COMPOSITES FROM RECY
CLED WOOD AND PLASTICS
by
John A. JYoungquist
George E. Myers
James iH.Muehl
Andrzej]M. Krzysik
Craig M. demons
USDA Forest Service
Forest Products Laboratory
Madison, WI 53705-2398
i
DWl
IAG DW|12934608-2
Project Officer
Lisa Brown
Waste Minimization, Destruction, and Disposal Division
Risk Reduction Engineering Laboratory
Cincinnati, OH 45268
' W2
This study was conducted
in cooperation with
U.S. Department of Agriculture
i
RISK REDUCTION ENGINEERING LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OH 45268
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NOTICE
The information in this document has been funded wholly or in part by the US
Environmental Protection Agency (EPA) under IAG DW 12934608r2 to USDA Forest Service,
Forest Products Laboratory (FPL). It has been subjected to the Agency's peer and administrative
review, and it has been approved for publication as an EPA document
The statements and conclusions of this document are those of the FPL, and are not
necessarily those of the EPA. The mention of | commercial products, their sources, or their use in
connection with materials reported therein is n0t to be construed either as actual or implied
endorsement of such products by EPA or FPli.
n
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FOE
IEWORD
Today's rapidly developing and changing technologies and industrial products and practices
frequently are accompanied by the increased generation of materials that, if improperly dealt with,
can threaten both public health and the enviroriment. The U.S. Environmental Protection Agency
(EPA) is charged by Congress with protecting! the Nation's land, air, and water resources. Under
a mandate of national environmental laws, the Agency strives to formulate and implement actions
leading to a compatible balance between human activities and the ability of natural systems to
support and nurture life. These laws direct the EPA to conduct research to define environmental
problems, measure impacts,, and search for solutions.
The Risk Reduction Engineering Laboratory is responsible for planning, implementing, and
managing research, development, and demonstration programs to provide an authoritative,
defensible engineering basis in support of the policies, programs, and regulations of the EPA with
respect to drinking water, wastewater, pesticides, toxic substances, solid and hazardous wastes,
Superfund-related activities, and pollution prevention. This publication is one product of that
research and provides a vital communication link between the researcher and the user community.
Passage of the Pollution Prevention Act of 1990 marked a strong change in U.S. policies
concerning the generation of hazardous and nonhazardous wastes. This bill implements the
national objective of pollution prevention by es'tabishing a source reduction program at the EPA
and by assisting States in providing information and technical assistance regarding source
reduction. In support of the emphasis on pollution prevention, the technology evaluation project
discussed in this report emphasizes the study and development of methods to reduce waste.
E. Timothy Oppelt, Director
Risk Reduction Engineering Laboratory
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ABSTRACT
Wastepaper and wood materials constitute more than 40 percent by weight of municipal solid
waste; waste plastics constitute approximately 7 percent. This materials resource offers
considerable potential as ingredients in wood fiber-plastic composites. These composite systems,
in turn, offer considerable potential for reducing municipal solid waste by the manufacture of an
array of value-added products that may themselves be recyclable.
The ultimate goal of this program was to develop technology to convert recycled wood fiber
and plastics into durable products that are recyclable and otherwise environmentally friendly, and
thereby effectively remove the waste materials from the waste stream. The program employed two
processing technologies to prepare the composites: air-laying and melt-blending. Research was
conducted in (1) developing laboratory methods for converting wastewood, wastepaper, and waste
plastics into forms suitable for processing into Composites; (2) optimizing laboratory methods for
making composite panels from the waste materials; (3) establishing a database on the effects of
formulation and bonding agent variables on composite physical and mechanical properties; (4)
establishing the degree to which the composites! can be recycled without unacceptable loss in
properties; and (5) reaching out to industry to p-ovide education, to develop applications, and to
extend the database as appropriate.
Overall, the program demonstrated that be th air-laid and melt-blended composites could be
made from a variety of wastewood, wastepaperl and waste plastics. These composites exhibit a
wide range of properties that should make them useful in a wide variety of commercial
applications. Specifically, improvements in laboratory methods to convert waste materials to
usable forms and improvements in methods to prepare composites provided the capability to make
composites with reproducible properties.
For air-laid composite technology, the waste materials emphasized were demolition wood
waste and waste plastics from milk bottles (polyethylene) and beverage bottles (polyethylene
terephthalate). Test results showed that air-laid composites made from these waste ingredients
possessed properties very similar to those for composites made from the virgin ingredients. In
addition, air-laid panels containing 20 percent reground panels as part of their filler possessed
some properties that were superior to those of the original panels. This finding provides strong
evidence that air-laid panels are recyclable.
For melt-blended composites, the waste materials emphasized were wastepaper, polyethylene
from milk bottles, and polypropylene from automobile battery cases or ketchup bottles. Waste
magazines were slightly inferior to waste newsp'apers as a reinforcing filler; the properties of
composites made from waste newspaper were better than those of composites made from wood
flour, which is currently used in some commercial composites. The various plastics resulted in
composite properties that were generally parallel to those of the plastics; thus, different balances in
composite properties are possible from using waste plastic. Two melt-blended composites and one
air-laid composite were subjected to five extrusi'on cycles without major changes in properties.
Extensive outreach activities were conducted, including the organization and presentation of
two international conferences on wood fiber-plastic composites, presentations at many confer-
ences, publication of several papers, and several spin-off cooperative studies with industry to
examine the potential of various waste material^ in composites. One major study with industry
demonstrated the commercial feasibility of melt-plended composites made from old newspapers
and polypropylene.
This report was submitted in fulfiUment oflEPA Interagency Agreement DW12934608-2 by
the USD A Forest Service Forest Products Laboratory. This report covers a period from May 1,
1990 to July 31, 1993.
IV
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CONTENTS
Notice
Foreword
Abstract
Abbreviations
List of Tables
List of Figures
Acknowledgment
1. Introduction
2. Conclusions
3. Recommendations
4. Studies on Air-Laid Composites
General Comments
General Procedures
Task AL-1. Raw Materials Preparation.
Task AL-2. Laboratory Methods for Making Composites.
Task AL-3. Development of a Performance Database.
Task AL-4. Recyclability |
5. Studies on Melt-Blended Composites j
General Comments j
General Procedures
TaskMB-1. Raw Materials Preparation..
Task MB-2. Laboratory Methods for Making Composites.
Task MB-3. Development of a Performance Database
Further Characterization of Melt-Blended Composites
TaskMB-4. Recyclability
6. Product Application and Database Extension (Task 5)
Commercial Implementation
Conferences, Presentations, and Publications......
7. Quality Assurance Objectives
Preparation of Ingredients for Incorporation
Into Composites.
Preparation of Composites
Characterization and Testing of Composites.
References
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. iii
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. vi
. vii
. viii
. x.
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LIST OF ABBREVIATIONS
AL
ASTM
BPP
BW40
DP
DNR
E10
E43
E43E
E43S
FPL
G3002
GPa
HF
HDPE
HDPE-MB
J
KPP
MB
MFI
MOE
MOR
MPa
MSW
OMG
ONP
PET
PP
PR
RH
RHDPE
RPET
SG
TAPPI
VHDPE
WET
VPP
WF
-- air-laid composite
— American Society for Testing
— polypropylene from recycled
-- Solka-Floc cellulose fiber
— demolition wood fiber obtain
and Materials
auto battery cases
d from wastewood
-- Wisconsin Department of Natural Resources
— Eastman Chemical Co. Epolejne E10, low molecular
weight maleated polyethylene
— Eastman Chemical Co. Epolene E43, low molecular
weight maleated polypropylene
-- emulsified potassium salt of E43
— solid powdered form of E43
— Forest Products Laboratory
— Eastman Chemical Co. Epoletie G3002, high molecular
weight maleated polypropylene
- gigapascal; 10^ Pa; unit of pressure
— virgin Western Hemlock fiber
- virgin high density polyethylene
-- recycled high density polyethylene from milk bottles
Joule; unit of energy (work, heat)
— recycled polypropylene from'.
:etchup bottles
melt-blended composite
- melt flow index
- modulus of elasticity
- modulus of rupture
- megapascal; 10^ Pa; unit of p -essure
- municipal solid waste
- old magazines
- old newspapers
- polyester fiber
- polypropylene
• phenolic resin
- relative humidity
recycled high density polyethylene from milk bottles (granulated)
- recycled polyester fiber from beverage bottles
- specific gravity
- Technical Association of the Pulp and Paper Industry
- virgin high density polyethylene (granulated)
• virgin polyester
• virgin polypropylene
• wood flour
VI
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LIST OF TABLES
1 Materials used in air-laid studies.. J
2 AL Series 1. Panel composition
3 AL Series 1. Panel selection .] ,
4 AL Series 1. Mechanical and physical properties of composites..
5 AL Series 2. Panel composition..
6 AL Series 2. Specimen selection
7 AL Series 2. Mechanical and physical properties of composites..
8 Recyclability: Panel composition
9 Recyclability: Specimen selection.
10 Recyclability: Mechanical and physical properties of composites.
11 Materials used in melt-blending stujdies
12 Coefficients of variation for measured mechanical properties
13 Study MB-1: Mechanical properties
14 Study MB-1: Analysis of variance summary
15 Study MB-1: Property changes ... .1 —
16 Composite melt viscosities..]
17 Study MB-2: Mechanical properties
18 Study MB-2-A: Main effects and interactions
19 Study MB-2-B: Main effects and interactions ,
20 Study MB-2: Useful mechanical property changes
21 Comparison of mechanical properties of HDPE-MB/ONP and
PPV/WF composites.....
22 Characteristics of Epolenes
23 Study MB-3: Mechanical properties'
24 Study MB-4: Mechanical properties
25 Study MB-4: Main effects of variables
26 Study MB-4: Change in property after addition of
40 percent filler to plastic
27 Water sorption of VPP with 42 percent ONP and 3 percent
G3002 (by weight of filler) 1
28 Water sorption of VPP with 42 percent ONP (no coupling agent).
. 29 Water sorption of VPP with 42 percent WF (no coupling agent)
30 Analysis of variance summary 1
31 Study MB-5: System 1 mechanical properties after recycling
32 Study MB-5: System 2 mechanical properties after recycling
33 Study MB-5: System 3 mechanical properties after recycling
34 Study MB-5: Analysis of variance summary
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LIST OF FIGURES
1 Schematic of air-laid web forming process 73
2 Task 3, AL Series 1. Bending strength (MOR) as a function of virgin
hemlock fiber (HP), recycled demolition fiber (DF) and polyester
fiber (PET). VPET and RPET designate virgin and recycled
polyester fiber, respectively j 73
3 Task 3, AL Series 1. Bending stiffness (MOE) as a function of virgin
HF, recycled DF and PET 74
4 Task 3, AL Series 1. Tensile strength as a function of virgin HF,
recycled DF, and PET ....] 74
5 Task 3, AL Series 1. Tensile modulus (MOE) as a function of virgin
HF, recycled DF, and PET 75
6 Task 3, AL Series 1. Impact energy as a function of virgin HF,
recycled DF and PET 75
7 Task 3, AL Series 1. Thickness swell as a function of virgin HF,
recycled DF and PET 1 76
8 Task 3, AL Series 1. Water absorption as a function of virgin HF,
recycled DF and PET | 76
9 Task 3, AL Series 1. Linear expansion at 30 percent RH as a
function of virgin HF, recycled] DF and PET 77
10 Task 3, AL Series 1. Linear expansion at 65 percent RH as a
function of virgin HF, recycled DF and PET 77
11 Task 3, AL Series 1. Linear expansion at 90 percent RH as a
function of virgin HF, recycled DF and PET ! .....78
12 Task 3, AL Series 2. Bending strength (MOR) as a function of
virgin HF, recycled DF and high density polyethylene (HOPE).
VHDPE and RHDPE designate virgin and recycled HOPE,
respectively I. 78
13 Task 3, AL Series 2. Bending stiffness (MOE) as a function of
virgin HF, recycled DF and HOPE.[ 79
14 Task 3, AL Series 2. Tensile strength as a function of
virgin HF, recycled DF and HOPE. 1 79
15 Task 3, AL Series 2. Tensile modulus (MOE) as a function of
virgin HF, recycled DF and HOPE 80
16 Task 3, AL Series 2. Impact energy
recycled DF, and HOPE
as a function of virgin HF,
___j 7 80
17 Task 3, AL Series 2. Thickness swe|ll as a function of virgin HF,
recycled DF and HOPE .[......, '. 81
18 Task 3, AL Series 2. Water absorption as a function of virgin HF,
recycled DF and HOPE ! 81
19 TaskS, AL Series 2. Linear expansion at 30 percent RH as a
function of virgin HF, recycled DF and HOPE ....82
20 Task 3, AL series 2. Linear expansion at 65 percent RH as a
function of virgin HF, recycled DF and HOPE 82
21 Task 3, AL Series 2. Linear expansion at 90 percent RH as a
function of virgin HF, recycled DF and HOPE 83
22 Task 4, Recyclability. Bending strength (MOR) as a function of
recycled DF, HOPE, and first-generation panels 83
23 Task 4, Recyclability. Bending stiffness (MOE) as a function of
recycled DF, HOPE, and first-generation panels 84
24 Task 4, Recyclability. Tensile strength as a function of recycled
DF, HDPE, and first-generation panels 84
Vlll
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Task 4, Recyclability. Tensile modulus (MOE) as a function of
recycled DF, HDPE, and first-generation panels
Task 4, Recyclability. Impact energy as a function of recycled
DF, HDPE, and first-generation panels
Task 4, Recyclability. Thickness swell as a function of recycled
DF, HDPE, and first-generation panels
Task 4, Recyclability. Water absorption as a function of
recycled DF, HDPE, and first-generation panels
Task 4, Recyclability. Linear expansion at 30 percent RH as a
function of recycled DF, HDPE, ajid first-generation panels
Task 4, Recyclability. Linear expansion at 65 percent RH as a
function of recycled DF, HDPE, and first-generation panels
Task 4, Recyclability. Linear expansion at 90 percent RH as a
function of recycled DF, HDPE, and first-generation panels
Schematic of single-screw extruder
Schematic of K-mixer
Study MB-L Flexural strength as a function of filler
content and type •
Study MB-1. Unnotched impact energy as a function of
filler content and type
Study MB-1. Apparent melt viscosity of composite blends. ONP is
old newspapers; WF, wood flour; and PP, polypropylene
Study MB-2. Tensile strength as a function of filler and polymer
types. PP-V is virgin polypropylene; HDPE-MB, melt-blended high
density polyethylene
Study MB-2. Flexural strength as a function of filler
and polymer types
Study MB-2. Tensile modulus as a function of filler
and polymer types
Study MB-2. Notched impact energy as a function of
filler and polymer types
Study MB-2. Unnotched impact energy as a function of
filler and polymer types
Study MB-3. Effect of coupling agent on tensile stress-strain curve
of ONP/PP composites.
Study MB-3. Effect of coupling agent
ONP/PP composites.
Study MB-3. Effect of coupling agent on impact energy of
ONP/PP composites.
on tensile strength of
Study MB-4. Effect of wastepaper on tensile stress-strain curve
of polypropylene from recycled auto battery cases (BPP). ONP is
old newspapers; OMG, old magazines
Study MB-4. Effect of polymer and wiastepaper types on tensile
strength. KPP is recycled polypropylene from ketchup bottles
Study MB-4. Effect of polymer and wiastepaper types on flexural
modulus
Study MB-4. Effect of polymer and Wastepaper types on notched
impact energy I •
Study MB-4. Effect of polymer and wastepaper types on
unnotched impact energy
Study MB-5. Processing flow diagram for recycling study
IX
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ACKNOWLEDGMENT
We are indebted to Jerome Saeman for cc ntinuing advice and counsel, to Donald Ermer for
advice on statistical design and analysis, to Haijry Fitzgerald who provided excellent advice and
guidance on Task 1 air-laid studies, to Jim McElvenny of Wood Recycling, Inc. for providing the
fiberized demolition wood for the air-laid portion of this research, to Rose Smyrski and Nicole
Stark for help hi laboratory testing, to Ray Woodhams and John Balatinecz of the University of
Toronto for their aid in carrying out the K-mixing for Phase I of Study MB-1, to Solvay Polymer
Corp. for supplying polypropylene, to Eastman Chemical Co. for supplying Epolenes, to James
River Corp. for supplying Solka-Floc, to American Wood Fibers for supplying wood flour, and
to Milwaukee Sentinel/Journal for supplying o] d newspaper.
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SECTION 1
INTRODUCTION
j • . -
-.,-,'-,,-.} - - ,'.',:,
Each year the United States has been attempting to dispose of 160 million tons of municipal
solid waste (MSW) and is finding it increasing
y difficult to find landfill sites that neighbors to
landfills will tolerate. In the next 15 years 75 pjercent of all our landfills will be closed, and by the
year 2000 this nation will be short 56 million tons per year of disposal capacity.
I
In 1986, paper and paperboard, wood, and plastics in the MSW stream accounted for
approximately 65, 5.8, and 10.3 million tons, respectively. By the year 2,000, these figures are
expected to increase to 86.5, 6.1 and 15.7 millipn tons annually. In addition to the wood fiber in
the MSW stream, there are vast quantities of low-grade wood, wood residues, and industry-
generated wood waste in the form of saw dust,j planer shavings, chips, and other such items that
are now being burned or otherwise disposed of.
Technology is evolving that holds promise for using waste or recycled wood and plastics to
make an array of high performance products that are, in themselves, potentially recyclable.
However, much research remains to be done. Preliminary research at the USDA Forest Service
Forest Products Laboratory (FPL) indicated that recycled plastics such as polyethylene,
polypropylene, or polyethylene terephthalate caln be combined with wastewood fiber to make
useful composites. Advantages associated witri these composite products include improved
stiffness and strength, acoustic, and heat reformability properties, all at costs lower than
comparable products made from plastics alone.
In addition, early research has shown that the
composite products can possibly be reclaimed and recycled for the production of second-generation
composites.
Many of the uses of wood fiber/plastic composites are such as to require them to be opaque,
colored, painted, or overlaid. Consequently, recovered fibers or resins used in these composites
do not require the extreme cleaning and refinement needed when they are to be used as raw
materials for printing paper or pure plastic resirls. This fact greatly reduces their cost as raw
materials and makes composite panels an unusually favorable option for the recycling of three of
our most visible and troublesome classes of MSW—newspapers, wastewood, and plastic bottles.
I.' '- ! . " • • ' -'
The research program outlined here focused on melt-blending and nonwoven web
technology.
Melt-blending technology—Melt-blending is an inherently low-cost, high-production rate
process in which wood and paper are mixfed with molten plastic. These blends can then be
formed into products using conventional plastics processing techniques such as extrusion or
injection molding. The plastic acts as a means to convey the wood/paper during processing
and the wood/paper fiber bears the load in the final composite, offering an effective balance
between processability and strength of the end-product. With melt-blending techniques,
wood flour and wood fibers offer a number of advantages as reinforcements in thermoplastic
composites. These include economy on a] cost per unit volume basis, desirable aspect ratios,
flexibility (hence less fiber breakage), andj low abrasiveness to equipment. Composite panels
can be produced containing up to 50 weight percent wood fiber and are low cost,
thermoformable, and relatively insensitive' to moisture.
Air-laid web technology—A wide variety of wood fibers and synthetic plastic fibers can be
assembled into a random web or mat using an air-forming web technology. In contrast to
melt-blended composites, air-forming technology involves room temperature mixing of
lignocellulosic fibers or fiber bundles with1 other long fibrous materials (usually synthetic
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fibers). Nonwoven processes allow and tolerate a wide range of waste paper and wood
types depending upon the end product under consideration. With this technology, the
amount of paper or wood fiber can be greater than 90 weight percent. After the fibers are
mixed they are air-laid into a continuous] loosely consolidated mat. The mat then passes
through a secondary operation in which the fibers are mechanically entangled or otherwise
bonded together. This low density mat nSiay be a product in itself, or the mat may be shaped
and densified by a thermoforming step. Alternatively, a thermosetting resin can be
incorporated to provide additional bonding of the fibers. Compared to products made by
melt-blending, the air-formed web composites have the potential for better mechanical
properties and the capability to make products having more intricate shapes.
Because of the increased processing flexibility inherent in both the melt-blending and air-
formed web technologies, a host of new natural fiber/synthetic plastic products can be made.
These can be produced in various thicknesses from a thin material of 3 mm to structural panels up
to several centimeters thick. A great variety ofj applications are possible because of the many
alternative configurations of the product. Three major use classifications can be defined as
packaging products, industrial products, and building materials. Taken together, these two
processing techniques provide options for balancing performance properties and costs, depending
upon the product application under consideration.
The ultimate goal of this research program was to develop technology to convert recycled
wood fiber and plastics into durable, long service life products that are recyclable and otherwise
environmentally friendly and will effectively remove the raw materials from the waste stream. In
support of this goal, specific research objectives included the following tasks:
Task 1. Raw materials preparation—developing laboratory methods for converting
wastewood and waste plastics into forms
web processing.
suitable for subsequent melt-blending and air-laid
Task 2. Laboratory methods for making composites—optimizing laboratory methods for
making composite panels from these waste materials.
Task 3. Development of a performance database—establishing a database on the effects of
formulation and bonding agent variables and the resultant physical and mechanical properties
of the composite.
Task 4. Recyclability—defining the degree to which the composites can be recycled without
unacceptable loss in processability or mechanical and physical properties.
Task 5. Product application and database extension—identifying, in partnership with
industry cooperators, product applications and extending the property database to these
applications.
Our approach was an exploratory and experimental pursuit of methods that may lead to the
fabrication of useful, long-living, recyclable composites from blends of recycled wood and plastic.
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SECTION 2
CONCLUSIONS
GENERAL
This program has demonstrated that air-laid and melt-blended composites can be made from a
variety of wastewood, wastepaper, and waste p'lastic materials in the postconsumer waste stream.
These composites exhibit a wide range of properties that should make them useful in a wide variety
of commercial applications and value-added products.
AIR-LAID COMPOSITES
(1) The Rando-Webber air-forming equipment can be adapted to handle both long and short
synthetic and natural fibers and as well as powders. Nonwoven air-laid webs can be
produced that have excellent uniformity in both the machine and cross machine direction.
(2) Postconsumer high density polyethylene from milk bottles cannot be respun into a fiber
using melt processing techniques. Granulating this material for further processing was
extremely successful. Recycled and granulated high density polyethylene can be used in the
FPL air-forming equipment to produce an
panels or shaped sections.
air-laid web that can be subsequently made into flat
(3) Pressure refining techniques can convert postconsumer demolition wood or construction
waste into fiber bundles that can be processed very successfully in the FPL air-forming
equipment and subsequently into pressed bat panels or shaped sections.
(4) There were statistical differences in the mechanical and physical properties of test panels
made with virgin fiber compared to recycled polyethylene terephthalate and test panels made
with hemlock fiber compared to demolition wood fiber. Statistically significant differences
were shown in 12 of 40 comparisons. However, the relative magnitude of the difference in
these 12 comparisons is small and would most likely have little or no influence on
commercial products.
(5) Demolition wood fiber, which consisi
softwood species, performed as well as p;
of a mixture of up to 15 different hardwood and
lels made from virgin hemlock fiber.
(6) Panels containing recycled high density polyethylene from milk bottles had mechanical
and physical properties similar to those of panels containing virgin high density polyethylene.
Sixteen of 40 comparisons exhibited statistically significant differences. However, the
character and relative magnitude of the differences in these comparisons would most likely
have little or no influence on commercial p'roducts.
(7) Second-generation panels made with ai portion of reground first-generation panels
performed better than first-generation panels.
MELT-BLENDED COMPOSITES
(1) Melt-blended composites cannot be prepared with wastepapers as reinforcing filler using
a conventional laboratory single-screw extruder. However, they can be prepared with a
laboratory high intensity K-mixer. They can also be prepared with an industrial scale
K-mixer or with a twin-screw extruder tha: employs a properly designed feeder for the fiber.
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(2) Old newspaper as reinforcing filler p rovides property advantages over wood flour,
which is currently used as filler in comm4rcial composites. With virgin polypropylene as
matrix, for example, tensile strength is increased nearly 30 percent and unnotched impact
energy is increased over 40 percent. Old magazines can also be used as a filler, but they are
less easily dispersed into the matrix plastijc and result in somewhat lower properties than
those of composites containing old newspaper.
zyc
(3) With the same filler, substituting recycled milk bottle polyethylene for virgin
polypropylene leads to lower strength (greater than 20 percent reduction), stiffness (greater
than 20 percent reduction), and unnotched impact energy (nearly 30 percent reduction), but
higher notched impact energy (nearly 30 percent increase).
(4) Use of recycled high density polyethylene from milk bottles and recycled polypropylene
from battery cases as a matrix in composites with old newspaper results in improved impact
performance when compared with the performance of composites of virgin polypropylene
and newspaper.
(5) The addition of Epolene G3002, a coupling agent, at 3 weight percent of filler results in
very useful increases in composite properties, for example, a 30 to 50 percent increase in
various strengths and a 70 percent increase in unnotched impact energy. These changes are
probably brought about by improved dispersion of the fiber.
(6) Select composite systems showed little or no loss in mechanical properties when
repeatedly reprocessed (re-extruded and injection molded).
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SECTION 3
RECOMMENDATIONS
Recommendations arising from this program, and other closely related efforts, logically fall
into two categories—those related to further research needs and those related to further efforts
towards commercialization of composites from wastewood fiber and waste plastics. The two
categories are not entirely separate, however, because progress in one may well influence the
course of the other.
RESEARCH
In several areas, additional research is needed on both air-laid and melt-blended composites
made from recycled wood fiber and plastics to improve properties and processing and thereby
increase the number of potential applications.
(1) Evaluate the potential for making valuable composite materials with other major
components of the waste stream, including low density polyethylene, polystyrene, and mixed
waste plastics. Investigations into some of these materials had to be eliminated from this
program because of funding limitations.
(2) Verify the recyclability of composites made with the above ingredients. In addition, the
improved behavior of second-generation air-laid panels, containing portions of reground
first-generation panels, may have major ramifications for recycling and should be further
investigated. I
(3) Improve melt-blending processes to achieve better fiber dispersion with minimal fiber
breakage.
(4) Improve the bonding between the wood fiber and plastic matrix in order to enhance
physical and mechanical properties. The ijnethods and/or materials used to achieve improved
bonding will very likely differ with the matrix plastic.
(5) Improve the impact energy and the creep resistance (decreased deflection under long-term
load). These are now the major limiting properties of these composite systems.
(6) Determine the resistance of these composite systems to relatively extreme environments
and develop means to enhance that resistance. Resistance to moisture, to biodegradation, amd
to fire are important properties for continued research.
COMMERCIALIZATION
(1) Major, continuing outreach efforts to ijndustry will be needed to acquaint companies with
these types of composite systems, to develop applications, and to cooperate with industry in
the development work that will be required to bring products to market.
(2) Commercial acceptance of melt-blended composites containing wastepaper fiber will not
occur to a major extent without additional (development work in two areas:
(a) Improvements are essential in methods to convert wastepaper on a commercial scale
to the physical forms and at costs that|are acceptable to industrial users. Costs must at
least approach the current cost of wood flour at about $0.22/kg.
-------
(b) Improvements are also critical in methods to melt-blend (compound) the fiber and
plastics on a commercial scale at costs acceptable to melt fabricators (extruders, injection
molders, etc). Several methods are already available but no systematic small or large
scale evaluations have been performed.
-------
SECT
STUDIES ON AIR-
ON 4
AID COMPOSITES
GENERAL COMMENTS
Many articles and technical papers have been written and several
both the manufacture and use of air-laid mats containing combinations
fibers This technology is particularly well-knoWn in the consumer products industry. For
e^SplI^iSe^W tadthat polyolefin pulps can serve as effective binders in air-laid
products.
Promising technology is evolving for using waste or low-grade wood blended with plastics
to matoZSSyofWgSperformancefeMorcel composite products. This technologyprovides a
stofeCT for producing advanced materials that tak advantage of the enhanced properties of both
wood and[plastics. B!refits associated with thes4 composite products include light weight and
improved properties (Youngquist and others 1992).
Brooks (1990) reviewed the history of technology development for the Production and use of
moldable wood products and air-laid nonwoven ^iat processes and products. Mo dable.wood -
S™£?ctmousing technologies developed by Deutsche Fibril in West Germany (Brooks 1990),
S^?SSSSoSSSLl Grove (1966). Caron and Allen (1966ab 1968), and Grove
andI Caron (1966]Jin the United States involved me use of wood fibers and binder icons.
In the early 1970s, Brooks (1990) developed
i . * i**1!. _ .. *__ _ __^,V»j»-. *~i*-» ,-»*-» xTM^rli O f'nATT
a process for producing a very flexible mat using
. . • • x*v _ ._ _ ^_i___^.*-- fm Cn+* m/-*»v^T-*«in'in rr \\Jt~\tn\f\
; aeveiopea a piuuc&t. iui jji^uu^^g, <*. ,~j — —-- . ---- <=>
atteinoomfl
with nonwood materials were reviewed by Wgqmst and Rowell (1989) Then ^aper^ncmded
discussion of the materials and properties of corhposites consisting of wood-biomass, wood
metal, wood-plastic, wood-glass, and wood-synthetic fibers.
i^
ed
ot bonding S-laid woodpolypropylene fiber composites when maleated polypropylene
was used as a coupling agent between wood and plastic materials.
Wood fiber and old newspaper composites provide a favorable
ese fibers can be chemically modified using an acetylation process. When these materials are
££SSi£^l£Wto P-els posfes greatly improved f-nsion^bi^ properties
and reduced susceptibility to biodegradation by decay fungi (Krzysik and others 1993).
Our research plan called for completing a systematic, statistically valid series of experiments
that com^a?ed&e mechanical and dimensional stability properties of flat panel composites made
from the following virgin and postconsumer wastewood and plastics:
AL Series 1 . PET systems
. Virgin wood fiber, virgin polyester fibe : (VPET), and phenolic resin (PR)
•• Virgin wood fiber, recycled polyester (RPET) fiber, and phenolic resin
• Demolition wastewood fiber, virgin PET fiber, and phenolic resin
-------
. Demolition wastewood fiber, recycled PET fiber, and phenolic resin
AL Series 2. HDPE systems
. Virgin wood fiber and granulated virgin high density polyethylene (VHDPE)
. Virgin wood fiber and granulated recycled high density polyethylene (RHDPE)
. Demolition wastewood fiber and granulated VHDPE
. Demolition wastewood fiber and granulated RHDPE
materials.
GENERAL PROCEDURES
proceeded through the
insure that umtotm machine and cros s
basis; (b) converting raw
weight; (e) consolidating
• -~-\ from which test
webs could be produced on a routine
use in our FPL air-forming equipment;
ectina and istacKing the webs to produce mats of a given
pS me s undersufficient heat and pressure to produce
platen Prcj>^ _^. m mlttino. specific test specimens; and
and AL-4.
TASK AL-1. RAW MATERIALS PREP
The raw materials studied in the ^-fonn^ portion
generaTclaSsTceUulosic fibers, plastics, and additives (Table 1).
ARATION
iI ,
are discussed in Tasks AL-3
^ program fall into three
Fibers
Two basic types of wood fiber were
The first was a virgin western h^'^^
the AL Series 1 and AL Series 2 —
/hich was produced in a pressurized
si was a vugm w^oi~i" **-« (,v,:r,0 The chios were steamed for 2 min at 759
lisk refiner from 100-percent pdp-g^rade^hip^ ine ^ ^ ^ ^ &
soften them t^^^^^SKus strands made o| mdividuaj ^ers, pieces
fibrous
fibers.
area. The demolition ^*S^cSSlSS offee volume of material needed I for tins
This process required pilot-sc ^e/e^f .^K^t was so old could even be processed into a
and softwoods wouid be feasib.e ,„ use
SEE.
-------
as a postconsumer wastewood fiber source. The wood waste chips were shredded,
harnmermilled, and cleaned before being pressure refined in a manner similar to the hemlock.
Laboratory trials conducted at FPL confirmed tiat fiber produced from these wood chips was very
similar in appearance and processing capability to that of western hemlock.
Both the hemlock fibers and demolition wood fibers were screened through a +0.9-mm
screen to remove the fine dust like material. Nineteen percent of the hemlock material was
removed through screening, and approximately 17 percent of the demolition wood was removed as
fines. The screening process was necessary for the Series 1 experiments because phenolic resin
was used as a binder for the experimental pane] s. In AL Series 2, phenolic resin was not used
and, therefore, the wood fiber was not screened.
Old newspapers were used in an ancillary experiment to determine what effect it would have
when added to hardboard. To be used in this study, the newspaper had to be reduced back to fiber
form. The refiberization involved hammermillihg followed by repulping. The fibers were then
mechanically dewatered and ovendried to a moisture content between 30 and 40 percent. They
were again hammermilled and then dried to a final moisture content of 4 to 5 percent. Half of the
ONP fibers was used at this point. The other half was hammermilled again using a smaller screen
to obtain a smaller fiber.
Plastics
The virgin polyester (VPET) was 5.5 denier (6.1 x 10"^kg/m), 38 mm long, crimped, and
had a softening temperature greater than 215°C.J The recycled polyester fiber was spun from
recycled soft drink containers and was 6.00 denier, 51 mm long, and crimped. For all of the air-
laid experiments, this fiber was used as a matrix fiber which served to hold the wood fibers
together within the mat.
The virgin high density polyethylene (VHDPE) was a blow-molding polymer normally used
as a feed stock for plastic milk bottles. It came in pellet form with a nominal melt flow index of
0.7. Because the HDPE pellets were too large tb be used in the air-laid mat forming process, they
were cryogenically ground to a nominal (-)35 mesh size. The recycled HDPE was prepared from
milk bottles which had been chopped into approximately 6-mm flakes. These flakes were also
cryogenically ground to a (-)35 mesh size in a manner similar to the virgin HDPE. The melt flow
index of the recycled HDPE was also 0.7.
We made a very intensive effort to obtain recycled HDPE in fiber form, but were
unsuccessful. Although we had granulated RHDPE available to blend with the wood fiber, a
textile fiber was preferred if it was available because previous research indicated that a granulated
thermoplastic had a greater tendency to shake out of the mat during the fabrication process.
Mr. Harry Fitzgerald, a well-known consultant in the textile industry, was assigned the task
of trying to locate a commercial source of HDPE fibers. He made hundreds of contacts with
various recycling firms and with companies that! process recycled plastics into fibrous forms of one
type or another. He also approached commercial laboratories to determine if they could produce
this type of fiber. All of these contacts were negative. We found there were a number of reasons it
was not available. First of all, economic factors make it very difficult to produce a recycled HDPE
fiber cheaper than a virgin HDPE fiber. The cost per pound of the virgin resin to produce HDPE
fibers is less than the cost of collecting, sorting,]cleaning, reprocessing, and spinning recycled
HDPE. Secondly, it is very difficult to get a 100 percent pure grade of HDPE. With impure
plastic resin, the melted plastic filament usually has a large variability in diameter. Because of this,
it often breaks as it is being spun. This results in chunks of plastic being thrown out from the
-------
spinnerette. These problems cause production of
virgin HDPE processed in a similar fashion. ,
worthwhile to try to produce a recycled HDPE
a low quality fiber which is not competitive with
Because of the lack of commercial availability of this type of material we felt that it was
"In,. ^ *~, *„ „„,*„.,» » r,»™rlPH RDPF, fi^er in the laboratory. We had a hot-melt extr
worthwhile to try to produce a recycieu n^-ro nuci m u^ ia^^^j. .. ~ Y 7;Wyn -11, u^«i»
for which we purchased a spinner head to make the fibers. When the recycled HDPE milk bottle
flakes were introduced into the extruder we found that the material was too viscous for our
equipment. We then coupled the spinner head to a vertical single-screw extruder in *n effort to
Screase the head pressure. This change resulted in some improvement, but we were still unable to
produce an acceptably uniform fiber with this eq lipment.
Since our work indicated that it was virtually impossible to buy or produce a recycled HDPE
fiber we found a tackifier, that when sprayed ori the wood fiber prior to web formation, resulted
in the granular HDPE being retained in the web during the web formation process.
Additives
Phenolic Resin--
The binder for the AL Series 1 panels was
a liquid phenolic resin (PR) which was sprayed on
the wood fiber at 25°C as it rotated in a drum-type blender. The resin was applied with a
pneumatic spray gun at a level of 10 percent solids by weight. The resin had a solids content of 51
to 53 percent, a pH of 9.5 to 10.0 at 25°C, and ii infinitely dilutable in water. After application of
the reS the wood fiber, the blend was allowed to air dry over night. This drying period was
necessary to prevent the wood fibers from cloggW the Rando-Webber forming equipment
because the resin was tacky immediately after applying it to the wood fiber.
Tarkifier--
In the AL Series 2 boards, the wood fiber was blended with granulated HDPE. During the
processing, web manufacturing, and panel makikg, we found that a lot of the.HDPE, was being
Lt throughout the process. This was because the HDPE granules were not held in the matmc of
the nonwwen mat. We discovered that the addition of a retention aid in the form of a tackifier on
the wo™fiber solved this problem. We found ti^e addition of this material almost eliminated the
loss of granulated HDPE from the fiber mats as they moved through the processmg steps
necessary to produce test panels. Preliminary letting also indicated that Je tackifier, which was a
wax emulsion of oxidized low molecular weigh{polyethylene (E-10), did not have an adverse
effect on the properties of the resultant test panels. This tackrfier was applied to the wood fibers m
a rotating drum blender with an air spVay gun in a manner similar to the way the phenolic resin was
applied to the wood fibers in the AL Series 1 stiidy.
Preparation of Second-generation Kprvcled Panels
The recyclability part of the study (Task 4 j required that we determine toe feasibility of
recyclmg panels made for AL Series 2, which contained DF and RHDPE. The panels were cut up
into approximately 2- to 4-cm. squares for processing. Hammermilling was found to reduce the
fiber length too much and this operation created too many fines. We therefore found we had to
recycle the boards through the pressurized refiner to be able to produce the desired fiber length
and bundles. Before refining, the composite material was softened by presteamingior 2CI rmnat
68 9 kPa steam pressure. Refining was done using course plates set at a gap of 0 127 mm. Wnen
finished, the fiber had an approximate moisture content of 60 percent, requiring it to be dried
before further processing. This was done by spreading it out m a thin layer to aur dry for 2 days
after which it was ready for forming into a nonwoven web. This procedure resulted in a high
quality fiber with few noticeable fines.
10
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TASK AL-2. LABORATORY METHODS FOR MAKING COMPOSITES
Equipment Additions and Modifications
The air-laid portion of this study used nonwoven mats made with a 305-mm-wide, lab scale,
Rando-Webber forming machine. Our initial efforts in this research program focused on
attempting to improve the density profile across the web as it was produced. Preliminary
experiments indicated that there was generally more fiber at the center of the web as it formed on
the condenser screen than there was on the edges of the mat. Thus, a density gradient across the
web was created. This, in turn, caused a density gradient in the test panels and erroneous test
results. The effect of the density gradient in an individual web was magnified in the finished panel
because as many as six mats were stacked toget ler to produce a finished test panel of the desired
thickness and specific gravity.
A number of alterations and improvements were made to the machine in an effort to minimize
the density gradient across the web. First, the djrive for the elevator which is used to feed the fiber
to the feed rolls (Figure 1) was separated from trie stripper apron. This allowed both the elevator
and the stripper to be driven independently, andlprovided more flexibility in delivering fiber to the
feed rolls. Further improvement in the web denlsity gradient was made by devising baffles in the
feeder condenser to divert air flow from the center of the feeder condenser. This directed more
fiber to the edges of the mat and away from the
center as the fiber was fed into the feed rolls.
Several other changes were made in an effort to further improve density profiles. New feed
rolls were machined with a variety of surface patterns to handle the various fibers and fiber blends
used in this experiment. These new feed rolls have helped to improve continuous feeding of the
fiber into the lickerin, thus allowing a more constant thickness formation of mat in the machine
direction. A new nose bar was purchased which had a larger radius than the one used previously.
The original nose bar was very sharp and caused some fiber breakage and the generation of a
relatively large proportion of fine material. The larger radius bar improved both of these problems
dramatically. Further improvement was made in reducing fiber damage and fines creation by using
a lickerin with many fewer teeth per increment. Finally, we found it is necessary to use different
patterns and styles of needles in the web needier, depending upon the material being processed and
the desired configuration of the final web produjct.
Two hydraulically operated, steam heatedj platten presses were obtained through government
surplus from the Agricultural Research Service at Peoria, Illinois. These two presses dramatically
improved our capability to make high quality panels for this project in a timely manner. Although
the presses were serviceable, considerable upgrading and retrofitting was necessary to bring them
to an acceptable condition for use on this study. Both presses were steam heated and required new
steam controls and temperature regulators. The platens were machined to remove surface flaws
and bring them back into parallel alignment. Exhaust fans were installed for the presses, and
exhaust hoods were placed above them to remove vapors present when panels are pressed. Both
presses were also fitted with thickness measuring gauges, thermocouple meters, and cold water
plumbing and controls to provide rapid platen cool down capabilities.
Web Selection Criteria
Webs measuring 305 by 305 mm were weighed and sorted into various weight categories.
Appropriate webs were then selectively stacked to arrive at the target panel basis weight. All web
sections containing any type of defect were discarded at this point in the panel fabrication process.
11
-------
target specific gravity. A manually controlled,
Panel Fabrication
The 305- by 305-rnm mats were stacked so as to construct multi-layer mattresses of the panel
steam heated press was used to press all panels.
Pressing was at 190°C for 4 min at a maximum pressure of 8.47 MPa; 3 min of cooling time were
needed while the board was still under compaction to reduce steam vapor pressure in the pressed
board and to maintain the target thickness. Stojps were used to produce 3.2-mm-thick panels.
After, pressing, the panels were trimmed to a final size of 279 by 279 mm.
TASK AL-3. DEVELOPMENT OF A PERFORMANCE DATABASE
Under this task, we carried out the performance evaluation of the panels made for AL Series
1 (PET) systems and AL Series 2 (HDPE) systems. Within each of these two series, a comparison
of virgin and recycled materials was made. A sjtatistically valid quantitative comparison of the
range of mechanical and dimensional stability properties obtainable for air-formed composites
made from virgin and wastewood fibers and two major postconsumer waste plastics is presented in
the following discussion.
Prior to mechanical and physical property testing at room temperature (about 23°C) for both
AL Series 1 and AL Series 2 studies, the specirnens were conditioned at 65 percent relative
humidity (RH) and 20°C until equilibrium conditions were achieved. Specimens had minimal
exposure to ambient humidity during the time required to complete the testing. Three-point static
bending modulus of rupture (MOR) and modules of elasticity (MOE) and tensile strength and MOE
tests were performed in conformance with ASTM D1037 (ASTM 1991) using an Instron testing
machine. Impact energy was measured in conformance with TAPPI standard T803 om-88 (TAPPI
1989) using a General Electric impact tester. T lickness swell and water absorption measurements
were made by immersing specimens in water in a horizontal position for 24 h at ambient
temperature. This test was performed in confoimance with ASTM D1037. For linear expansion
tests, the specimens were first ovendried prior t) taking specimen length measurements. Linear
expansion tests were conducted on length measurements made at equilibrium at 30, 65, and
90 percent RH at 27°C. Linear expansion values were calculated over the following ranges:
ovendry to 30 percent RH, ovendry to 65 percejnt RH, and ovendryjo 90 percent RH. Linear
expansion tests were determined in conformanc
with ASTM D1037.
The mechanical, water resistance, and din ensional stability properties of the composite
panels in AL Series 1 and 2 are presented in Figures 2 through 21. Each of these figures includes
four sets of bar graphs. The first two sets of bar graphs compare performances between
composites made with virgin or recycled plastic blended with hemlock fiber in one set and
demolition fiber in the second set. Statistical results are discussed for these comparisons. The
third and fourth sets of bar graphs in each figure are included for the convenience of the reader and
present the same data presented in bar graph setjs 1 and 2, but rearranged to point out different
comparisons between different combinations of materials.
AL Series 1. PET Systems
Background Information—
This experimental series compared the performance of panels made from virgin wood fiber,
virgin polyester fiber, recycled demolition wastewood fiber and recycled polyester fiber. The
virgin wood fiber was hemlock (HF) and the demolition wastewood fiber (DP) came from
fiberized wood waste from demolished buildings. The recycled polyester fiber was respun from
recycled soft drink bottles (Table 1).
12
-------
Experimental Details—
The experiment consisted of four formulations of wood fiber/synthetic fiber/phenolic resin
contents, based on the ovendry fiber weight (Table 2). A total of 160 panels was made for this AL
Series 1 experiment. Each formulation was considered a replicated set that consisted of 40
individual panels. A total of 15 panels was then selected from each set of 40 based upon how
close they were to the target specific gravity (Table 3). The selected panels were then cut into
specimens for mechanical and physical property testing.
Mechanical and physical property tests were conducted on specimens cut from the selected
experimental panels. For all of the formulation's, each panel was weighed, measured and the
specific gravity was calculated. Panels, from which test specimens came, were selected on the
basis of which ones were closest to the target specific gravity of 1.0 ± 0.03 (Table 3), and the
target thickness of 3.2 mm. This method of panel selection allowed us to narrow the variability in
specific gravity between individual experimental panels.
In this test series, no data outliers were found. Each data set was tested for normality at the
95 percent confidence level using the Shapiro-Wilk statistical analysis. Because there was no
indication of non-normality, an analysis of variance was performed and the means were compared
at the 95 percent confidence level using Tukey'k method of multiple comparisons.
Results and Discussion--
Mechanical and physical property data are presented in Table 4 and in Figures 2 to 11 as bar
charts. In all of these figures, bars connected by a solid line indicate that the results are not
significantly different at the 95 percent confidence level. A gap in the line indicates a statistically
significant difference exists. Each value is an average of 20 tests, with the exception of impact
energy, which is an average of 5 tests.
Mechanical properties-The panels made with the HF/VPET formulation had the highest
bending MOR value at 50.6 MPa, although no statistically significant differences were observed
for MOR values for either wood fiber or PET vjariations (Figure 2).
A pattern different to that found for bending MOR values was noted for MOE values
(Figure 3). In both wood fiber groups, the MOE values of boards containing RPET were
significantly higher than those of boards contaii ing VPET. The total average increase for this
property was 16 percent for both groups.
For the HF/VPET formulation, tensile strength was 33.0 MPa, whereas it was 14 percent
less when RPET fibers were used (Figure 4). However, when RPET or VPET fibers were used
with DF fibers, no significant differences were noted.
In contrast to tensile strength, tensile modulus (MOE) (Figure 5) for both HF and DF
formulations were increased by 6 and 7 percent by incorporating RPET fibers, although these
differences were not statistically significant.
Impact energy of specimens from the HF md DF formulations showed a consistent trend
(Figure 6). Formulations containing VPET fibers had impact energy values that were higher by
20 and 10 percent, respectively, compared to formulations containing RPET.
Physical and dimensional stability properties—A 24-h water soak test was used to measure
thickness swell and water absorption of boards made from the four formulations. In this AL
Series 1 study, formulation had a consistent influence on thickness swell values (Figure 7).
Specimens of HF/RPET had the smallest thickness swell values at 22.3 percent, whereas
specimens of the DF/VPET formulation had the, largest values at 29.8 percent. For these two
groups, the values obtained were statistically different from each other.
1; ' ' •'-
-------
Results similar to those for the thickness
tests, except that no statistical differences were
Linear expansion values at 30 percent RH
and 90-percent RH conditions (Figures 10 anc
slightly higher values and were statistically different from
andDF/VPET.
swell test were observed for the water absorption
noted for any of the formulations (Figure 8).
were statistically equivalent (Figure 9). At the 65-
11), the HF/RPET and DF/RPET formulations had
the other two formulations of HF/VPET
Conclusions--
In general, the mechanical, water resistance and dimensional stability properties of all panels
made from recycled materials were all equivalent to similar properties obtained from panels
containing all virgin or virgin/recycled materials. Therefore, the recycled ingredients tested in AL
Series 1 could replace virgin materials with minor consequences.
AL Series 2. HDPE Systems
Background Information--
This experimental series compared the performance of panels made from virgin wood fiber,
virgin granulated high density polyethylene (VHDPE), virgin polyester fiber (VPET), recycled
demolition waste fiber (DF), and postconsumer recycled high density polyethylene (RHDPE)
particles. The virgin wood fiber was hemlock (HF) and the demolition wastewood fiber (DF)
came from fiberized waste from demolished buildings. The recycled high density polyethylene
(RHDPE) particles came from chipped and ground postconsumer milk bottles.
Experimental Details—
This experiment was similar to AL Series' 1, except that VHDPE or RHDPE were used as the
thermoplastic panel bonding resin, in place of the thermosetting phenolic resin. A tackifier
(Epolene E-10) was used in this Series as an aid in retaining the granulated HDPE in the web
during the formation process. The experiment consisted of four formulations of wood
fiber/granulated HDPE/PET fiber/tackifier content based on ovendry fiber weight (Table 5).
A total of 160 panels (40 per formulation) was made for this AL Series 2 experiment.
For the AL Series 1 composite panels, each panel was weighed, measured and the specific
gravity (SG) was calculated. The panels, from which test specimens were obtained, were then
selected on the basis of which panels were closest to the target SG of 1.0 and target thickness of
3.2 mm. We found that this method of selection led to a large variability in specimen specific
gravity due to a considerable variation in specific gravity within the panel. This fact resulted in us
having to make many more panels than were needed to do the actual tests. Therefore, a change in
the method of specimen selection was made foil the AL Series 2 portion of the program.
Specimens were cut from test panels and the specimen specific gravities were calculated. Then,
only specimens closest to the specific gravity of 1.0 were used for testing. For AL Series 2 the
acceptable range for specimen SG was 1.0 ± O.|06 (Table 6).
Data were first checked for unusual values. Where there were outliers, the analysis was done
with and without these values. Each data set was tested for normality at the 95 percent confidence
level using the Shapiro-Wilk statistical analysis!. If the Shapiro-Wilk statistic indicated that the
data were normal, an analysis of variance was djOne and the means were compared at the 95 percent
confidence level using Tukey's method of multiple comparisons. In the cases where normality
was rejected, a ranked analysis of variance was
using Tukey's method of multiple comparisons
done and means (of ranks) were again compared
Results and Discussion--
Mechanical and physical property data are presented in Table 7 and Figures 12 to 21 as bar
charts. In all the figures, the bars connected by a solid line indicate that the results are not
-------
significantly different at the 95 percent confidence level. A gap in the line indicates that a
statistically significant difference exists. Each value is an average of 20 tests for static bending
MOR and MOE, 20 tests for tensile strength and MOE, 10 tests for impact energy, 40 tests for
water soak, and 25 tests for linear expansion.
Mechanical properties-The DF/VHDPE panels had the highest bending MOR value at 19.1
MPa, followed by 18.7 MPa for HF/RHDPE formulation (Figure 12). Generally no statistically
significant differences were observed for MOR values for either wood fiber or HDPE variations.
In contrast to MOR values, bending MOE values for panels containing HF/RHDPE exhibited
the highest value of 2.13 GPa. The panels made from DF/VHDPE formulation had the lowest
value of 1.75 GPa. No statistical differences were noted for MOE values for these test panels
(Figure 13).
For tensile strength, the highest value of
12.4 MPa was observed for the DF/VHDPE
formulation, whereas the DF/RHDPE panels vtare 7 percent lower (Figure 14). With both wood
fiber variations, the use of either virgin or recycled HDPE did not significantly influence tensile
strength values.
The tensile modulus of the HF/VHDPE panels had the highest value at 2.81 GPa, whereas
incorporation of RHDPE lowered these values!by 21 percent, and the noted difference was
statistically significant (Figure 15). The tensile modulus of the DF formulations were about equal,
averaging 2.11 GPa.
Impact energy values for specimens made from HF and DF fibers and for specimens made
from virgin or recycled HDPE were not statistically different from each other (Figure 16).
Physical and dimensional stability properties--A 24-h water soak test was used to measure
thickness swell and water absorption propertied of panels made from the four formulations.
Thickness swelling increased by an average of 22 percent as the formulation changed from
HF to DF, and the highest value of 53 percent >vas observed for the DF/RHDPE formulation
(Figure 17). It was particularly noticeable that
the use of RHDPE significantly influenced only the
DF formulation and not the HF formulation. The HF/RHDPE panels exhibited the lowest
thickness swell values of 43 percent.
In this study, formulation had a consister t influence on water absorption values (Figure 18).
Incorporating RHDPE with either type of wood fiber produced a statistically significant increase in
this property by 13 percent on the average. Specimens of the HF/VHDPE and DF/VHDPE
formulations exhibited the lowest water absorption values of 55 percent and 59 percent,
respectively. 1
Linear expansion values for all formulations at the 30 percent RH condition ranged from 0.15
to 0.17 percent (Figure 19). At 65 and 90 perdent RH, the HF/RHDPE and DF/RHDPE
formulations had slightly higher values (Figures 20 and 21). Generally, no obvious trends were
observed for linear expansion values at the 30,
formulations.
65, and 90 percent RH levels for any of the
Conclusions--
Mechanical and physical properties of panels containing virgin and recycled wood fiber and
virgin and recycled polyethylene milk bottle stock had equivalent property values. Therefore, as in
AL Series 1, the recycled materials used in AL
minor consequences.
Series 2 could also replace virgin materials with
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TASK AL-4. RECYCLABILITY
Background Information
The purpose of research presented here w as to study the recyclability of air-laid composites
back into an air-laid composite panel. For this series, the first-generation panels consisted of 60
percent DF, 30 percent RHDPE, 5 percent VPET and 5 percent E-10. The second-generation
panels contained 40 percent DF, 20 percent refiberized first-generation, 30 percent RHDPE,
5 percent VPET, and 5 percent E-10. I
To be able to recycle the panels made from the first-generation panels, they first had to be cut
into approximately 2- by 4-cm squares and thejn processed into fiber form through pressurized
refining. It has been suggested that this process of fiberizing the first-generation panel created
shorter and narrower fiber bundles and more small particles, or fines, than were present in the
materials that originally were used to make the jfirst-generation panels. This may have allowed a
better interfelting of the fibers and could have allowed the fines to fill in gaps between the plastic
and wood fibers in the second-generation panels.
Experimental Details
The experiment involved two formulations of wood fiber, granulated HOPE, PET fiber, and
tackifier based upon the ovendry fiber weight (Table 8). Each formulation was considered a
replicated set that consisted of 40 individual panels. A total of 80 boards was made for this
experiment. The panels of each formulation we re cut into specimens for testing mechanical and
physical properties (Table 9).
The data were checked for unusual values. Where there were outliers, the analysis was done
both with and without these values in the data sj?t Each data set was tested for normality at the 95
percent confidence level using the Shapiro-Wilk statistical analysis technique. If the Shapiro-Wilk
statistic indicated that the data were normal, an analysis of variance was done and the means were
compared at the 95 percent confidence level using Tukey's method of multiple comparisons. In the
cases where normality was rejected, a ranked analysis of variance was done and means (of ranks)
were again compared using the method of Tukey.
Mechanical and physical property tests were conducted on specimens cut from the
experimental panels which were made according to AL Series 2 procedures, and test procedures
for Task 4 were similar to those used for Task 3, AL Series 1 and 2.
Results and Discussion
Mechanical and physical property data are presented in Table 10 and Figures 22 to 31 as bar
charts. These charts are described in the Results and Discussion section for AL Series 2. Each bar
on a chart is an average of 20 tests for static bending MOR and MOE, 20 tests for tensile strength
and MOE, 10 tests for impact energy, 40 tests for water soak, and 25 tests for linear expansion.
Mechanical Properties—
The second-generation panels had higher
jending modulus of rupture (MOR) values at 19.6
MPa, compared to 17.4 MPa for the first-generation formulation (Figure 22). On the other hand,
the bending MOE values of panels containing the first-generation formulation exhibited higher
values than the second-generation panels (i.e., 2.01 to 1.77 GPa, respectively (Figure 23)). No
statistical differences were noted for the formulations.
16
-------
Sctthatlncorporationo
17
-------
SECTION 5
STUDIES ON MELT-BLENDED COMPOSITES
from four waste or virgin plastics three waste
iroHi luu research program.
led out in this pnase 01 UK ^ . A»J?^,
GENERAL COMMENTS
Systematic comparisons of comP°s1^ „, carried Out in this phase oi tne rescaiun F^s—
lignocellulosics, and one ^^^K^^^^g recycled milk bottle high density
Wood flour (WF) was used as the ^erj ^^feosity of HDPE-MB leads to potential
™?vrthvlene (HDPE-MB) because the high melt yscosuy ™™f & j lt viscosities of
_ , ^ ^L.j,. A/TD ^ rpfprs to Task 4.
to Task 3; study MB-5 refers to Task 4.
• • 1VMODV
Old newspaper (ONP) in virgin polypropy
at three filler/plastic ratios
ene (VPP) (melt flow index (MFI) 3,12, and 30)
. WF in VPP (MFI 3, 12, and 30) at one
. Epolene E43 at one level (coupling agent)
Study MB-2
. ONP or cellulose (BW-40) in VPP (MFI
filler/plastic ratio
12) at one filler/plastic ratio
polypropylene at one filler/plastic ratio
/
. E43 at one level (coupling agent)
Study MB -3
. ONP in VPP (MFI 12) at one
. E43 or Epolene G3002 at zero or 3
Study MB-4
. G3002 at one level (coupling agent)
Study MB-5 (Recyclability)
• System 1
. ONP in VPP (MFI 12) at one ONP/PI
. No coupling agent
System 2
filler/plastic ratio
percent (coupling agent)
ketchup bottle polypropylene (KPP) or recycled
ratio
18
-------
• WF in HDPE from milk bottles (HDPE-MB)
• No coupling agent
System 3
• Air-laid composite as filler in HDPE-MB
• No coupling agent
GENERAL PROCEDURES
at one WF/ONP ratio
at one filler/HDPE-MB ratio
lerally
apparatus; (b) quantitative dry mixing; (c) melt^nding, ^injecuon^moiu^ ^ ^ H£raissed ^
^j /_ \ ,,,-arviont rvf nrnnftrtlP.S. EllOltS Ul UllS
appararas; w qumiuuiuv^"^ "-~—o> x-/- .
and (e) measurement of properties. Efforts in this
Task 1, and to (c) and (d) in Task 2. All property
Most studies were statistically designed and
« . ,1 r*_n .:««. "LJ,-*TT7*v\7or \xr(* nntp, tnf
;J1Q1I1HS \*-*-y JJiJt'^'l-lvri1 iAAWJ.v*iii^ v^. ^— c —
program related to (a) and (b) are discussed
data are discussed in Tasks 3 and 4.
analyzed, and the results of those analyses are
j. _i_j.:«<-:««l rn-iolrrc-if Vioc twi~> nnnnsin0
.__1L.^ .,- . ^^r,fiH<,n^A IP.VP.I nf 95 oercent. Discussion, however, centers on me
performance.
TASK MB-1. RAW MATERIALS PREPARATION
Three general classes of raw materials were studied: plastics, cellulosics, and additives.
These materials are described in Table 11.
Plastics
Plastics act as the matrix in the composite.
In this program we employed virgin
and the program would have been incomplete w
for melt-processed composites-its relatively hig
difficulties in melt processing operations. Despi
beverage bottles, we did not include that material
19
nout 11. riowevei, jnLjri^—iva-u n"^ ~"~ ~-
ti melt viscosity (low MFI) can lead to some
te the ready availability of PET from recycled
1 in the melt-processing portion of the prograr
-------
because PET melts at temperatures well above those at which cellulose begins rapid thermal
degradation. * .. * ' '
or (Ball atd Jewel BP-68-SCS, Mimgranulator) was
(ersj iviore JLUIU.IGLIGIJXHI. VYHO ^.~,~~~
serial, with its high content of clays and other
5 over ONP in composites. The OMG material
obtained and put into operation.
Cellulosics
materials, possessed advantages or disadvantage
is of course, readily separable from MSW.
properties were seen.
-------
grinding methods, and on obtaining ONP fiber L the fines from recyling pulp operations. We
expect some of these options will be pursued in future cooperative programs.
Additives
Additives aid the dispersion of filler into the matrix plastic and/or enhance the bonding (act as
a "coupling agent") between filler and matrix. Sbch materials can be very helpful to the
proceSility and/or the mechanical properties of these composites by enhancing fee compatibility
oftaffi$Tnpolar matrix (PP, HDPE) with ^e highly polar filler (ceUulosicsIntos
programfwe restricted ourselves to Eastman Epkenes These are maleated&*?*&%**
"waxes" in which the small degree of maleation provides polar groups capable of bonding to the
cSse wMe the polypropylene segments in theory offer compatibility with the P°^opylene
matrix. Earlier work demonstrated that they improved the mechanical properties of WF/PP
111 . xUi—_ 1 r>m TV/T,,^O ^A nfh<*ra 1 QQl a M Although these additives are in the $.
composites (Olsen 1991, Myers and others 199
t«
-------
We carried out several blending experiments with the University of Toronto's K-mixer and
were able to verify their findings. Microscopic | examination of molded samples made from the K-
mixer blends showed the blends to be more uni-form than those from extrusion blending.
Moreover, preliminary measurements of mechalnical properties showed that the K-mixer blends of
ONP and PP possessed better mechanical properties than those of WF in PP—as they should if the
ONP fibers are well-dispersed. |
> . I '
As a consequence of these results, a 1-L IjL-mixer was ordered and placed into operation at
the FPL shortly before the end of the first year pf this program. During the interim, compounding
with wastepaper fibers was carried out at the Uhiversity of Toronto. Upon receipt of the K-mixer
at the FPL, screening experiments were carried put to approximately optimize the operating
parameters for blending wastepapers and several plastics, as a prerequisite to conducting the
studies described in Task 3. The relevant parameters included chamber starting temperature, blade
speed, mixing time, batch size, cooling water flow rate, and discharge temperature. As noted
under Task 1, Task 3, Study MB-2 also describes a study that included comparisons of the
properties of composites (non-ONP) prepared by compounding in the 1-L K-mixer or in the
laboratory single-screw extruder. ]
Compounding of Composites for Commercial Applications
As in Task 1, the success in preparing O£JP/plastic composites with the laboratory-sized
K-mixer by no means meant that similar succesjs would be met with that type of apparatus on a
commercial scale or that the K-mixer was the b$st compounder for commercial applications of
ONP/plastic composites. Consequently, our Dl^E. program included tests of scale-up to a 40-L
pilot plant K-mixer and of the ability of a pilot plant twin-screw extruder to compound ONP and
PP (Task 5). In addition, we have held discussions on this aspect with a variety of compounding
equipment manufacturers and expect to carry oiit a cooperative program to compare several types
of equipment. ,1
TASK MB-3. DEVELOPMENT OF A IfERFORMANCE DATABASE
I
Under this task, we carried out several studies which were essentially independent of one
another. In some cases, the same parameter wajs examined in the context of different studies; this
duplication allowed us to optimize the significance of conclusions within each study. We describe
each study separately in the following. j
i
In all studies, test specimens were prepared by injection molding using a Frohring Minijector
model SP50. At least five specimens of each blend were tested for each mechanical property.
After molding, the specimens were stored over desiccant for at least 3 days before testing.
Mechanical properties were measured on the dry specimens at approximately 23 C. Specimens and
test methods followed ASTM specifications (ASTM 1984a-c, 1990). Strain rates were 5 rnm/min
for tensile and 1.5 mm/min for flexure tests. Table 12 summarizes the mean standard deviations
observed in the program for various mechanical properties.
|
2:1
-------
f PP MQl
_
form (Myers and others 1992).
^^i^^'^^^sxss
3^<^™'v^
known for our composite systems.
'
Matrix A
PPMFI
ONP/PP ratio
Matrix B
Filler type
PPMFI
3,12, or 30 g/10 min
32, 37, 42
by weight
WF or ONP (42 percent by weight)
3, 12, or 30 g/10 min
Ml, viscosittes were measured on
and apparent ™Sd Ste^iusioninaBrabender
^^
ateotLo^:
. No interaction terms were observed in *e sjtistica! analysis (Table !4).
ofPPMHwerenegHsMefromiprac^viewpoint-tHeyweree^er
no,
23
-------
hange (Tables 14 and 15)
greatest effects of ONP/PP ratio were on
increase at best (Table 15).
tnodutas, but on!y amounted to a 12-percent
• r:- -3£ Table 16 summarizes the values obtained
nt melt viscosities are shown in F igure 36 >. lan Q0 ^ sheaj. rates; ^
wttageeffects on composite performance.
ONP
ge changes
view.
composites, it aj
and PP mt is, viscosity
performance.
ffect
rnmpnunder
Pp at a 42/58
Jlle
nri Plasti
Iditic
included as the customary baseline
dSnces translate into composite properies?
24
-------
(c) Coupling agents may be incorporated
material at the interface where it is active
into composites in different ways to concentrate the
Does the addition of solid powdered E43 in its
anhydride form produce differences in mechanical properties from precoating fiber with the
emulsified potassium form of E43?
(d) Fibrous fillers are more effective rein forcing agents if their length is above a so-called
. critical value and if they are fully disaggregated into individual fibers. The high shear forces
existing in the K-mixer should produce good fiber dispersion but probably will
simultaneously reduce the fiber length. In contrast, a single-screw extruder will probably be
less efficient in dispersing the fibers but less likely to reduce the fiber length. What is the net
effect of these influences on mechanical f roperties?
Portions of this study were published (Gonzalcs and others 1992).
Experimental Details—
Because ONP could not be dispersed into the plastics using a single-screw extruder, it was
necessary to divide this study into two separate experiments. Experiments A and B were both three
variable, two-level full-factorial matrices that were replicated and carried out in random order.
Experiment A
Polymer
Filler
FormofE43
PPV (MFI12) or HDPB-MB
ONP or BW40 cellulose-
Powdered anhydride or anionic emulsion
The filler/polymer ratio was kept constant at 40/60 by weight. E43 was added at 5 percent of filler
by weight. Powdered anhydride was incorporated during melt-blending. Anionic emulsion was
precoated on filler by evaporating a slurry. Compounding was done with the 1-L K-mixer.
Experiment B
Polymer
Filler
Compounder
PPV (MFI 12) or HDP&-MB
WF or BW40 I
K-mixer or extruder
The filler/polymer ratio was the same as in Exp jriment A. E43 was added at 5 percent of filler by
weight, incorporated as the solid anhydride during melt-blending. Extruder was a 38-mm Modern
Plastics Machinery single-screw extruder.
For K-mixing, the fillers were mixed for approximately 1 min, polymer was added, and
mixing was continued for approximately anothe'r min. A 185°C discharge temperature and a speed
of 2800 rpm were used for the HDPE systems;Jfor PPV the conditions were 200°C and 3000 rprn.
Extrusion was carried out at 170, 180, and 190^ for the three barrel sections and 190°C for the die
and at a screw speed of 15 rpm. Other details were as in Study MB-1.
Results and Discussion--
Table 17 summarizes the mechanical property data. Tables 18 and 19 present the main
effects and two-way interactions found at the 95 percent confidence level. Figures 37 to 41
illustrate some of the observed effects by combining the results of Experiments A and B, and
Table 20 summarizes the "useful" percentage changes as a result of replacing HDPE-MB with PP,
WF with BW40, and BW40 with ONP. We note the following:
• A small preference existed for the solid form of E43, although the effects are relatively small arid
without practical significance (Table 18). It appears that concentrating the emulsified additive at
25
-------
the fiber/matrix interface by precoating the fibers was counteracted by the much lower chemical
reactivity of the potassium salt with the cellulose compared with the reactivity of the anhydride
with cellulose. Perhaps the E43 functions more to enhance dispersion of the cellulosic fillers
than to bond the cellulose to the polymer.
Little preference was shown for either comp Bunding method with WF or BW40 (Table 19).
However, those fillers are relatively easily dispersed, and we reiterate that the ONP could not be
melt-blended with the extruder employed here. Moreover, the small interaction terms between
filler and compounder also indicated some differences in dispersibility between WF and BW40.
In general, the fibrous fillers provided greatef reinforcement (greater strength and modulus)
(Figures 37 to 39) to either matrix than did the wood flour. Moreover, the inexpensive ONP
was, for the most part, at least as beneficial £s the cellulose fiber (BW40). Despite the fiber
breakage during melt processing, therefore, the fibrous fillers appear to have retained a greater
aspect ratio than did the wood flour.
The PPV composites consistently had greate:1 strength and modulus than did the HDPE-MB
composites (Figures 37 to 39, Table 20). This difference reflects the differences in the matrix
polymers themselves and not the fact that the HDPE-MB is recycled (cf. Task 4).
• Impact behavior was less straightforward in its reaction to variable changes. The most
meaningful change probably was the loss in notched impact upon substituting PP for HDPE-
MB (Figure 40); this too is consistent with th'e behavior of the matrices themselves.
Table 21 compares the properties of the system using recycled ingredients (HDPE-MB and
ONP) with those of the current commercial system (PPV and WF). Notched impact energy for the
"recycled" system was greatly improved wherejas all other properties were identical within
experimental error. Based on these mechanica
Fibrous cellulose or ONP caused greater re
properties, the recycled HDPE-MB/ONP system
could therefore advantageously substitute for the PPV/WF system. However, this mechanical
property advantage may be offset in some com nercial melt processes by the greater melt viscosity
of the HDPE-MB system.
Conclusions--
• Neither E43 form nor compounding method produced meaningful changes on composite
properties.
nforcement of PP and HDPE-MB than does WF.
ONP was essentially equivalent to cellulose as a reinforcing filler.
• PP composites were stronger and stiffer than HDPE-MB composites but possessed lower
notched impact. Composite properties qualitatively followed those of the matrix polymers.
• A recycled ONP/HDPE-MB system had at
commercial WF/PP system.
Studv MB-3. Coupling Aeent Comparison
east as good mechanical properties as the current:
Background Information--
Coupling agents are often used in composites to enhance the bonding between matrix and
filler, thereby increasing the stress transfer between the two phases and improving strength and
stiffness. As noted, previous studies demonstrated that Eastman Chemical's Epolene E43 and
G3002 enhanced some properties of WF/PP cojmposites (Olsen 1991; Myers and others 1991a,b),
the G3002 being particularly effective. Consequently, it was important to establish the relative
effects of these two Epolenes on the mechanical properties of ONP/PP composites.
26
-------
amounts of maleic anhydride have been graftec
These materials are relatively low molecular weight polypropylenes onto which small
(Table 22). They differ in molecular weight and
amount of grafted maleic anhydride per molecule; however, the frequency of anhydride groups
along the Epolene molecular chain (number of polymer repeat units per anhydride) was equal.
Portions of this study are in the process of publication (Sanadi and others, in press).
Experimental Details-
The ONP/PP composites were prepared a
: a 40/60 weight ratio containing no additive or
containing 3 percent by weight of E43 or G3002. Blending was performed with the K-mixer at
4600 rpm for 2 min to complete fiberization and then at 5500 rpm until the discharge temperature
of 200°C was reached. Batch sizes were 150 g and the matrix was replicated.
Results and Discussion--
It is important to note that this study was performed as a preliminary examination of the
effectiveness of these additives. Therefore, no statistical analysis of the results is presented. The
preliminary results are highly encouraging, however, and additional testing is planned.
Table 23 summarizes the mechanical properties. Strength values increased regularly from no
additive to E43 to G3002, as illustrated in Figures 42 and 43 where tensile strength increased 50
percent with G3002. Increase in tensile strength was accompanied by greater energy absorption
(100 percent with G3002) and by a 50 percent ilncrease in elongation with G3002. Figure 42
shows the tensile stress strain curves for the three systems and graphically illustrates the positive
effects of G3002. The greater energy absorptiojn during tensile failure was paralleled by increases
in unnotched impact energy (70 percent with G3002) (Figure 44). Surprisingly, the additives, if
anything, decreased the moduli.
Conclusions--
The higher molecular weight maleated po
ypropylene, G3002, was very beneficial to
composite strength, energy absorption, and unnptched impact behavior and warranted further
investigation. These increases indicate that G3002 is not acting as a strong coupling agent but
instead is probably enhancing dispersion of the libers and reducing aggregates which would act as
failure loci. Unnotched impact, for example, is more affected by removal of failure loci than is
notched impact because the notch already is an overwhelming failure locus. The apparently greater
interaction of G3002 with the PP relative to E43 may be attributable to the higher molecular weight
of G3002.
Study MB-4. Effects of Wastepapers a^d Waste Polvpropvlenes
Background--
In this study, we extended the database on waste plastic and wastepaper to define the
potential of some waste polypropylenes combined with old newspaper or old magazines. The
rationale for selecting the particular materials was discussed in Task 1. Most of this study has
been published (demons and Myers 1993).
27
-------
Experimental Details—
The following full-factorial matrix was inVesti
ONP/PPV systems were obtained from other s
the unfilled polymers.
Polymer
Filler
Filler/polymer ratio
Epolene G3002
Compounding
igated in replicate. Data for the comparable
udies. Comparisons were also made with each of
KPP or BPP
ONP or OMG
40/60 by weight
3 weight percent of filler
1-L K-mixer
The ONP and OMG were fed to the K-mixer as approximately 5-mm flakes. Blending was
carried out for approximately 1.5 min at 4,500 ipm, with a discharge temperature of 170°C to
190°C. Fiberizing the OMG in the K-mixer was more difficult than fiberizing ONP, resulting in
poorer dispersion of the OMG in the matrix plastic.
Results and Discussion--
Table 24 summarizes the mechanical properties, and Table 25 gives the results of the
statistical analysis of the two-variable, two-level factorial. No interactions were found at the 95
percent confidence level. Unnotched impact erlergy showed no statistically significant change,
probably because of the relatively large data scatter.
Table 26 shows the property changes brought about when 40 percent filler was added to each
polymer. Some property changes are illustrate^ in Figures 45 to 49. Both tensile and flexure
moduli improved more than 100 percent for KPP and more than 150 percent for BPP (Figure 47).
Modest improvements in strength properties were observed (~30 to 75 percent), but BPP was
again reinforced to a greater extent (Figure 46). Energy to maximum load and elongation at
maximum load decreased, and the related impact energy dropped sharply (e.g., -50 percent
reduction in unnotched impact energy for KPPland 80 percent for BPP) (Figures 48 and 49).
Thus, incorporating wastepaper fibers led to stiffer and stronger but more brittle materials
compared to the unfilled plastics. j
All tensile and flexure properties improved when OMG was replaced with ONP (Tables 24
and 25, Figures 46 and 47); the largest increases were 50 percent in tensile energy absorbed and
34 percent in tensile strength. The greater reinforcement produced by ONP is consistent with its
better fiberization and dispersion in- the the K-mixer. In addition, the large amounts of clay in
OMG may have diluted the total reinforcing effi ciency of the OMG.
When BPP was used instead of KPP, all properties except notched impact energy were
decreased by only small amounts (Table 25). The observed changes qualitatively followed the
properties of the matrices. The softer, weaker, and tougher BPP was more sensitive than was
KPP to filler addition, but overall BPP did not achieve as good a balance of properties as did KPP
(Table 24). In particular, the superior impact energy of the unfilled BPP (an ethylene-propylene
copolymer) was poorly transferred to the composite system. Nevertheless, both the KPP and BPP
composites had notched impacts significantly greater than that of the VPP composite (Figure 48).
Thus, BPP and KPP in certain composite applications could provide attractive cost and
performance benefits compared to the virgin PP|.
Conclusions--
• Adding 40 percent fiber to recycled plastics leads to stiffer, stronger, but more brittle materials.
The composite properties qualitatively followed those of the matrix plastics.
28
-------
OMG was more difficult to disperse than ONP
little less desirable than the balance producec
and produced a balance of properties that was a
by ONP.
Because ONP is more available, is more easily processed and produces better composite
properties, it offers more promise for commercial applications than does OMG.
Because BPP is less expensive, is more available, and produces a good balance of properties, it
should be of more interest than KPP and a useful replacement for virgin PP in some applications.
FURTHER CHARACTERIZATION OF
Background
MELT-BLENDED COMPOSITES
Work has been started to further characte ize melt-blended composites. Soil-block tests are
being conducted which will determine the susceptibility of the composites to fungal attack. Tests
have also been initiated on composite fire resistance and the effects of water absorption on
dimensional stability and mechanical properties. Only the water absorption experiments are
sufficiently advanced to report here.
Because of the hydrophilic nature of woe d and paper fiber, absorption of water could
adversely affect the performance of these composites. The following summarizes a preliminary
study investigating these water sorption effects.
Experimental Details
The following three composite systems v, ere investigated at a 42/58 weight ratio of filler to
PP. Systems 1 and 2 evaluate the effect of water exposure on ONP/PP composites and the
influence of G3002 coupling agent thereon. Systems 2 and 3 compare ONP and WF composites.
System 1. ONP/PP with 3 percent G3002 (by weight of the fiber)
System 2. ONP/PP without coupling age nt
System 3. WF/PP without coupling ager t
Two different exposure tests were performed:
(1) 24-h submergence in water at ambiem
temperature. This was performed because it
conforms to an ASTM standard for plastics.
(2) 24-h submergence in boiling water. This was performed because early screening tests
suggested a more severe exposure than th
short time.
Cantilever and impact properties, weight.
e above was needed to observe large changes in a
and thicknesses of composite specimens were
measured before (dry) and after (wet) the exposures. Weights and thicknesses were measured on
the cantilever specimens. Surface moisture was removed before any measurements were made.
-------
Results and Discussion
Tables 27 to 29 summarize the physical and mechanical properties before and after the water
exposures. Table 30 is a summary of the statistics for the study. The following points are
noteworthy:
• Little change in physical and mechanical properties was found after the 24-h water soak. Even at
this relatively high level of filler (42 percent), the encapsulation of the fibers by the
polypropylene matrix inhibits absorption of jwater.
• Comparing the property values before and after the 24-h water boil (last column of Tables 27
through 29), it is clear that the largest change occurred in cantilever modulus; it is the only
property that decreases by more than 10 percent after the exposure to boiling water. This
decrease in performance may be attributable to the decrease in modulus of the wood/paper fibers
themselves when exposed to moisture (Morton and Hearle 1962). The sharp rise in unnotched
impact in System 2 (Table 28) was inconsistent with the other two systems and was probably an
anomaly.
• Property decreases were probably independc nt of filler type and the presence of G3002. The
latter observation is consistent with other findings that indicate these maleated polypropylenes are
not strongly bonded to the filler.
Conclusions
• Additional testing is desirable to establish whether the moduli in other test modes are also
sensitive to moisture and to clarify the conclusion that impact is not altered by the water boil.
However, it seems likely that routine testing of sensitivity to moisture will not be necessary in the
future.
If the modulus reduction is shown to be
agents that actually bond to the wood
a practical problem, additional investigation of coupling
fiber rr ay be desirable.
TASK MB-4. RECYCLABILITY
Background
In Study MB-5, we investigated the effects of reprocessing on the mechanical and rheological
performance of three different composite blends. Although much work on the use of recycled
ingredients in composites has been published, very little work has been done to determine the
recyclability of the composites themselves. This is not to say that composites are not routinely
recycled as part of industrial processes, but fe\| studies have been published which quantify the
effects of continued recycling on the mechanical properties of the composite. One notable
exception is work performed at the University jof Toronto where composites made from virgin PP
or HDPE and telephone directories were put through several cycles of K-mixing and granulation
(Schmidt and others 1992). Small changes in some mechanical properties and large changes in
melt flow index were observed. However, recycling by repeated K-mixing is not a realistic
scenario, and we selected a cycle involving repeated extrusion instead.
30
-------
Experimental Details
Three composite formulations were investigated:
System 1 Virgin PP/40 percent ONP (no coupling agent)
System 2 HDPE-MB/40 percent WF |(no coupling agent)
System 3 HDPE-MB/40 percent air-laid composite (air-laid composite
contains 80 percent fiberized demolition wood/10 percent
phenolic resin/10 percent PET)
The first two systems are representative cjf melt-blended systems investigated in other parts
of the research program. The filler for System 3 was an air-laid composite panel selected to
determine the feasibility of recycling air-laid composites containing both a thermosetting resin and
the high melting PET by employing the air-laid
This feasibility was in question because neither
composite as a filler in a melt-processed composite.
the phenolic resin nor the PET would melt at the
temperatures suitable for melt processing a wood-containing composite but would retain their
particulate form; it was uncertain, therefore, wh1 at effect those ingredients would have on either the
processing or the mechanical properties of the resultant composite. To use the air-laid panel as a
filler, it was ground to -35 mesh and added to HDPE-MB at a level of 40 percent by weight.
Figure 50 is a processing flow chart for, the study. Each system was initially melt-blended in
a K-mixer and then granulated. The granulated! material was used as the initial feedstock for the
study. The material was then extruded and granulated five times, each extrusion and granulation
constituting a cycle. Initially, and after each cycle, enough material was removed for
mechanical/rheological measurement. Additional stabilizers were incorporated after the second and
fourth cycles to minimize polymer degradation.!
Each system was initially blended in the K-mixer at 5500 rpm for approximately 30 s with a
discharge temperature of 194°C. Extrusion was carried out in a Killion 25.4-mm single-screw
1 , n f* • ,-t , j ._ _P*1 _ _ f. -1 rt^O^t J -I f\f\Qf~\ * j_1 "I L — T — _— J _ _].!_.
extruder at 35 rpm with a temperature profile of
temperature of 204°C.
192°C and 199°C in the barrel and a die
Mechanical properties of injection-moldec specimens were measured initially and after each
cycle. The MFI was measured for System 1 only. MFI was not measured on the HDPE systems
because the high viscosity of HDPE-MB causes such low MFI values that the variability made the
measured values meaningless. Fiber dimensions of ONP and WF (Systems 1 and 2) were
measured by image analysis. Fibers from initial blends and after five cycles were measured.
Results are summarized as follows:
Fiber
ONP (initial)
ONP (5 cycles)
WF (initial)
WF (final)
Length
(microns)
225
138
162
111
31
Width
(microns)
19
18
88
.57
Aspect
ratio
11.9
7.4
2.0
2.0
-------
Results and Discussion
Tables 31 to 33 summarize the data and s atistics for each system, and Table 34 is a summary
of the analysis of variance. We note the following.
• For almost all of the mechanical and rheological properties for all three systems, very little
change was found as the material was recycle'd. However, several small, statistically significant,
changes in mechanical properties resulted from the first cycle. This was probably the result of
further mixing in the extruder and enhanced fiber dispersion as well as some minor fiber attrition.
The cantilever strength and modulus for System 1 dropped significantly during the fifth cycle.
These changes are not reflected in the tensile
practical point of view.
jroperties, however, and are not very large from a
• Mechanical properties for Systems 2 and 3 were roughly equal, showing that the air-laid filler
performed as well as wood flour. This fact demonstrates the potential for recycling air-laid
composites in this manner if the issues of cos:, quality, and quantity could be met.
• Over the course of five cycles, the length and. therefore, the aspect ratio of the ONP fiber
decreased. These decreases, however, were apparently not large enough to result in any large
reductions in composite performance. WF was reduced both in thickness and length, as smaller
bundles of wood fibers were sheared off the larger particles. These changes in dimension
resulted in no overall change in aspect ratio and, ultimately, composite performance.
Conclusion
We conclude from these results that there are no serious drawbacks to recycling these
representative melt-blended and air-laid composite systems through several melt-processing cycles.
32
-------
SECTION 6
PRODUCT APPLICATION AND
Efforts on Task 5 were not always easily
Therefore, we present Task 5 as a separate sec
COMMERCIAL IMPLEMENTATION
DATABASE EXTENSION (TASK 5)
divided into melt-blended or air-laid technologies.
ion. v
The EPA program at the FPL provided opportunities for developing additional experience in
the theory and practice of wood fiber-plastic composites and for developing industry and
university contacts in this area. As a consequence, the program was instrumental in leading to
numerous cooperative studies with industry and academia, all of which had as their ultimate goal
the commercialization of composites containing ingredients from the waste stream. In addition, the
FPL was able to provide advice and information on these systems to a large number of companies
and government agencies. In the following, we summarize some of the cooperative studies that.
arose out of the EPA program.
Commercial Feasibility of Waste Newspaper-Thermoplastic Composites
Laboratory experiments demonstrated tha
thermoplastics by melt-blending, resulting in substantial improvements in some properties
compared with the unfilled plastic or compared
ONP could be dispersed as fibers into
with the plastic filled with wood flour
(Recommendations, Tasks 2 and 3). The FPL and the University of Wisconsin Industry Research
Office held several meetings with a variety of industrial firms to plan a cooperative study that
would demonstrate whether the laboratory succkss could be scaled up to commercial operations to
produce commercial products. The program was partially funded by the FPL and the Wisconsin
Department of Natural Resources (DNR) and by in-kind contributions from the eight cooperating
companies. The program and its accomplishments are described in the accompanying final report
from FPL to DNR (Myers and demons 1993) and in the accompanying manuscript that has been
submitted to Plastics Engineering (demons and others, submitted). We summarize the major
conclusions here:
(1) ONP/PP composites can be compound id on a commercial scale using either the K-mixer
with ONP flakes as feed or using a twin-screw extruder with ONP fibers fed separately from
the plastic. I
(2) ONP/PP sheet containing 42 weight percent ONP can be prepared by extrusion on a
commercial scale. This sheet meets existing specifications for automobile panels and can be
thermoformed into a variety of shapes. I
(3) Given proper design of melt processing equipment, a wide variety of other commercial
products could be manufactured from ONP/PP composites with similar ONP content.
(4) Firm estimates of production costs for
DNP/PP composite products must await
(a) additional examination of compoun ling methods to define the optimum balance of
dispersion ability, throughput rate, and cost
33
-------
(b) improvement in methods to deliver wastepaper in a form and at a cost acceptable to a
compounder or a manufacturer of plasjtic products, keeping in mind that wood flour is
available in quantity at approximately ^0.22/kg
Waste LDPE Program
A consortium of" companies have recently come together to investigate the use of waste LDPE
that is "contaminated" by residual fiber from a hydropulping operation that scavenges wood fiber
from coated paper stock. The program consists of raw material processors, compounders, plastics
processors, and research institutions and is being coordinated by the FPL. A research program has
been finalized and work is just beginning. Major hurdles in this program are the residual moisture
from the hydropulping process left in the raw ntiaterial and product applications.
Waste Jute-Polyester Panels As Reinforcing Filler
A U.S. company was interested in the possibility of recycling panels that they produced by
impregnating jute fibers with thermosetting polyester. We granulated the panels and investigated
the ability to use the resultant mixture as reinforcing filler in melt-blended composites with a
polypropylene matrix. Overall, it appeared thai! this waste material produced composite mechanical
properties that were approximately equivalent tjo those of similar composites containing wood flour
as the reinforcement (Schneider and others, submitted).
Waste Kenaf Core As Reinforcing Filler
The Agrecol Corporation of Madison, Wisconsin, had a grant from the Wisconsin
Department of Agriculture to investigate the potential of kenaf as a commercial agricultural product
in Wisconsin. Kenaf is a very rapidly growing plant whose outer fibers produce high quality
paper. However, the kenaf core material is muph less fibrous than the outer fibers and of less
interest for paper manufacture. Agrecol requested FPL to determine whether the kenaf core
material could be useful as a reinforcing filler in plastic composites. We granulated the core
material and successfully melt-blended the -40 mesh fraction with polypropylene. The composite
properties were also approximately equivalent to those of similar composites containing wood
flour. Therefore, where the kenaf core may be teadily available at low cost, it very likely could
substitute for wood flour as a reinforcing filler
Wastewood Composite As Reinforcing
(Schneider and others, submitted).
Filler
The University of Tennessee extension requested an evaluation of wastewood composite as a
reinforcing filler in thermoplastic composites. Such solid waste is available in large quantity; it
contained plywood, particleboard, and fiberboara and several percent of cured thermoset adhesives
which might cause problems in melt-processed composites because it would not melt at processing
temperatures. We granulated the plywood and successfully melt-blended the -40 mesh fraction
with polypropylene. The composite properties were approximately equivalent to those of similar
composites containing wood flour. This waste material could therefore substitute for wood flour
as a reinforcing filler in melt-processed composites (Schneider and others, submitted).
CONFERENCES, PRESENTATIONS, AND PUBLICATIONS
• We have actively pursued efforts to bring
for commercial applications to the attention o:
been accomplished by sponsoring conferences;
technical meetings; and by publishing papers in
34
wood fiber-plastic composites and their potential
if both the research community and industry. This has
by presentations at conferences, workshops, and
scientific and semitechnical journals.
-------
sponsored with the University of Wiscon
Wood Fiber-Plastic Composites Conferences—Two international conferences were co-
t • .1 ,1 TT • _'j._ _ *? IT 7"T ____•_ 11__1J-__A^"«Jj^^.*-. *.t A •*-%«! "1 f\O 1 *-i*-s <-4 TV /ff
;in and held in Madison, in April 1991 and May
1993. Each was attended by approximately 200 people from the United States, Canada, and
several other countries, representing academia, industry, and public agencies. We presented
several papers and posters at each conference on results that resulted directly from this EPA
program and on other composites studies! Both conferences were highly productive in terms
. of developing interest in these systems and industrial contacts. The University of Toronto
held two similar, but smaller, conferences, in February 1991 and May 1992. We presented
two papers at each conference.
American Chemical Society Meeting—A paper entitled "Lignocellulosic/Plastic Composites
from Recycled Materials" was presented at the spring 1991 ACS national meeting. It was
subsequently published in Emerging Tecrmologies for Materials and Chemicals from
Biomass: Proceedings of Symposium; 19J90 August 26-31; Washington, DC: American
Chemical Society; 1992. Chap. 4. ACS symposium series 476.
Focus 95+ Landmark Recycling Symposium—A paper entitled "Alternative Uses of
Recovered Fibers" was presented on March 21, 1991 at a symposium sponsored by primary
paper manufacturers, technical and management associations, academia, and government.
I
International PartideboardlComposite Materials Symposium—A paper entitled "Composites
From Recycled Raw Materials" was presented at this annual symposium on April 11, 1991.
Annual Technical Meeting of the Society of Plastics Engineers (ANTEC)—Papers were
presented at two meetings, in 1992 and 1993. These were published in the meeting
proceedings (Myers and others 1992, Clejmons and Myers 1993).
Materials Research Society Meeting—A paper was presented at the national meeting in 1992
(Gonzales and others 1992).
Other Papers Submitted to Journals—Se\
journals and should be published in 1993
others; Schneider and others). The Task <
a scientific journal in 1993.
ral additional papers have been submitted to
or early in 1994 (Sanadi and others; demons and
studies on Recyclability will also be submitted to
Reports to Cooperators—Several reports
cooperators, including the final
and demons 1993).
Jiave been submitted to industry and public agency
report for the DNR program on commercial feasibility (Myers
-------
SECTION 7
QUALITY ASSURANCE OBJECTIVES
A Quality Assurance Project Plan for this
The Plan identified the following areas to whicl.
applicable:
program was submitted to the EPA in June 1990.
quality assurance objectives were primarily
(1) Preparation of ingredients for incorp< >ration into composites
(2) Preparation of composites
(3) Characterization and testing of composites
With regard to the preparation of ingredients and composites (areas 1 and 2), our work
emphasized innovative experimentation and trial and error runs to improve or develop methods to
the point where reproducible, but not necessarily optimized, processes could be used. Process
parameters were apparatus-specific and were controlled as necessary to provide reproducible
material.
The emphasis throughout the program was on product quality, and therefore area 3 was of
primary concern. In this case, the situation was much different from that in areas 1 and 2. The
criteria, methods, and calculation procedures are mostly well-documented in standards maintained
by the American Society for Testing and Materials (ASTM) or by the Technical Association of the
Pulp and Paper Industry (TAPPI). Specifications for experimental precision were based on our
own laboratory experience, from our in-house statisticians, and as specified by ASTM or TAPPI
standards when those were available. Wherever possible, experiments were statistically designed
and analyzed, using standard statistical methods.
We summarize below the experimental methods that were actually employed in the program
and their precision, following the criteria outlined in the preceding comments.
PREPARATION OF INGREDIENTS EC
INTO COMPOSITES
Air-Laid Composites
R INCORPORATION
During air-forming, it is essential that all the materials introduced into the air stream remain
intimately mixed during the web formation process. This requirement necessitates that materials of
similar configuration be used, or that materials, like powders, are introduced into the air stream just
prior to web formation to insure that they remain evenly distributed in the formed web.
Alternatively, powders can be used if a tackifier is added to either the wood or plastic fibers so that
the powder adheres to the fiber during the air-forming operation. The primary criterion for
acceptability of the raw materials is that they be capable of being distributed evenly and uniformly
during the web formation process.
Hemlock fiber (HF), virgin and recycled polyethylene terephthalate (VPET, RPET), phenolic
resin (PR), and tackifier (E-10) were used as recjeived. The following materials required further
processing to make them suitable for use in our processing equipment:
Demolition wood fiber (DF)—received in
or fiber bundle format using refining met
, chipped form and had to be converted into a fiber
adology.
Virgin high density polyethylene (VHDPEl)—required grinding to a nominal (-)35 mesh size.
-------
Recycled high density polyethylene (RHD(PEI
chipped and then ground to a (-)35 mesh
')—obtained from old milk bottles that were
size.
Melt-Blended Composites
During melt-blending, the plastic melts and completely loses its original solid geometry. The
high shear and extensional forces within the molten plastic cause the reinforcing fiber to be
dispersed into the plastic, but they simultaneously break the fiber into shorter lengths. Because of
these changes in the starting ingredients, their original form and size are not highly critical. The
primary criterion for acceptability of the starting ingredients is that they be relatively easy to handle
and to feed into the melt-blending apparatus.
Virgin plastics were obtained in pellet or jowder form and were not further treated prior to
melt-blending. Waste plastics were obtained a^ flakes or particles and were granulated to
approximately 1 to 3 mm using a Ball and Jewe 1BP-68-SCS Minigranulator equipped with a
3-mm screen. Granulation times were kept to a
plastics.
minimum to prevent heating and melting of the
Wood flour was obtained as -40+80 rnest material. Wastepapers were treated in two ways
depending on the method used to perform subsequent melt-blending. For blending in the K-mixer,
the wastepapers were passed rapidly through the Ball and Jewel granulator equipped with a 6-mm
screen to produce flakes approximately 4 to 8 mm in size. For melt-blending with an extruder, the
wastepaper was hammermilled in a small hamn errnill with a 3-mm screen.
PREPARATION OF COMPOSITES
Air-Laid Composites
A uniform air-formed web profile across i nd along the air-forming machine must be obtained
to insure that the pressed composite panel has uniform properties throughout. Extensive efforts
were made to optimize our air-forming process to insure that web uniformity was obtained to the
maximum extent possible. Uniformity can also be achieved from panel to panel or from test
specimen to test specimen by close control over the criteria for acceptablity of the composites to be
tested. Accordingly, panels for AL Series 1 were selected to ensure that they were within the
specific gravity range of 1.0 ± 0.03. Target thicknesses were maintained at 3.2 mm.
In a further effort to maintain close speci
specimens for AL Series 2 and AL Task 4 we:
gravities were determined. In this series, only
0.06 were used for testing purposes. Again,
All of the panels made in this program
for 4 min at a maximum pressure of 8.47 MPa.
during compaction to reduce steam vapor pressure
thickness of 3.2 mm.
were fabricated using a pressing temperature of 190°C
Three minutes of cooling time was necessary
in the pressed board and to maintain the target
37
gravity control over the actual test specimens, test
cut from test panels and the specimen specific
st specimens with an acceptable range of 1.0 ±
et thicknesses were maintained at 3.2 mm.
-------
Melt-Blended Composites
An ideal melt-blending process would pr )duce a composite in which the reinforcing filler is
completely dispersed into individual particles without any damage to either the filler or the plastic
arising from the temperature or the stresses within the melt. Unfortunately, complete dispersion
and lack of damage are likely to be contradictory achievements. Therefore, in practice one must
usually compromise and carry out melt-blending at the lowest temperature, the shortest times, and
the lowest shear rates that will produce a degree of dispersion that yields composites with
reproducible properties. These conditions differ for different plastics and fillers, for different filler
equipment. In every case, approximately optimized
The ranges in blending parameters used in this
concentrations in the plastics, and for different
conditions were determined by screening tests.
program were as follows:
Melt-blending by extrusion
Modern Plastic Machinery extruder
Barrel temperature, 170°C to 190°C
Screw speed, 15 rpm
Residence time, 1 to 2 min
Killion extruder
Barrel temperature, 192°C to 204°C
Screw speed, 34 rpm
Residence time, 1 to 2 min
Melt-blending by K-mixing
University of Toronto K-mixer
Speed, 2800 to 3300 rpm
Discharge temperature, 185°C
Residence time, 30 to 300 s
FPL K-mixer
Speed, 4500 to 5500 rpm
Discharge temperature, 171°C to 200°C
Residence time, 30 to 150 s
CHARACTERIZATION AND TESTING OF COMPOSITES
Air-Laid Composites
All tests were done on the INSTRON test) machine USPN 8176. Calibration was done at the
beginning of each new test and checked throughout the test. The INSTRON has an electric load
cell to measure forces of 444.8 N or less, and is calibrated by National Bureau of Standards (NBS)
dead weights. It is calibrated by Morehouse rings with NBS-traceable calibration data when more
'than 444.8 N. Displacement is measured by linbar variable displacement transducers (LVDTs)
calibrated with gauge blocks. Total system calibration is within 1 percent of full scale.
All testing of the air-laid composite panels in this program were conducted using the test
procedures specified in detail in the referenced Duality Assurance Project Plan. The observed
values obtained on all of the test specimens for each of the AL Series were consistent with data that
we have obtained in other test programs using •\ irgin raw material resources. Our results
38
-------
demonstrated that both our laboratory techniqu
consistent.
Melt-Blended Composites
:s and our testing procedures were uniform and
To determine mechanical and physical pr jperties of melt-blended composites, specimens
were prepared by injection molding using a Frohring Minijector model SP50. Control parameters
for this machine were barrel temperature, residence time, and injection pressure. Here also,
compromises must be adopted. High temperature causes polymer degradation, whereas low
temperature, particularly when combined with low pressure, makes it difficult to fill the mold
cavity and produce a complete specimen. Again, conditions may differ with different systems and
formulations. However, exact control of parameters is not necessary. Typical conditions
employed in the program were 205°C barrel ter iperature, approximate residence time of 1 min, and
3.4 to 8.9 MPa injection pressure.
A minimum of five specimens was tested for each type of measurement at each variable being
investigated. Except for the moisture sensitivity tests, the dry specimens were stored under
desiccant at 25°C + 2°C for a minimum of 3 days after injection molding and were tested at that
temperature immediately after removal from the desiccant.
Table 2.3 A of the Quality Assurance Plan lists the various properties measured, the methods
used, the ASTM standard, and the anticipated precision. The precisions obtained in actual practice
during the program are given in Table 12 of thijs report. The observed values were consistent with
those reported in the literature for these types of materials, thus demonstrating that both our
production processes and our testing procedure s were satisfactory.
REFERENCES
ASTM. 1984a. ASTM D638-84, Standard test
Book of ASTM Standards, Vol. 08.01, Sec. 8,
Philadelphia, PA.
method for tensile properties of plastics. Annual
American Society for Testing and Materials,
ASTM. 1984b. ASTM D747-84a, Standard test method for apparent bending modulus of plastics
by means of a cantilever beam. Annual Book of ASTM Standards, Vol. 08.01, Sec. 8, American
Society for Testing and Materials, Philadelphia, PA.
ASTM. 1984c. ASTM D256-84, Standard test
electrical insulating materials. Annual Book ol
method for impact resistance of plastics and
ASTM Standards, Vol. 08, Sec. 8, American
Society for Testing and Materials, Philadelphia. PA.
ASTM. 1990. ASTM D790, Standard test method for flexural properties of reinforced and
unreinforced plastics and electrical insulating materials. Annual Book of ASTM Standards, Vol.
8.01, Sec. 8, American Society for Testing and Materials, Philadelphia, PA.
ASTM. 1991. ASTM D1037-91,Standard methods of evaluating the properties of wood-base
fiber and particle panel materials. Annual Book of ASTM Standards, Vol. 04.09, American
Society for Testing and Materials, Philadelphia PA.
Either, P. 1980. Polyolefin pulps as nonwoven
Advanced Forming Conference, November
binders. In: Proceedings of the Air-Laid and
16-18, 1980, Hilton Head Island, SC.
39
-------
Brooks, S.H. 1990. Air lay non woven moldat le mat process and products produced by using this
mat process. In: Proceedings of the 1990 TAPPI Nonwovens Conference, pp. 87-108.
Caron, P.E. and G:D. Allen. 1966a. Process for manufacturing moldable fibrous panels. U.S.
Patent 3,230,287. U.S. Patent Office, Washington, DC.
Caron, P.E. and G.D. Allen. 1966b. Productic n of hot-pressed three-dimensional fiber articles.
U.S. Patent 3,261,898. U.S. Patent Office, Washington, DC.
Caron, P.E. and G.D. Allen. 1968. Reinforced moldable wood fiber mat and method of making
the same. U.S. Patent 3,367,820. U.S. Patent Office, Washington, DC.
Caron, P.E. and G.A. Grove. 1966. Method of die-baking moldable wood fiber parts. U.S.
Patent 3,265,791. U.S. Patent Office, Washington, DC.
demons, C.M. and G.E. Myers. 1993. Properties of melt-blended composites from post-
consumer polypropylenes and wastepapers. In!: Proceedings of the 1993 Annual Conference of
the Society of Plastics Engineers (SPE/ANTEC), New Orleans, MS, Vol. 3, pp. 3213-3215.
demons, C.M., G.E. Myers, J.F. Saeman and D.S. Ermer. Waste newspaper-polypropylene
thermoplastic composites: Research- and plant-scale studies of commerical feasibility. Submitted
to Plastics Engineering. .
Gonzalez, C., C.M. demons, G.E. Myers and T.M. Harten. 1992. Effects of several ingredient
variables on mechanical properties of wood fiber-polyolefin composites blended in a thermokinetic
mixer. In: Proceedings of the Materials Research Society Symposium, San Francisco, CA, Vol.
266, pp. 127-135.
Grove, G.A. and P.E. Caron. 1966. Method of making moldable wood fiber mat with metal
insert. U.S. Patent 3,279,048. U.S. Patent Office, Washington, DC.
Krzysik, A.M. and J.A. Youngquist. 1991. B
composites. Int. J. Adhesion and Adhesives 1
Hiding of air-formed wood-polypropylene fiber
L(4):235-240.
Krzysik, A.M., J.A. Youngquist, R.M. Rowell, J.H. Muehl, Poo Chow and S.R. Shook. 1993.
Feasibility of using recycled newspapers as a fiber sourcefor dry-process hardboards.
Forest Prod. J. 43(7/8):53-58.
Morton, W.E. and J.W.S. Hearle. 1962. Physical properties of textile fibres, Butterworths,
Manchester, p. 411.
Myers, G.E. and C.M. demons. 1993. Wastepaper fiber in plastic composites made by melt
blending: demonstration of commercial feasibility. Final report for Solid Waste Reduction and
Recycling Demonstration Grant Program, Project No. 91-5, Wisconsin Department of Natural
Resources. USDA Forest Service, Forest Products Laboratory, Madison, WI, 32 pp.
Myers, G.E., I.S. Chahyadi, C.A. Coberly and D.S. Ermer. 1991a. Wood flour/propylene
composites: influence of maleated polypropylene and process and composition variables on
mechanical properties. Int. J. Polymeric Matei. 15:21-44.
Myers, G.E., I.S. Chahyadi, C. Gonzalez, C.A. Coberly and D.S. Ermer. 1991b. Wood flour
and polypropylene or high density polyethylene- composites: influence of maleated polypropylene
concentration and extrusion temperature on properties. Int. J. Polymeric Mater. 15:171-186.
43
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Myers, G.E., C.M. demons, J.J. Balatinecz and R.T. Woodhams. 1992. Effects of
composition and polypropylene melt flow on polypropylene-waste newspaper composites. In:
Proceedings of the 1992 Annual Conference of the Society of Plastics Engineers (SPE/ANTEC),
Detroit, MI, Vol. 1, pp. 602-604.
Olsen, D.J. 1991. Effectiveness of maleated p alypropylenes as coupling agents for wood flour
polypropylene composites. In: Proceedings of jhe 1991 Annual Conference of the Society of
Plastics Engineers (SPE/ANTEC), Montreal, Canada, pp. 1886-1890.
Roberts, J.R. 1955. Moldable cellulose com
product therefrom. U.S. Patent 2,714,072. U.
J..
ipqsiti
sition containing pine wood resin and molded
S. Patent Office, Washington, DC.
Roberts, J.R. 1956. Process of forming molded cellulose products. U.S. Patent 2,759,837.
U.S. Patent Office, Washington, DC.
Sanadi, A.R., R.A. Young, C.M. demons and
R.M. Rowell. Recycled newspaper fibers as
reinforcing fillers in thermoplastics: Part I. Analysis of tensile and impact properties in
polypropylene. J. Reinforced Plastics and Conjiposites, in press.
Schmidt, R.G., J.J. Balatinecz and R.T. Woodhams. 1992. Effects of recycling on the properties
of wood fibre-polyolefin composites. In: Proceedings of a workshop on economic viability of
recycled wood fibre-plastic composites, sponsored by the Ontario Centre for Materials Research
and the University of Toronto, Mississauga, Ontario.
Schneider, J.P., C.M. demons, G.E. Myers
reinforcing fillers in thermoplastic composites.
TAPPI. 1989. TAPPI test methods. Puncture
B. English. Comparison of several biofibers as
Submitted to Int. J. Polymeric Mater.
test of containerboard. TAPPI T803 om-88,
Vol. 2. Technical Association of Pulp and Paper Industry, Atlanta, GA.
Woodhams, R.T., S. Law and JJ. Balatinecz. 1991. Properties and possible applications of
wood fiber-polypropylene composites. Presented at Wood Fiber-Plastic Composite Conference,
sponsored by the University of Wisconsin, the USDA Forest Service, Forest Products Laboratory,
and the University of Toronto, Madison, WI, May 1991.
Youngquist, J.A. and R.M. Rowell. 1989. Opportunities for combining wood with nonwood
materials. In: Proceedings of the 23rd Washington State University International
Particleboard/Composite Materials Symposiumj, T. Maloney, ed,, Washington State University,
Pullman, WA.
Youngquist, J.A., A.M. Krzysik, J.H. Muehl
properties of air-formed wood-fiber/polymer-1
and
C.G. Carll. 1992. Mechanical and physical
•fiber composites. Forest Prod. J. 42(6):42-48.
41
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TABLES
Tables 1-10 and Figures 1—31 pertain to air-
(Tables 11-34 arid Figures 32-50) pertain to
laid (AL) studies. The remaining tables and figures
melt-blending (MB) studies.
AND FIGURES
42
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TABLE 1. MATERIALS USED IN AIR-LAID STUDIES
Material
Abbreviation
Description
Source
Hemlock fiber
HF
Demolition wood DF
fiber
Virgin PET
polyester
fiber
Recycled RPET
polyester
Virgin high VHDPE
density
polyethylene
Recycled high RHDPE
density
polyethylene
Phenolic .resin PR
Epolene-maleated E10
polyethylene
Virgin western hemlock
|ood fiber
Waste wood pressurized;
refined into wood fiber
Polyester 280, 5.5 denier
38 mm, white, staple,
srimped fiber
Spun
from 2-L soft drink
containers, 6.0 denier,
51 mm,, bright, crimped
fiber
Fotftiflex A 60-70-119 blow-
molding polymer-milk
bottle feedstock
Chopped, recycled milk
bottles; ground to
35 mesh
Liquid phenol-formaldehyde
dP 2341, 51 to 53 percent
olids
Wax emulsion of low
molecular weight
polyethyelne
Canfor Ltd.,
Vancouver, BC
Wood Recycling,
Peabody, MA
E.I. DuPont deNemours,
Inc., Wilmington,
DE
Wellman Co., Inc.,
Johnsonville, SC
Solvay Polymers,
Houston, TX
Plastic World,
Madison, WI
Georgia-Pacific
Corp.
Eastman Chemical Co.,
Kingsport, TN
Recycled
composite
panel
Second
generation
DF
F
and RHDPE composite
anels pressurized,
refined into fiber form
Refined at FPL
43
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TABLE 2. AL SERIES 1: PANEL
COMPOSITION
Wood
fiber PET Pheno
content fiber resi
(percent) (percent) (perc
HF 80 VPET 10 10
HF 80 RPET 10 , 10
DF 80 VPET 10 10
DF 80 RPET 10 10
^
ent)
TABLE 3. AL SERIES 1: PANEL SELECTION
Formulation
HF/VPET
HF/RPET
DF/VPET
DF/RPET
Panel
size
(mm)
279 by 279
279 by 279
279 by 279
279 by 279
Pan
pe
compo,
40
40
40
40
2ls Number of
r selected
a • b
site panels
15
15
15
15
Total number of panels per composite formulation.
Final number of selected panels at specific gravity
range 1.0 ± 0.03.
44
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TABLE 4 . AL SERIES 1 : MECHANICAL
OF COMPOSITES
HF-80%
VPET-10%
Property PR-10%
Static bending MOR 50.6 (16)
(MPa)
Static bending MOE 3.66 (19)
(GPa)
Tensile strength 33.0 (9)
(MPa)
Tensile MOE (GPa) 4.84 (14)
Impact energy (J) 36.1 (5)
Water -soak 24 -h'
thickness swell 25.2 (9)
Water soak 24 -h
water absorption 43.4 (20)
Linear expansion
at 30% -RH (%) 0.19 (10)
at 65% RH (%) 0.42 (4)
at 90% RH (%) 0.61 (6)
AND PHYSICAL PROPERTIES
HF-80% DF-80% DF-80%
RPET-10% VPET-10% RPET-10%
PR-10% PR-10% PR-10%
47.1 (22) 43.2 (25) 47.8 (20)
4.26 (20) 3.23 (27) 3.74 (19)
28.4 (11) 28.3 (10) 30.0 (10)
5.12 (13) 4.26 (18) 4.56 (13)
28.7 (8) 34.2 (6) 30.7 (4,)
22.3 (9) 29.8 (14) 26.9 (8)
41.3 (25) 48.2 (25) 44.1 (16)
0.21 (13) 0.20 (11) 0.20 (12)
0-44 (8) 0.43 (6) 0.45 (6)
0.70 (7) 0.64 (7) 0.71 (6)
Values in parentheses are coefficients of variation (%).
45
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TABLE 5. AL SERIES 2: PANEL COMPOSITION
Wood fiber
content
(percent)
HF 60
HP 60
DF 60
DF 60
VPE'
r E10 wax
HOPE fiber tackifier
(percent) (percent) (percent)
VHDPE 30 5
RHDPE 30 5
VHDPE 30 5
RHDPE 30 5
5
5
5
5
TABLE 6 . AL SERIES 2 : SPECIMEN SELECTION
Testa
Static bending MOR and MOE
Tensile strength and MOE
Impact energy
24 -h water soak
Linear expansion
Specimen Specimens Number of
size per selected
(mm) composite specimens
51 by
51 by
254 by
51 by
13 by
127 60 20
254 50 20
254 20 10
51 150 40
152 100 25
b,
Forty panels were produced in every composite formulation
I
Total number of specimens per composite formulation.
-t
'Final number of selected specimens at specific gravity range
1.0+0.06.
46
-------
TABLE 7. AL SERIES 2: MECHANICAL
AND
PHYSICAL PROPERTIES OF COMPOSITES
Property
HF 60%
VHDPE 30%
VPET 5%
E10 wax 5%
HF 60%
RHDPE 30%
VPET 5%
E10 wax 5%
DF 60%
VHDPE 30%
VPET 5%
E10 wax 5%
DF 60%
RHDPE 30%
VPET 5%
E10 wax 5%
Static bending MOR 16.8 (19)
(MPa)
Static bending MOE 2.01 (19)
(GPa)
Tensile strength 10.8 (15)
(MPa)
Tensile MOE (GPa) 2.81 (15)
Impact energy (J) 27.6 (9)
Water soak 24-h
thickness swell 43.8 (14)
Water soak 24-h
water absorption 54.9 (17)
Linear expansion
at 30% RH (%)
at 65% RH (%)
at 90% RH (%)
0.15 (9)
0.39 (5)
0.68 (7)
18.7 (15)
2.13 (19)
9.5 (19)
2.23 (22)
27.6 (7)
42.7 (21)
61.8 (19)
0.17 (12)
0.42 (12)
0.69 (12)
19.1 (14)
1.75 (16)
12.4 (14)
45.2 (13)
58.7 (13)
0.17 (5)
0.40 (7)
0.64 (9)
17.4 (20)
2.01 (24)
11.5 (12)
2.12 (15) 2.09 (13)
30.9 (8) 31.1 (7)
52.8 (15)
65.8 (16)
0.16 (7)
0.44 (6)
0.74 (6)
Values in parentheses are coefficients of variation (%).
47
-------
TABLE 8. RECYCLABILITY:
Recycled
Wood fiber panel
content content ,
(percent) (percent)
DF 60 0
DF 40 20
TABLE 9. RECYCLABILITY:
Test3
Static bending MOR and MOE
Tensile strength and MOE
Impact energy
24 -h water soak
Linear expansion
PANEL COM
HDP
(perc
RHDPE
RHDPE
SPECIMEN
POSITION
VPET E10 wax
3 , fiber tackifier
2nt) (percent) (percent)
30 5 5
30 5 -5
SELECTION
Specimen Specimens Number of
size per selected
(mm!) composite specimens0
51 by
51 by
254 by
51 by
13 by
127 60 20
254 50 : , . 20
254 20 10
51 150 40
152 100 25
Forty panels were produced in every composite formulation.
'Total number of specimens per composite formulation.
-t
"Final number of selected specimens at specific gravity range
1.0 + 0.06.
-------
TABLE 10'. RECYCLABILITY: MECHANICAL AND PHYSICAL
PROPERTIES OF COMPOSITESa
Property
DF 60%
RHDPE 30%
VPET 5%
E10 wax 5%
DF 40%
Recycled panel 20%
RHDPE 30%
VPET 5%
E-10 wax 5%
Static bending MOR 17.4 (20)
(MPa)
Static bending MOE 2.01 (24)
(GPa)
Tensile strength (MPa) 11.5 (12)
Tensile MOE (GPa) 2.09 (13)
Impact energy (J) 31.1 (7)
Water soak 24-h
thickness swell (%) 52.8 (15)
Water soak 24-h
water absorption(%) 65.8 (16)
Linear expansion
at 30% (RH) (%) 0.16 (7)
at 65% (RH) (%) 0.44 (6)
at 90% (RH) (%) 0.74 (6)
19.6 (13)
1.77 (19)
13.7 (12)
2.70 (25)
33.2 (7)
42.0 (12)
54.3 (12)
0.15 (11)
0.37 (9)
0.52 (11)
Values in parentheses are coefficients of variation (%).
49
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TABLE 12. COEFFICIENTS OF VARIATION
MEASURED MECHANICAL PROPERTIES51
FOR
Property
COV
>ercent)
Tensile
Strength
Modulus
Energy to maximum load
Elongation at maximum load
Flexural
Strength
Modulus
Cantilever
Strength
Modulus
Izod impact
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Unnotched
4
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TABLE 15. STUDY MB-1:
PROPERTY CHANGES
Variables
Property
ONp/PP ratio
([32 to 42)
Filler type
(WF to ONP)
Cantilever
Strength
Modulus
Flexural
Strength
Modulus
Tensile
Strength
Impact
Unnotched
11
12
17
24
29
43
Values are given only when statistically
significant at 95 percent confidence level and
change is above 10 percent.
Averaged over MFI from 3 to 30 g/10 min.
54
-------
TABLE 16. COMPOSITE MELT VISCOSITIES
PP MPI
(g/12 min)
3
12
30
Filler
--
WF
ONP
ONP
ONP
ONP
Filler/PP
(weight)
0
0 '
42/58
32/68
37/63
42/58
42/58
Viscosity
100
1,230 (3.4)
359 (1.0)
452 (1.3)
618 (1.7)
728 (2.0)
881 (2.5)
572 (1.6)
at shear
500
--
149 (1.0)
195 (1.3)
227 (1.5)
269 (1.8)
301 (2.0)
208 (1.4)
rate(s )
1000
--
102 (1.0)
136 (1.3)
148 (1.5)
175 (1.7)
190 (1.9)
135 (1.3)
Values in Pa-s. Parenthetical values are ratios of filled system to
unfilled PP at 10 MFI and particular shear rate. E-43 present at
5 weight percent of filler.
Extrapolated from log-log plot of
500 s .
55
data measured between 100 and
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TABLE 20. STUDY MB-2: USEFUL MECHANICAL PROPERTY CHANGES*
Property
Cantilever
Strength
Modulus
Flexural
Strength
Modulus
Tensile
Strength
Modulus
Impact
Notched
Unnotched
HDPE-MB t
23
23
41
34
21
23
-29
29
Variables
b c
o PP WF to BW40
(e)
(e)
21
(e)
19
(e)
(e)
(e)
d
BW40 to ONP
(e)
(e)
(e)
(e)
(e)
(e)
(e)
-19
a.
Percent relative to mean values.
b
Averaged over other variables in Study MB2-A and Study MB2-B.
Averaged over other variable, 3 in Study MB2-A.
IS 11
Averaged over other variables in Study MB2-B.
"Changes less than 20 percent
59
-------
TABLE 21. COMPARISON OF MECHANIC-
CAL PROPERTIES OP HDPE-MB/ONP AND
PPV/WF COMPOSITES
Property
Tensile strenc
Tensile moduli
Flexural strer
Flexural moduJ
Notched impact
Unnotched imps
Ratio
th
,s
gth
us
energy
ct energy
1.07
0.98
0.95
0.97
1.55
0.95
Average value for HDPE-MB/ONP
systems to value for PPV/WF
systems.
TABLE 22. CHARACTERISTICS OF
EPOLENES
Epolene
Acid number
(mg KOH per
g Epolene)
M
Anhydrides
per Epolene
molecule
(no.)
Polymer
repeat units
per anhydride
(no.)
E43
G3002
47
63
4,200
11,000
1.76
6.18
36
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TABLE 25. STUDY MB-4:
MAIN EFFECTS OF VARIABLES
Property
Tensile
Modulus (GPa)
Strength (MPa)
Energy ( J)
Elongation (%)
Flexural
Modulus (GPa)
Strength (MPa)
Impact
Notched (J/m)
Unnotched (J/m)
Over
me a
3
61
0
3
3
61
35
145
all
a
n .
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.4
.55
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.0
.2
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Main effect
KPP to BPP
**
-8.4 (-18)
-0.13 (-20)
-0.2 (-6)
-0.2 (-7)
-13.3 (-19)
+5.6 (+18)
**
OMG
+ 0.
+12.
+ 0.
+ 0.
+ 0.
+11.
-5.
to
5
1
22
4
4
3
6
**
ONP
(+15)
(+34)
(+50)
(+17)
( + 12)
(+17)
(-14)
Average over all variables and trials.
Main effect is change in property resulting from the
particular variable, averaged over the other variable.
Numbers in parentheses are percent change. Interactions
were not significant at
Not significant at 95 percent confidence level.
the 95 percent confidence level.
-------
TABLE 26. Study MB-4: CHANGE IN PROPERTY
AFTER ADDITION OF 40 PERCENT FILLER TO PLASTIC**
Property
Tensile
Modulus
Strength
Energy
Elongation
Flexural
Modulus
Strength
Impact
Notched
Unnotched
Fi
KPP
2.49
1.49
0.65
i 0.47
2.29
1.52
0.49
<0.21
lied/unfilled
BPP
3.00
1.66
0.73
0.46
3.01
1.91
0.21
<0.19
VPP
—
1.66
•--
--
2.94
2.00
0.86
0.29
Based on values for ONP systems.
indicate data not available.
Dashes
64
-------
TABLE 27. WATER SORPTION OF VPP
3 PERCENT G3002 (BY WEIGHT OF FILLER)
WITH 42 percent ONP AND
Initial
24-h
ambient
soak 24-h boil Boil/initial
Cantilever
Secant modulus (GPa)
Max strength (MPa)
Izod impact
Notched (J/m)
Unnotched (J/m)
Thickness (mm)
Weight (g)
2.69
2.58
83.3
84.9
1.73
71. 6
0.6
0.9
24.5
25.6
26.2
131
150
3.15
3.15
6.02
6.06
145
3.28
6.32
1.0
1.0
indicate
Continuous lines over numbers i
statistically significant at the 95
that they are not
percent confidence level.
65
-------
TABLE 28. WATER SORPTION OF VPP
AGENT)a
WITH 42 PERCENT ONP (NO COUPLING
Initial
24-h
ambient
soak 24-h boil Boil/initial
Cantilever
Secant modulus (GPa) 2.63
Max strength (MPa) 68.5
Izod impact
Notched (J/m) 24.5
Unnotched (J/m) 102
Thickness (mm) 3 .14
Weight (g) 6.03
2.51
68.3
1.68
62.0
0.6
0.9
24.8
27.0
105
3.15
6.08
145
3.24
6.43
1.4
1.0
1.1
indicate
Continuous lines over numbers i
statistically significant at the 95
that they are not
percent confidence level.
66
-------
TABLE 29. WATER SORPTION OF VPP
AGENT)S
WITH 42 PERCENT WF (NO COUPLING
Initial
24-h
aniBient
soak 24-h boil Boil/initial
Cantilever
Secant modulus (GPa)
Max strength (MPa)
Izod impact
Notched (J/m)
Unnotched (J/m)
Thickness (mm)
Weight (g)
2 .22
2.24
65.6
64.7
1.59
59.4
0.7
0.9
23.9
21.8
24.4
102
3.17
99
3.20
5.97
6.01
101
3.26
6.25
1. 0
1.0
Continuous lines over numbers indie
statistically significant at the 95
ite that they are not
percent confidence level.
67
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-------
RANDO-WEB8 PROCESS
MODEL B RANDO-
RANOO-PREFEEDER©© RANOO-OPENER BLENDER
IVEB" PROCESS
RANDO-FEEDER- AIR_OyT_
RANDO-WEBBER
© Anti-Static Spray System
© Ftoor Apron
© Elevating Apron
© Stripper Apron
© Doffer Rd
© Ftoor Apron
© Worker Rob
© Stripper Rd
© Hopper Cover
® Small Worker Rote
© Smaa Striper Rote
® Air Brush
Figure 1. Schematic of air-laid web-forming proces;
60
50
o 40
Q.
IE 30
J20
10
VPET • RPET
0
50.6
143.2
Figure 2.
® Ffcer Separator
® Ftoor Apron
® Bavating Apron
© Stripper Apron
® Hopper Level Control
® ArEJridge
® Feed Mat Condenser Screen
® AutoLeveter
® Refer Conveyor
Feed Plate
FeedRoi
Nose Bar
Uckerin
Saber
Venturi
Duct Cover
Condenser for Forming
RANDO-WEB
Takeaway Conveyor
WEBBER Fan
FIBR-SAVR
SJiner Assembly
Split/Air System
50.6
47.1
47.8
HF/DF
Task 3, AL Series 1. Bending strength (MOR) as a function of virgin hemlock fiber (HF), recycled
demolition fiber (DF) and polyester fiber (jPET). VPET and RPET designate virgin and recycled
polyester fiber, respectively.
-------
VPET
(0
Q-
CO
JD
3
O
o>
I 2
c
0)
QQ
O
t/)
0
4.26
3.66
3.74
3.23
HRPET
4.26
3.66
3.23
3.74
HF/DF
HF/DF
Figure 3. Task 3, AL Series 1. Bending stiffness (MOE) as a function of virgin HF and recycled DF and PET.
IVPET •RPET
40 r-
35
S. 30
jr 25
•M
O)
o 20
CO
w
c
15
10
0
3O
128.4
28.3E
HF DF
Figure 4. Task 3, AL Series 1. Tensile strength as a
28.3
30
28.4
HF/DF HF/DF
function of virgin HF and recycled DF and PET.
-------
5.12
4.56
HF/DF
HF/DF
Figure 5. Task 3, AL Series 1. Tensile modulus (MOE) as a function of virgin HF and recycled DF and PET.
IVPET
40
30
en
c
UJ
•M
o
CO
Q.
E
20
10
0
36.1
Figure 6.
HF DF
Task 3, AL Series 1. Impact energy as
RPET
36.1
30.7
HF/DF HF/DF
a function of virgin HF and recycled DF and PET.
7!
-------
IVPET
35
30
25
o>
$
w
-------
VPET HRPET
0.25
0.2
c
o
'en
c
CO
Q.
X
CO
CD
c
0.1
0.05
0.21
0.20 0.20
0.21
0.19.
0.20
0.20
HF/DF
HF/DF
Figure 9. Task 3, AL Series 1. Linear expansion at BO percent relative humidity (RH) as a function of virgin HF
and recycled DF and PET. |
I VPET BRPET
0.5
0.4
c
o
'55
co
Q.
X
LU
v_
CO
0)
c
0.2
0.1
0.44
0.45
0.42
Figure 10. Task 3, AL Series 1,
and PET.
O.43
0.44
0.45
HF/DF HF/DF
Linear expansion at 65 percent RH as a function of virgin HF and recycled DF
77
-------
0.70
0.71
HF/DF
HF/DF
Figure 11. Task 3, AL Series 1. Linear expansion at 90 percent RH as a function of virgin HF and recycled DF
and PET. I
P
VHDPE lilRHDPE
25 i-
20
CD
B 15
Q.
D
CC
*-
0 10
TJ
O
la?
HF
HF/DF
17.4
HF/DF
Figure 12. Task 3, AL Series 2. Bending strength (MpR) as a function of virgin HF and recycled DF and high
density polyethylene (HDPE). VHDPE and RHDPE designate virgin and recycled HOPE, respectively.
78
-------
2.13
2.01
HF/DF
HF/DF
Figure 13. Task 3, AL Series 2. Bending stiffness (MOE) as a function of virgin HF and recycled DF and HOPE.
IVHDP
HF DF
Figure 14. Task 3, AL Series 2. Tensile strength as
79
RHDPE
12.4
11.5
9.5
HF/DF HF/DF
function of virgin HF and recycled DF and HOPE.
-------
IVHDPE • RHDPE
CD
— 2.5
o
+3 2
OT z
_ra
LU
N—
O 1.5
w
_
•|0.5
I
2.81
2.23
2.09
HF/DF
HF/DF
Figure 15. Task 3, AL Series 2. Tensile modulus (MOE) as a function of virgin HF and recycled DF and HDP'E."
RHDPE
35
30
25
-2- 20
O)
c
LLJ
10
31 31
28 28
w HF DF
Figure 16. Task 3, AL Series 2. Impact energy as
31
28
HF/DF HF/DF
a filnction of virgin HF and recycled DF and HDPE.
80
-------
VHDPE LJRHDPE
60
50
= ^
TO
40
30
20
10
0
HF DF
Figure 18. Task 3, AL Series 2. Water absorption as
81
66
62c—I
65
HF/DF HF/DF
i function of virgin HF and recycled DF and HDPE.
-------
IVHDP
0.2
c
o
0.1
X
LU
CD
0)
-10.05
0.17
0.17
0.1
DF
Figure 19. Task 3, AL Series 2.
and HOPE.
IVHDPE
0.5
0.4
c
•i °-3
c
CO
Q.
X
LU
0.2
CO
-------
0.74
0.69 ITT
HF/DF
HF/DF
Figure 21.
Task 3, AL Series 2. Linear expansion at 90 percent RH as a function of virgin HF and recycled DP
andHDPE.
25 r-
ro 20
Q.
0>
§15
CL
U
DC
(0
3
10
1 st Gen. Pane
2nd Gen. Panels
19.6
17.4
Figure 22. Task 4, Recyclability. Bending strength (MOR) as a function of recycled DF and HDPE and first-
generation panels.
83
-------
2.5 i-
1st Gen. Panels • 2nd Gen. Panels
03
0.
-^
|o 1.5
•M
(A
_CO
LU
D
T3
Figure 23. Task 4, Recyclability. Bending stiffness (11OE) as a function of recycled DF and HDPE and first-
generation panels.
,i
1st Gen. Panels m2nd Gen. Panels
14 i-
12
to
9: 10
O)
c
8
03 6
C 4
Figure 24. Task 4, Recyclability. Tensile strength as •<
panels.
84
function of recycled DF and HDPE and first-generation
-------
1 st Gen. Board
2nd Gen. Panels
3f-
03
Q_
£2.5
+3 2
-------
1 st Gen. Pane
s H 2nd Gen. Panels
60 r-
50 -
-- 40
I
(0
w 30
10
Q>
^
.y 20
10
Figure 27. Task 4, Recyclability. Thickness sweU as a function of recycled DF and HDPE and first-generation
panels.
1 st Gen. Panels M 2nd Gen. Panels
70 r-
0
Figure 28. Task 4, Recyclability. Water absorption a i a function of recycled DF and HDPE and first-generation
panels.
86
-------
1st Gen. Pane
2nd Gen. Panels
0.18 r-
0.16
_ 0.14
^
o~-
"JT 0.12
O
'£ 0.1
(0
£0.08
S 0.06
"~" 0.04
0.02
0
16
0.15
Figure 29. Task 4, Recyclability. Linear expansion at
first-generation panels.
30 percent RH as a function of recycled DF and HDPE
-------
231st Gen. Pane
2nd Gen. Panels
0.8 i-
r^r 0.6
c
o
c
co
Q.
X
LU
CO
CD
C
0.4
0.2
0
Figure 31.
Task 4, Recyclability. Linear expansion •<
first-generation panels.
it 90 percent RH as a function of recycled DF and HDPE and
Y//////y/y/y/y/ys////w^^
A. Screw
B. Barrel
C. Heater
D. Thermoc'ouple
E. Feed throat
F. Hopper
G. Thrust bearing
H. Gear reducer
I. Motor
Figure 32. Schematic of single-screw extruder.
88
-------
Figure 33. Schematic of K-mixer.
BO
'nT
Q_
^
r 70
-1— •
D)
I
+-»
w
"I 60
•»J
X
o
u_
c;n
ONP
-
Unfilled = 41.1
i
•
WF
A
\/IPa
i
30
35
40
45
Filler content (%)
Figure 34. Study MB-1. Flexural strength as a function of filler content and type.
89
-------
3
Q.
O
c:
150
130
110
90
70
ONP
Unfilled = 650
30
Figure 35. Study MB-1. Unnotched impact energy a;
•5* 100001
v>
a. 7000
35 40
Filler content (%)
a function of filler content and type.
(0
o
o
(0
c
0
h.
CO
Q.
Q.
4000-
2000
1000
1 0
20
50
Figure 36. Study MB-1. Apparent melt viscosity
and PP, polypropylene.
9(
WF
J/m
45
42% ONP
37% ONP
32% ONP
42% WF
Unfilled PP
00 200 500 1000
Apparent shear rate (1/s)
of c Mnposite blends. ONP is old newspapers; WF, wood flour;
-------
*m
D.
S
j=
4->
o>
c
0>
*••
"55
c
0
h-
50-
40-
30-
20-
10-
a— ™
— i
Pr
• HL
i • i
x
o> 40-
4-1
w
g 20-
3
X
O/\
__ 0
LL
m, •
• ™
&• ,
•i nr
• PR
A, LJI™
• HL
1- — , . ,
ONP BW-
IPE-MB
• i
40 WF
Filler
Figure 38. Study MB-2. Flexural strength as a function of filler and polymer types.
Type
-------
re
Q.
o
V)
•o
O
c
o
5-
4-
3-
2-
1-
0
PP-V
HDPE-MB
ONP
BW
Filler
•J
Figure 39. Study MB-2. Tensile modulus as a functic n of filler and polymer types.
re
Q.
.§ 30 -
-
S >.
O)
T3 0>
® c
£ o>
o
4_>
O
20-
40
Type
WF
PR-V
HDPE-MB
ONP
BW
Filler
40
Type
WF
Figure 40. Study MB-2. Notched impact energy as a function of filler and polymer types
92
-------
o
CO
Q.
120-
100-
•o I 80-1
o 3-
- >* 60-|
D)
40-
20-
0
•g S
*-•
o
c
c
ID
HDPE-MB
ONP
BW
Filler
40
Type
Figure 41. Study MB-2. Unnotched impact energy as a function of filler and polymer types
U),
CD
•!->
CO
WF
'G-3002
' No additive
Strain
Figure 42. Study MB-3. Effect of coupling agent on tensile stress-strain curve of ONP/PP composites.
93
-------
CO
0.
0)
C
0>
I_
+-I
V)
c
None
Coupling
Figure 43. Study MB-3. Effect of coupling agent on
2001
G-3002
agent
tensile strength of ONP/PP composites.
None E-43 G-3002
Coupling agent
Figure 44. Study MB-3. Effect of coupling agent on impact energy of ONP/PP composites
94
-------
Max. Load
Figure 45. Study MB-4. Effect of wastepaper on tensile stress-strain curve of polypropylene from recycled auto
battery cases (BPP). ONP is old newspapers; OMG, old magazines.
03
OL
CO
e
V)
Unfilled
ONP
OMG
Virgin KPP
Polymer type
Figure 46. Study MB-4. Effect of polymer and waste saper types on tensile strength. KPP is recycled
polypropylene from ketchup bottles.
93
BPP
-------
CO
QL
O
V)
_3
3
•a
o
E
"re
X
0>
Unfilled
ONP
OMG
Virgin
Figure 47. Study MB-4. Effect of polymer and waste; >aper types on flexural modulus,
165 J/m
Unfilled
ONP
OMG
VIRGIN KPI
Polypropylene
BPP
Type
Figure 48. Study MB-4. Effect of polymer and waste] >aper types on notched impact energy
96
-------
> 800 J/m >800 J/m
t
UNFILLED
ONP
OMG
VIRGIN KFJP BPP
Polypropylene Type
Figure 49. Study MB-4. Effect of polymer and wastepaper types on unmatched impact energy.
Raw Materials
V7 U
ZA /A
Compounded
Material
(Initial)
K Mixer
(Initial Compounding) •
xz
Extruder
(Cycles
1-5)
Mechanical Testing
Granulator
Injection
(Specimen
Molder
preparation)
Figure 50. Study MB-5. Processing flow diagram for recycling study,
PRINTED WITH
SOY INK
on recycled paper
-------
PROJ
COMPOSITES FROM R
John A. Youn
ECT SUMMARY
ECYCLED WOOD AND PLASTICS
jquist, George E. Myers,
James H. Muehl, Andrzej M. Krzysik, and Craig M. demons
USDfK Forest Service
Forest Products Laboratory
Madison, Wl 53705-2398
Lisa Brown, Project Officer
Waste Minimization, Destruction, and Disposal Division
Risk Reduction Engineering Laboratory
Cincinnati, OH 45268
ABSTRACT
The ultimate goal of our research was to develop technology to convert recycled
wood fiber and plastics into durable products that are recyclable and otherwise
environmentally friendly. Two processing technologies were used to prepare wood-
plastic composites: air-laying and melt-blending. Research was conducted in
(1) developing laboratory methods foj- converting waste wood, wastepaper, and
waste plastics into forms suitable for processing into composites; (2) optimizing
laboratory methods for making composite panels from the waste materials; (3)
establishing a database on the effects of formulation and bonding agent on physical
and mechanical properties of composites; (4) establishing the extent to which the
composites can be recycled without unacceptable loss in properties; and (5)
reaching out to industry to provide education, to develop applications, and to extend
the database. Overall, the program demonstrated that both air-laid and melt-blended
composites can be made from a varie'ty of waste wood, wastepaper, and waste
plastics. The composites exhibit a broad range of properties that should make them
useful in a wide variety of commercial applications. For air-laid composites, the waste
materials were demolition wood waste and waste plastics from milk bottles
(polyethylene) and beverage bottles (polyethylene terephthalate). Results showed
that air-laid composites made from these waste ingredients possessed properties very
similar to those of composites made from the virgin ingredients. In addition, air-laid
-------
composites containing 20% reground panels possessed some properties that were
superior to those of the original cdinpjosites. For melt-blended composites, waste
materials were wastepaper, polyethylene from milk bottles, and polypropylene from
automobile battery cases or ketchup bottles. Waste magazines were slightly inferior to
waste newspapers as a reinforcing filler; the properties of composites made from
waste newspaper were better than those of composites made from wood flour, which
is currently used in some commercia
composites were generally parallel to
papers, and several spin-off coopera
composites. Properties of wood-plastic
those of the plastics; thus, different balances in
composite properties are possible fro n using waste plastic. Outreach activities
included the organization and presentation of two international conferences on wood
fiber-plastic composites, presentations at many conferences, publication of several
ive studies with industry. One major study with
industry demonstrated the commercial feasibility of making melt-blended composites
from old newspapers and polypropylene.
STUDIES ON AIR-LAID COMPOSITES
Air-laid (AL) web composites provide
properties and costs, depending upon
poor attraction and low interfacial bonding
hydrophobic polyolefin limit the reinfo
wood component. We compared the
of flat panel composites made from virgin
in two series of tests:
AL Series 1. PET systems
• Virgin hemlock wood fiber (HF), virgin polyester fiber (VPET), phenolic resin
• HF, recycled PET (RPET), phenolic resin
options for balancing performance
the application under consideration. However,
between the hydrophilic wood and
'cement imparted to the plastic matrix by the
mechanical and dimensional stability properties
and postconsumer waste wood and plastics
(DF), VPET, phenolic resin
• Demolition waste wood fiber
• DF, RPET, phenolic resin
AL Series 2. HOPE systems
• HF and virgin high-density polyethylene (VHDPE)
• HF and recycled HOPE
• DF and VHDPE
• DF and RHDPE
-------
Proportions of components were based on ovendry fiber weight. For AL Series 1,
the proportions were 80% wood fiber/10% PET/10% phenolic resin. For AL Series 2,
the proportions were 60% wood fiber/30% HDPE/5% PET/5% tackifier (E-10).
We also studied the recyclability of air-laid composites by testing the mechanical
properties of second-generation panels made from AL Series 2 panels. Two
formulations were tested. Each formu ation consisted of 30% RHDPE, 5% VPET, and
5% E-10 tackifier. In addition, one fornulation had 60% DF and no refiberized first-
generation panels; the other formulation had 40% DF and 20% refiberized first-
generation panels.
Methods and Materials
Experiments consisted of the fol
air-forming equipment to ensure that
owing sequence of steps: (a) modifying the FPL
uniform machine- and cross-machine direction
webs could be produced routinely; (m converting raw materials into forms suitable for
use in this equipment; (c) producing air-formed webs; (d) selecting and stacking the
webs to produce mats of a given weight; (e) consolidating the mats in a platen press to
produce test panels; (f) cutting test specimens from panels; and (g) testing properties.
For both test series, each data set was tested for normality at the 95%
confidence level using Shapiro-Wilk
performed and the means were compared at the 95% confidence level using Tukey's
method of multiple comparisons.
The raw materials studied in the
into three general classes: cellulosic
statistical analysis. An analysis of variance was
air-forming portion of this research program fell
fibers, plastics, and additives.
Cellulosic Fibers
Two basic types of wood fiber were used in the AL series of tests. The first was
virgin western hemlock wood fiber (HF), which was produced in a pressurized single-
disk refiner from 100% pulp-grade ch
which was derived from waste wood
Boston, Massachusetts, area.
ps. The second was demolition wood fiber (DF),
rom buildings that had been torn down in the
-------
Plastics
The virgin polyester (VPET) Was 5.5 denier (6.1 x 10"7 kg/m), 38 mm long, and
crimped, and had a softening temperature greater than 215°C. The recycled polyester
fiber, which was spun from recycled soft drink containers, was 6.00 denier, 51 rnm
long, and crimped. For all the air-laid
the fibers together within the mat.
The virgin high-density polyethy
experiments, VPET served as a matrix to hold
ene (VHDPE) was a blow-molding polymer
normally used as a feedstock for plastic milk bottles. The flakes were cryogenically
flow index of the recycled HOPE was 0.7.
ground to a (-)35 mesh size/The mel
Additives
Liquid phenolic resin was used as the binder for the AL Series 1 panels; it had a
solids content of 51% to 53% and a prl of 9.5 to 10.0 at 25°C. The resin was sprayed
10% solids by weight as it rotated in a drum-
on the wood fiber at 25°C at a level of
type blender.
For the AL Series 2 boards, the wood fiber was blended with granulated HOPE.
Previous work had showed that a tackifier was needed to retain the granule HOPE in
the web during the web formation process. Preliminary testing had also indicated that
the tackifier, a wax emulsion of oxidized low molecular weight polyethylene (E-10),
did not have an adverse effect on the properties of the resultant test panels. The
tackifier was applied to the wood fibers in a rotating drum blender with an air spray
gun in a manner similar to the application of phenolic resin in the AL Series 1 studies.
T
Equipment Modifications and Additions
A 305-mm-wide, laboratory-scale Rando-Webber forming machine was used to
make nonwoven mats for the air-laid composites. The equipment was modified to
minimize the density gradient across the web, a problem encountered in preliminary
experiments.
Panel Fabrication
Nonwoven webs were weighed,
sorted, and stacked on the basis of weight and
specific gravity. A steam-heated platen press was used to press the panels to a
thickness of 3.2 mm and a specific giavity of 1.0. A cooling cycle was used to
maintain target thickness.
The recyclability part of the study required that we determine the feasibility of
recycling panels made for AL Series 2, which contained DF and RHDPE. We found
-------
that we needed to recycle the boards
produce the desired fiber length and
Tests on Mechanical and Physical Properties
We evaluated the performance
through the pressurized refiner to be able to
bundles.
panels made for AL Series 1 (PET systems),
AL Series 2 (HOPE systems), and recyclability.
Results of Tests on PET Systems (AL
Series 1)
In general, the mechanical, water resistance, and dimensional stability
properties of panels made from recycled materials were equivalent to similar
properties obtained from panels containing all virgin or virgin/recycled materials.
Therefore, the recycled ingredients tested in AL Series 1 could replace virgin
materials with minor consequences.
Mechanical Properties
Panels made with the HF/VPET
formulation had the highest bending MOR value
(50.6 MPa), although no statistically significant differences were observed for MOR
values for either wood fiber or PET variations. The modulus of elasticity (MOE) values
followed a different pattern. In both the HF and DF groups, the MOE values of boards
containing RPET were significantly higher than those of boards containing VPET; total
average increase for this property was 16% for both groups.
For the HF/VPET formulation, tensile strength was 33.0 MPa; tensile strength
decreased by 14% for the HF/RPET fbrmulation. However, when RPET or VPET fibers
were used with DF fibers, no significant differences were noted. In contrast to tensile
strength, the incorporation of RPET fibers increased tensile modulus (MOE) by 6%
and 7% for HF and DF formulations,
respectively, although these differences were
not statistically significant.
Impact energy of specimens frorri the HF and DF formulations showed a
consistent trend. Impact strength was respectively 20% and 10% higher for HF and
DF formulations containing VPET fibers compared to formulations containing RPET
fibers.
-------
Table 1. Results of water soak and linear expansion tests for AL series3
l
Composite0
AL Series 1
HF-80%
VPET-10%
PR-10%
HF-80%
RPET-10%
PR-10%
DF-80%
VPET-10%
PR-10%
DF-80%
RPET-10%
PR-10%
AL Series 2
HF-60%
VHDPE-30%
VPET-5%
E10 wax-5%
HF-60% ,
RHDPE-30%
VPET-5%
E10 wax-5%
DF-60%
VHDPE-30%
VPET-5%
E10 wax-5%
DF-60%
RHDPE-30%
VPET-5%
E10 wax-5%
24-h water soak
Thickness
swell
25.2 (9)
22.3 (9)
29.8 (14)
26.9 (8)
43.8 (14)
42.7 (21)
45.2 (13)
52.8 (15)
Water
absorption
43.4 (20)
41.3 (25)
48.2 (25)
44.1 (16)
54.9 (17)
61.8 (19)
58.7 (13)
65.8 (16)
Linear expansion (%)
30% RH
0.19 (10)
0.21 (13)
0.20 (11)
0.20 (12)
0.15 (9)
0.17 (12)
0.17 (5)
0.16 (7)
65% RH 90%
0.42 (4) 0.61
0.44 (8) 0.70
0.43 (6) 0.64
0.45 (6) 0.71
0.39 (5) 0.68
0.42 (12) 0.69
0.40 (7) 0.64
0.44 (6) 0.74
RH
(6)
(7)
(7)
(6)
(7)
(12)
(9)
(6)
aValues in parentheses are coefficients of variation (%).
^DF is demolition wood fiber; E10, epolene-maleated polyethylene; HF, hemlock
fiber; VPET, virgin polyester fiber; RPET, recycled polyester; RHDPE, recycled
high-density polyethylene; and VHDPE, virg n high-density polyethylene.
Physical and Dimensional Stability Properties
Thickness swell values were significantly different for HF/RPET and DF/VPET
specimens (Table 1). The HF/RPET specimens had the lowest thickness swell value
(22.3%), and the DF/VPET specimens the highest value (29.8%). Water absorption
values were not significantly different
6
-------
Linear expansion values at 30%
65% and 90% RH, the HF/RPET and
and were statistically different from tl
RH were statistically equivalent (Table 1). At
DF/RPET formulations had slightly higher values
e HF/VPET and DF/VPET formulations.
Results of Tests on HOPE Systems (AL Series 2)
Panels containing virgin and re
:ycled wood fiber/polyethylene had equivalent
mechanical and physical properties. Therefore, as in AL Series 1, the recycled
materials used in AL Series 2 could replace virgin materials with minor
consequences.
Mechanical Properties
The DF/VHDPE panels had the highest bending MOR value at 19.1 MPa,
followed by 18.7 MPa for the HF/RHDPE panels. Generally no statistically significant
differences were observed for MOR values for either wood fiber or HOPE variations.
In contrast, the HF/RHDPE panels had the highest bending MOE value (2.13 GPa)
and the DF/VHDPE panels the lowes
were not statistically significant.
For tensile strength, the highest
MPa). For both wood fiber variations,
not significantly influence tensile stre
MOE value (1.75 GPa); however, these results
value (12.4 MPa) was observed for the
DF/VHDPE formulation; tensile strength of the DF/RHDPE panels was 7% lower (11.5
the use of either virgin or recycled HOPE did
igth values. The HF/VHDPE panels had the
highest tensile MOE (2.81 GPa); incojrporation of RHDPE lowered tensile MOE by
21% (2.23 GPa), a significant change. Tensile MOE values of DF formulations were
about equal, averaging 2.11 GPa.
Type of wood fiber and formulation did not significantly affect impact energy.
Physical and Dimensional Stability Properties
Thickness swelling of DF specimens was an average of 22% higher than that of
HF specimens; the highest value (53%) was observed for the DF/RHDPE formulation
(Table 1). Particularly notable is the fact that RHDPE had a significant effect on only
the DF formulation and not the HF fornulation. Thickness swelling was lowest in the
HF/RHDPE panels (43%).
The formulation had a consisted
Incorporating RHDPE with either type
influence on water absorption (Table 1).
of wood fiber produced a statistically significant
-------
increase in this property (average 13
formulations showed the lowest wate
% increase). The HF/VHDPE and DF/VHDPE
absorption values.
Linear expansion values for all formulations at 30% RH ranged from 0.15 to
0.17% (Table 1). At 65% and 90% RH, the HF/RHDPE and DF/RHDPE formulations
had slightly higher values.
Results of Tests on Recyclability
In general, the mechanical, water resistance, and dimensional stability
properties of second-generation panels made from recycled materials were
essentially equivalent to or better thaji properties obtained from first-generation
panels. Therefore, the second-generation composites, or possibly higher generation
composites, can be produced using recycled materials without the consequence of
reduced property values.
Mechanical Properties
The MOR of second-generation
panels (19.6 MPa compared to 17.4
values of first-generation panels were higher than that of second-generation panels
(2.01 vs. 1.77 GPa). These differences were not statistically significant. The tensile
sanels was higher than that of first-generation
MPa). On the other hand, the bending MOE
strength of second-generation panels
panels. Similar results were obtained
was 19% higher than that of first-generation
or tensile modulus. The higher properties of the
second-generation panels indicate th at wood fiber/RHDPE composites can benefit by
the addition of refiberized material from first-generation panels.
Impact energy values of specimens made from first-generation panels and
second-generation panels were nearly equal and not statistically different.
Physical and Dimensional Stability Properties
In the 24-h water-soak tests, firs;t-generation panels showed 53% thickness swell
(Table 2). Incorporating first-generation panel fibers into second-generation panels
improved this property by 21%. Similar trends were observed for water absorption
values (Table 2). Water absorption or second-generation panels was 18% lower than
that of first-generation specimens. These differences were statistically significant. The
results suggest that the additional HOPE from refiberized first-generation panels
further encapsulated the wood fibers,
thus limiting water uptake by the wood fibers.
-------
the differences were statistically sign
panels into second-generation pane
both 65% and 90% RH.
Linear expansion values were similar for both formulations at 30% RH, although
ficant (Table 2). The incorporation of recycled
s significantly decreased linear expansion at
The positive influence of incorporating 20% first-generation panels into the
second-generation panels may be the result of several factors. The incorporation of
20% refiberized first-generation pane
from 60% to 40%. The actual amount
52%, and the total amount of RHDPE
s reduced the percentage of wood fiber (DF)
of total wood fiber was reduced from 60% to
was increased from 30% to 36%. Likewise, the
percentage of PET and E-10 each was increased by 1%. The increase of these
components, particularly the HOPE, and the decrease of the wood fiber may be a
direct cause for some improvements in property values. More wood fiber was able to
be encapsulated by plastic, thereby rsducing exposure of the wood to moisture.
Table 2. Results of water soak and linear expansion tests on recyclability
specimens3
24-h water soak
Linear expansion (%)
Composite
Thickness Water
swell absorption 30% RH 65% RH 90% RH
First-generation 52.8 (15) 65.8 (16) 0.16 (7) 0.44 (6) 0.74 (6)
panels'3
Second-generation 42.0 (12) 54.3 (12) 0.15 (11) 0.37 (9) 0.52 (11)
panels6
aValues in parentheses are coefficients of variation (%).
bDF-60%, RHDPE-30%, VPET-5%, E10 wax-5%. DF is demolition wood fiber;
RHDPE, recycled high-density polyethylene;
epolene-maleated polyethylene.
CDF-40%, recycled panel-20%, RHDPE-30%
Conclusions
VPET, virgin polyester fiber; and E10,
, VPET-5%, and E10 wax-5%
The Rando-Webber air-forming equipment can be adapted to handle both long and
short synthetic and natural fibers as well as powder. Nonwoven air-laid webs can
be produced that have excellent uniformity in both the machine- and cross-machine
directions.
Recycled and granulated HOPE can be used in the FPL air-forming equipment to
produce an air-laid web that can be subsequently made into flat panels or shaped
sections.
-------
Pressure refining techniques can convert postconsumer demolition wood or
construction waste into fiber bundles that can be processed very successfully in
the FPL air-forming equipment and
sections.
Panels made with recycled materia
materials. Mechanical and physica
subsequently pressed into flat panels or shaped
s compare favorably to those made of virgin
properties of panels made with recycled
polyester fiber or high-density polyethylene and demolition waste wood are similar
to those of panels made with virgin
Second-generation composites, or
produced using recycled materials
materials.
possibly higher generation composites, can be
without the consequence of reduced property
values. Mechanical and physical properties of second-generation panels made
from recycled materials were essentially equivalent to or better than properties
obtained from first-generation panels.
STUDIES ON MELT-BLENDED COMPOSITES
Melt-blending is an inherently low cost, high production rate process in which
wood and/or paper are mixed with molten plastic. These blends can then be formed
into products using conventional plastics processing techniques such as extrusion
and injection molding. The plastic act|s as a means to convey the wood/paper during
processing and the wood/paper fiber bears the load in the final composite, offering an
effective balance between processab lity and strength of end product. With melt-
blending techniques, wood fiber provides several advantages as reinforcement in
thermoplastic composites. These incl jde economy on a cost per unit volume basis,
desirable aspect ratios, flexibility (hence less fiber breakage), and low abrasiveness
to equipment. Composites can be produced containing up to 50 weight percent wood
fiber and are low cost, thermoformab
Methods and Materials
e, and relatively insensitive to moisture.
In laboratory investigations of malt-blended composites, experimental operations
generally proceed through the following sequence of steps: (a) conversion of raw
materials into forms suitable for preparing dry mixtures quantitatively and feeding
those mixtures into the melt-blending
blending by either an extruder or a K-
and (e) measurement of properties.
apparatus, (b) quantitative dry mixing, (c) melt-
mixer, (d) injection molding of test specimens,
10
-------
Five major studies were underta
-------
Plastics
Plastics act as the matrix in the composite. In this program, a baseline matrix
plastic, virgin polypropylene (VPP) homopolymer, was compared to three waste
plastics: polypropylene from auto battery cases (BPP), recycled ketchup bottle
polypropylene (KPP), and recycled high-density polyethylene from blow-molded milk
bottles (HDPE-MB). These plastics were chosen on the basis of low melting
temperature (necessary for use with j/vood/paper fiber), cost, performance, and
availability.
Cellulosic Fibers
Celluloses act as the reinforcing
polypropylene in extruded sheets for
filler in the composite. We used wood flour (WF)
as the primary baseline filler because it is currently used commercially with
automobile interior panels. We included
relatively expensive (several times th 3 price of WF) pure cellulose fibers (BW40) as
another baseline filler for comparing against recycled fibers—waste newspaper
(ONP) and old magazines (OMG).
Both plastics and additives can
machinery. However, wood or paper
De readily used in traditional plastics processing
Ibers present difficulties during the melt-
blending step. Cellulosic filler must be in a form that can be completely dispersed into
the molten plastic by the shear forces exerted during melt-blending. Wood flour was
readily disaggregated and fully dispersed into individual particles in the plastic using
a simple laboratory single-screw extruder. Although difficult to disperse with an
extruder, a usable blend of BW40 eel ulose fibers was also obtained in this way.
Wastepaper fibers were much more cifficult to handle because of their low bulk
density. For melt-blending in a high ir tensity K-mixer, the paper was milled or ground
into approximately 4- to 8-mm flakes using a small granulator. For melt-blending in an
extruder, the paper was first reduced into fibers by a small modified hammermill.
Coupling Agents
Additives aid the dispersion of fi
ler into the matrix plastic and/or enhance the
bonding (act as a "coupling agent") between filler and matrix. In this program, we
restricted ourselves to Eastman Epolenes (E43, G3002)—maleated polypropylene
"waxes" in which the small degree of
bonding to the cellulose while the po
compatibility with the polypropylene matrix.
12
maleation provides polar groups capable of
ypropylene segments, in theory, offer
-------
Mechanical and Physical Properties
Materials were compounded in either a 38-mm single-screw extruder or a 1 -L K-
mixer. Extrusion parameters were temperature profile 170°C to 190°C, screw speed 15
rpm, and residence time 1 to 2 min. The K-mixer parameters were 4500 to 5500 rpm
and discharge temperature 171°C to 200°C. In all studies, test specimens were
prepared by injection molding. At least five specimens of each blend were tested for
each mechanical property. After mole ing, the specimens were stored over dessicant
for at least 3 days before testing.
Mechanical properties were met sured on the dry specimens at approximately
23°C. Specimens and test methods followed ASTM D256, D638, D747, and D790.
Apparent melt viscosities and shear rates were calculated from measured volumetric
throughput rates and pressure drops across the die during steady-state extrusion in a
single-screw extruder at 190°C.
Selected properties from the various studies are summarized in Table 4. This
table shows the larger effects of some more-sensitive variables. Because the
conditions of each study varied somei/vhat, care must be taken when comparing data.
General trends rather than actual values will be emphasized in the following
discussion.
Reinforcement Effects
Addition of 30%-40% of any of the wood/paper reinforcing fillers to the plastics
resulted in a composite with higher modulus and strength but lower impact energy and
o maximum load. These effects are not
thermoplastics in general. Table 5 summarizes
property changes with addition of 40% ONP to several virgin and recycled
polypropylenes.
Most major changes in composite performance occurred at filler contents below
30%. For example, aside from an app roximate 10% increase in modulus, no major
changes in mechanical performance were found over the rather narrow range of 32%
to 42% ONP in VPP. '
percentage of elongation and energy
surprising and are typical of reinforce
13
-------
Table 4. Selected mechanical property data from various studies
Plastic
PPV
HDPE-MB
PPV
KPP
BPP
Filler
None
40% ONP
40% BW40
40% WF
40% ONP
40% BW40
40% WF
40% ONP
40% ONP
40% ONP
None
40% ONP
40% OMG
None
40% ONP
40% OMG
Coupling
agent
None
E43
E43
E43
E43
E43
E43
None
E43
G3002
None
G3002
G3002
None
G3002
G3002
Tensile
modulus
(GPa)
—
4.89
4.80
3.72
3.80
3.79
2.61
4.97
4.90
4.56
1.62
4.03
3.55
1.32
3.98
3.44
Tensile
strength
(MPa)
31.5
47.1
48.2
34.1
37.6
36.6
27.8
34.0
47.4
52.3
36.5
52.3
38.9
24.5
42.5
31.8
Izod impact energy
Notched Unnotched
(J/m) (J/m)
23.8
20.8
24.7
18.7
28.6
30.8
36.4
20.8
19.8
20.4
62.0
30.6
34.2
165.0
34.3
41.8
650
109
114
72
73
68
81
113
144
190
>800
167
138
>800
150
125
aCoupling agent was added at a lever of 3%'-5% of fiber weight depending on the study
Typically, the more fibrous fillers
(ONP and BW40) resulted in composites with
superior mechanical properties but were more difficult to process when compared to
WF. However, the presence of clays and other impurities in the OMG made the
material more difficult to disperse and interfered with bonding, resulting in decreased
mechanical performance when compared with other fibrous fillers.
Figure 1 demonstrates some effects on viscosity at low shear rates. Viscosity
measurements showed dramatic increases when WF was replaced with ONP and as
fiber content was increased. This incrjease in viscosity demonstrated the effects of
both aspect ratio and filler contents on composite melt behavior. Even at a fiber
loading of 32% ONP, PPV composite
42% WF-filled PPV.
melts were significantly more viscous than a
14
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Table 5. Change in property after
Filled/Unfilled
Property
Tensile
Modulus
Strength
Energy
Elongation
Flexural
Modulus
Strength
Impact
Notched
Unnotched
KPP
2.49
1.49
0.65
0.47
2.29
1.52
0.49
<0.21
BPP
3.00
1.66
0.73
0.46
3.01
1.91
0.21
<0.19
VPP
—
1.66
2.94
2.00
0.86
0.29
o
Q.
e
0)
a
Q.
a.
10000.T
,
7000-
'
4000
2000
1000
1
t
"VS. * — 42%ONP j
N\i 0 — 37%ONP
\V\ » — 32%ONP (
^»XS». n — 42% WF
Dsx~NV* f— unrated PP *
•L N.™
X
0 ~20 50 100 200 500 1000.
Apparent shear rate (Ms)
Figure 1. Apparent melt viscosity of composite blends.
Matrix Effects
Changing the melt flow index (IviFI) of VPP had a significant effect on viscosity
but little effect on mechanical performance over the range studied (3-30 g/10 min).
This result suggests that MFI could be used to compensate for increased viscosity of
the higher performance fibrous composites.
The polypropylene composites v/ere stronger and stiffer than the HDPE-MB
composites but had lower notched impact energy values. The unfilled plastic
composites showed the same trend;
those of the matrix polymers. Similar
BPP and KPP. For example, the use
impact strength) instead of VPP resu
strength, although the difference in tr is property was not nearly as great as that in the
unfilled polymers. In other words, although choice of plastic can affect composite
.e., composite properties qualitatively followed
rends were also seen for composites made with
of BPP (a block copolymer with higher notched
ted in composites with higher notched impact
properties, addition of reinforcement
can affect the mechanisms by which the plastic
achieves its performance.
Analysis of the results of both the filler and plastic effects can lead to some
interesting conclusions. For example, the mechanical properties of a recycled
ONP/HDPE-MB system were at least as good as those of the current commercial
WF/polypropylene system. This may
with the high viscosity of the recycled system can be overcome.
offer some practical utility if problems associated
15
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Coupling Agent Effects
Coupling agents may be incorporated into composites in different ways to
concentrate the material at the interface where it is active. In our studies, adding solid
coupling agent (E43) to the melt or applying emulsified E43 directly to the fiber had
little effect on mechanical performance of composites. Concentrating the emulsified
additive at the fiber/matrix interface by precoating the fibers was apparently
counteracted by the much lower chenical reactivity of the potassium salt with the
cellulose compared with the reactivity of the anhydride with cellulose. Perhaps the
E43 functions more to enhance dispersion of the cellulosic fillers than to bond the
cellulose to the polymer.
The higher molecular weight maleated polypropylene, G3002, had a very
beneficial effect on composite streng
behavior. Initial moduli were approxirr
:h, energy absorption, and unnotched impact
ately the same but ultimate strength and area
under the curves (a measure of toughness) were much greater for systems with
coupling agent (especially G3002). Tie fact that unnotched rather than notched
impact energy was increased indicates that G3002 probably enhances dispersion of
the fibers and reduces aggregates that would act as failure loci. For example,
unnotched impact energy was more affected by removal of failure loci than was
notched impact energy because the notch itself constitutes a failure locus. The
apparently greater interaction of G30Q2 with polypropylene relative to E43 may be
attributable to the higher molecular weight of G3002.
Processing Effects
Little preference was shown for compounding in a K-mixer or a single-screw
extruder with WF or cellulose fiber. However, those fillers are relatively easily
dispersed, and the ONP could not be melt-blended with a single screw. Moreover, the
small interaction terms between filler and compounder in the statistical analysis also
indicated some differences in dispersibility between WF and cellulose fiber.
We investigated the effects of re-extrusion on the mechanical and rheological
performance of three different composite blends. For almost all mechanical and
rheological properties, very little change occurred as the material was recycled over
five cycles. The length and therefore
these decreases were apparently not
composite performance. The WF was
tie aspect ratio of the ONP fiber decreased, but
great enough to result in any large reductions in
reduced in both thickness and length, as
smaller bundles of wood fibers were sheared off the larger particles. These changes in
16
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dimension resulted in no overall change in aspect ratio and, ultimately, in composite
performance.
Conclusions
• Melt-blended composites cannot be prepared with wastepapers as reinforcing filler
using a conventional laboratory single-screw extruder. However, these composites
can be prepared with a laboratory high-intensity K-mixer, an industrial-scale K-
mixer, or a twin-screw extruder that
employs a properly designed feeder for the fiber.
Old newspaper (ONP) as reinforcing filler provides better properties than wood flour,
which is currently used as filler in commercial composites. Old magazines (OMG)
can also be used as a filler, but they are less easily dispersed into the matrix plastic
and result in somewhat lower propejrties than those of composites containing ONP.
With the same filler, substituting recycled milk bottle polyethylene for VPP leads to
lower strength, stiffness, and unnotched impact energy, but higher notched impact
energy.
Use of recycled high density polyethylene from milk bottles and recycled
polypropylene from battery cases as a matrix in composites with ONP results in
improved impact performance when
VPP and ONP.
compared with that of composites made from
Addition of the coupling agent Epolene G3002 at 3 weight percent of filler results in
very useful increases in composite
dispersion.
Select composite systems showed
Droperties, probably as a result of improved fiber
ttle or no loss in mechanical properties
when repeatedly reprocessed (re-extruded and injection molded).
COMMERCIAL
IMPLEMENTATION
The research program led to many cooperative studies with industry and
academia, all with the ultimate goal o
materials.
commercializing composites made with waste
Commercial Feasibility of Waste Newspaper-Thermoplastic Composites
The program was partially funded by the Forest Products Laboratory (FPL) and
the Wisconsin Department of Natural
Resources (DNR) and by in-kind contributions
from the eight cooperating companies. Laboratory experiments demonstrated that old
newspapers could be dispersed as fi
bers into thermoplastics by melt-blending,
17
-------
resulting in substantial improvements
plastic or plastic filled with wood flout
in some properties compared with the unfilled
. Major conclusions are as follows:
Old newspaper/polypropylene (ON D/PP) composites can be compounded on a
commercial scale using either the K-mixer with ONP flakes as feed or using a twin-
screw extruder with ONP fibers fed
separately from the plastic.
An ONP/PP sheet containing 42 weight percent ONP can be prepared by extrusion
on a commercial scale. This sheet
neets existing specifications for automobile
panels and can be thermoformed into a variety of shapes.
Given proper design of melt processing equipment, a wide variety of other
commercial products could be manufactured from ONP/PP composites with similar
ONP content.
Firm estimates of production costs
or ONP/PP composite products must await
additional examination of compounding methods to define optimum balance of
dispersion ability, throughput rate' and cost
improvement in methods to deliver wastepaper in a form and at a cost acceptable
to a compounder or a manufacturer of plastic products
Waste LDPE Program
A consortium of companies is im
"contaminated" by residual fiber from
estigating the use of waste LDPE
a hydropulping operation that scavenges wood
fiber from coated paper stock. The pr Dgram involves raw material processors,
compounders, plastics processors, and research institutions and is being coordinated
by the FPL. Major hurdles in this program are the residual moisture in the raw material
from the hydropulping process and p
'oduct applications.
Waste Jute-Polyester Panels As Reinforcing Filler
In response to interest expressed by a U.S. company in the possibility of
recycling panels produced by impreg lating jute fibers with thermosetting polyester,
we granulated the panels and investigated the ability to use the resultant mixture as
reinforcing filler in melt-blended composites with a polypropylene matrix. Overall, this
waste material produced composite mechanical properties approximately equivalent
to those of similar composites containing wood flour as the reinforcement.
18
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Waste Kenaf Core As Reinforcing Filler
This program resulted from a request by the Agrecol Corporation (Madison,
Wisconsin) to determine whether kenaf core material could be useful as a reinforcing
filler in plastic composites. We granulated the core material and successfully melt-
blended the -40 mesh fraction with polypropylene. The composite properties were
approximately equivalent to those of similar composites containing wood flour.
Therefore, where kenaf core is readi
substitute for wood flour as a reinforc
y available at low cost, it could very likely
ng filler.
Wastewood Composite As Reinforcing Filler
The University of Tennessee extension requested an evaluation of waste wood
composite as a reinforcing filler in thermoplastic composites. Although such solid
waste is available in large quantity; it contains wood with cured thermoset adhesives
that might cause problems in melt-processed composites because the adhesives do
not melt at processing temperatures. We granulated the plywood and successfully
melt-blended the -40 mesh fraction with polypropylene. The composite properties
were approximately equivalent to those of similar composites containing wood flour.
This waste material could therefore substitute for wood flour as a reinforcing filler in
melt-processed composites.
19
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RECOMMENDATIONS
Research
Additional research is needed on both air-laid and melt-blended composites
made from recycled wood fiber and plastics to improve properties and processing and
to thereby increase potential applicai ions.
1. Evaluate the potential for making c omposite materials with other major components
of the waste stream, including low-density polyethylene, polystyrene, and mixed
waste plastics.
2. Verify the recyclability of composites made with reground first-generation
ingredients.
3. Improve melt-blending processes
fiber breakage.
o achieve better fiber dispersion with minimal
4. Improve bonding between wood fiber and plastic matrix to enhance physical and
mechanical properties.
5. Improve impact energy and creep
resistance (decreased deflection under long-
term load), currently the limiting properties of these composite systems.
6. Determine the resistance of these
environments and develop means
biodegradation, and fire.
Commercialization
composite systems to relatively extreme
to enhance resistance to moisture,
1. Continue extensive outreach to in dustry to acquaint companies with these types of
composite systems, to develop applications, and to cooperate in product
development.
2. To obtain commercial acceptance
wastepaper fiber,
of melt-blended composites containing
a. improve methods for converting wastepaper at costs acceptable to industrial
users; costs must at least approach current cost of wood flour (about $0.22/kg)
idir
b. improve methods for melt-blending fiber and plastics on a commercial scale at
costs acceptable to melt fabricators (extruders, injection molders, etc.)
20
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