practices designed to protect the aluminum skins.
After the mechanical polishing of the sheets and final inspection, the material is readied for
delivery to the airframe manufacturer.
The individual polished panels are separated in their packing container by interleaving of kraft
paper and polyester foam. The panels on most aircraft are of various sizes, and extreme caution
must be used during packing to ensure the panels do not move during transportation.
Following inspection at the airframe facility the aluminum sheets are coated with a hand-peelable
material. This provides surface protection to the polished exterior side of the aluminum sheet. This
coating remains on the sheets until removed for painting or final delivery in an unpointed
condition.
The fuselage of commercial jetlines is comprised of many different thicknesses and size
combinations. The vast number of sizes made it extremely important that the aluminum mills and
airframe manufacturers work closely to designate the appropriate aluminum product for the
individual fuselage part. The ability to use large panels reduces the need for riveting and
minimizes the number of joints.
CHEMICAL AND PHYSICAL PROPERTIES OF THESE MATERIALS
Alloy 2024 has been used for decades because of Its strength, high fracture toughness, damage
tolerance characteristics and because it retains the damage tolerant characteristics
at the -65°F temperatures aircraft fly. Alloy 7075 is a high-strength alloy that is
used in areas requiring high strength that do not have the damage-tolerant needs of
fuselage skins. These areas include fuselage sections in the rear of the aircraft and
on many stringers and frames. Alloy 2219 is used primarily in areas of elevated
temperatures such as leading edges where deicing air is located and around engines.
Clad aluminum is very corrosion resistant whereas uncladded is not and therefore must
be protected by anodizing or another type of protection.
MAINTENANCE PRACTICES AND PROCEDURES
Alclad aluminum is obviously a vital element in protecting aircraft exteriors from corrosion. Another
method of corrosion protection is an ongoing washing and polishing program of the exterior
alclad skins. Polishing has been accomplished on American Airlines aircraft since the early 1930s.
The early model aircraft had what was referred to as commercial mill finish sheets. The skins were
polishable but were not the skin quality sheets ALCOA introduced in 1959 on 707 aircraft or the
Specul-Air aluminum skins currently used by Boeing and Douglas. The Specul-Air sheet is delivered
in a highly polished condition that offers an attractive finish without the expense and
environmental problems associated with painted aircraft.
B-19
-------
The Use of Uncooted Aluminum as the Major
Component of American Airlines Aircraft
American currently washes aircraft in TUL SAN, JFK, ORD, SJU, MCO, DFW, and DTW. Washing
aircraft exteriors is accomplished approximately every 90 days.
Polishing is accomplished only at the Main Base in Tulsa, Oklahoma. The frequency of polishing
varies with the aircraft type, but generally it is accomplished every 12 to 15 months.
Polishing aircraft exteriors is not necessarily an easy task nor is it a hard task if certain criteria and
requirements are met. Some of these are as follows:
* Adequate air pressure to operate several buffers simultaneously.
* Polishing bonnets that are not abrasive enough to scratch or remove alclad.
+ Access to the areas to be polished. This access can be in the form of scaffolding,
manlifts, scissors lifts and space stacks.
* A buffer that is versatile enough to polish inaccessible areas such as the crown skin,
bottom of horizontal stabilizer, bellies, etc.
American uses a rotary drum buffer commonly referred to as an Astro-Buffer. This apparatus
weighs approximately 10 pounds. The pneumatically driven motor develops 0.9 peak horse power
at approximately 1500 rpm with 90 psi at the buffer inlet. The rotary drum measures 5 inches in
diameter and is 7Vi inches long.
Various attachments are available to allow for polishing of areas as far as 12 feet away.
During the polishing operation an area about 6x4 feet is treated. After the polish is applied to
the surfaces to be treated, it is buffed at a speed of approximately 1500 rpm and gone over
again at speeds between 800 and 1200 rpm to achieve the best finish.
A polish referred to as Perfect is currently in use for polishing American Airlines aircraft. This
material replaced the product Alumin-Nu. which had been used since the early 1930s. Use of
Perfect Polish results in a shinier more uniform finish and requires fewer man-hours to achieve the
desired results. Perfect Polish is a blend of natural materials that cleans, polishes, and protects
aluminum surfaces. It is nonflammable, nontoxic and has a neutral pH. Perfect Polish contains
no waxes or silicones which for various reasons are undesirable to use on aircraft exterior surfaces.
COMPARISON OF ENVIRONMENTAL/COST IMPLICATIONS OF PAINTED VERSUS NONPAINTED AIRCRAFT
Table 1 summarizes a cost analysis of maintaining a painted aircraft versus a bare polished aircraft.
The information was gathered from several airlines in the United States. Each individual airline
should address its own value placed on the importance of fuel savings/weight cost and their logos
or color schemes.
The paint and stripping costs involved in this table include only the decorative color schemes and
not any areas painted for corrosion or composite protection that must be protected at all times.
B-20
-------
Jim L. Kotopodis
The area considered is a full white top and bottom with three colors and a complete tail paint
scheme.
CASE STUDIES
American Airlines has always been recognized for flying unpointed airplanes. Within the past
decade we have been joined by others. U.S. Air and Atlantic Southeast Airlines currently fly and
successfully maintain unpointed airplanes. Other airlines to fly and successfully maintain unpointed
airplanes were Western and Eastern. Both, however, were unsuccessful in their attempts to
continue to fly and maintain unpointed airplanes. Not because the unpointed concept was bad,
but other circumstances were encountered. In the case of Western, they were acquired by Delta
and Delta elected to convert the Western airplanes to their colors. Eastern at the time of its
bankruptcy was flying unpointed airplanes. It can be assumed that both of these carriers would
still be flying unpointed aircraft if it were not for their particular situations.
POTENTIAL APPLICATIONS TO OTHER INDUSTRIES
the Specul-Air aluminum skins used on modem day jet aircraft are very expensive. Therefore use
of this type material in the Ground Transportation Industry would be prohibitive. However,
aluminum alloys, such as the 5000 series, do have corrosion resistance characteristics that would
not require paint systems in many applications.
More widespread use of aluminum in the construction industry would be a viable alternative to
other types of construction metals. Anodized aluminum comes in a wide variety of colors and is
readily available in today's market place. Anodized aluminum is very corrosion resistant and does
not require painting.
CONCLUSION
There are a lot of pros and cons about flying and maintaining unpointed versus painted aircraft,
but for American Airlines it is flying well-maintained aircraft that takes on immaculate, shining
appearance that reminds one of quality and excellence.
ACKNOWLEDGMENT
The author wishes to thank the Aluminum Company of America (ALCOA), especially Del F. Skluzak,
for their assistance in preparing this paper.
B-21
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The Use of Uncoc;ed Aluminum as the Major
Component of American Airlines Aircraft
TABLE 1. MAINTENANCE COST OF A DECORATIVE PAINT SCHEME
(Standard Three Color, White Painted Fuselage, Full Tail Paint)
AIRCRAFT
Weight of Decorative Paint in
Pounds
Repaint Frequency In Years
(Average)
Sand & Overcoat Manhours
Airline Cost $30.00/hour
Strip & Repaint Manhours
(10 Years) Airline Cost
$30.00/hour
Paint Stripper/Clean Up Solvent
Gallons
Cost of Stripper and Disposal
Cost ( $40.00/Gallon)
Masking/Other Material Cost
White Top and Bottom
Gallons $37.50/GaUon
Decorative Colors Gallons
$42JSO/Gallon
1 Primer Gallons
$21.00/Gallon
Total Cost S, id and Repaint
Total Cost Chemical Strip and
Repaint
Polishing Manhours
(Aluminum)
Polish Maintenance Interval
(Times/Year)
Yearly Polish Aluminum Cost
$18.00/Hour
747
240
5
14200
36,000
1,600
48,000
1,000
40,000
3,000
60 *Elec
70 **PP
10
20*Elec
28**PP
42,180
94,180
600
1
9,000
DC-10
165
5
900
27,000
1,100
33,000
700
28,000
2,600
36 Elec
46 PP
6
16 Elec
18 PP
31,732
66,732
460
1
8,100
787
136
5
600
18,600
1,000
30,000
400
16,000
14200
22 Elec
27 PP
6
9 Elec
11 PP
20,622
48,522
350
1
6^)00
767
132
5
526
15,750
900
27,000
400
16,000
1,000
20 Elec
23 PP
4
8 Elec
10 PP
17,980
454225
310
1
5,580
MD80
110
5
450
13,500
780
23,400
300
12,000
1,400
16 Elec
19 PP
4
7 Elec
8PP
16,880
37,778
160
1
2,700
*Elec Electrostatic
**PP Pressure Pot
B-22
-------
UNCOATED TITANIUM » COMPATIBLE
WITH THE ENVIRONMENT
Author
Edward E. Mild
TIMET
INTRODUCTION
The recognition by the EPA of the deleterious effects of volatile organic compounds
(VOCs) on both the environment and its inhabitants is an important step forward. This awareness
has generated a unique opportunity for the development of creative solutions to material
degradation problems commonly solved by using coatings containing these VOCs. Coatings
containing VOCs have been used to retard the degradation effects of sun. rain, wind, mist.
humidity, water (including seawater). soil, and other environmental pollutants. In various forms.
organic compounds have been used for hundreds of years to retard atmospheric degradation
because they are inexpensive and compatible with most materials of construction. Reducing
emissions from VOCs can be accomplished by reducing their use, using less-polluting alternative
coating materials, or using alternative materials that do not require coatings of any kind for
protection. The coatings industry is working on the first two options and the materials industry is
promoting the third. Stainless steels, aluminum, nickel, copper, and titanium all have attractive
degradation resistance properties that will help to reduce the amount of VOCs released into the
atmosphere. Each of these metals has Its own niche in which it will work best. Uncoated titanium
metal provides a maintenance-free and highly reliable construction material that can and has
replaced many coated materials in applications in which long-term reliability is critical. The
increased use of uncoated titanium, in place of materials that require VOC-containing coatings
for protection from degradation, is a simple life-cycle-cost-effective solution to the increasing
pollution problems caused by VOCs.
WHAT IS TITANIUM?
Titanium is the generic name given to the group of alloys and commercially pure metal
of the 22nd element in the periodic chart. Titanium is the fourth most abundant structural metal
and the ninth most abundant element in the earth's crust (Table 1). Its mineable ores are found
all over the world (Figure 1). which allows the raw material to remain accessible and geopolitically
stable. The metal-producing industry, which consumes less than 10 percent of the ore that is
mined annually, primarily uses the ore dredged from the western beach sands of Australia. The
pigment industry, which uses over 90 percent of the mined ore, gets its supply from Australia and
the rest of the world, including Canada, South Africa, and Sri Lanka.
B-23
-------
Uncooted Titanium - Compatible
with the Environment
Titanium is a gray-colored metal with a density about half that of steel and nickel end
slightly more than double that of aluminum. The yield strength of the family of titanium alloys
varies from about 25.000 psi. which is roughly the strength of mild steel, to over 200XXX) psi, which
corresponds roughly to that of high-strength steel. Tables 2 and 3 present physical and
mechanical properties of several titanium alloys and compare them with steel and aluminum.
However, respectively, the property of titanium that separates it from the other common
construction metals is its corrosion resistance in many environments, including the effects of erosion
and corrosion in all naturally occurring waters. Titanium is immune to the erosion and corrosion
effects of both still and flowing water. This lightweight, strong, corrosion-resistant metal, has been
used for nearly 40 years in jet engines and jet airframes to allow these planes to perform as they
were designed. Jet air travel would not be possible without titanium, because steel is too heavy
and aluminum melts at too low a temperature to work satisfactorily.
Titanium is won from its ores through a multistage process (Figure 2). The process begins
with the chlorination of the ore to titanium tetrachloride, which can be used to make either
pigment or metal depending on the next step in the process. In the manufacture of pigment, the
tetrachloride is oxidized to titanium dioxide, which is the brilliant white opaque matter in paint and
plastics. In the manufacture of metal, the tetrachloride is combined with either liquid sodium or
liquid magnesium under vacuum or argon pressure to produce titanium metal (called sponge at
this point) and either sodium or magnesium chloride. The salt is removed from the titanium metal
and recycled back into the process to generate chlorine and sodium or magnesium, each of
which Is recycled back into the process; chlorine is combined with the ore to make the
tetrachloride. and sodium or magnesium is again reacted with the tetrachloride to make titanium
sponge and salt. The titanium sponge is then mixed with alloying elements, if necessary, and then
melted under vacuum or argon pressure and solidified into ingot form. These ingots are then
processed into all of the common mill product forms in which metals of construction are found
(Table 4).
THE TITANIUM INDUSTRY
The titanium industry was bom in 1950 based on a process developed by Dr. Wilhelm Kroll
in the 40's to manufacture the sponge commercially. TIMET and MALLORY SHARON TITANIUM (now
RMI TITANIUM) were incorporated in that year in the USA. The rest of the world industry (Table 5)
evolved from that core of companies. About 52 percent of the world titaniunrf industry is located
in non-Communist countries and 48 percent is located in the USSR and China (Figure 3). In the
United States. TIMET. RMI TITANIUM, and OREMET are the only integrated producers, i.e.. they
manufacture sponge, ingots, and mill products. All other producers buy sponge, ingot, or
intermediate mill product and convert them to mill products. Although titanium is not as
ubiquitous as steel or aluminum, It now can be bought off-the-shelf in all of its product forms from
numerous warehouses and service centers.
The current free-world titanium industry capacity is about 126 million pounds (52XJOO tons)
of sponge and 196 million pounds (98 XXX) tons) of ingot melting compared to a current demand
B-24
-------
Edward E. Mild
of about 65 million pounds (33.000 tons) of mill product demand. This indicates that there is plenty
of industry capacity to support the growth of new applications. The goal of the U.S. industry is to
double in size by the year 2010 and the infrastructure has been put in place to support this growth.
The anticipated growth will occur in applications that utilize titanium's corrosion and erosion
resistance. Currently, only about 25 percent of the entire consumption of titanium mill products
goes to non-aerospace applications for which resistance to environmental degradation is the
driving force for titanium's use.
WHY IS TITANIUM CORROSION RESISTANT?
Titanium's corrosion resistance is based on the formation of an extremely tenacious and
stable surface oxide film that is illustrated in Figure 4. This oxide layer, which forms instantaneously
when a fresh surface is exposed to air or moisture, is only 12 to 15 one hundred millionths of a
centimeter thick. This film continues to grow slowly in air until it reaches about 250 one-hundred-
millionths of a centimeter in thickness in 4 years. When the surface of titanium is scratched .the film
heals itself instantly in any environment containing even a trace of oxygen or moisture. However,
the film will not regenerate ftself when damaged in anhydrous conditions in the absence of
oxygen. Only a few substances, such as hot, concentrated hydrochloric acid, sulfuric acid sodium
hydroxide and. most notably, hydrofluoric acid, attack this stable oxide film.
Titanium is immune to a long list of environments as shown in Table 6. Titanium's corrosion
resistance is extended in many environments in which heavy metal ions are present. This allows
titanium to be used, for example, in hydrochloric acid in which iron copper or chromium ions are
present. These corrosion resistance properties of titanium make it ideal for use in many chemical
and petrochemical processing applications.
USES FOR UNCOATED TITANIUM
Applications for uncoated titanium exist in many areas. Its use is a function of its ability to
withstand environmental degradation, which precludes the use of alternative materials or
coatings. We will discuss three main applications areas: architecture, power plant flue gas
desulfurization systems, and seawater applications.
Architecture: Why would anyone want to use titanium in architectural applications? The
answer is that in coastal construction, titanium withstands the degradation effects of the sea spray
and salt water environment in addition to having the necessary strength and fabricability to be
used as a siding or roofing material. Other metals such as aluminum and stainless steel have been
used in roofing, siding, window frames, and doors for many years. However, in sea coastal areas
these applications require frequent maintenance and replacement due to the corrosive nature
of the salt water environment. Although titanium has not been used in the United States for
architectural applications, it has been used extensively in Japan to reduce the degradation
effects of sea mist. Titanium has been used successfully in Japanese coastal cities in many
architectural applications to eliminate the deleterious effects of the environment. Figures 5
through 8 show typical titanium applications in Japanese architecture. From an esthetic
B-25
-------
Uncooted Titanium - Compatible
with the Environment
perspective, titanium can be used in its natural metallic gray color or it can be anodized to hues
of red, blue, gold, or purple to provide a variety of decorative appearances. Although the cost
of titanium in these applications is greater than the cost of stainless steel, titanium is preferred
because maintenance and replacement are reduced. On a 40-year life-cycle cost basis, the full
cost of titanium changes to roughly half that of stainless steel based on reduced maintenance
and no replacement of the titanium.
Power plant flue gas desulfurization (FGD) systems: FGD systems are used to remove sulfur
dioxide and other harmful stack emissions from power plants. The gases produced from the
burning of fossil fuels are scrubbed in the FGD system to remove sulfur dioxide, which produces
acid rain. The use of metallic linings in these flue gas desulfurizing systems is a major step toward
decreasing maintenance and increasing the operating time of these air pollution (acid rain)
reducing units. Ceramics, glass block, and organic linings were originally installed prior to the use
of metal linings in this application. As shown in Figures 9 and 10. nickel-based alloys and stainless
steels, which were used after the nonmetallic, were found to be lacking in long-term corrosion
resistance to the aggressive environment of the gaseous effluent stream. Titanium's use in the
outlet ducts and stacks of FGD systems has replaced the nickel-based alloys and stainless steels.
Uncoared titanium is used based on its corrosion resistance against gaseous effluents, in particular
hot acidic chlorides and sulfate species, which are by-products of sulfur dioxide removal from the
gases produced from the burning of high-sulfur-containing fossil fuels (coal and oiD. In addition
to its corrosion resistance, titanium is preferred in these field-installed applications because of its
low density (half that of steel or nickel-based alloys) and Its ease of fabrication and welding.
Currently. 110 power plants, mostly in the Midwest, have been identified by the Federal
Government as requiring new or improved FGD systems. Uncoated metals, in particular titanium.
will be used as a lining material in the great majority of these units because of the severity of the
corrosive gases passing through these systems.
Seawater applications: By far the largest potential for the use of uncoated titanium is in
applications in which titanium's resistance to seawater corrosion and erosion is of prime
importance. Titanium's other engineering properties are also used to advantage in these
corrosion-susceptible applications.
Heat exchangers and power plant main steam condensers cooled by seawater are the
largest of the current seawater applications. Figure 11 shows the tube bundle of a power plant
main steam condenser being welded. This 100- foot condenser is made of welded titanium tubes.
a titanium tube sheet, and titanium spacers. Typical heat exchangers used in a chemical or
petrochemical plant are shown in Figure 12. Titanium heat exchangers and condensers utilize the
corrosion and erosion resistance of titanium by increasing seawater flow rates through or around
the tubing in order to optimize heat dissipation. The reduced weight of titanium heat exchangers
is an added advantage when they are used on offshore oil and gas exploration and production
platforms because a reduction in equipment weight will allow lighter supporting structures to be
built, reducing the buoyancy requirements.
B-26
-------
Edward E. Mild
Seawater piping systems of titanium including pipe, valves, pumps, and fittings (Figures 13
through 15). are commonly used in chemical and petrochemical processing plants. These systems
use uncoated titanium except where color is used to designate the type of system. Any piping
system that transports seawater or brackish water should be made of titanium because of
titanium's corrosion and erosion resistance and because exterior painting is unnecessary.
Oil and gas well piping, transmission lines, and riser systems are currently evaluating the use
of titanium because of its mechanical properties as well as its corrosion resistance. Although
coatings will still be used initially, the potential for eliminating these coatings is real. The coatings
will be used not because they are necessary but because they have always been used on the
steel that titanium will replace, and one change at a time is all that the conservative oil and gas
industry is willing to make.
There are numerous other current and potential applications for uncoated titanium in
seawater. Some of these include tether anchors and ballast water systems used on offshore oil
production and drilling platforms; heat exchangers and natural gas coolers for use on offshore
platforms; sheathing for steel pilings to protect against corrosion and erosion at the seawater
surface and the spray zone just above the surface; hulls for submersibles and surface ships;
propulsion pumps and shafts for hydrofoils and other vessels; and exhaust stacks and structures on
merchant and military ships. Although each of these applications has Its own distinct requirements
for mechanical and physical properties, each utilizes to its advantage the corrosion-resistant
nature of the titanium surface, which needs no coating to protect it from the ravages of seawater.
SUMMARY
The EPA's goal of the reduction of volatile organic compounds released into the
environment can be accomplished through the use of uncoated titanium. Because titanium is
resistant to degradation by any naturally occurring water, soil, typical atmospheric species, or
atmospheric pollution, it can be used as a material of construction in applications where coatings
are needed to prevent corrosion or degradation on less stable materials. Titanium can be used
in its natural gray metallic color or it can be anodized to various decorative colors. Whether in
architecture, seawater. industrial gas effluent cleaning systems, or in other service where corrosion
resistance is of importance, titanium, the youngest of the industrial metals, can and is being used
effectively. Its use on a wider basis should be explored and promoted by the Environmental
Protection Agency as one of their programs aimed at reducing the release of VOCs into the
atmosphere.
B-27
-------
Uncooted Titanium - Compatible
with the Environment
LIST OF FIGURES AND TABLES
Page
Figure 1 Mineable Titanium Ore Deposits. B-29
Figure 2 Schematic of Titanium Winning Process. B-30
Figure 3 Distribution of World Titanium Shipments. B-31
Figure 4 Schematic of Oxide Film on Titanium Surface. B-32
Figure 5 Titanium Dome Roof Erected in Japan. B-33
Figure 6 Titanium Residential Roof in Japan. B-34
Figure 7 Anodized Titanium Used for Interior Decorative Trim in B-35
Japanese Office Building.
Figure 8 Titanium Curtain Wall Siding on a Japanese Office Building. B-36
Figure 9 Corrosion Test Samples Taken from the Stack of an Operating B-37
FGD System.
Figure 10 Corrosion Test Samples Taken from the Outlet Duct of an B-38
Operating FGD System.
Figure 11 Power Plant Main Steam Condenser with Titanium Tubes and B-39
Tubesheet.
Rgure 12 Typical Titanium Heat Exchanger Bundle Used in the Chemical B-40
Processing Industry.
Figure 13 Titanium Ball Used in a Seawater Ball Valve Compared to a Corroded B-41
Stainless Steel Ball.
Figure 14 Typical Titanium Tubing Fittings. B-42
Figure 15 Titanium 1000 Gallon per Minute Seawater Pump for Navy B-43
Surface Ships.
Table 1 Average Amounts of the Elements in the Earth's Crust.
Table 2 Comparison of Physical Properties.
Table 3 Comparison of Mechanical Properties.
Table 4 Mill Products Available.
Table 5 Titanium Production Capacity by Region.
Table 6 Titanium Corrosion Rate Data.
B-44
B-45
B-46
B-47
B-48
B-49
B-28
-------
MAJOR TITANIUM ORE DEPOSITS
9th Most Abundant Element
4th Most Abundant Metal
Source: DoD MCIC 1981.
FIGURE 1. MINEABLE TITANIUM ORE DEPOSITS
-------
DO
UJ
o
TAR OR COKE
RUTILE ORE
STRIP MINED
IN AUSTRALIA
INGOT
TiO2
ORE
HEAT
CHLORINE
TiCI
Mg -*
REMELT(S)
Chlorine
HEAT
Mg
RECOVERY
PRIMARY
MELT
Mg
Tl
SPONGE
LEACH
SPONGE
(+ ALLOY)
FIGURE 2. SCHEMATIC OF TITANIUM WINNING PROCESS
-------
WORLD TITANIUM SHIPMENTS
MILL PRODUCTS
29%
11%
w
U)
48%
PERCENT OF SHIPMENTS
D USA
B3 JAPAN
Q EUROPE
M USSR
OTHER
FIGURE 3. DISTRIBUTION OF WORLD TITANIUM SHIPMENTS
-------
U)
NJ
TITANIUM
FIGURE 4. SCHEMATIC OF OXIDE FILM ON TITANIUM SURFACE
-------
00
U)
FIGURE 5. TITANIUM DOME ROOF ERECTED IN JAPAN
-------
DO
FIGURE 6. TITANIUM RESIDENTIAL ROOF IN JAPAN
-------
to
W
Ul
FIGURE 7. ANODIZED TITANIUM USED FOR INTERIOR
DECORATIVE TRIM IN JAPANESE OFFICE BUILDING
-------
Ul
I 1 I I 1X1 IJl 1 lilll
FIGURE 8. TITANIUM CURTAIN WALL SIDING ON A
JAPANESE OFFICE BULGING
-------
00
OJ
R D MORROW CREVICE S0RR0SION SPECIMENS
j- ,£ x *- ,4 "V'l.i.-.-?-:' -x^- - - , , •
FIGURE 9. CORROSION TEST SAMPLES TAKEN FROM
THE STACK OF AN OPERATING FDG SYSTEM
-------
CO
to
00
FIGURE 10. CORROSION TEST SAMPLES TAKEN FROM
THE OUTLET DUCT OF AN OPERATING FGD SYSTEM
-------
••••••••••••••*••••
•••••••••»••*•*
FIGURE 11. POWER PLANT MAIN STEAM CONDENSER
WITH TITANIUM TUBES AND TUBESHEET
-------
ro
•r*
o
FIGURE 12. TYPICAL TITANIUM HEAT EXCHANGER BUNDLE
USED IN THE CHEMICAL PROCESSING INDUSTRY
-------
7
FIGURE 13. TITANIUM BALL USED IN A SEAWATER BALL
VALVE COMPARED TO A CORRODED STAINLESS BALL
-------
DO
^
KJ
FIGURE 14. TYPICAL TITANIUM TUBING FITTINGS
-------
GO
£k
OJ
FIGURE 15. TITANIUM 1000 GALLON PER MINUTE SEAWATER
PUMP FOR NAVY SURFACE SHIPS
-------
TABLE 1
AVERAGE AMOUNTS OF THE ELEMENTS
IN THE EARTH'S CRUST
In parts per million
1
2
3
4
5
6
7
8
9
10
ELEMENT
Oxygen
Silicon
Aluminum
Iron
Calcium
Sodium
Potassium
Magnesium
Titanium
Hydrogen
QUANTITY
466,000
277,200
81,300
50,000
36,300
28,300
25,900
20,900
4,400
1,400
Source: Handbook of Materials Science. 1974.
© 1974, CRC Press
B-4.4
-------
TABLE 2
COMPARISON OF PHYSICAL PROPERTIES
Density, Ib/cu.in.
El. Modulus,1000ksi
Therm. Exp, in/in/F
Therm. Cond.BTU/h-ft
Titanium
CP Grade 2
0.163
14.900
4.900E-OS
9.500
Titanium
T1-6AI-4V ELI
0.16
16.50
1.01E-05
4.20
31 6 Stainless Steel
0.29
28.00
8.90E-06
7.50
Aluminum
0.097
10.500
1.250E-05
79.860
B-45
-------
TABLE 3
COMPARISON OF MECHANICAL PROPERTIES
Tensile Str'nth, ksi
Yield Strength, ksi
Elongation, %
Fract.Tough..(K1c)
(ksi) ofa)
Fatigue Limit, ksi
Titanium
CP Grade 2
50
40
20
60
25
Titanium
Ti-6AI-4V ELI
130
120
10
90
60
31 6 Stainless Steel
85
30
50
100+
40
Aluminum
30
25
22
15
10
B-46
-------
TABLE 4
MILL PRODUCTS AVAILABLE
• INGOT
• BLOOM
• BILLET
• SLAB
• BAR
• PLATE
• SHEET
• STRIP
• WELDED TUBE/PIPE
• SEAMLESS TUBE/PIPE
• WIRE
• EXTRUSIONS
• CASTINGS
B-47
-------
TABLE 5
TITANIUM PRODUCTION CAPACITY
BY REGION
(millions of pounds)
USA
JAPAN
EUROPE
USSR
PRO
TOTAL
SPONGE
61
54
11
110
6
242
VAR MELT
132
45
19
120+
8
324+
COLD HEARTH MELT
20
5
0
3
10
30
SOURCE: Titanium Development Association
B-48
-------
TABLE 6
TITANIUM CORROSION RATE DATA
*»
VD
Acetic acid
Benzene
Boric acid
Chlorine gas, wet
Ferric chloride
Magnesium chloride
Nitric acid
Phosphoric acid
Seawater
Silver nitrate
Sodium hydroxide
Sulfuric acid
CONCENTRATION, %
5 to 99.7
liquid
satuataed
1 .5% water
10 to 30
5 to 20
10
10 to 30
50
5 to 10
3
TEMPERATURE, F
255
80
80
392
212
212
80
80
80
212
140
CORROSION RATE, mpy
nil
nil
nil
nil
<0.5
nil
0.19
0.8 to 2.0
nil
nil
<.85
0.5
-------
UNCOATED WEATHERING STEEL FOR BRIDGES
AND OTHER STRUCTURES
Author
BERNARD R. APPLEMAN
Steel Structures Painting Council
4400 Fifth Avenue
Pittsburgh, Pennsylvania 15213-2683
Abstract
Weathering steel is a high-strength steel containing low amounts of chromium and other alloys.
Under certain circumstances, these alloys promote the formation of a tightly adhering dense oxide
layer (patina) which precludes the need for a surface coating. This property provides distinct
advantages over conventional carbon steel, which requires a coating system for corrosion
protection in virtually all exterior atmospheric environments.
Questions have been raised regarding the specific conditions under which the patina will form.
Chlorides, continuous moisture, and tunnel-like" configurations have been shown to interfere with
the formation of the patina.
Data are presented on case histories of successful uses of unpainted weathering steel, as well as
instances in which this material has shown unacceptably high rates of corrosion. Also discussed
are circumstances under which portions of a structure may be left uncoated. while the portions
subject to the most aggressive conditions (which are often also the most critical elements) are
coated. Guidelines are being developed for identifying and selecting conditions and procedures
for making the greatest use of unpainted weathering steel while still providing adequate corrosion
protection.
INTRODUCTION
The Steel Structures Painting Council (SSPC) is a not-for-profit technical association. The SSPC
mission is to develop and promote good practice for corrosion protection of industrial structures
primarily through the use of protective coatings. The three major activities of SSPC are to conduct
research and development, develop standards, and disseminate information.
B-50
-------
Bernard R. Appleman
The primary means of protecting steel from corrosion is through protective coatings or paint. SSPC
is also interested in alternative, coating-free technology, which can help the facility owners (e.g.,
Pridges. power plants, petrochemical plants) achieve cost-effective protection.
CarPon steel is a primary construction material Pecause of its high strength, its favoraPle
faPrication and welding properties, and its relatively low cost compared to alternative structural
materials. In most industrial environments, which are suPject to moisture, condensation, and even
slightly polluted air, carbon steel will react with the environment to form oxides (rust) which flake
away and gradually erode the steel. Normally, therefore, carPon steel is painted or coated to
provide a Parrier Petween the steel and the environment. Coatings for industrial structural steel
do not last indefinitely, and most often structures must Pe maintained Py repainting after 10-20
years.
Accordingly, any technology which can permit the use of steel as a structural material Put avoid
the need for initial coating and recoating would elicit keen interest among the many industries
that utilize steel for construction. Weathering steel, which can meet these criteria, is the suPject
of this paper.
The topics to Pe addressed are as follows:
* What is Weathering Steel?
+ Brief History of Weathering Steel
+ Conditions to Achieve and Avoid
+ Remedial Maintenance
* Ufe Cycle and Economics
+ Summary of Advantages and Limitations
* Recommendations
What is Weathering Steel?
Weathering steel is a high-strength, low-alloy steel (HSLA) for structural use. Small amounts of
copper, chromium, manganese, and phosphorus are added to give it its special strength and
protective properties. Weathering steel, under certain conditions, can form a protective oxide
layer on the steel. Unlike the oxide that forms on mild (carPon) steel, which readily hydrates and
flakes off as rust, the oxide on weathering steel is tightly adherent and consequently can protect
the steel against further reaction with oxygen and moisture. The term "weathering steel" refers to
the fact that this protective oxide layer (also known as patina) is formed after the steel has Peen
exposed to the atmosphere (weathered) for a certain length of time.
B-51
-------
Uncoated Weathering Steel for
Bridges and Other Structures
The major advantage of weathering steel claimed by the manufacturers is the elimination of the
need for painting. Painting not only adds to the cost of a bridge or other structure but raises
environmental and toxicity concerns because of the ingredients used in the paint and the
operations to remove aged and deteriorated paint.
Another way that weathering steel differs from carbon steel is in its appearance. Weathering steel
typically has a rough, grainy appearance because of the manner in which the oxide is formed.
This involves alternate solubiiization and crystallization of oxides and alloys. In addition, the color
typically ranges from an orange-brown to a deep, dark almost black brown. Thus, unlike painted
bridges, where virtually any color or gloss is attainable, with weathering steel the color and
appearance are severely limited.
Brief History of Weathering Steel
Weathering steel is not exactly a new material. The improved corrosion resistance of steels
containing copper was noted in the 1800s. The first commercial use of weathering steel was in
the 1930s on coal hopper rail cars. More than 1 million cars were constructed of weathering steel,
which was considered a very successful use of the product. ASTM issued the first standards on
weathering steel in the 1940s. Weathering steel actually consists of several different types of alloys
with minimum levels of the alloying elements required.
The alloy development and testing continued in the 1950s and 1960s. In the mid-60s. the steel
industry, convinced that this product had extremely wide potential usage, began heavily
promoting It for architectural uses (e.g.. office buildings, warehouses) and industrial uses (highway
bridges, utility towers). The first bridges were erected in 1964 and 1965. Over the next 15 years,
over 2X00 such bridges were constructed. The largest users were Michigan (with over 500
structures by 1980). North Carolina. New Jersey Turnpike, and New Hampshire. Electric utility
companies such as Virginia Power and New York Power Authority also used weathering steel to
construct thousands of utility towers during the same time period.
Thus, the promise of a coating-free structural steel was apparently being realized by two major
industries. However, as the bridges and utility towers aged and weathered, it became evident
that the formation of the protective oxide and the reduction in corrosion were not always
achieved.
In the late 1970s. Michigan DOT engineers noticed continuous heavy scaling and pitting in Detroit's
bridges, which were 10 years old. They concluded that these structures would not last their
designed lifetime because of the loss of metal, and that critical areas, such as joints, could present
structural safety problems. In 1979. Michigan DOT issued a moratorium (i.e.. ban) on new
weathering steel bridges because of the above-noted corrosion problems.
A major controversy erupted within the steel construction industry, which has not yet been
resolved among the varying parties, which included bridge engineers, consultants, and the steel
industry. A number of studies were initiated to determine the extent of corrosion, the number of
bridges affected, and to determine what, if any, corrective measures were needed. SSPC
B-52
-------
Bernard R. Appleman
became involved as one of the considerations was the painting of weathering steel, both for new
construction and for existing structures.
As a result of the research and evaluation studies, a series of conferences, negotiations, and even
some court cases, the steel industry accepted the fact that weathering steel was not suitable for
many conditions or environments. In addition, the steel was NOT maintenance free, and design
changes were recommended for different types of structures.
Also in the early 1980s, electrical utility engineers noticed that many of the tower joints were
suffering from a condition known as "pack-out." Corrosion products of the weathering steel buitt
up in crevices, causing severe distortion of the steel members. Subsequent research funded by
the utility industry indicated that this condition did not present a significant structural safety risk for
the vast majority of the structures. Nevertheless, some utilities have elected to protectively coat
these joints, and further use of weathering steel for this application has been limited. Concern has
also been expressed about the joint areas of weathering steel light poles.
In the late 1980s, the steel industry launched a new promotional strategy which recognized the
limitations of weathering steel and sought to inform engineers and architects on how to best utilize
the product. In the last year or so. several comprehensive consensus type reports and guidelines
have been issued, codifying the results and experience of the previous 10 years.
Conditions for Forming Protective Oxide
The precise mechanisms of oxide formation and the structure of the oxides are not fully
understood. However, the conditions for forming the protective oxide have been clearly
identified. It is essential that the steel be subject to alternate wet and dry cycles. The oxide must
be able to absorb and desorb water to form the tight crystalline structure needed for the patina.
If the steel is continually or even mostly wet, the oxide will be loose and flaking like that for carbon
steel.
Another requirement is that the surface be free of chlorides or other aggressive species such as
sutfides. The chlorides interfere with the oxide formation, causing pitting and localized corrosion.
Other contaminants such as sulfur compounds, acids, and chemical fumes should also be
avoided.
In order to achieve the alternate wetting and drying, a condition known as "open bold" exposure
has been stipulated. This allows the steel to be exposed to the elements (i.e.. rain, wind, and sun)
to produce the wetting and drying action.
Conditions to Avoid
In order to help ensure that the protective oxide is properly formed, industry has identified certain
environmental and structural conditions that should be avoided. Tunnel-like" configurations on
highway overpasses can result in increased corrosion rates. This results from a depressed roadway
with high sidewalls, creating a tunnel-like condition. This allows salt, dust, and dirt to accumulate,
and shelters the steel from the atmosphere.
Marine conditions (e.g.. from road de-icing salts or proximity of salt water) are detrimental
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Uncoated Weathering Steel for
Bridges and Other Structures
because of the effects of chloride. Thus, a major cause of corrosion on bridges is leaking bridge
joints, which allow salt-laden water to run over vertical surfaces and collect on bolts, flanges, and
other horizontal surfaces.
Weathering steel was also not designed for immersion service or burial in soil. Also, a poorly
protective coating will do more damage and harm as it allows moisture to penetrate between
the coating and the steel and to collect there.
Remedial Maintenance
The previous conditions are primarily suitable for designing and planning of new bridges and
structures. What can be done about the thousands of bridges and other structures which were
previously erected and which may include some of the conditions described?
Several guidelines are available for retrofitting weathering steel bridges. Remedial Maintenance
Options are as follows:
* No action (deferral)
The first option is to defer any painting or other action at least until the next
inspection period (should be no more than 2 years). This option is recommended
when scaling of the oxide is moderate, corrosion is uniform, and there are no
critical joints affected.
* Protect damaged areas only
A second option is to clean and paint only those areas most vulnerable to
corrosion damage. These include leaky joints and bottom flanges. Several state
DOTs require painting within 5 to 10 feet of the joint.
* Protect entire structure
A third option is to clean and paint the entire structure. This is recommended for
bridges where salt is deposited or condensing humidity conditions prevail on large
portions of the bridge. Where a contractor has erected scaffolding or brought in
blast cleaning equipment, it may be more economical to clean and paint the
entire structure rather than limit It to the areas considered most vulnerable.
* Preventive maintenance (nonpainting)
This option includes drainage improvements such as troughs and periodic
inspection and maintenance of joints.
Because of the tighter oxide and rougher surface, removal of the oxide (e.g.. by blast cleaning)
is more difficult and costly than similar operation on carbon steel. Also, a larger amount of paint
will be needed to fill in the profile. Another factor which increases the cost of cleaning and
painting weathering steel is the lack of familiarity of most contractors in working with this material.
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Bernard R. Appleman
Therefore they do not have the experience in optimizing the type of abrasive, the angle, distance,
and pressure, and other practical aspects.
The particular option chosen depends on factors such as the economics, the perceived risk to
safety. DOT or other agency policy, and environmental factors.
Life Cycle and Economics
In order to analyze the life cycle cost of weathering steel, one requires a certain amount of data.
These data may differ significantly among different bridges so there is no single analysis that can
be done to determine the economic comparison of different bridge construction and protection
methods. The following types of data are necessary to do a thorough analysis:
* Steel fabrication and erection costs
carbon v. HSLA steel
painted v. unpointed
+ Time until maintenance required
+ Cost and effectiveness of maintenance
+ Savings/cost to environment.
Some analysis has been done comparing unpointed weathering steel, painted weathering steel
and painted carbon steel. Oftentimes the data used are based on estimates or projections and
reflect the bias of the person presenting the data.
Generally the cost for the initial fabrication, erection, and painting are readily available, although
these also depend on the specific structure, configuration, and environment. The time until
maintenance required is more difficult to determine, as it is based on judgment about condition
of the steel and design life and safety factors. Aesthetics can also be a factor here.
To determine the cost and effectiveness of maintenance therefore requires developing specific
criteria for the need for maintenance and the measure of effectiveness.
An important new element in the equation is the impact of these operations on the environment.
Use of unpointed weathering steel eliminates VOC emissions. There may be a value that can be
assigned to that environmental savings. There is a need. then, for an objective, comprehensive
evaluation of the cost and life cycle of weathering steel to determine how well it competes with
conventional painted carbon steel.
ADVANTAGES OF WEATHERING STEEL
The major advantages in using uncoated weathering steel are as follows:
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Uncoated Weathering Steel for
Bridges and Other Structures
* No surface coating needed
Elimination of need for a coating is the reason this technology has been presented at this
conference. The material thus eliminates the planning, execution, inspection and maintenance
which are necessitated by the inclusion of a protective coating on a steel substrate. Related
advantages are given below:
* Eliminate VOCs and other hazards
Coatings are a major source of VOCs which contribute to ground-level ozone. This aspect would
be eliminated, along with the health risks from solvents and other paint ingredients and the health
and safety risks from blast cleaning and other removal operations.
* Reduce construction and maintenance costs
The application of a coating is estimated to add 10-20 percent of the construction and erection
cost of a bridge. Painting is also a major component of the maintenance cost for bridges or other
industrial structures.
* Higher strength steel
Weathering steel being a high-strength steel would require a reduced amount (and therefore
weight) of steel for construction purposes. This would also reduce the cost and allow alternative
designs to be utilized.
Disadvantages
Weathering steel also has a number of disadvantages which are summarized below:
* Not suited for certain conditions
Among conditions where weathering steel should not be used are high-chloride, continuous
condensing conditions, areas where moisture can collect, "tunnel-like" conditions, and any
configuration or environment where alternate wetting and drying will not be achieved.
* Not maintenance-free
Regular maintenance of weathering steel is required, even where the required oxide formation
conditions are expected. Joints should be inspected and cleaned periodically, and steel
members should be measured for corrosion loss and pitting. Other maintenance practices may
also be needed.
* More costly to protect if corroded
Removing the tight oxide layer is more difficult and costly for weathering steel than for carbon
steel. In addition, if chlorides become embedded in the steel, special methods (e.g., wet blasting)
may be required.
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Bernard R. Appleman
* May pose structural (safety) risk
The buildup of scale on the protective oxide layer may hide problems such as fatigue cracks, or
pitting, which could affect the structural integrity.
* Questionable aesthetics
One aesthetic factor is the color, which ranges from a dull light brown to a dark dull brown, and
which has a rusted appearance. Another concern is the staining. The oxidation of weathering
steel produces continual light flaking, which can produce a sometimes unsightly stain on the
adjacent concrete or other surfaces.
Recommendations
Recommendations are categorized as shown below:
Recommendations for New Structures
* OK for most non-salt environments
* Use new designs to avoid water collection
* Consider partial painting for corrosion-prone areas
+ Plan for maintenance
Recommendations for Existing Structures
* Inspect every 2 years
+ Clean and paint salt- or moisture-laden areas
+ Retrofit to improve drainage
General Recommendations
* Follow design and maintenance guidelines
* Develop database and model on performance and cost
* Emphasize environmental benefits
* Identify new uses
+ Objectively encourage use (do not over-sell)
ACKNOWLEDGMENTS
The SSPC acknowledges the support of the Federal Highway Administration under Research
Contract DFH61-84-C-00063. John Peart, Contracting Officer's Technical Representative. Also
acknowledged are the American Iron and Steel Institute (AISI) for support of SSPC activities related
to weathering steel, and to Bethlehem Steel for furnishing some slides and other materials. SSPC
staff members contributing to this effort included Dr. Simon Boocock, Raymond Weaver, and
Aimee Beggs.
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Uncoated Weathering Steel for
Bridges and Other Structures
REFERENCES
J. D. Gulp and G. L. Tinklenberg, "Interim Report on Effects of Corrosion on Bridges of Unpointed
A-588 Steel, and Painted Steel Pipes," Research Report R-l 142, Michigan Department of
State Highways and Transportation, Lansing, Ml 1980.
AISI Task Group on Weathering Steel Bridges, •Performance of Weathering Steel in Highway Bridges,
First-Phase Report," American Iron and Steel Institute, Washington, DC 1982.
P. Albrecht, and A. H. Naeemi, "Performance of Weathering Steel in Bridges," National Coop-
erative Highway Research Program (NCHRP) Report 272, Transportation Research Board,
July 1984.
P. Albrecht, S. K. Cobum, F. M. Wattar, G. L. Tinklenberg, and W. P. Gallagher, "Guidelines for the
Use of Weathering Steel in Bridges," NCHRP Report 314, Transportation Research Board,
June 1989.
B. R. Appleman and R. E. F. Weaver, "Maintenance Coating of Weathering Steel: Interim Report,"
Report FHWA-RD-91-087, Federal Highway Administration, October 1991 (expected issue
date).
N. Congress, "Forum on Weathering Steel for Highway Structures: Summary Report; FHWA-TS-89-
016, Federal Highway Administration. Washington, DC. June 1989.
E. J. Goodwin III, "Corrosion of Weathering Steel Towers,' Proceedings of 1987 Engineering and
Operations Conference, Southeastern Electric Exchange. May 28.1987.
B. R. Appleman, J. A. Bruno. Jr., and R. E. F. Weaver. "Protective Coatings for Weathering Steel
Tower Joints." SSPC Report 87-03. June 1987. Steel Structures Painting Council.
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PAINTING THERMOPLASTICS
WITH A FILM
Co-authors
CHARLES H. FRIDLEY
Director, Automotive Business
A very Dennison, Automotive Division
Troy, Michigan 48099
VICTOR H. RAMPELBERG
Vice President & General Manager
A very Dennison, Decorative Films Division
Schererville, Indiana 46375
Abstract
Today, thermoplastic parts can be 'painted" with film. This is accomplished by laminating the
'paint" film onto a variety of plastic substrates. Either injection or vacuum moldings exit the
molding operation painted. There is no further processing required. The traditional painting
operation can be eliminated from the production process.
This process has been proven to yield parts that exhibit very smooth surfaces, which are extremely
durable. Exterior automotive coatings, as well as more 'normal" coatings, have shown superior
weather resistance. A multitude of automotive parts have been produced by this method. Some
include: truck fairings, van claddings, automobile trim parts, tractor fenders and automobile
doors.
The process has been commercialized and used on interior automotive parts for several years.
The development of exterior coatings that maintain appearance and durability characteristics is
what is broadening its use. Both Chrysler and General Motors have approved the system for use
on 1993 model automobiles.
INTRODUCTION
One of the biggest drivers of change in the U.S. and Europe is the need to reduce solvent
emissions from our paint shops. This need to reduce solvent emissions has forced the automotive
industry to convert to high solid paint systems even though they do not produce an appearance
that is as smooth and glamorous as low solid paint systems. Now. spurred by the Bush
administration's tougher stance on clean air, the industry has accelerated toward even less
polluting systems such as waterbome paints, which still contain up to 25% solvent.
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Painting Thermoplastics
With a Film
This movement to a clean environment is not without its costs. A paint shop typically makes up
30 to 50 percent of an assembly plant's costs. Building an automotive paint shop can cost from
$ 150 million to $450 million or more, and the new environmental regulations will add to those costs.
Despite these rising costs, the paint job is one of the first things a shopper notices about a new
car. Fit and finish became household words in the 1980s.
This focus on environment, quality and cost has led to increased technological activity in coatings.
One of these recent developments is the paint film laminate process.
This process offers a production-ready method for painting thermoplastic parts without spray
painting. This is accomplished by insert molding a paint film laminate that has been themnoformed
into the shape of the finished part. The injection molded part is ready for assembly without
subsequent finishing.
Since the 1970s, insert molding of thermoplastics has been used extensively for putting woodgrain
patterns on instrument panels, consoles, gloveboxes and doors. The Decorative Films Division of
Avery has been a leader in this field.
In the 1980s, weatherable exterior films have been laminated to thin gauge aluminum and used
on pillar posts, window surrounds and rocker moldings as a replacement for spray painting.
The purpose of this paper is to describe how these two technologies can be joined to produce
a painted thermoplastic part without spray painting. We will cover how the paint laminate is
manufactured, how the paint laminate is used to produce a painted part, and the benefits of the
process versus spray painting.
Painting by the insert molding process offers several unique advantages over spray painting,
including:
* elimination of volatile organic compound (VOCs) from the painting
operation
+ very smooth, high glamour finishes and bright metallics
+ ability to use designs with multiple coats or printed pattern included
in the paint
+ removing the paint bake oven temperature requirements for
thermoplastics.
Paint film laminates and insert molding technology is at a point where It can be considered a
viable method to paint exterior thermoplastic parts. Designers and engineers can now have the
option of using this process for production applications.
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Charles H. Fridley
Victor H. Rampelberg
DEFINITIONS
At this point in the paper it is best to define the terms that will appear later in the text to give
readers a common understanding.
Paint Film - A cast-dried continuous coating of paint. It can be a monocoat, a clear coat over
a base coat, or a clear coat that has been reverse printed (gravure) with a pattern before the
base coat has been cast behind the clear.
Laminate - A composite of a paint film adhered to a thermoplastic backing sheet.
Backing Sheet • A thin (generally .020"), smooth, gel-free, thermoplastic sheet to which the paint
layers are adhered.
Carrier Sheet- A flexible, foldable, heat-resistant, self-supporting sheet of polyester film on which
the paint coating is cast and dried. The carrier sheet is only temporary and is removed prior to
vacuum forming the laminate.
Size - A thin layer of resin that promotes the adhesion of the paint film to the backing sheet.
Preform - A laminate that has been vacuum thermoformed into the shape of the final part (or the
painted area of the part) and the excess laminate has been trimmed away.
Insert Molding - An injection molding technique where a preformed and trimmed laminate is
inserted in the cavity side of the injection mold, and this preform is fused to the face of the
injection molding substrate during the molding cycle.
Injection Cladding - The process of insert molding a painted or decorated preform to obtain a
finished part. Often used interchangeably with insert molding.
Weatherabilitv - The property of being resistant to gloss loss, cracking, color change or otherwise
degrading when exposed to severe climates for extended periods of time; meeting automotive
exterior durabitty requirements.
MANUFACTURING OF THE PAINT FILM LAMINATE
Coatings
The paint laminate requires the use of unique high-performance paints that are capable of
retaining their properties during thermoforming and injection molding. The paints used must not
only provide the appearance, durability and weatherability required for the finished part, but must
also exhibit elongation of 150% or more to thermoform properly.
The paints are coated via a reverse roll process onto a heat-resistant, smooth, tiigh-gloss polyester
film. The coating is dried in a long multi-stage oven. Coating is done in the reverse order as the
first coat on the polyester becomes the first layer seen after the process is completed. The
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Painting Thermoplastics
With a Film
polyester film is discarded. It is the carrier or solvent of the paint film.
For clear coat/base coat systems, the clear coat is cast first (1 to 2 mils in thickness depending
upon the application and the part geometry). Next, the color coat is coated behind the clear
coat (generally to a thickness of .8 to 1 mil) and dried in a second pass through the multi-stage
oven. Finally, a thin layer of size is coated on the back of the color coat to promote aahesion to
the backing sheet.
Volatile Organic Compounds
VOCs are routed through an incinerator for destruction. This control of VOC emissions is reauired
to meet environmental standards even through a very low solids paint is used to provide high
glamour finishes.
Smooth Finish
Paint smoothness and high brightness are other significant advantages of the paint laminate
process over spray painting. Using the reverse roll coater. it is possible to lay down extremely
smooth paint coatings, providing a surface without orange peel or texture. This smoothness is
especially evident with metallics. Because the paint is applied horizontally to the carrier film to
a precise thickness, color consistency can be tightly controlled. This can provide an aavantage
over spray painting where part geometry and position on the vehicle affect the film build and
color control.
In addition to bright metallics and the elimination of orange peel, the laminate painting process
offers printed patterns or designs. In this case, the clear coat can be reverse printed by gravure
to produce most any type of graphic, vignette or other pattern desired for the end application.
The laminate painting process provides the ability to apply three or four coats including
intermediate peartescent or double clear coats. This is generally considered to be uneconomical
by spray painting.
The process can obtain different textures or gloss by varying the injection mold tooling. The paint
film replicates the surface of the mold so if extremely high gloss is reauired. the mold should be
highly polished.
Laminating to the Backing Sheet
After the coating process, the paint film is dry-laminated to a backing sheet by the use of heat
and pressure. The backing sheet must be composed of a thermoplastic material that can be
extruded into a readily thermoformable. gel-free sheet that will provide a smooth surface.
Typically, an injection molding resin will not provide a backing sheet of acceptable quality.
The backing sheet must be compatible with the injection molding resin since, during molding, the
two must form a permanent bond. A backing sheet of (ABS) would generally be used for injection
molding with ABS and thermoplastic polyolefins (TPO) with TPO.
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Charles H. Fridley
Victor H. Rampelberg
But it is possible, and sometimes preferable for part performance, to use a different modulus for
the backing sheet than for the injection molding resin.
Other important considerations for the backing sheet are its sensitivity to moisture, its thermoform-
ing process window, its brittleness and its ability to be pigmented when required.
The typical thickness of a backing sheet, excluding the paint layer, is .020". This is thick enough
to handle the paint laminate in production yet not too thick to significantly reduce melt flow
during injection molding. Also, a backing sheet of this thickness has the capability of hiding glass
or other fillers used in many injection molding resins.
Protective Carrier Film
The paint film laminate is supplied in roll form in the desired width with the temporary carrier sheet
left on to protect the paint surface during shipment. However, the carrier sheet must be removed
prior to thermoforming.
Alternative Laminating Process
It is also possible to extrusion laminate the paint film to a thick thermoplastic sheet (.075 to .500").
This would be done by introducing the paint film at the extruder nip just prior to the embossing
rolls. This "prepainted" thick sheet would be used for thermoforming parts such as truck fairings,
snowmobile covers and fenders that would otherwise be spray painted.
HOW THE PAINT LAMINATE IS USED TO PROVIDE A PAINTED PART
The paint laminate system is designed to be applied to the surface of the molded part in a two-
step process. First, the laminate is thermoformed in the shape of the finished part and the formed
laminate (preform) is inserted into the cavity of the injection mold for the part. As the part is
molded, the backing sheet of the laminate bonds to the injection molding resin and creates a
painted surface on the part.
Thermoforming
Thermoforming the paint laminate is similar to thermoforming other materials of like polymers and
gauge. They can be formed on standard thermoforming equipment. However, a web-fed, in-line
former with pressure assist would be preferred. Adequate control in the heating step is critical to
provide proper part definition. The process conditions for thermoforming are primarily dictated
by the backing sheet; the paint film has a very broad range of thermoformability.
The laminate is unwound from the roll and secured on its outer edges, indexed by transport chains
through the heating oven zones, and thermoformed over a male mold with the unpointed surface
in contact with the mold surface. The preform is then indexed onto a trimming station and
trimmed.
Most molds will be constructed of aircraft gauge cast aluminum with cooling/heating channels
to maintain the mold surface temperature at a specified level. Thermoforming detail and precise
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Painting Thermoplastics
With a Film
fit of the preform to the injection mold is critical to achieving a high-auality finished part.
Dimensioning of the thermoform mold is based on the area of the finished injection mold surface
as well as the allowance for the preform thickness and the shrinkage of the preform. Also, part
geometry and themnoforming conditions will affect the preform shrinkage.
Hardened steel matched metal shear trimming die set is recommended for trimming the preform
on a mechanical or hydromechanical press. Proper planning of how the preform is to be trimmed
is important to avoid unpointed edges showing in the finished part. Care must also be taken to
avoid damage ana to maintain cleanliness of the preform - which will become the painted
surface of the part - during handling, storage and shipping.
To recap, critical variables for thermoforming include tooling, forming temperature and cycles,
preform definition, fit of the preform in the injection mold cavity and edge trimming.
Injection Clodding
The trimmed preform is placed in the cavity side of the mold with the paint surface against the
mold. A highly polished mold surface, without pores or defects, is reauired. The mold is clamped
and the molten resin is injected into the mold cavity. The heat ana pressure of the molten resin
partially melts the backing sheet and forms a melt bond with the preform.
The mold must be rear- or edge-gated so that the polymer is directed onto the backside of the
preform. Gating should be designed to provide a smooth, even flow front with a minimum of weld
lines. The gate opening should be larger than normal to minimize the high viscosity flow and shear
heat input on the preform.
When the mold is opened, a Class A finished part can be removed. This part should be handled
with the same care as any other painted part.
Standard injection molding machines can be used. Access should be made for inserting the
preforms and for removing the parts. A robot arm can be used to insert the preform and later
remove the finished part. The molding cycle should only increase a few seconds for the insertion
of the preform.
It is important that the preform be inserted property. Misalignment could cause pinching, scuffing
or polymer intrusion resulting in a visually defective part. Also, cleanliness of the mold surface and
the preform is critical to achieving a auality finish. It is recommended that the mold area of the
injection mold machine be isolated from the surrounding area.
Parts Considerations
Although painting an entire injection molded plastic car with the paint laminate process is possible
today, it will be a few years before these automobiles are built. We will spend the next several
years painting a multitude of parts on the automobile. Injection molded parts of many geometries
have been molded using a painted preform. These include body side claddings, filler panels,
doors, body panels and wheel covers.
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Charles H. Fridley
Victor H. Rampelberg
Limitations of part geometry have not been fully explored, but parts with deep, side-by-side
pockets, multiple undercuts or a series of thin slits would, at the very least, be difficult to
thermoform and trim. Parts should be designed for this insert molding process rather than trying
to adapt a part originally designed to be molded and spray painted.
ADVANTAGES OF THE PAINT LAMINATE PROCESS VERSUS SPRAY PAINTING
The advantages of the paint laminate process can be separated into those that are attributable
to the process itself and those that are attributable to the paint system chosen by Avery for their
Avloy® Painted Sheet product line.
Process Advantages
The advantages of the process can be separated into three areas: Environmental, Appearance
and Manufacturing.
Elimination of VOCs generated during the painting process has a significant long-term benefit for
a cleaner environment. The expense of continuously reducing emissions from existing paint
facilities is eliminated. A safer work environment is provided. The painted thermoplastic parts can
be recycled as injection molding resin behind the backing sheet.
Appearance advantages include low solids/high glamour looks and bright metallics. Graphics
can be introduced along with color. Orange peel can be eliminated. The backing sheet can
hide fillers and provide a smooth surface. The same paint can be used over multiple substrates
and will still match.
Manufacturing advantages include the use of low-heat-distortion plastics or solvent-sensitive
plastics and no capital for paint shops. The process is also compatible with modular assembly.
Avloy® Point System Advantages
The thermoplastic paint system chosen for Avloy® products meets all of the paint requirements for
a leading automotive (OEM). In addition, it is more weatherable than existing commercial
automotive clear coat/base coat enamels. It has superior resistance to gasoline, solvents,
chemicals and acids, including acid rain, when compared to existing commercial automotive
finishes.
CONCLUSION
It is now possible to obtain a high-quality, extremely smooth paint finish on thermoplastic exterior
body claddings and moldings without spray painting. This can be achieved by insert molding a
paint film lominate that has been thermoformed into the shape of the finished part. The injection
molded part is then ready for assembly without subsequent finishing.
Unlike in-mold coating and mold-in-color, this laminate painting process provides high-gloss
metallics and nonmetallic finishes. Graphics in combination with paints are also available.
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Painting Thermoplastics
With a Film
Even though most of the examples on the paint film have been directed at the automotive
industry, the technology and process can be adapted to any injection molded or vacuum formed
part.
The laminate coating process has proven to be cost competitive with spray painting when the
total cost of producing a part is considered.
The paint laminate finish provides superior weatherability and acid etch resistance. Perhaps best
of all, the paint laminate process is virtually pollution-free and provides a safe worker environment.
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TEDLAR PVF FILM COATING
APPLICATIONS
Author
JOHN H. ROGERS, JR.
Technical Consultant
Polymeric Films
DuPont Polymers
P. O. Box 80712
Wilmington, Delaware 19880-0712
When I was asked to talk about the possibility of lowering VOC emissions through the use of Tedlar
PVF film I realized that I had an easy task. Tedlar has been used commercially as a weatherable
surface on many substrates for over 30 years. With that long a history, Tedlar provides a
benchmark of what has happened in the reduction of VOC emissions over that time span. Tedlar
has reduced VOC emissions in three phases of coating operations. First, emissions during the man-
ufacture of the surfacing material. Tedlar; second, emissions while coating materials with Tedlar;
and third, emissions that occur during refinishing operations over the life of the coated product.
Let's take a look at just what Tedlar is. It's a film made from polyvinyl fluoride, a product of Du
Pont's fluorocarbon research in the 1940s. PVF is a polymer made from vinyl fluoride or mono-
fluoroethylene monomer. Other products from that same research include PVF2 made from vinyl-
idene fluoride or di-fluoroethylene and Teflon made from tetra-fluoroethylene. As part of the
scouting to determine the properties of these new polymers, films were prepared. The weather
resistance of these films was evaluated in both accelerated and actual exposures. After 10 years
outdoors the PVF sample had lost little of its physical properties. In the mid 1950s DuPont began
a program to make a weatherable film product. Tedlar was the result of that program. Building
products coated with Tedlar have been commercially available since 1961.
What makes PVF a weatherable polymer? Partly It's the fact that PVF is transparent to UV down
to 280 nm. The lowest wavelength in sunshine that reaches the surface of the earth is about 320
nm. So PVF suffers no degradation by sunlight. The chemical resistance, though, is the phase of
weatherability most germane to today's discussion. This, as you all remember from junior high
school chemistry, is the Periodic Chart of the Elements. As you further recall, the closer to the top
and the further to the right an element falls, the more electronegative it is. That means the
element has a strong tendency to attract electrons. That's fluorine in yellow in the upper right.
This slide depicts the fluorine atom with its nucleus as a light blue circle at the center and its two
electron shells. The atom needs one electron to complete its outer shell. The yellow circle
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Tedlar PVF Film Coating
Applications ,
represents the missing electron. All other elements either need more electrons to complete the
outer shell or, because they have a greater atomic number, have more electron shells. This puts
the missing electron farther from the protons in the nucleus. In either case, the attraction for the
electron is lessened. Here's a schematic of the PVF molecule. You can see the carbon/flourine
bonds in yellow. They form the major portion of the polymer. On a weight basis the one carbon
atom and the fluorine atom together comprise two-thirds of the mass. This next chart shows the
energy needed to break various organic bonds. Far more energy is required to sever the
carbon/fluorine bond than to sever the bonds found in other polymers. This energy to deteriorate
a polymer can come from UV, chemical reactions, or solvents. The more energy needed to break
the bonds, the more stable the polymer is. Looking at the PVF molecule again you can see that
it has more than just carbon/fluorine bonds. While these other bonds, carbon/carbon for
example, are not as strong as the carbon/fluorine bonds, they are protected by the steric
hindrance of the fluorine atom. The explanation of steric hindrance is beyond junior high
chemistry. It's even beyond chemistry for chemical engineers, so we'll end our science lesson now.
Suffice it to say Tedlar is not damaged by UV, oxidation, hydrolysis or other chemical reactions.
These properties are impressive but they remind me of the dilemma of the old alchemist who was
searching for the universal solvent that would dissolve all matter. A simple peasant on hearing
what the alchemist was looking for asked him. "What are you going to keep it in once you find
it?" The chemical resistance of PVF lead us to the dilemma that since it is such an intractable
polymer, how do you make a film from it? A second question could be what does this have to
do with reduced VOC emission? First let's look at the way Tedlar is made. At our plant in Buffalo,
New York, we begin by polymerizing vinyl fluoride monomer. The resulting PVF polymer cannot
be dissolved in a solvent and cast as a film. It cannot be melt extruded. We make Tedlar by
mixing the polymer with dimethyl acetamide, DMAc. Under the heat and pressure of an extruder
the DMAc causes the PVF to form a gel film. The gel film is stretched and the DMAc evaporated
in the orientation step. All the DMAc is recovered by distillation and cycled back to the mix area.
The process was designed in the 1960s as a closed system because of the cost of DMAc and,
more importantly, a lack of knowledge of the harmful effects of DMAc. With 30 years' experience
we have found that some of our fears were groundless but we still operate a closed system and
recover all the volatile matter. We make and ship film with no emission of volatile organic
substances.
How do our customers apply Tedlar as a surfacing material and how does this affect their VOC?
This is a good time to look at how the whole field of applying coatings has changed over the last
30 years. In the early 1960s the major concern with solvent-based coatings was fire. As long as
the solvent concentration in the coating room, in the processing ovens and in the exhaust stack
stayed below 25 percent of the lower explosive limit, the operation was considered safe. Other
than fire safety, little concern was expressed about what went up the stack. Solvents were
cheap and most coating operations were small. Two things happened in the early 1970s to
change this attitude. Solvent costs rose with the rapid increase in petrochemical prices, and air
pollution control legislation such as Los Angeles' Rule 66 went into effect. At this time it became
evident that venting solvents to the air was a bad practice both socially and economically. These
actions gave impetus to the concept of prefinishing articles rather than postfinishing them. In
prefinishing, stock is coated in its flat state and the finished material is shaped and assembled into
the final part. This is in contrast to postfinishing where the assembled part is fabricated and then
B-68
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John H. Rogers
coated, usually by spraying or brushing on the finish. Here a sheet of plywood is being laminated
with Tedlar in a plant. This military housing at Loring Air Force Base in Maine is sided with
prefinished wood. No field painting was needed. The housing was completed with no VOC
emission. Here the reduction in solvent emissions during the original installation was further
enhanced by the long life of the Tedlar surface. The Department of Defense expects to have to
refinish painted siding every 5 years. These houses were 15 years old when the photo was taken
and still looked new. Prefinishing reduces emissions in two ways. First, since the prefinishing
tends to operate on a larger scale than post painting, the emissions are concentrated in one
location and can be monitored and controlled. In some instances the control costs nothing. The
solvent is removed from the exhaust air by a catalytic burner. The heat gained in burning the
waste solvent is pumped into the coating ovens. The fuel saved pays for the cost of the
equipment used to clean the exit air. Here's a brochure from a company called REECO. Their
customers are recovering 85 percent of the energy from the solvent in the coating oven exhaust.
That's not just removing 85 percent of the solvent; all the solvent is removed and 85 percent of
the theoretically available energy is recycled to the oven.
In addition to plywood siding, steel, aluminum and hardboard siding came into use; even windows
were supplied with a factory applied finish for replacement and new home construction. The
products are coated in 20 or so plants around the country. These plants operate in compliance
with specific standards both of measurement and control. Solvent emission is far less than that
which would be produced by painting tens of thousands of homes by hand. Emissions are also
reduced in prefinishing by coating a flat sheet rather than painting a complex shape. With
prefinishing, a uniform coating is applied so less material is used to ensure a minimum coating.
Less coating material means less solvent used.
Even compared to other coating materials used on a prefinishing line, Tedlar has the advantage
of a longer service life. This reduces the VOC emission over the life of a structure by eliminating
repainting. Here is a 15-year- old home in Columbus, Ohio. The siding is surfaced with Tedlar but
the window sill was covered with aluminum prefinished with a baked enamel. The factory applied
paint has eroded away; the Tedlar is as good as new. This house at the New Jersey shore used
factory-painted aluminum for the downspout. In 20 years the paint is long gone. The Tedlar is fine.
Based on 20-year-old installations, we estimate that Tedlar will last 50 to 60 years before erosion
of the finish produces an objectionable appearance. The 80s brought a further reduction in VOC.
Tedlar business in residential siding saw a drop in wood and aluminum substrates and a
commensurate rise in solid PVC siding. A process for laminating to plastic materials has been used
since the mid 60s. This process has been used to laminate Tedlar to scrim-reinforced PVC for
awnings, air-supported structures and recently for blimps. The system worked perfectly for the new
siding. Adhesive-coated Tedlar is combined with freshly extruded polymer in a nip roll. The heat
of the extrudate metts the thermoplastic adhesive forming the bond. Since the Tedlar is supplied
adhesive coated, no solvents are used in the surfacing operation. By using adhesive-coated
Tedlar, our customers reduce the number of sites where solvents are used. Worldwide just three
facilities are used for applying adhesive to Tedlar for plastic laminations. Twenty to thirty plants.
surface plastic materials with adhesive-coated Tedlar and produce no VOC. In fact, solvent-free
coating has become the norm in this industry. Surfacing equipment consists of a series of rolls.
No solvent coating facilities exist. No ovens; no exhaust stacks. Because both the adhesive and
substrate are thermoplastic, this application requires only one-third as much adhesive in
comparison with lamination to aluminum. The adhesive melts and flows into the substrate. A 67
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Tedlar PVF Film Coating
Applications ___________
percent reduction in adhesive means a 67 percent reduction in solvent used to apply the
adhesive.
Another solvent-free coating operation provides panels for trailers used in the trucking industry.
Tedlar is laminated in a press setup to cured polyester-coated wood panels large enough to
provide the entire wall of this trailer. Here the reduction in solvent emissions is the result of the
durability of the Tedlar surface. This truck will not need painting for at least 10 years. Depending
on the weathering conditions, an average trailer will be repainted three to five times over that
time span. A trailer uses 3 gallons of paint with a total of 6 Ib. of VOC for each refinishing job.
That's 30 Ib. of volatile organic solvents saved for each truck. Decals based on Tedlar film also
reduce VOC emissions. More and more trailers are being thought of as moving billboards. A
decal applied to the side of the truck produces no VOC emission. Painted decorations do. The
decal retains its 'like-new' appearance longer than paint. When a replacement is desired, the
decal has to be stripped by hand and replaced with a new design. No painting is ever needed.
Even small decals can add up to a large reduction in VOC emissions when a large number of
those decals are used.
What's my outlook for the future of reducing VOC emissions after 30 years of using Tedlar as a
surface coating? I'd say optimistic. The technology is there and it works. The desire is there. And
certainly the need is there. It seems to me that change has come about more rapidly when tied
in to a distinct economic advantage as in the case of vinyl siding replacing aluminum siding or
in the case of a more durable finish on truck trailers reducing the need for repainting. The
reduction in VOC emission was just coincidental in those cases. It probably isn't even
appreciated. Maybe a public awareness campaign showing what has been accomplished can
produce even more significant reductions. I also feel there is a place for legislation. This is a
slower method of effecting change but in some cases it is the only effective way to clean up
emissions. Legislation is also valuable in setting goals. Lastly I'm optimistic because groups like this
are getting together to bring about progress.
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MATERIALS RELATED TO THE NATIONAL
AERO-SPACE PLANE
Co-Authors
TERENCE M. F. RONALD
Head, Materials Technology
NASP Joint Program Office
Wright-Patterson Air Force Base, Ohio 45433
(Paper presented by Mr. Lawrence Hjelm)
LAWRENCE J. HJELM
U. S. Air Force Materials Laboratory
Wright-Patterson Air Force Base, Ohio 45433
INTRODUCTION
The ultimate goal of the U. S. National Aero-Space Plane Program (NASP) is the construction and
flight testing of an experimental, fully reusable hypersonic aerospace plane. Called the X-30 it will
be used as a piloted demonstrator of hypersonic flight and will be designed to have the capability
of achieving earth orbit. It will use hydrogen-fueled, air-breathing ramjet/scramjet engines and
will be capable of horizontal takeoff and landing. Representing a practical demonstration of a
new generation of space flight, ft will join a notable line of experimental aircraft that have been
built and flown in the past to explore expanded flight capabilities. First flight is planned before the
end of the century.
To meet weight and performance requirements, the NASP X-30 engines and airframe will make
extensive use of uninsulated, load-bearing, lightweight structures. Active cooling with the
hydrogen fuel will be used in many cases to keep temperatures within the capabilities of the
materials, but to minimize weight ft will be vital to have materials that combine low density with
the highest possible temperature performance. Because of their potential for satisfying these
needs, the materials classes of primary interest include titanium alloys, titanium-based metal-matrix
composites, carbon-carbon composites, ceramic-matrix composites, and copper-matrix
composites.
These and other advanced materials are important for use in load-bearing structures that will see
high temperatures in both the airframe as well as the engines of the vehicle. They would be used
on the airframe as lightweight skin panels of honeycomb-core, truss-core, or integrally stiffened thin
sheet configuration. Where necessary, they would be cooled with the gaseous hydrogen fuel by
incorporating coolant passages into the structures. They would be used in the engines as the wall
panels in the hot gas path of the ramjet/scramjet and also in the inlet and nozzle areas. The
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Materials Related to the National
Aero-Space Plane
engine application represents a particularly challenging problem because of the severe
environment, involving high thermal, acoustic and mechanical loading. In this case, the structural
components will almost certainly have to be actively cooled, meaning that the materials may be
in contact with hot hydrogen from the fuel in addition to hot oxygen and the gaseous products
of combustion.
This paper describes the major classes of materials that are being developed and scaled up for
the NASP program. It reviews the technical approaches in each of the materials classes and
indicates the progress being made toward meeting the challenging structural requirements of
NASP
TITANIUM ALLOYS
Titanium-based candidates for airf rame structures include high-temperature conventional titanium
alloys as well as titanium intermetallics. The intermetallics are of special interest because they
have essentially the same density as titanium but open up the possibility of much higher use
temperatures. The two intermetaliic systems that have been of primary interest are based on the
Ti3Al and TiAl compositions, which have potential maximum temperature capabilities of about
815 °C and 980 °C, respectively.
The principal drawback of the aluminides is their limited ductility and toughness
properties at temperatures less than a few hundred degrees. Coupled with the
requirement for higher fabrication temperatures than conventional titanium alloys,
this makes mechanical working methods - such as sheet rolling - more difficult to
accomplish. The processing of product forms that require a large amount of metal
deformation, such as thin sheet for honeycomb-core or truss-core panels, must be done
in a carefully controlled manner to avoid cracking of the material during the
reduction of the starting material to finished form. In addition, the practical use
of the aluminide components in load-bearing structures must take account of the
probability that their ductility and toughness characteristics will be limited in
comparison to other materials, such as conventional titanium alloys. This mandates
the careful use of well-characterized materials, in conjunction with reliance on
behavior understanding and the employment of analytical life prediction methods.
In the NASP program, composition modifications and advanced thermal-mechanical
processing methods are being applied to the intermetallics to improve their
properties. The goal is to achieve a balanced set of properties that combines useful
levels of strength with the best possible toughness and ductility characteristics.
These modffications-particulariy composition changes-must be done in a way that
retains the low density and high temperature characteristics that make the aluminides
good candidates as structural materials.
Such alloying and processing modifications have improved the properties of the T13A1-
based alloys significantly, and good quality sheet products are being produced that have
reasonable levels of ductility. Sheet-processing methods for the harder-to-work TiAl-based
materials have also been developed, but have yet to be scaled up to an economical production
B-72
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Terence M. F. Ronald
Lawrence J. Hjelm
level. In terms of mechanical properties, the TijAl-based materials can be regarded as good
candidates for selected structural uses on NASP. In the case of the higher temperature TiA 1 -based
aluminide materials, a balanced set of mechanical properties - a suitable mix of strength,
toughness, ductility, fatigue, and high-temperature properties - is still to be achieved;
consequently, it is probable that their use on the vehicle will be limited to lightly loaded structures
where their low ductility is not as critical.
Because much of the airframe and engine structure will be actively cooled, hydrogen at various
temperatures and pressures will be in contact with many of the structural materials. Depending
on Its temperature, pressure and concentration, the hydrogen can interact adversely with most
titanium alloys, leading to embrittlement. The titanium aluminides are more resistant than
conventional alloys, but hydrogen-resistant barrier coatings will be needed for all the materials to
some extent. The development of effective barrier coatings is an integral part of the program,
and significant progress has been made using oxide-based coatings; however the severity of the
hydrogen effects may limit the uses of titanium-based materials to non-actively cooled regions of
the structure. Coatings for protection of the titanium-based materials against high-temperature
oxidation are also required. In this case, surface modifications of the titanium, together with the
application of glass-forming materials, appear to be promising and are being evaluated.
TITANIUM COMPOSITES
Metal-matrix composites based on titanium alloys and titanium aluminides offer significant
improvements in stiffness and strength overtheir unreinforced. monolithic counterparts. This makes
them important for the thin-gauge skin structures required for the NASP airframe skins. The basic
technical challenge in making these composites Is to incorporate reinforcing fibers into the matrix
without creating excessive interactions at the fiber/matrix interface. If allowed to occur, these
reactions would prevent the attainment of the full property potential of the materials.
The conventional method for fabricating metal-matrix composites - involving the hot pressing of
sandwiches of matrix material and fibers - is normally difficult to accomplish with titanium
aluminides. They require higher forming temperatures than conventional titanium alloys, and this
leads to unwanted interaction of the matrix with the embedded fibers at the temperatures and
times needed for consolidation. In addition, the thermal expansion mismatch between the fiber
and the matrix can lead to cracking of the low-ductility matrix on cooling from the consolidation
temperature. Similar cracking may also be seen during subsequent thermal cycling of the kjnd
that would be seen in service.
An alternative consolidation approach that is aimed at circumventing these problems uses a
rapid-solidification plasma-deposition (RSPD) process. In this method, the matrix material starts as
a powder that is fed through a plasma arc to convert It into molten droplets. These are deposited
onto reinforcing fibers that are spiral-wrapped on a large diameter drum, where the droplets are
rapidly quenched to a solid state. Rotation and translation of the drum allows the buildup of a
layer of matrix material on and between the fibers. This solidified deposit of matrix material.
containing a single layer of fibers, can subsequently be slit and stripped off the drum, and several
of these layers can be stacked together and hot pressed to make a multilayer composite.
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Materials Related to the National
Aero-Space Plane
The RSPD process has been demonstrated successfully with SIC reinforcements in TijAl matrix
materials, and useful mechanical properties can be obtained. The eauipment itself has been
scaled up to a pilot plant size that will allow the production of reinforced sheet material that is
about 1 x 3 m in size. In addition, using modified alloy compositions, Ti3Al composites are being
made using the more conventional foil/fiber/foil methods. For the higher temperature TiAl-based
matrix materials, it is still not possible to make SiC fiber reinforced composites with reliability
characteristics that are sufficient to prevent them from cracking on exposure to thermal cycling.
Alternative fibers are under development that have a closer expansion match and a better
chemical compatibility than is the case with the SiC fiber. While these appear to be promising.
this class of composites will reauire further development to make them reliable structural materials,
and It appears that the Ti3Al-based materials will have a clear advantage for practical, load-
bearing structural applications.
In recent development, it has been shown that advanced conventional beta titanium alloys - as
distinct from the intermetallic aluminides - can provide useful properties when reinforced with
fibers such as silicon carbide. It appears that such materials have the potential for use at
temperatures up to about 800 °C, and they could well find extensive airframe use as load-bearing
skin structure. They have the additional advantage that conventional foil/fiber/foil consolidation
methods and tooling can be used to make them. Using such processes, the NASP program has
successfully demonstrated the fabrication of various structural shapes that have been built up into
large airframe components. These components make use of multi-ply panels and complex-
shaped stiffeners. and they include cross-plied fiber layers and tapered cross sections. They are
currently being tested in simulated NASP thermal and mechanical loading cycles. Data from small
specimens of these materials indicate that they can withstand the thermal cycling that would be
required for use on the NASP skin.
CARBON-CARBON COMPOSITES
Carbon-carbon composites have the potential for use as lightweight structures exposed to
temperatures in excess of 1400 °C without the need for active cooling. Because of their inherent
high-temperature capability, they are regarded as candidates for use on the NASP airframe as
large, integrally stiffened skin panels on the hotter parts of the vehicle. In this case, they may be
used either as structural, load-bearing components or as lightly loaded thermal protection panels
located over a metallic substructure. They may be useful also for engine applications, though it
is not yet clear whether they could withstand the high heat fluxes and severe operating conditions
in the hot gas path of the engine.
In terms of availability as structural shapes, carbon-carbon composites are mature materials. There
is a large base of knowledge available regarding their fabrication and practical use. and they
have been used in a variety of applications. Several companies specialize in the manufacturing
of carbon-carbon components, and there are several basic methods available for making them.
Many of these methods start with an organic-matrix composite precursor, using additional
processing steps that subsequently convert the matrix to carbon. The precursor composites are
made using a variety of methods that range from multi-ply lay-ups to three-dimensional woven
structural shapes. The actual carbon-carbon manufacturing stages themselves are time-
consuming, and must be controlled carefully to give uniform properties and to avoid batch-to-
batch variations, but the essential manufacturing processes are well-established.
B-74
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Terence M. F. Ronald
Lawrence J. Hjelm
Before they can be used as load-bearing, thin-gauge structural components for NASP, there are
several special technical problems to solve. Chief among these is the need for effective oxidation
protection in the hypersonic flight environment. Existing protection schemes, developed for other
applications, usually involve multilayer coatings and sealants. These work reasonably well in
situations where the material is taken up to a single high temperature and then cooled, but they
face significant problems when exposed to the complex time and temperature cycles of the kind
that would be experienced on the NASP vehicle.
The basic difficulty with the existing protection schemes is that they use outer protection layers of
refractory materials such as silicon carbide. These work well chemically, but they can crack due
to the induced stresses caused by the thermal expansion coefficient mismatch between the silicon
carbide and the carbon-carbon substrate. To alleviate this problem, use has been made of
additional interiayers that oxidize to form a glass that can flow and seal cracks. Unfortunately,
these glasses do not flow readily at intermediate temperatures, which reduces their effectiveness
over part of the temperature range of interest.
Recent advances in oxidation protection technology have improved the situation, and small
coated coupons have withstood the cyclic-temperature loading typical of an NASP environment.
The improvements include the careful tailoring of compositions and thicknesses of the various
layers of protective coating and the use of additives to the matrix that inhibit the effect of oxygen
that may pass through the coatings. These improved protection schemes are being scaled up
and applied to the large, complex-shaped components needed for NASP. and flight-weight
oxygen-protected panels about 1.3 x 3 m have been made.
In addition to structural shape fabrication, methods for joining or fastening carbon-carbon
composites to themselves or to other materials are being developed. These include the
evaluation of fasteners fabricated from carbon-carbon composites or ceramic-matrix composites,
which would be used in place of refractory metal fasteners.
CERAMIC-MATRIX COMPOSITES
Like carbon-carbon composites, ceramic-matrix composites have the potential for use at
temperatures in excess of 1300 °C, with the added advantage of a much higher degree of
inherent oxidation resistance. Unlike the carbon-carbon materials, however they are not as
mature as a class of structural materials, they have not been as widely used, and they do not
possess the same broad base of manufacturing experience.
There are two general classes of ceramic-matrix materials that may be important for NASP: glass-
ceramic-matrix composites, useful up to temperatures of about 800-900 °C. and advanced
ceramic-matrix composites, potentially applicable at much higher temperatures. Glass-ceramic-
matrix composites are relatively well characterized and can be fabricated into product forms such
as honeycomb-core panels and truss-core panels, but they have a limited temperature capability.
From an NASP point of view, there is a much greater interest in the advanced ceramic-matrix
materials, such as silicon carbide fiber reinforced silicon carbide (SiC/SiC) and carbon fiber
reinforced silicon carbide (C/SiC).
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Materials Related to the National
Aero-Space Plane
Significant improvements have been made in advanced ceramic-matrix composites technology
over the last few years, and It is now possible for specialist companies to make quite large,
complex-shaped parts that have the potential of withstanding the temperature cycles required
by NASP. These are being evaluated for their structural capabilities, and they could find important
uses in areas exposed to very high temperatures - such as the region behind the nosecap or
leading edges. A particular interest in the ceramic-matrix materials for NASP stems from their
inherent resistance to hot hydrogen, and they may be useful for actively cooled engine
components.
The extent to which the ceramic-matrix composites can be used reliably in structurally loaded
components has yet to be determined, but there is evidence that materials such as C/SiC have
great potential. Like carbon-carbon, they could be used either as thermal protection panels or
as structurally loaded components. It has been demonstrated that they can be fabricated into
the needed structural forms, and it is now a case of fully characterizing their properties and
determining the limits of their applications.
COPPER-MATRIX COMPOSITES
Because the NASP vehicle will make extensive use of actively cooled skin structure, there is a
particular interest in materials that have a high coefficient of thermal conductivity. Heat
exchangers or actively cooled skin panels must be designed to transfer large quantities of heat
quickly and efficiently from one location to another. In addition, the high-temperature differences
that could exist across sections of heated skin structure could lead to unacceptably high thermal
stresses. For these applications, the structural materials themselves must hove adequate thermal
conductivity or else they must be protected with an actively cooled, high thermal conductivity
barrier layer.
Copper-matrix composites are potentially useful for these applications. Copper in Itself has good
thermal conductivity, but it is heavy, and Its upper use temperature is limited by its low mechanical
properties. Pitch-based, high modulus graphite fibers that were developed for their high stiffness
and strength properties also have excellent thermal conductivity along the length of the fiber -
significantly better than that of copper Itself. The addition of these fibers to copper to make a
fiber-reinforced composite can reduce density, increase stiffness, raise the use temperature, and
significantly improve the thermal conductivity of the composite compared to the unreinforced
copper.
One approach to the fabrication of these composites starts with a process that places a layer of
copper around each fiber in a graphite fiber tow. The coated fibers are subsequently packed
together and hot pressed into a fully dense material containing a high volume percent of fibers.
Individual plies of the composite are then stacked together and consolidated, using cross-ptying
to compensate for the directional effects of the fiber. Using available metal matrix processing
methods, it is possible to fabricate complex-shaped parts that contain coolant passages within
the structure. Experimental actively cooled components have been built for the NASP program
and tested successfully.
Additional work in the general area of high thermal conductivity materials addresses discontinu-
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Terence M. F. Ronald
Lawrence J. Hjelm
ously reinforced copper composites. These are made by melting and casting alloys of copper
and elements such as niobium. Because the niobium is essentially insoluble in the copper in the
solid state, it is possible to use appropriate mechanical processing methods to form a material
where the copper matrix contains a very fine strengthening distribution of niobium particles. The
resultant composite retains the high thermal conductivity of the copper matrix but is strengthened
by the dispersoid distribution.
More recently, powder metallurgy methods have been used to make higher strength discontinu-
ously reinforced copper-matrix composites. The rapid solidification powder process allows the use
of other alloying elements and leads to a finer distribution of the strengthening phase. While the
thermal conductivity of the discontinuously reinforced composites is not as high as in the
graphite/copper materials, the properties are more isotropic than those of the graphite/copper.
Conventional processing methods can be used to fabricate various product forms from these
materials, and rolled sheet material has been machined, formed and joined to make heat
exchanger panels that contain an intricate network of cooling passages.
Both classes of copper-matrix composites probably will be used on the NASP vehicle, in both the
airframe and the engines. In many cases, the copper composites may be used as a thermal
protection barrier that is bonded or joined to an underlying structure of another material, such as
titanium composites.
COATINGS
Coatings will play an important role for all materials used in the NASP airframe and engines, and
they are a key part of the development activities for each material system. They can perform
several critical functions, including control of temperature and protection against the environment.
For temperature control, they are designed to have high emissivity and to be noncatalytic to the
recombination of the dissociated gases present in the hypersonic airflow across the skin. This can
lead to a reduction of several hundred degrees in surface temperature. For oxidation resistance.
they can provide a suitable barrier that prevents contact of hot oxygen with the underlying
material.
The coating issue unique to NASP arises from the need to protect the materials against the effects
of the hydrogen used for cooling. Hydrogen diffuses readily through many materials, and. in some
cases, it can react with the material to form brittle compounds. The development of hydrogen
barrier coatings is a critical challenge, especially for coatings that are thin, lightweight, resistant
to damage, and can be applied to complex shapes, including internal passages. Successful
coatings most likely will incorporate multilayer protection schemes involving several thin layers of
materials, each performing a contributing function. However, even with suitable coatings, it is
probable that hydrogen-sensitive materials, such as the titanium alloys and composites, will not
be used in contact with hydrogen-at least, not where the hydrogen is in hot gas form. Instead.
the hydrogen will be routed through resistant materials, such as the copper-based composites,
or through cooling tubes of suitable materials.
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Materials Related to the National
Aero-Space Plane
SUMMARY
The structural materials requirements for NASP are challenging. This is true for any air-breathing
hypersonic vehicle, but this is particularly the case for a vehicle intended to have a single-stage-
to-orbit capability. A vital requirement for such a vehicle to achieve its goal is the attainment of
a low structural weight fraction. This drives the interest in high-temperature, lightweight materials
that can be used in the vehicle structure.
The paper describes the general development activities underway in several key materials areas.
Over the past few years, significant improvements have been made in these lightweight, high-
temperature materials, and in many cases they are at a stage where large structural components
are being built and tested. The paper does not cover several other materials classes that will be
important also; these include organic-matrix composites for cryogenic tanks, aluminum alloys for
internal structure and nickel-base superalloys for hot engine structure. In general, these other
materials are well established and readily available for fabrication of demonstration structural
components of the right size and shape.
While rapid progress has been made in the development of the advanced materials of interest,
their intended use must be approached with caution. In addition to their high-temperature and
lightweight capabilities, the materials must have the reliability needed for use on piloted vehicles.
Thus, properties such as fatigue behavior, creep resistance, toughness, and ductility are especially
important. Many of the newer materials will have some of these properties-such as ductility-that
are at levels less than traditionally acceptable for long-lifetime conventional aircraft. In
recognition of this fact, an important part of the NASP program is addressing behavior analysis,
life prediction methods, and nondestructive evaluation techniques, in the belief that they will be
the key to successful application of these newer materials on NASP.
The rate of progress over the last few years gives confidence that the materials and structures
requirements for NASP can be met by the current advances being made in their development.
While the exact configuration of the X-30 vehicle is still being defined, it is probable that many of
these materials will find extensive use on this experimental aerospace plane that is intended to
pave the way for the next generation of space flight.
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Appendix C
Conversion Factors
c-l
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Table C-l. Conversion Factors
To convert from:
length
centimeters (cm)
meters (m)
mil
nanometers (nm)
area
ft2
weight
pounds (Ib)
tons (t)
temperature
°F
volume
gallons (g)
boardfoot (bf)
pressure
pound per square inch (psi)
Ib/ft2
kip/in2 (ksi)
density
kg/m3
Ib/in3
flgw rate
g/minute
misc.
watt/ meter K
in/ln/°F
Btu/hr-ft2
Into:
inches (in)
feet (ft)
inch
mil
m2
kilograms (kg)
kg
°C
liters (1)
ft3
kg/m2
kg/m2
Ib. force/in2
Ib/ft3
gm/cm3
l/min.
cal/ (sec)(cm)(°C)
cm/cm/°C
watt/m2
Multiply by:
0.393
3.280
0.001
3.937 x 10'5
0.092
0.453
907.184
0.555 (°F-32)
3.785
0.083
2.926 x 10-4
4.882
1000
0.062
27.679
3.78
0.002
0.555
3.154
C-2
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