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EPA/310-R-05-003
EPA Office of Compliance Sector Notebook Project
Profile of the Rubber and Plastic Industry
2nd Edition
Chapters I., II. and III.
February 2005
Office of Compliance
Office of Enforcement and Compliance Assurance
U.S. Environmental Protection Agency
1200 Pennsylvania Avenue, NW (MC 2224-A)
Washington, D.C. 20460
http://www.epa.gov/compliance/resources/publications/assistance/sectors/notebooks/rubber.html
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Rubber and Miscellaneous Plastics Products
Introduction to the Sector Notebook Project
I. INTRODUCTION TO THE SECTOR NOTEBOOK PROJECT
I.A. Summary of the Sector Notebook Project
Environmental policies based upon comprehensive analysis of air, water, and land
pollution (such as economic sector and community-based approaches) are becoming an
important supplement to traditional single-media approaches to environmental protection.
Environmental regulatory agencies are beginning to embrace comprehensive, multistatute
solutions to facility permitting, compliance assurance, education/outreach, research, and
regulatory development issues. The central concepts driving the new policy direction are that
pollutant releases to each environmental medium (air, water and land) affect each other, and that
environmental strategies must actively identify and address these interrelationships by designing
policies for the "whole" facility. One way to achieve a whole facility focus is to design
environmental policies for similar industrial facilities. By doing so, environmental concerns that
are common to the manufacturing of similar products can be addressed in a comprehensive
manner. Recognition of the need to develop the industrial "sector-based" approach within
EPA's Office of Compliance led to the creation of this document.
The Office of Compliance within the Office of Enforcement and Compliance
Assurance (OECA) initiated the Sector Notebook Project to provide its staff and managers with
summary information for 18 specific industrial sectors. As other EPA offices, states, the
regulated community, environmental groups, and the public became interested in this project, the
scope of the original project was expanded. The ability to design comprehensive, common-sense
environmental protection measures for specific industries is dependent on knowledge of several
interrelated topics. The key elements chosen for inclusion in this project are: general industry
information (economic and geographic); a description of industrial processes; pollution outputs;
pollution prevention opportunities; federal statutory and regulatory framework; compliance
history; and a description of partnerships that have been formed between regulatory agencies, the
regulated community, and the public.
For any given industry, each topic listed above could alone be the subject of a
lengthy volume. However, to produce a manageable document, this project focuses on providing
summary information for each topic. This format provides the reader with a synopsis of each
issue, and references where more in-depth information is available. EPA used a variety of
sources to compile each profile and usually condensed the information from more detailed
sources pertaining to specific topics. This approach allows for a wide coverage of activities that
can be further explored using the references listed at the end of this profile. As a check on the
information included, each Notebook went through an external document review process. The
Office of Compliance appreciates the efforts of all those that participated in this process and
enabled us to develop more complete, accurate and up-to-date summaries. Many of those who
reviewed this Notebook are listed as contacts in Section IX and may be sources of additional
information. The individuals and groups on this list do not necessarily concur with all
statements within this notebook.
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Introduction to the Sector Notebook Project
I.B. Additional Information
Providing Comments
OECA's Office of Compliance plans to periodically review and update the
notebooks and will make these updates available both in hard copy and electronically. If you
have any comments on any of the existing notebooks, or if you would like to provide additional
information, please send a hard copy and computer disk to: EPA Office of Compliance, Sector
Notebook Project (2224-A), 1200 Pennsylvania Ave., NW, Washington, D.C. 20460. Comments
can also be sent via the Sector Notebooks web page at: http://www.epa.gov/compliance/
sectornotebooks.html. If you are interested in assisting in the development of new Notebooks, or
if you have recommendations on which sectors should have a Notebook, please contact the
Office of Compliance at (202) 564-2310.
Adapting Notebooks to Particular Needs
The scope of the industry sector described in this Notebook approximates the
national occurrence of facility types within the sector. In many instances, industries within
specific geographic regions or states may have unique characteristics that are not fully captured
in these profiles. The Office of Compliance encourages state and local environmental agencies
and other groups to supplement or repackage the information included in this Notebook to
include more specific industrial and regulatory information that may be available. Additionally,
interested states may want to supplement the "Summary of Applicable Federal Statutes and
Regulations" section with state and local requirements. Compliance or technical assistance
providers may also want to develop the "Pollution Prevention" section in more detail.
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Introduction to the Products Industry
II. INTRODUCTION TO THE RUBBER AND MISCELLANEOUS
PLASTICS PRODUCTS INDUSTRY
This section provides background information on the size, geographic
distribution, employment, production, sales, and economic condition of the Rubber and
Miscellaneous Plastics Products industry. The type of facilities described within the document
are also described in terms of their Standard Industrial Classification (SIC) codes. Additionally,
this section contains a list of the largest companies in terms of sales.
II.A. Introduction, Background, and Scope of the Notebook
The Rubber and Miscellaneous Plastics Products (RMPP) industry, as defined by
the SIC code 30, includes establishments that manufacture products from plastic resins, natural
and synthetic rubber, reclaimed rubber, gutta percha, balata, and gutta siak. The production of
the rubber mixture is commonly performed in facilities manufacturing rubber products and is
covered under SIC code 30; however, the production of plastic resins is at plastic resin (polymer
and resin) manufacturing facilities (SIC code 28). The majority of plastics products facilities
purchase plastic resins to manufacture products.
Although this SIC code covers most rubber and plastics products, some important
rubber and plastics products are classified elsewhere. These products include boats, which are
classified under SIC code 37 (Transportation Equipment), and buttons, toys, and buckles, which
are classified under SIC code 39 (Miscellaneous Manufacturing Industries). Buttons, toys, and
buckles are grouped according to the final product rather than by process because not all of these
products are made out of rubber or plastic. The RMPP industry does include tire manufacture;
however, tread manufacturing and associated recapping and retreading are classified under SIC
code 7534. EPA recognizes the recapping and retreading process for passenger and truck tires as
similar to original equipment tire operation, specifically, tire production. An in-depth discussion
of the recapping and retreading industry is not included here. The operations and materials used
in retreading tires are similar to the original equipment tire rubber compounding for treads, tire
building, grinding for carcass preparation, vulcanizing, and finishing as described in the new tire
manufacturing process herein.
Although SIC code 30 groups rubber and plastics products together under some of
the three-digit industry codes (e.g., rubber and plastic footwear under SIC code 302), the
majority of economic and process information separates plastic from rubber products. In
addition, because tire manufacturing accounts for such a large portion (almost 50 percent) of all
rubber product manufacturing, tire process and economic information is often discussed
separately from that of other rubber products. Therefore, this industry profile often discusses
plastics products, rubber products, and rubber tires separately.
The Office of Management and Budget (OMB) established SIC codes to track the
flow of goods and services within the economy. OMB has changed the SIC code system to a
system based on similar production processes called the North American Industrial
Classification System (NAICS). Because most of the EPA data systems still compile data based
on SIC codes, this Notebook continues to use the SIC system to define this sector. Table 1
presents the SIC codes for the RMPP industry and the corresponding NAICS codes.
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Table 1: SIC and NAICS Codes
1987
SIC
SIC Description
1997
NAICS
NAICS Description
3011
Tires & inner tubes
326211
Tire mfg (except retreading)
3021
Rubber & plastics footwear
316211
Rubber & plastics footwear mfg
3052
Rubber & plastics hose & belting
326220
Rubber & plastics hose & belting mfg
3053
Gaskets, packing, & sealing devices
339991
Gaskets, packing & sealing devices mfg
3061
Mechanical rubber goods
326291
Rubber product mfg for mechanical use
3069
Fabricated rubber products, n.e.c.
313320
Fabric coating mills (pt)
326192
Resilient floor covering mfg (pt)
326299
All other rubber product mfg
3081
Unsupported plastics film & sheet
326113
Unsupported plastics film & sheet (except
packaging) mfg
3082
Unsupported plastics profile shapes
326121
Unsupported plastics profile shape mfg
3083
Laminated plastics plate & sheet
326130
Laminated plastics plate, sheet, & shape mfg
3084
Plastics pipe
326122
Plastics pipe & pipe fitting mfg
3085
Plastics bottles
326160
Plastics bottle mfg
3086
Plastics foam products
326140
Polystyrene foam product mfg
326150
Urethane & other foam product (except
polystyrene) mfg
3087
Custom compound purchased resins
325991
Custom compounding of purchased resin
3088
Plastics plumbing fixtures
326191
Plastics plumbing fixture mfg
3089
Plastics products, n.e.c.
326122
Plastics pipe & pipe fitting mfg
326199
All other plastics product mfg
335121
Residential electric lighting fixture mfg
II.B. Characterization of the RMPP Industry
The following subsections describes the types of products produced by rubber and
miscellaneous plastics products facilities, the size and distribution of these types of facilities, and
the current and projected economic trends for the RMPP industry.
II.B.l. Product Characterization
The Bureau of the Census divides SIC code 30 into industry groups according to
the type of product manufactured. The following is a list of all the three-digit industry groups
under SIC code 30:
• SIC Code 301- Tires and Inner Tubes;
• SIC Code 302- Rubber and Plastics Footwear;
• SIC Code 305 - Hose and Belting and Gaskets and Packing;
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SIC Code 306 - Fabricated Rubber Products, Not Elsewhere
Classified; and
SIC Code 308 - Miscellaneous Plastics Products, Not Elsewhere
Classified.
Several of these three-digit classifications group rubber and plastics products
together. However, the four-digit classifications clearly segregate the two industries. The
following are four-digit SIC code breakdowns of the rubber and plastics products industries as
shown in Figure 1 for SIC code 308:
• Plastics Products, Not Elsewhere Classified (N.E.C.) (SIC code 3089)
account for approximately 55 percent of all plastic product production in
the United States;
• Unsupported Plastics Film & Sheet (SIC code 3081) account for
approximately 12 percent;
• Plastics Foam Products (SIC code 3086) account for approximately 10
percent;
Custom Compound Purchased Resins (SIC code 3087) account for
approximately 6 percent;
Plastics Bottles (SIC code 3085) account for approximately 5 percent;
Unsupported Plastics Profile Shapes (SIC code 3082) account for
approximately 4 percent;
Plastics Pipe (SIC code 3084) and Laminated Plastics Plate & Sheet (SIC
code 3083) account for approximately 3 percent each; and
Plastics Plumbing Fixtures (SIC code 3088) for approximately 2 percent.
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Figure 1: Diversity of the Miscellaneous Plastics Products Industry (SIC Code 308)
Unsupported plastics
profile shapes
4%
Laminated plas plate &
sheet
3%
Plastics bottles
5%
Custom compound
purchased resins —
6%
Plastics foam products
10%
Plastics plumbing fixtures
2%
Unsuppo rted plastics film
& sheet
12%
Plastics products, n.e.c.
55%
Source: 1997 Bureau of the Census Data.
As shown in Figure 2, in the rubber industry:
• Tire & Inner Tubes (SIC code 3011) manufacturing accounts for
approximately 36 percent of all rubber product production in the United
States;
• Fabricated Rubber Products, Not Elsewhere Classified (SIC code 3069)
account for approximately 22 percent;
• Mechanical Rubber Goods (SIC code 3061) account for approximately 16
percent;
• Gaskets, Packing, & Sealing Devices (SIC code 3053) account for
approximately 13 percent;
• Rubber & Plastics Hose & Belting (SIC code 3052) account for
approximately 10 percent; and
• Rubber & Plastics Footwear (SIC code 3021) account for 3 percent.
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Figure 2: Diversity of the Rubber Products Industry
Rubber & plastics
footw ear
products, n.e.c.
22%
Source: 1997 Bureau of the Census data.
II.B.2 Industry Size and Geographic Distribution
Variation in facility counts occur across data sources due to many factors,
including reporting and definitional differences. This document does not attempt to reconcile
these differences, but rather reports the data as they are maintained by each source.
The Bureau of the Census estimates that in 1997, 789,200 people were employed
by the miscellaneous plastics products industry and 247,800 were employed by the rubber
products industry, of which the tire industry employed 64,400. The value of shipments (revenue
associated with product sales) totaled $120.3 billion in 1997 for the miscellaneous plastics
products industry and $40.4 billion for the rubber products industry, of which the tire industry
contributed $14.7 billion.
Plastic
Because of the wide range of products produced, plastics products are
manufactured in all parts of the country. As shown in Table 2, approximately 47 percent of
miscellaneous plastics products establishments have fewer than 20 employees. This indicates
that there are a large number of small businesses in this industry. Approximately 37 percent of
the industry have between 20 and 100 employees, and only 1 percent have more than 500
employees.
Although miscellaneous plastics products facilities are not concentrated in any
particular region, a few states account for a large percentage of the facilities, as shown in
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Introduction to the Products Industry
Figure 3. These states include California, Ohio, Texas, Michigan, New York, Pennsylvania, and
New Jersey.
Table 2: Facility Size Distribution of the Miscellaneous Plastics Products Industry
Employees per
Facility
Number of Facilities
Percentage of
Facilities
1 to 4
2649
19
5 to 9
1719
12
10 to 19
2182
16
20 to 49
3107
22
50 to 99
2058
15
100 to 249
1685
12
250 to 499
485
3
500 to 999
117
0 (0.8)
1,000 to 2,499
20
0(0.1)
2,500 or more
1
0 (0.007)
Total
14,023
100
Source: 1997 Bureau of the Census data.
Figure 3: Geographic Distribution of the Miscellaneous Plastics Products Industry
(Number of Facilities)
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Rubber
Like the miscellaneous plastics products industry, the rubber products industry
produces a wide range of products. Rubber products manufacturing establishments are located
all across the country. As shown in Table 3, approximately 57 percent of rubber products
establishments, not including tire manufacturers, have fewer than 20 employees. This indicates
that there are a large number of small businesses in this industry. Approximately 26 percent of
the industry have between 20 and 100 employees and only 3 percent have more than 500
employees.
Although these facilities are not concentrated in any particular region, a few states
account for a large percentage of the facilities, as shown in Figure 4. These states include
California, Ohio, Texas, Indiana, Pennsylvania, Florida, Michigan, and Georgia.
Table 3: Facility Size Distribution of the Rubber Products Industry
Employees per
Facility
Number of Facilities
Percentage of
Facilities
1 to 4
770
27
5 to 9
401
14
10 to 19
460
16
20 to 49
520
18
50 to 99
237
8
100 to 249
246
9
250 to 499
103
4
500 to 999
44
2
1,000 to 2,499
31
1
2,500 or more
2
0 (0.07)
Total
2,814
100
Source: 1997 Bureau of the Census data.
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Rubber and Miscellaneous Plastics Products Introduction to the Products Industry
Figure 4: Geographic Distribution of the Rubber Products Industry (Number of Facilities)
Tires
According to the 1997 Census of Manufacturers, there are 160 tire-manufacturing
plants (SIC code 3011) in the United States. During the 2002 National Emission Standards for
Hazardous Air Pollutants (NESHAP) development for tire manufacturing, EPA identified 112
major facilities along with 19 reporting retreading operations. As shown in Table 4, 46 percent
of the identified 160 facilities have less than 20 employees. Labor costs currently represent
about 26 percent of the cost of tire and tube production for U.S. manufacturers. States that
account for a large percentage of facilities include Ohio, Pennsylvania, and Alabama.
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Introduction to the Products Industry
Table 4: Facility Size Distribution of the Tire Industry
Employees per Facility
Number of Facilities
Percentage of
Facilities
1 to 4
30
19
5 to 9
21
13
10 to 19
23
14
20 to 49
16
10
50 to 99
8
5
100 to 249
15
9
250 to 499
10
6
500 to 999
9
6
1,000 to 2,499
26
16
2,500 or more
2
1
Total
160
100
Source: 1997 Bureau of the Census data.
Figure 5: Geographic Distribution of the Tire Industry
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The two largest producers of tires, Goodyear and Michelin, accounted for
approximately 54 percent of tire production in 2001. As shown in Figure 6, the five largest
producers, Goodyear, Michelin, Bridgestone/Firestone, Continental, and Cooper, accounted for
87 percent of production.
Figure 6: North American Tire Sales
Other
13% Goodyear/Dunlop
23%
Source: Tire Business 2001 Annual Report
II.B.3. Economic Trends
Plastic
Consumption of miscellaneous plastics products is highest in the electronics,
health care, construction, transportation, automotive, and food packaging industries. According
to Plastics Data Source, shipments in the U.S. plastics industry decreased 6.6 percent from 2000
to 2002. The compound annual growth rate (CAGR) from 1995 to 2000 was 2.2 percent and the
CAGR from 2000 to 2002 was -5.4 percent, signifying a downturn in the domestic plastics
industry. Categories accounting for the largest increases in growth included Polystyrene Foam
Products (16.2 percent) and Plastics Bottles (14.5 percent). Categories accounting for the largest
decreases included Resilient Floor Covering (15.5 percent) and Urethane and Other Foam
Products (13.9 percent). Long-term, the aging population in the United States will make plastics
in healthcare a growth industry but pressures to cut costs will squeeze margins. Plastics in the
construction industry will continue to be strong as maintenance, repair, and remodeling
expenditures grow, even as new housing construction might slow. Packaging demand growth
has slowed during the economic downturn but plastics have continued to gain on other materials
based on performance, price, and convenience.
The three largest export markets for the U.S. plastics industry are Canada,
Mexico, and Japan. In 2000, the U.S. had a trade surplus in plastics products of $894 million.
That surplus turned into a deficit of $132 million in 2001 and a deficit of $1.38 billion in 2002
with the deficit expected to continue to increase. In 2002, the trade deficit in plastics products
with China was $3.72 billion. Plastics products from China had been mostly consumer goods
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Rubber and Miscellaneous Plastics Products
Introduction to the Products Industry
like cups, plates, curtains, and kitchenware. Now, products like doors, windows, shutters, and
builders' ware are hitting the U.S. market. In 2002, Canada accounted for 28.9 percent of U.S.
plastics products imports while China accounted for 27 percent. U.S. plastics products exports
no longer compete favorably against lower cost producers in many third-country markets.
Rubber
The sales of industrial rubber products are expected to rise 5.7 percent per year to
more than 18 billion in 2006, outpacing growth in the general economy. This market is closely
linked to durable goods shipments. Sales for mechanical rubber goods, hose, and belting will be
aided by the auto industry. The trend to create quieter and more comfortable cars is promoting
sales of weather stripping and vibration control materials. Slower growth is expected in the
construction industry through 2006, resulting in lower demands for industrial rubber products
such as roofing, flooring, and weatherstripping. The U.S. industrial rubber products industry has
been undergoing a major restructuring process for over a decade.
Trading patterns reflect the U.S. rubber industry's position as a moderately
competitive producer; the United States is both a major exporter to industrialized nations and an
importer of lower-cost products from developing countries. Imports continue to make inroads in
the domestic market and stand at a nearly 2:1 ratio to exports.
Tires
The tire industry shows signs of stabilizing after undergoing a period
characterized by massive restructuring, the effects of recession in the domestic market, and
consistently high levels of imports. With tire durability pushed to what many consider the
practical limit, industry strategy has shifted to servicing the fast-growing emerging markets for
high-performance, light truck, and recreational vehicle tires.
Replacement tires for passenger cars dropped 4 percent in 2001 while
replacement tires for commercial truck tires dropped 10 percent. These declines were offset by
10.6 percent growth in high-performance tires and 10.2 percent growth in light truck tires. The
tire industry saw a 2.6 percent growth (anticipated negligible growth) in 2002 and a slight
increase of 0.6 percent over 2002 and 2003 (but anticipated growth of over 4 percent in 2003).
Industry shipments reached record levels in 2000, with higher than average growth expected for
the high-performance, truck, and light truck tires and little or no growth projected for passenger
tires installed on new cars.
Key growth figures for segments in the tire industry include the following:
• Original Equipment Passenger Tires - Little or no growth is anticipated
from 2004 through 2009 (growth through 2007 expected to be less than
0.3 percent annualized), partially due to greater light vehicle production
outside the United States.
• Original Equipment Light Truck Tires - Growth through 2009 expected to
be 2.7 percent annualized.
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Introduction to the Products Industry
• Original Equipment Medium/Wide-Base Truck Tires - Growth through
2006 expected to be 50 percent from 2003 level, topping out in 2006 due
to EPA restrictions on emission standards for these trucks.
• Replacement Passenger Tires - Growth through 2009 expected to be
slightly over 2 percent annualized.
• Replacement Light Truck Tires - Growth through 2009 expected to be just
under 3 percent annualized.
• Replacement Medium/Wide-Base Truck Tires - The market grew at a 5.5
percent rate in 2003. This growth rate is expected to continue through
2006 and then remain at this level through 2009.
• Tread rubber for retread tires rebounded in the second half of 2003.
Shipments through 2005 are expected to increase with an annual growth
rate of 2.7 percent through 2005.
During the 1980s, corporate restructuring, mergers, and acquisitions resulted in
the globalization of the tire industry. More than half of domestic production capacity is now
owned by foreign-based tire manufacturers, mainly European and Japanese. Among the
advantages realized by the surviving companies are increased resources for research and
development, and economies of scale across procurement, manufacturing, distribution, and
service.
All four of the major tire producers in the United States are involved in the
production of the synthetic rubber used in tire production, and two of these producers own and
operate natural rubber plantations. More than 80 percent of the sales revenue of the four major
producers (both foreign and domestic) is derived from tires and related transportation products
such as rubber belts and hoses.
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Industrial Process Description
III. INDUSTRIAL PROCESS DESCRIPTION
This section describes the major industrial processes within the RMPP industry,
including the materials, equipment, and processes used. The section is designed for those
interested in gaining a general understanding of the industry, and for those interested in the
interrelationship between the industrial process and the topics described in subsequent sections
of this profile - pollutant outputs, pollution prevention opportunities, and federal regulations.
This section does not attempt to replicate published engineering information that is available for
this industry. Refer to Section IX for a list of reference documents that are available.
This section describes commonly used production processes, associated raw
materials, the by-products produced or released, and the materials either recycled or transferred
off site. Coupled with schematic drawings of the identified processes, this section concisely
describes where wastes may be produced in the process and also describes the potential fate (air,
water, land) of these waste products.
III.A. Industrial Processes in the RMPP Industry
The processes used to manufacture plastic and rubber are very diverse; therefore,
this section presents them individually.
III.A.1. Plastic
The production of plastics products, both solid and foam, is a relatively diverse
industry. Simpler processes consist of: (1) imparting the appropriate characteristics to the plastic
resin with chemical additives; (2) converting plastic materials in the form of pellets, granules,
powders, sheets, fluids, or preforms into either intermediate or final formed plastic shapes or
parts via molding operations; and (3) finishing the product, as shown in Figure 7.
There are also several methods of reacting plastic resin and catalyst materials to
form a thermoset plastic material into its final shape, as shown in Figure 8.
Additives are often mixed with the plastic materials to give the final product
certain characteristics (some of these additives can also be applied to the shaped product during
the finishing process). These plastic additives and their functions, in terms of their effect on the
final product, are listed below.
• Additive Lubricants assist in easing the flow of the plastic in the molding
and extruding processes by lubricating the metal surfaces that come into
contact with the plastic.
• Antioxidants inhibit the oxidation of plastic materials that are exposed to
oxygen or air at normal or high temperatures.
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Rubber and Miscellaneous Plastics Products
Industrial Process Description
Figure 7: Plastics Products Manufacturing Process
/ to Iff Jllf .igiIt C 3 V.Nr;K. I !>fr ''•
i- .1 f?
FORMING £TEP
il\i L in-j * u ; r
v j ; I' •!: ¦ < - .
IIci/r1 b. *<> t uii.
III.--!' r!",n('
MOLDING
OPERATIONS
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Traiufet 4 Csisi^ttssiBB, Blew
MUbtag, koUlxutl)
-~ Fugitive mi Sttck Air
-~ S;I:a |C 3ttJ!n; R«-i:hei
-~ Fufitivi it J S: ; k A;l
-~ \Va;i5'
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Rubber and Miscellaneous Plastics Products
Industrial Process Description
• Antistats impart a minimal to moderate degree of electrical conductivity
to the plastic compound, preventing electrostatic charge accumulation on
the finished product.
• Blowing Agents (foaming agents) produce a cellular structure within the
plastic mass and can include compressed gases that expand upon pressure
release, soluble solids that leach out and leave pores, or liquids that
change to gases and, in the process, develop cells.
• Colorants impart color to the plastic resin.
• Flame Retardants reduce the tendency of the plastic product to burn.
• Heat Stabilizers assist in maintaining the chemical and physical
properties of the plastic by protecting it from the effects of heat such as
color changes, undesirable surface changes, and decreases in electrical and
mechanical properties.
• Impact Modifiers prevent brittleness and increase the resistance of the
plastic to cracking.
• Organic Peroxides initiate or control the rate of polymerization in
thermosets and many thermoplastics.
• Plasticizers increase the plastic product's flexibility and workability.
• Ultraviolet Stabilizers (UV light absorbers) absorb or screen out ultra-
violet radiation, thereby preventing the premature degradation of the
plastic product.
After adding the necessary additives to the plastic pellets, granules, powders, etc.,
the plastic mixture is formed into intermediate or final plastics products. To form solid plastics
products, a variety of molding processes are used, including injection molding, reaction injection
molding, extrusion, blow molding, thermoforming, rotational molding, compression molding,
transfer molding, casting, encapsulation, and calendering. Slightly different processes are used
to make foamed plastics products. The choice of which plastic forming process to use is
influenced by economic considerations, the number and size of finished parts, the adaptability of
particular plastic to a process (various plastic will mold, process, etc., differently), and the
complexity of the post-forming operations. Below are brief descriptions of the most common
molding and forming processes for creating solid plastics products.
Injection Molding: In the injection molding process, plastic granules or pellets
are heated and homogenized in a cylinder until they are fluid enough to be injected (by pressure)
into a relatively cold mold where the plastic takes the shape of the mold as it solidifies.
Advantages of this process include speed of production, minimal post-molding requirements,
and simultaneous multipart molding. The reciprocating screw injection machine is the dominant
technology used in injection molding. The screw acts as both a material plasticizer and an
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Rubber and Miscellaneous Plastics Products
Industrial Process Description
injection ram. The buildup of viscous plastic at the nozzle end of a cylinder forces the screw
backwards as it rotates. When an appropriate charge accumulates, rotation stops and the screw
moves forward, thereby becoming an injection ram, forcing the melt (liquefied plastic) into the
mold. The screw remains forward until the melt solidifies and then returns to repeat the cycle, as
shown in Figure 8. Products made in this way include CDs, DVDs, kitchen utensils, automotive
components, garbage cans, and countless others.
Figure 8: Injection Molding
hopper slide
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metering zone
25%
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25%
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Source: McGraw-Hill Encyclopedia of Science and Technology.
Reaction Injection Molding: In the reaction injection molding process, two
liquid plastic components, polyols and isocyanates, are mixed at relatively low temperatures (75
-140 degrees F) in a chamber and then injected into a closed mold to form polyurethane
products. The parts molded using this process can be foams or solids, and they can range from
being flexible to extremely rigid. Products include large polyurethane foams for noise
abatement and large panels for any indoor or outdoor application. Polyurethane is also used to
encapsulate items and protect them from the environment.
Reaction injection molding requires far less energy than other injection molding
systems because an exothermic reaction occurs when the two liquids are mixed. Reaction
injection molding is a relatively new processing method that is quickly becoming common in the
industry. Reinforced reaction injection molding involves placing long fibers or fiber mats in the
mold before injection.
Extrusion: In the extrusion process, plastic pellets or granules are fluidized,
homogenized, and formed continuously as the extrusion machine feeds them through a die, as
shown in Figure 9. The result is a very long plastic shape such as a tube, pipe, sheet, or coated
wire. Extruding is often combined with post-extruding processes such as blowing,
thermoforming, or punching. Extrusion molding has an extremely high rate of output (e.g., pipe
can be formed at a rate of 2,000 lb/hr (900 kg/hr)).
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Figure 9: Extrusion
feed thermocouple hardened screen adapter
Source: McGraw-Hill Encyclopedia of Science and Technology.
Blow Molding: Blow molding describes any forming process in which air is
used to stretch and form plastic materials. In one method of blow molding, a tube is formed
(usually by extrusion molding) and then made into a free-blown hollow object by injecting air or
gas into the tube. Blow molding can also consist of putting a thermoplastic material in the rough
shape of the desired finished product into a mold and then blowing air into the plastic until it
takes the shape of the mold, similar to blowing up a balloon. Examples of products include a
wide variety of beverage and food containers.
Thermoforming: In the thermoforming process, heat and pressure are applied to
plastic sheets, which are then placed over molds and formed into various shapes. The pressure
can be in the form of air, compression, or a vacuum, as shown in Figure 10. This process is
popular because compression is relatively inexpensive. Products include clam shells and blister
packaging for the shipping industry as well as thin plastic components for retail packaging.
Rotational Molding: In the rotational molding process, finely ground plastic
powders are heated in a rotating mold to the point of either melting and/or fusion. The inner
surface of the rotating mold is then evenly coated by the melted resin. The final product is
hollow and produced scrap-free. Products include fuel tanks, side paneling for vehicles, and
carrier cases.
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Figure 10: Thermoforming
plastic sheet clamp
Source: McGraw-Hill Encyclopedia of Science and Technology.
Compression and Transfer Molding: In the compression molding process,
plastic powder or a preformed plastic part is plugged into a mold cavity and compressed with
pressure and heat until it takes the shape of the cavity. Transfer molding is similar, except that
the plastic is liquefied in one chamber and then injected into a closed mold cavity by a
hydraulically operated plunger, as shown in Figure 11. Transfer molding was developed to
facilitate the molding of intricate plastics products that contain small deep holes or metal inserts
because compression molding often ruins the position of the pins that form the holes and the
metal inserts.
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Figure 11: Transfer Molding
Casting and Encapsulation: In the casting process, liquid plastic is poured into
a mold until it hardens and takes the shape of the mold. In the encapsulation or potting process,
an object is encased in plastic and then hardened by fusion or a chemical reaction, as shown in
Figure 12.
Calendering: In the calendering process, plastic parts are squeezed between two
rolls to form a thin, continuous film.
Foamed Plastic: Manufacturing foamed plastics products involves slightly
different forming processes than those described above. The three types of foam plastic are
blown, syntactic, and structural. Blown foam is an expanded matrix, similar to a natural sponge;
syntactic foam is the encapsulation of hollow organic or inorganic micro spheres in the plastic
matrix; and structural foam is a foamed core surrounded by a solid outer skin. All three types of
foam plastic can be produced using processes such as injection, extrusion, and compression
molding to create foam products in many of the same shapes as solid plastics products. The
difference is that creating foam products requires processes such as chemical blowing agent
addition, different mixing processes that add air to the plastic matrix, or a unique injection
molding process used to make structural plastic.
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Figure 12: Encapsulation
/ casting material
potting / y/C
Source: McGraw-Hill Encyclopedia of Science and Technology.
The following are some basic processes that occur in conjunction with the
standard molding and forming operations to produce blown foam plastic and syntactic foam
plastic:
• A chemical blowing agent that generates gas through thermal
decomposition is incorporated into the polymer melt;
• Gas that is under pressure is injected into the melt and then expands
during pressure relief;
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• A low-boiling liquid hydrocarbon is incorporated into the plastic
compound and volatilized through the exothermic heat of reaction;
• Nonchemical gas-liberating agents (adsorbed gas on finely divided
carbon) are added to the resin mix and released during heating;
• Air is dispersed by mechanical means within the polymer (similar to
whipping cream); or
• The external application of heat causes small beads of thermoplastic resin
containing a blowing agent to expend.
Structural foam plastic is made by injection molding liquid resins that contain
chemical blowing agents. Less mixture is injected into the mold than is needed to mold a solid
plastic part. At first the injection pressure is very high, causing the blowing agent mixture to
solidify against the mold without undergoing expansion. As the outer skin is formed, the
pressure is reduced and the remaining resin expands to fill the remainder of the mold. Structural
foam plastic parts have a high strength-to-weight ratio and often have three to four times greater
rigidity than solid plastic molded parts of equal weight that are made of the same material.
After the solid or foam plastic shape is created, post-forming operations such as
welding, adhesive bonding, machining, applying of additives, and surface decorating (painting
and metalizing) are used to finish the product.
Thermoset Resin: To produce a thermoset plastic material, liquid resins are
combined with a catalyst. Resins used for thermoset plastic products include urethane resins,
epoxy resins, polyester resins, and acrylic resins. Fillers are often added to the resin-catalyst
mixture prior to molding to increase product strength and performance and to reduce cost. Most
thermoset plastic products contain large amounts of fillers (up to 70 percent by weight).
Commonly used fillers include mineral fibers, clay, glass fibers, wood fibers, and carbon black.
After the thermoset material is created, a final or intermediate product can be molded.
Various molding options can be used to create the intermediate or final thermoset
product. These processes include vacuum molding, press molding, rotational molding, hand
lamination, casting and encapsulation, spray-up lamination, resin transfer molding, filament
winding, injection molding, reaction injection molding, and pultrusion.
III.A.2. Rubber
Rubber product manufacturing is as diverse as the number of rubber products
produced. Even with this diversity, there are several basic, common processes. This profile
focuses on the basic processes of mixing, milling, extruding, calendering, building, vulcanizing,
and finishing, as shown in Figure 13.
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Figure 13: Rubber Manufacturing Process
------- Fugitive ud Siici Ail
Fs»isle4 Ribktr Froifirt
Potential 7;pe 3: ZPCR A Ssdio-s 31.3 Chemkii Release ci Otlei IFsals Maitpmeit
Source: Emergency Planning and Community Right-To-Know Act (EPCRA) Section 313 Reporting Guidance
for Rubber and Plastics Manufacturing, May 2000.
Mixing: The rubber product manufacturing process begins with the production
of a rubber mix from polymers (i.e., raw and/or synthetic rubber), carbon black (the primary
filler used in making a rubber mixture), oils, and miscellaneous chemicals. The miscellaneous
chemicals include processing aids, vulcanizing agents, activators, accelerators, age resistors,
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fillers, softeners, and specialty materials. The following is a list of these miscellaneous
chemicals and the functions they perform:
• Processing Aids modify the rubber during the mixing or processing steps,
or aid in a specific manner during the extrusion, calendering, or molding
operations.
• Vulcanizing Agents create cross links between polymer chains.
• Activators, in combination with vulcanizing agents, reduce the curing
time by increasing the rate of vulcanization.
• Accelerators form chemical complexes with activators and thus aid in
maximizing the benefits from the acceleration system by increasing
vulcanization rates and improving the final product's properties.
• Age Resistors slow down the deterioration of the rubber products that
occurs through reactions with materials that may cause rubber failure
(e.g., oxygen, ozone, light, heat, radiation).
• Fillers reinforce or modify the physical properties of the rubber, impart
certain processing properties, and reduce costs by decreasing the quantity
of more expensive materials needed for the rubber matrix.
• Softeners either aid in mixing, promote greater elasticity, produce tack, or
extend (replace) a portion of the rubber hydrocarbon (without a loss in
physical properties).
• Specialty Materials include retarders, colorants, blowing agents, dusting
agents, odorants, etc. Specialty materials are used for specific purposes,
and are not required in the majority of rubber compounds.
Rubber mixes differ depending upon the desired characteristics of the product
being manufactured. The process of rubber mixing includes the following steps - mixing,
milling (or other means of sheeting), antitack coating, and cooling. The appropriate ingredients
are weighed and loaded into an internal mixer known as a "Banbury" mixer, which then
combines these ingredients. The area where the chemicals are weighed and added to the
Banbury is called the compounding area. The polymers and miscellaneous chemicals are
manually introduced into the mixer hopper, while carbon black and oils are often injected
directly into the mixing chamber from bulk storage systems. The mixer creates a homogeneous
mass of rubber using two rotors that shear materials against the walls of the machine's body.
The rubber is then cooled as this mechanical action also adds considerable heat to the rubber.
Milling: The mixed rubber mass is discharged to a mill or other piece of
equipment that forms it into a long strip or sheet. The hot, tacky rubber then passes through a
water-based "antitack" solution that prevents the rubber sheets from sticking together as they
cool to ambient temperature. The rubber sheets are placed directly onto a long conveyor belt
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that, through the application of cool air or cool water, lowers the temperature of the rubber
sheets.
After cooling, the sheets of rubber are sent through another mill. These mills
"warm up" the rubber for further processing on extruders and calenders. Some extruders can be
"cold fed" rubber sheets, making this milling step unnecessary.
Extruding: Extruders transform the rubber into various shapes or profiles by
forcing it through dies via a rotating screw. Extruding heats the rubber, which remains hot until
it enters a water bath or spray conveyor where it cools.
Calendering: Calenders receive hot strips of rubber from mills and squeeze them
into reinforcing fibers or cloth-like fiber matrices, thus forming thin sheets of rubber-coated
materials. Calenders are also used to produce nonreinforced, thickness-controlled sheets of
rubber.
Building: Extruded and calendered rubber components are combined (layered,
built-up) with wire, polyester, aramid, and other reinforcing materials to produce various rubber
products. Adhesives, called cements, are sometimes used to enhance the bonding of the various
product layers. This assembling, reinforcing, precuring, and bonding process is called building.
Vulcanizing: All rubber products undergo vulcanization (curing). This process
occurs in heated compression molds, steam-heated pressure vessels (autoclaves), hot air and
microwave ovens, or various molten and fluidized bed units. During the curing process, the
polymer chains in the rubber matrix cross-link to form a final product of durable, elastic,
thermoset rubber. Increasing the number of cross-links in the rubber matrix gives rubber its
elastic quality. One way to visualize this is to think of a bundle of wiggling snakes in constant
motion. If the bundle is pulled at both ends and the snakes are not entangled, then the bundle
comes apart. The more entangled the snakes are (like the rubber matrix after vulcanization), the
greater the tendency for the bundle to bounce back to its original shape.
Finishing: Finishing operations are used to prepare the products for delivery to
the end user. Finishing operations might include balancing, grinding, printing, washing, wiping,
and buffing.
Due to the diversity of products and facilities, not all of the processes shown in
Figure 13 are necessary for every product. For example, many plants do not mix rubber but
purchase uncured rubber from other facilities.
Figure 14 illustrates the processes used to manufacture the following rubber
products:
• Belts - A typical belt plant does not have an extruder but uses many layers
of calendered material assembled on a lathe type builder to produce a
rubber cylinder from which individual belts can be cut.
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Figure 14: Processes Used to Manufacture Various Rubber Products
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Rubber and Miscellaneous Plastics Products Industrial Process Description
• Hoses - A hose plant uses an extruder to produce a tube that is reinforced
with cord or wire and covered with a layer of rubber applied by an
extruder. The same extruder may be used to produce the initial tube and
then to extrude the final "cover" layer onto the reinforced tube.
• Molded Products - A molded products plant uses extruded material to
feed compression molds, or may cut strips directly from the mixing
process to feed the molds.
• Roofing - Roofing manufacturers processes rubber through mills and
calenders to produce the necessary sheeting.
• Sealing - Sealing products manufacturing plants uses extrusion and
continuous vulcanization in hot air ovens.
III.A.3. Tires
The tire manufacturing process is similar to that of manufacturing other rubber
products. The main difference between the two processes is that the building process for
manufacturing tires is generally more complex because there are many rubber components.
As shown in Figure 15, the tire production process in its most basic form consists
of the following sequential steps:
Compounding and mixing elastomers, carbon blacks, pigments, and
other chemicals such as vulcanizing agents, accelerators, plasticizers, and
initiators. The process begins with mixing basic rubbers with process oils,
carbon black, pigments, antioxidants, accelerators and other additives,
each of which contributes certain properties to the compound. These
ingredients are mixed in Banbury mixers operating under tremendous heat
and pressure. They blend the many ingredients into a hot, black gummy
compound that will be milled again and again.
Milling. The cooled rubber takes several forms. Most often it is processed
into carefully identified slabs that will be transported to breakdown mills.
These mills feed the rubber between massive pairs of rollers, over and
over, feeding, mixing, and blending to prepare the different compounds
for the feed mills, where they are slit into strips and carried by conveyor
belts to become sidewalls, treads or other parts of the tire.
Extruding operations use warming mills and either a hot or cold extruder.
The equipment forces the rubber compound through dies that create
individual or a continuous sidewall and tire tread components for future
tire building.
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Figure 15: Tire Manufacturing Process
Ckemksii Feed
Pransui Rubbers
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r'.ig::n e ici Stick Air
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Froce
-~ Fc':e;i:i.ii Tv^e si
?F.A ietticE : I.5 Chemical Release oi Other Waste I-,i r-Liseoeat
Source: Emergency Planning and Community Right-To-Know Act (EPCRA) Section 313 Reporting Guidance
for Rubber and Plastics Manufacturing, May 2000.
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• Tire cord manufacturing and calendering. Processing fabrics and
coating them with rubber is a calendering operation. A specific rubber
coats the fabric that is used to make up the tire's body. The fabrics come in
huge rolls, and they are as specialized and critical as the rubber blends.
Many kinds of fabrics are used, including polyester, rayon, and nylon.
• Bead wire processing. It has high-tensile steel wire forming its
backbone, which will fit against the vehicle's wheel rim. The strands are
aligned into a ribbon coated with rubber for adhesion, then wound into
loops that are then wrapped together to secure them until they are
assembled with the rest of the tire.
• Tire building. Tires are manually built on one or two tire machines. The
tire starts with a double layer of synthetic gum rubber called an inner liner
that will seal in air and make the tire tubeless. The operator uses the tire
building machine to preshape tires into a form very close to their final
dimension to make sure the many components are in proper position
before the tire goes into the mold. The resulting tire is called a "green"
tire, which is uncured.
• Lubricating. The lubrication or spraying system provides a coating,
primarily silicon, on the green tire to afford mold release after curing.
• Vulcanizing and molding. The curing press is where tires get their final
shape and tread pattern. Hot molds like giant waffle irons shape and
vulcanize the tire. The molds are engraved with the tread pattern, the
sidewall markings of the manufacturer, and those required by law.
• Finishing and quality assurance. The operation includes balancing,
grinding, and painting and marking the tire.
The main piece of equipment used in tire-building is the drum, which is a
collapsible cylinder shaped like a wide drum that the tire builder can turn and control. The
building process begins when carcass plies, also known as rubberized fabric, are placed on a
drum one at a time, after which the cemented beads (rubber coated wires) are added and the plies
are turned up around them. Narrow strips of fabric are then cemented on for additional strength.
At this stage, the belts, tread, and sidewall rubber are wrapped around the drum over the fabric.
The drum is then collapsed and the uncured (green) tire is coated with a lubricant (green tire
spray) and loaded into an automatic tire press to be molded and cured. Prior to curing, the tire
looks like a barrel that is open at both ends. The curing process converts the rubber, fabric, and
wires into a tough, highly elastic product while also bonding the various parts of the tire into one
single unit, as shown in Figure 16. After curing, the tire is cooled by mounting it on a rim and
deflating it to reduce internal stress. Finishing the tire involves trimming, buffing, balancing,
and quality control inspection.
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Figure 16: Tire Formation
1—Bead 5—Shoulder pad
2—Bead filter 6—Belt edge insulation
3—Cord plies 7—Nylon cap plies
4—Belts 8—Tread elements
Source: "Tire Materials and Construction " in Automotive Engineering. October 1992.
III.B. Raw Material Inputs and Pollution Outputs in the Production Line
III.B.1. Plastic
Most plastic products are grouped into one of three classifications:
• Thermoplastics. Thermoplastics are plastics that can be heated to become
soft and harden when cooled. This process can be done repeatedly and the
plastics do not normally undergo a chemical change during the forming
process. Thermoplastic products are usually manufactured from solid
pellets purchased from resin manufacturers. Includes: polyethylene -
(HDPE, LDPE, LLDPE, PET); polypropylene - (PP); polystyrene - (PS);
polyvinyl chloride - (PVC); and saturated polyester.
• Thermosets. Thermosets undergo a chemical reaction to make them
permanently solid from heating, pressurizing or reacting with a hardening
agent. They are usually available in liquid or powder form for reacting
into products. Unlike thermoplastics, thermosets are not easily remelted
or refabricated. Includes: epoxy, phenolic, polyurethanes, unsaturated
polyester, and urea-formaldehyde.
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• Foamed Plastics (formed using either thermoplastics or thermosets).
Includes: polyurethane foam, polystyrene foam, and polyethylene foam.
Four general types of pollution and resource material outputs can occur at one or
more stages of the plastics products manufacturing process. In addition, there are some plastics
products disposal concerns. Manufacturing outputs include spills, leaks, and fugitive emissions
of chemicals when additives are applied prior to molding or during finishing; wastewater
discharges during cooling and heating, cleaning, and finishing operations; plastic pellet releases
to the environment prior to molding; and fugitive emissions from molding and extruding
machines, as shown in Figure 17. Each of these is discussed below. Section 4.2 of the
Emergency Planning and Community Right-To-Know Act (EPCRA) Section 313 Reporting
Guidance for Rubber and Plastics Manufacturing contains a good description of pollution
sources for this industry.
Chemicals
One concern during the plastics products manufacturing process is the potential
release of the additive chemicals prior to molding and during the finishing process. Releases
could be in the form of: spills during weighing, mixing, and general handling of the chemicals;
leaks from chemical containers and molding machines; or fugitive dust emissions from open
chemical containers. It should be noted that not all plastics products manufacturers use additives
because many purchased pellets already contain the necessary additives. The chemicals used in
the plastics products manufacturing process are usually added in such small amounts that most
manufacturers do not track them closely; however, some of the additives could be toxic and
therefore releases of even small quantities could present significant problems. According to a
National Enforcement Investigations Center (NEIC) inspector, the plastic industry is currently
looking into both the characteristics of plastic additives and their releases so they can better
understand and address any related environmental or worker safety issues. The following is a
list of some of the typical chemicals used as additives in the plastics products manufacturing
process:
• Lubricants - stearic acid, waxes, fatty acid esters, and fatty acid amines.
• Antioxidants - alkylated phenols, amines, organic phosphites and
phosphates, and esters.
• Antistats - quaternary ammonium compounds, anionics, and amines.
• Blowing/foaming agents - azodicarbonamide, modified azos, and
4,4'-Oxybis(benzenesulfonyl hydrazide). Auxiliary blowing agents are
used to modify foaming and insulation properties. In the past, they were
CFCs such as CFC-11, CFC-12, 113, and 114. CFCs are being replaced
by butane, pentane, HCFC-22, 134a, 142, and liquid C02. A 1992 EPA
rule that implemented the CAA Section 604 gradually phased out methyl
chloroform and CFCs.
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Figure 17: Plastics Products Manufacturing Process Pollution Outputs
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• Colorants - titanium dioxide, iron oxides, anthraquinones, and carbon
black.
• Flame Retardants - antimony trioxide, chlorinated paraffins, and
bromophenols.
• Heat Stabilizers - lead, barium-cadmium, tin, and calcium-zinc.
• Organic Peroxides - methyl ethyl ketone (MEK) peroxide, benzoyl
peroxide, alkyl peroxide, and peresters.
• Plasticizers - adipates, azelates, trimellitates, and phthalates.
• Ultraviolet Stabilizers (UV light absorbers) - benzophenones,
benzotriazole, and salicylates.
Wastewater
Contaminated wastewater is another concern in the miscellaneous plastics
products industry. Water used in the plastic molding and forming processes falls into three main
categories: (1) water to cool or heat the plastics products; (2) water to clean the surface of both
the plastics products and the equipment used in production; (3) and water to finish the plastics
products.
Cooling and heating water usually comes into contact with raw materials or
plastics products during molding and forming operations for the purpose of heat transfer. The
only toxic pollutant that is found in a treatable concentration in some wastewater discharged by
contact cooling and heating processes is bis(2-ethylhexyl) phthalate (BEHP). Since many
facilities do not process materials containing BEHP, this is not an issue for those manufacturers.
Cleaning water includes water that is used to clean the surface of the plastic
product or the molding equipment that is or has been in contact with the formed plastic product.
The types of pollution resulting from cleaning water in treatable concentrations are biochemical
oxygen demand (BOD5), oil and grease, total suspended solids (TSS), chemical oxygen demand
(COD), total organic carbon (TOC), total phenols, phenol, and zinc.
Finishing water consists of water used to carry away waste plastic material or to
lubricate the product during the finishing operation. TSS, BEHP, di-n-butyl phthalate, and
dimethyl phthalate are the pollutants identified in finishing water in treatable concentrations.
Of the pollutants found in all three types of process water, BOD5, oil and grease,
TSS, and pH are considered conventional pollutants, TOC and COD are considered non-
conventional pollutants, and BEHP, di-n-butyl phthalate, dimethyl phthalate, phenol, and zinc
are considered priority toxic pollutants.
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Pellet Release
The third concern in the miscellaneous plastics products industry is the release of
plastic pellets into the environment. Plastic pellets and granules used to mold intermediate and
final plastics products are often lost to floor sweepings during transport or while being loaded
into molding machines, and may end up in wastewater. Although they are inert, plastic pellets
are an environmental concern because of the harm they can cause if runoff carries them to
wetlands, estuaries, or oceans where they may be ingested by seabirds and other marine species.
EPA stormwater regulations classify plastic pellets as "significant materials," and therefore the
discovery of a single pellet in stormwater runoff is subject to federal regulatory action.
Fugitive Emissions
Fugitive emissions from the molding processes may be an environmental concern
because of the many additives, including cadmium and lead, that can be released during the
application of high heat and pressure. Officials from trade associations (e.g., American Plastic
Council and The Society of the Plastics Industry, Inc. (SPI)) are currently researching the
composition of these emissions and their possible effects on air quality.
Solid Waste Disposal
Plastics products also pose solid waste disposal concerns. Discarded plastics
products and packaging make up a growing portion of municipal and solid waste. Because only
a small percentage of plastic is recycled (less than one percent), virtually all discarded plastics
products are put into landfills or incinerated. Current estimates show that plastic constitutes 14
to 21 percent of the waste stream by volume and 7 percent of the waste stream by weight.
Because of its resistance to degradation, improper plastic disposal can have particularly serious
ecological risks and aesthetic effects in the marine environment.
In terms of landfill disposal, the slow degradation of plastic is not a significant
factor in landfill capacity; research has shown that other constituents (e.g., metals, paper, wood,
food wastes) also degrade very slowly. However, the additives contained in plastic, such as
colorants, stabilizers, and plasticizers, may include toxic constituents such as lead and cadmium,
which can leach out into the environment as the plastic degrades. Plastics contribute 28 percent
of all cadmium and approximately 2 percent of all lead found in municipal solid waste. Data are
too limited to determine whether these and other plastic additives contribute significantly to the
leachate produced in municipal solid waste landfills. Plastic that contains heavy metal-based
additives may also contribute to the metal content of incinerator ash.
III.B.2. Rubber
In the rubber products industry, the primary environmental concerns are fugitive
emissions, solid wastes, wastewater, and hazardous wastes, as shown in Figure 18. Each of these
is discussed below.
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Figure 18: Rubber Products Manufacturing Process Pollution Outputs
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Fugitive Particulate Matter (PM) and Volatile Organic Compound (VOC)
Emissions
The compounding area, where dry chemicals are weighed and put into containers
prior to mixing, can be a source of fugitive emissions and possibly spills and leaks. Because
additives must be preweighed, in some facilities the chemicals sit in big open bins on the scales
or while waiting to get on the scales, thus increasing the potential for significant fugitive dust
emissions. Most mixing facilities have eliminated this problem by purchasing their chemicals in
small, preweighed, sealed polyethylene bags. The sealed bag is put directly into the Banbury
mixer thus eliminating a formerly dusty operation. If chemicals are not in preweighed bags,
fugitive emissions are also produced as the chemicals are loaded into the mixer. Emissions from
the internal mixers are typically controlled by baghouses. Exhausts from the collection hoods
are ducted to the baghouses to control particulate and possibly particle-bound semivolatiles and
metals. The following is a list of the major chemicals used in the rubber compounding and
mixing processes that can constitute these fugitive emissions:
• Processing Aids - zinc compounds.
• Accelerators - zinc compounds, ethylene thiourea, and diethanolamine.
• Activators - nickel compounds, hydroquinone, phenol, alpha
naphthylamine, and p-phenylenediamine.
• Age Restorers - selenium compounds, zinc compounds, and lead
compounds.
• Initiator - benzoyl peroxide.
• Accelerator Activators - zinc compounds, lead compounds, and
ammonia.
• Plasticizers - dibutyl phthalate, dioctyl phthalate, and bis(2-ethylhexyl)
adipate.
• Miscellaneous Ingredients - titanium dioxide, cadmium compounds,
organic dyes, and antimony compounds.
VOC and hazardous air pollutant (HAP) emissions are also an environmental
concern in the rubber product manufacturing processes. A 1994 Rubber Manufacturers
Association (RMA) Emissions Factors study analyzed data on VOC and HAP emissions
resulting from the mixing, milling, extruding, calendering, vulcanizing, and grinding processes.
The findings showed extremely low VOC and HAP emissions for each pound of rubber
processed. A facility must process 100,000 pounds of rubber to produce 10 pounds of VOCs
during the mixing process. These emissions may add up, however, at large tire facilities
producing 50,000 tires a day. The average weight of finished passenger and light truck tires is
23.5 pounds (approximately 21 pounds without steel and beads); thus, a 50,000 tire per day
production facility must process at least 1,050,000 pounds of rubber compound.
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Rubber and Miscellaneous Plastics Products
Industrial Process Description
The RMA VOC emissions factors have been sent to EPA for review and are
included in Chapter 4 of the AP-42, in draft. EPA used the emission factors, which include
individual HAP emission factors, in establishing the Maximum Achievable Control Technology
(MACT) standards subpart XXXX for rubber tire manufacturing.
Solvent, cement, and adhesive evaporation is another source of VOC and HAP
emissions. Solvents are used in various capacities during the rubber product manufacturing
process. For example, solvents are used to degrease equipment and tools and as a type of
adhesive or cement during building. Typically, releases of solvents occur either when the spent
solvent solutions are disposed of as hazardous wastes or when degreasing solvents are allowed to
volatilize. Solvent use is decreasing as water, silicon, and non-solvent-based release compounds
are now common.
Wastewater
Wastewater from cooling, heating, vulcanizing, and cleaning operations is an
environmental concern at many facilities. Contaminants can be added to wastewater in direct
contact cooling applications such as extruder cooling conveyors and from direct contact steam
used in vulcanizing operations. The residual in adhesive-dispensing containers and
contaminated adhesives can also be sources of contaminated wastewater.
Zinc is of particular concern as a constituent of stormwater for the facilities
involved in manufacturing and processing rubber products. A study by the RMA identified
several processes through which zinc might be introduced into stormwater. Inadequate
housekeeping is considered to be the primary source of zinc. Inefficient, overloaded, or
malfunctioning dust collectors and baghouses are another source of zinc.
Studies have shown that concern about the leaching potential of rubber products
in landfills is unfounded. The RMA assessed the levels of chemicals, if any, leached from waste
rubber products using EPA's June 13, 1986 proposed Toxicity Characterization Leaching
Procedure (TCLP). TCLP tests were performed on 16 types of rubber products to assess the
leaching potential of over 40 different chemicals, including volatile organics, semivolatile
organics, and metals. Results of the TCLP study indicate that none of the rubber products tested,
cured or uncured, exceeded proposed TCLP regulatory levels. Most compounds detected were
found at trace levels (near method detection limits) from 10 to 100 times less than proposed
TCLP regulatory limits. The TCLP regulatory levels adopted after June 13, 1986 were even less
stringent than the original proposal.
Solid Waste
Solid wastes are also an issue at rubber products manufacturing facilities. Surface
grinding activities that generate dust and rubber particles are typically controlled by a primary
cyclone and a secondary baghouse or electrostatic precipitator. This baghouse-captured PM
(e.g., chemicals, ground rubber) from compounding areas, Banburys, and grinders is a source of
solid waste. Used lubricating, hydraulic, and process oils are also prevalent at most
manufacturing facilities.
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Rubber and Miscellaneous Plastics Products
Industrial Process Description
Scorched rubber from mixing, milling, calendering, and extruding is a major solid
waste source within rubber products manufacturing facilities, as is waste rubber produced during
rubber molding operations. A rubber is scorched when chemical reactions begin to take place in
the rubber as it is being heated. A scorched rubber is no longer processable. Waste rubber can
be classified into three categories: (1) uncured rubber waste; (2) cured rubber waste; and (3) off-
specification products. Currently, much of the uncured rubber waste is recycled at the facility.
Cured rubber waste is either recycled at the facility or sold to other companies that use it to make
products such as mud flaps and playground mats. Off-specification products can be sold to other
companies that make products from shredded or scrap rubber or it can be disposed of. Much of
the off-spec, uncured rubber is sold, reprocessed, or recycled. These practices are discussed
further in Section V.
Tires
The resource material and pollution outputs from the tire manufacturing process
include all of the outputs discussed above in the rubber products manufacturing process. There
is, however, an emphasis on the VOC and HAP emissions that result from solvent use in
cementing and spraying operations, as shown in Figure 19, and on scrap tire disposal.
Volatile Organic Compound Emissions
VOC and HAP emissions from the rubber tire manufacturing process are caused
by solvent application, as a process aide, to the different tire components before, during, and
after the building process (these VOC and HAP emissions can also result from the manufacture
of other rubber products that require cementing or gluing). The principal VOC and HAP
emitting processes affected by New Source Performance Standards (NSPS) and NESHAP
regulations are undertread cementing operations, sidewall cementing operations, tread end
cementing operations, bead cementing operations, green tire spraying operations, Michelin-B
operations, Michelin-C automatic operations, and processes that use solvents and cements in tire
production and puncture sealant operations.
All cementing operations refer to the system used to apply cement to any part of
the tire. The green tire spraying operation refers to the system used to apply a mold release
agent and lubricant to the inside and/or outside of green tires as a process aide during the curing
process and to prevent rubber from sticking to the curing press. VOCs and HAPs are also
emitted in very limited amounts from operations where rubber is heated, including mixing,
milling, extruding, calendering, vulcanizing, and grinding.
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Rubber and Miscellaneous Plastics Products
Industrial Process Description
Figure 19: Tire Manufacturing Process Pollution Outputs
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Rubber and Miscellaneous Plastics Products
Industrial Process Description
Scrap Tires
Probably the biggest environmental concern related to rubber tires is the disposal
of scrap tires. In 2001, it was estimated that the United States generated approximately 300
million scrap tires. Approximately 80 percent of these tires were recycled, reused, or recovered.
Scrap tires pose three environmental threats. One is that tire piles are a fire hazard and burn with
an intense heat that gives off dense black smoke. These fires are extremely difficult to
extinguish in part because tire casings form natural air pockets that supply the oxygen that feeds
the flames. The second threat is that the tires trap rain water, which serves as a nesting ground
for various insects such as mosquitoes; areas where there are scrap tire piles tend to have severe
insect problems. The third and most important environmental threat associated with scrap tires
is that discarded tires are bulky, virtually indestructible, and, when buried, tend to work their
way back to the surface as casings compressed by the dirt slowly spring back into shape and
"float" the tire upward. This problem has led to either extremely high tipping fees for scrap tires
in landfills - at least twice the fee for municipal solid waste - or total bans on whole tires in
landfills. As discussed above, the RMA has conducted testing to verify that tires are not
hazardous wastes based on TCLP analysis. The many efforts underway to address this problem
are discussed in Section V of this profile.
III.C. Management of Chemicals in Waste Stream
The Pollution Prevention Act of 1990 requires facilities to report information
about the management of Toxic Release Inventory (TRI) chemicals in waste and efforts made to
eliminate or reduce those quantities. EPA has collected these data annually in Section 8 of the
TRI reporting Form R beginning with the 1991 reporting year. The data summarized below
cover the years 1998-2001 and is meant to provide a basic understanding of the quantities of
waste handled by the industry, the methods typically used to manage this waste, and recent
trends in these methods. TRI waste management data can be used to assess trends in source
reduction within individual industries and facilities and for specific TRI chemicals. This
information could then be used as a tool in identifying opportunities for pollution prevention
compliance assistance activities.
The quantities reported for 1998 to 2001 are estimates of quantities already
managed. EPA requires these projections to encourage facilities to consider future waste
generation and source reduction of those quantities as well as movement up the waste
management hierarchy.
Table 5 shows that the RMPP industry managed approximately 250,000,000
pounds of production-related waste (total quantity of TRI chemicals in the waste from routine
production operations) in 2001 (column B). Approximately 40 percent of the industry's TRI
wastes were managed on site through recycling, energy recovery, or treatment, as shown in
columns D, E, and F, respectively. The majority of waste that is released or transferred off site
can be divided into portions that are recycled off site, recovered for energy off site, or treated off
site as shown in columns G, H, and I, respectively. The remaining portion of the production-
related wastes (43.0 percent), shown in column J, is either released to the environment through
direct discharges to air, land, water, and underground injection, or it is disposed of off site.
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Rubber and Miscellaneous Plastics Products
Industrial Process Description
Table 5: Quantity of Production-Related Waste Managed by the RMPP Industry
A
B
D
E
F
G
H
I
J
Year
Production-
Related
Waste
Volume
(106 lbs.)
On Site
Off Site
Remaining
Releases
and
Disposal
% Recycled
% Energy
Recovery
% Treated
% Recycled
% Energy
Recovery
% Treated
1998
263
19.53%
7.26%
17.14%
6.66%
3.15%
3.68%
42.57%
1999
251
19.49%
5.77%
15.78%
7.54%
3.23%
3.74%
44.46%
2000
229
18.78%
6.68%
15.16%
6.66%
2.97%
4.12%
45.63%
2001
205
17.07%
11.38%
14.23%
6.48%
3.66%
4.23%
42.95%
Source: Reduction and Recycling Activity for SIC code 30.
The yearly data presented in Table 5 show that the portion of TRI wastes reported
as recycled on site has decreased slightly and the portions treated or managed through energy
recovery on site have increased slightly between 1998 and 2001.
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