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OAR Box 1392 

Prepped by Ollie Stewart 

Document Number: 

126) ll-A-1 

Docket Number: 

A-94-52 

Printed 7/7/2008 9:45:58 AM Sheet 126 of 136 
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A-94-52 

%4r\ 

4.12 POLYESTER RESIN PLASTICS PRODUCT FABRICATION 

4.12.1 General Description1-2 

OCT! 91995 ill 

EPA AIR DOCKET 

A growing number of products are fabricated from liquid polyester resin 

reinforced with glass fibers and extended with various inorganic filler 

materials such as calcium carbonate, talc, mica or small glass spheres. 

These composite materials are often referred to as fiberglass reinforced 

plastic (FRP), or simply "fiberglass". The Society Of The Plastics Industry 

designates these materials as "reinforced plastics/composites" (RP/C). Also, 

advanced reinforced plastics products are now formulated with fibers other 

than glass, such as carbon, aramld and aramld/carbon hybrids. In some 

processes, resin products are fabricated without fibers. One major product 

using resins with fillers but no reinforcing fibers istthe synthetic marble 

used in manufacturing bathroom countertops, sinks and related items. Other 

applications of nonreinforced resin plastics include automobile body filler, 

bowling balls and coatings. 

Fiber reinforced plastics products have a wide range of application in 

industry, transportation, home and recreation. Industrial uses include storage tanks, skylights, electrical equipment, ducting, pipes, machine components, and corrosion resistant structural and process equipment. In 

transportation, automobile and aircraft applications are increasing rapidly. 

Home and recreational items include bathroom tubs and showers, boats (building and repair), surfboards and skis, helmets, swimming pools and hot tubs, 

and a variety of sporting goods. 

The thermosetting polyester resins considered here are complex polymers 

resulting from the cross-linking reaction of a liquid unsaturated polyester 

with a vinyl type monomer, most often styrene. The unsaturated polyester is 

formed from the condensation reaction of an unsaturated dibasic acid or 

anhydride, a saturated dibasic acid or anhydride, and a polyfunctional 

alcohol. Table 4.12-1 lists the most common compounds used for each component of the polyester "backbone", as well as the principal cross-linking 

monomers. The chemical reactions that form both the unsaturated polyester 

and the cross-linked polyester resin are shown in Figure 4.12-1. The emission factors presented here apply to fabrication processes that use the 

finished liquid resins (as received by fabricators from chemical manufacturers);, and not to the chemical processes used to produce these resins. 

(See Chapter 5, Chemical Process Industry.) 

In order to be used ln the fabrication of products, the liquid resin 

must be mixed with a catalyst to initiate polymerization into a solid thermoset. Catalyst concentrations generally range from 1 to 2 percent by original 

weight of resin; within certain limits, the higher the catalyst concentration, 

the faster the cross-linking reaction proceeds. Common catalysts are organic 

peroxides, typically methyl ethyl ketone peroxide or benzoyl peroxide. 

Resins may contain inhibitors, to avoid self curing during resin storage, 

and promoters, to allow polymerization to occur at lower temperatures. 

9/88 Evaporation Loss Sources 4.12-1 
P.3 

TABLE 4.12-1. TYPICAL COMPONENTS OF RESINS 

To Form the Unsaturated Polyester 

Unsaturated Acids 

Malelc anhydride 

Fumaric acid 

Saturated Acids 

Phthalic anhydride 

Isophthalic acid 

Adipic acid 

Polyfunctional Alcohols 

Propylene glycol 

Ethylene glycol 

Diethylene glycol 

Dipropylene ^glycol 

Neopentyl glycol 

Pentaerythrltol 

Cross-linking Agents (Monomers) 

Styrene 

Methyl methacrylate 

Vinyl toluene 

Vinyl acetate 

Diallyl phthalate 

Acrylamide 

2-ethyl hexylacrylate 

The polyester resin/fiberglass industry consists of many small facilities (such as boat repair and small contract firms) and relatively few 

large firms that consume the major fraction of the total resin. Resin 

usage at these operations ranges from less than 5,000 kilograms per year 

to over 3 million kilograms per year. 

Reinforced plastics products are fabricated using any of several 

processes, depending on their size, shape and other desired physical 

characteristics. The principal processes include hand layup, spray layup 

(sprayup), continuous lamination, pultrusion, filament winding and various 

closed molding operations. 

Hand layup, using primarily manual techniques combined with open 

molds, is the simplest of the fabrication processes. Here, the reinforcement is manually fitted to a mold wetted with catalyzed resin mix, after 

which it is saturated with more resin. The reinforcement is in the form 

of either a chopped strand mat, a woven fabric or often both. Layers of 

reinforcement and resin are added to build the desired laminate thickness. 

Squeegees, brushes and rollers are used to smooth and compact each layer 

as it is applied. A release agent is usually first applied to the mold 

to facilitate removal of the composite. This is often a wax, which can 

be treated with a water soluble barrier coat such as polyvinyl alcohol to 

promote paint adhesion on parts that are to be painted. In many operational 

4.12-2 EMISSION FACTORS 9/88 
OS 

3aporatl" c m Loss 

REACTION 1 

0 0 

p-HC - CH + 2nH0H2C-CH2OH + e-C-O-C 

a 

Ifcteic EtbyhM HrthaSe 

•Rfcyrffi* tfycol MkytfMt 

REACTION 2 

0 0 0 0 

I I • • 

-C C-O-CH2-CH2-O-C C-O-CM2-CH2-O-

. ^y HC — CH 

• 

Uaotantod! patywtar 

w 

0 

ro I 

u> 

CH2-CH -

Styrant 

Unsaturated 

+

 polyester 

0 

(-o-c-^ 

0 0 0 0 

I I I • /= \ I 

—«. (-CH2 -CH2 -0-C-CH-CH-C-0-CH2 -CH2 -0-C-£A-C-0-)n 

H-C-H 

_C-0-CH2-CH2-O-C-CH-CH-C-O-CH I 2-CH2-)n 

0 H-C-H 

l 

H-C1 

Cross-linked 

polyester resin 

Figure 4.12-1, Typical reactions for unsaturated polyester and 

polyester resin formation. 
P.5 

the mold is first sprayed with gel coat, a clear or pigmented resin mix 

that forms the smooth outer surface of many products. Gel coat spray 

systems consist of separate sources of resin and catalyst, vith an airless 

hand spray gun that mixes them together into an atomized resin/catalyst 

stream. Typical products are boat hulls and decks, swimming pools, bathtubs 

and showers, electrical consoles and automobile components. 

Spray layup, or "sprayup", is another open mold process, differing from 

hand layup in that it uses mechanical spraying and chopping equipment for 

depositing the resin and glass reinforcement. This process allows a greater 

production rate and more uniform parts than does hand layup, and often uses 

more complex molds. As ln hand layup, gel coat is frequently applied to the 

mold before fabrication to produce the desired surface qualities. It is 

common practice to combine hand layup and sprayup operations. 

For the reinforced layers, a device is attached to the sprayer system to 

chop glass fiber "roving" (uncut fiber) into predetermined lengths and project it to merge with the resin mix stream. The stream precoats the chop, 

and both are deposited simultaneously to the desired layer thickness on the 

mold surface (or on the gel coat that was applied to the mold). Layers are 

built up and rolled out on the mold as necessary to form the part. Products 

manufactured by sprayup are similar to those made by hand layup, except that 

more uniform and complex parts can generally be produced more efficiently with 

sprayup techniques. However, compared to hand layup, more resin generally Is 

used to produce similar parts by spray layup because of the inevitable overspray of resin during application. 

Continuous lamination of reinforced plastics materials involves impregnating various reinforcements with resins on an in-line conveyor. The 

resulting laminate is cured and trimmed as it passes through the various conveyor zones. In this process, the resin mix is metered onto a bottom carrier 

film, using a blade to control thickness. This film, which defines the panel's surface, Is generally polyester, cellophane or nylon, and may have a 

smooth, embossed or matte surface. Methyl methacrylate is sometimes used as 

the cross-linking agent, either alone or in combination vith styrene, to 

increase strength and weather resistance. Chopped glass fibers free-fall 

into the resin mix and are allowed to saturate with resin, or "wet out". A 

second carrier film is applied on top of the panel before subsequent forming 

and curing. The cured panel is then stripped of its films, trimmed and cut 

to the desired length. Principal products Include translucent Industrial skylights and greenhouse panels, wall and ceiling liners for food areas, garage 

doors and cooling tower louvers. Figure 4.12-2 shows the basic elements of 

a continuous laminating production line. 

.Pultrusion, which can be thought of as extrusion by pulling, is used to 

produce continuous cross-sectional lineals similar to those made by extruding metals such as aluminum. Reinforcing fibers are pulled through a liquid 

resin mix bath and into a long machined steel die, where heat initiates an 

exothermic reaction to polymerize the thermosetting resin matrix. The composite profile emerges from the die as a hot, constant cross-sectional that 

cools sufficiently to be fed Into a clamping and pulling mechanism. The product can then be cut to desired lengths* Example products Include electrical 

insulation materials, ladders, walkway gratings, structural supports, and 

rods and antennas. 

4.12-4 EMISSION FACTORS 9/8f 
P.6 

Recto mewnng dtvica— 

CunJirtt 

Bonom l*n 

^"^r^r^i" 

fim Crou cui uw or tfmi 

Edgttrim 

r«* 

U

- — J Pud roll 

Inspection art* 

Slacking dtvict 

Figure 4.12-2. Typical continuous lamination production process.2 

Filament winding is the process of laying a band of resin impregnated 

fibers onto a rotating mandrel surface in a precise geometric pattern, and 

curing them to form the product. This is an efficient method of producing 

cylindrical parts with optimum strength characteristics suited to the 

specific design and application. Glass fiber is most often used for the 

filament, but aramld, graphite, and sometimes boron and various metal wires 

may be used. The filament can be wetted during fabrication, or previously 

impregnated filament ("prepreg") can be used. Figure 4.12-3 shows the 

filament winding process, and indicates the three most common winding 

patterns. The process Illustration depicts circumferential winding, while 

the two smaller pictures show helical and polar winding. The various winding patterns can be used alone or in combination to achieve the desired 

strength and shape characteristics. Mandrels are made of a wide variety of 

materials and, in some applications, remain inside the finished product as 

a liner or core. Example products are storage tanks, fuselages, wind 

turbine and helicopter blades, and tubing and pipe. 

Hellcat Winding 

Polar Winding 

9/88 

Figure 4.12-3. Typical filament winding process.3 

Evaporation Loss Sources 4.12-5 
P.7 

Closed, such as compression or injection, molding operations involve 

the use of two matched dies to define the entire outer surface of the part. 

Vhen closed and filled with a resin mix, the matched die mold is subjected 

to heat and pressure to cure the plastic. For the most durable production 

configuration, hardened metal dies are used (matched metal molding). 

Another closed molding process is vacuum or pressure bag molding. In bag 

molding, a hand layup or sprayup is covered with a plastic film, and vacuum 

or pressure is applied to rigidly define the part and Improve surface 

quality. The range of closed molded parts includes tool and appliance 

housings, cookware, brackets and other small parts, and automobile body and 

electrical components. 

Synthetic marble casting, a large segment of the resin products industry, involves production of bathroom sinks, vanity tops, bathtubs and 

accessories using filled resins that have the look of natural marble. No 

reinforcing fibers are used in these products. Pigmented or clear gel coat 

can either be applied to the mold itself or sprayed onto the product after 

casting to simulate the look of natural polished marble. Marble casting 

can be an open mold process, or it may be considered a semlclosed process 

if cast parts are removed from a closed mold for subsequent gel coat spraying. 

4.12.2 Emissions And Controls 

Organic vapors consisting of volatile organic compounds (VOC) are emitted from fresh resin surfaces during the fabrication process and from the 

use of solvents (usually acetone) for cleanup of hands, tools, molds and 

spraying equipment. Cleaning solvent emissions can account for over 36 

percent of the total plant VOC emissions.4 There also may be some release 

of particulate emissions from automatic fiber chopping equipment, but these 

emissions have not been quantified. 

Organic vapor emissions from polyester resin/fiberglass fabrication 

processes occur when the cross-linking agent (monomer) contained in the 

liquid resin evaporates into the air during resin application and curing. 

Styrene, methyl methacrylate and vinyl toluene are three of the principal 

monomers used as cross-linking agents. Styrene is by far the most common. 

Other chemical components of resins are emitted only at trace levels, 

because they not only have low vapor pressures but also are substantially 

converted to polymers.5~6 

Since emissions result from evaporation of monomer from the uncured 

resin, they depend upon the amount of resin surface exposed to the air and 

the time of exposure. Thus, the potential for emissions varies with the 

manner ln vhich the resin is mixed, applied, handled and cured. These factors vary among the different fabrication processes. For example, the 

spray layup process has the highest potential for VOC emissions because the 

atomization of resin into a spray creates an extremely large surface area 

from which volatile monomer can evaporate. By contrast, the emission 

potential in synthetic marble casting and closed molding operations is 

considerably lower, because of the lower monomer content in the casting 

resins (30 to 38 percent, versus about 43 percent) and of the enclosed 

nature of these molding operations. It has been found that styrene 

4.12-6 EMISSION FACTORS 9/8<; 

, INC. 
P.8 

evaporation increases with increasing gel time, wind speed and ambient 

temperature, and that increasing the hand rolling time on a hand layup or 

sprayup results in significantly higher styrene losses.1 Thus, production 

changes that lessen the exposure of fresh resin surfaces to the air should 

be effective in reducing these evaporation losses. 

In addition to production changes, resin formulation can be varied to 

effect the VOC emission potential, In general, a resin with lower monomer 

Content should produce lower emissions. Evaluation tests with low-styreneeaisslon laminating resins having a 36 percent styrene content found a 60 

to 70 percent decrease ln emission levels, compared to conventional resins 

(42 percent styrene), with no sacrifice in the physical properties of the 

laminate.7 Vapor suppressing agents also are sometimes added to resins to 

reduce VOC emissions. Most vapor suppressants are paraffin waxes, stearates 

Of polymers of proprietary composition, constituting up to several weight 

percent of the mix. Limited laboratory and field data Indicate that vapor 

suppressing resins reduce styrene losses by 30 to 70 percent.7"^ 

Emission factors for several fabrication processes using styrene content resins have been developed from the results of facility source tests (B 

Rating) and laboratory tests (C Rating), and through technology transfer 

estimations (D Rating).1 Industry experts also provided additional Information that was used to arrive at the final factors presented ln Table 

Aa!2~2.6 Since the styrene content varies over a range of approximately 30 

to 50 weight percent, these factors are based on the quantity of styrene 

•oaoaer used in the process, rather than on the total amount of resin used. 

The factors for vapor-suppressed resins are typically 30 to 70 percent of 

those for regular resins. The factors are expressed as ranges, because of 

the observed variability in source and laboratory test results and of the 

Apparent sensitivity of emissions to process parameters. 

Emissions should be calculated using actual resin monomer contents. 

Vheii epeciflc Information about the percentage of styrene is unavailable, 

the representative average values in Table 4.12-3 should be used* The sample calculation Illustrates the application of the emission factors. 

Sample Calculation - A fiberglass boat building facility 

consumes an average of 250 kg per day of styrene-containing 

resins using a combination of hand layup (75Z) and spray layup 

(25Z) techniques. The laminating resins for hand and spray layup contain 41.0 and 42.5 weight percent, respectively, of styrene. 

The resin used for hand layup contains a vapor-suppressing agent. 

From Table 4.12-2, the factor for hand layup using a vapor-suppresed 

resin is 2 - 7 (0.02 to 0.07 fraction of total styrene emitted); 

the factor for spray layup is 9 - 13 (0.09 to 0.13 fraction emitted). Assume the midpoints of these emission factor ranges. 

Total VOC emissions are: 

(250 kg/day) [(0.41)(0.045)(0.75) + (0.425)(0.11)(0.25)] 

» 6.4 kg/day. 

A/88 Evaporation Loss Sources 4.12-7 

m P S IM<" 
P.9 

TABLE 4.12-2. EMISSION FACTORS FOR UNCONTROLLED POLYESTER RESIN 

PRODUCT FABRICATION PROCESSES4 

(100 x mass of VOC emitted/mass of monomer input) 

Process 

Hand layup 

Spray layup 

Continuous lamination 

Pultruslond 

Filament windinge 

Marble casting 

Closed moldingg 

Resi 

NVS 

5-10 

9-13 

4 - 7 

4 - 7 

5-10 

1 - 3 

1 - 3 

.n 

VSh 

2 - 7 

3 - 9 

1 - 5 

1 - 5 

2 - 7 

1 - 2 

1 - 2 

Emission 

Factor 

Rating 

C 

B 

B 

D 

D 

B 

D 

Gel 

NVS 

26 - 35 

26 - 35 

c 

c 

c 

f 

c 

Coat 

VSh 

8-25 

8-25 

c 

c 

c 

f 

c 

Emission 

Factor 

Rating 

D 

B 

— 

— 

— 

— 

— 

aReference 9. Ranges represent the variability of processes and sensitivity of emissions to process parameters. Single value factors should be 

selected with caution. NVS • nonvapor-suppressed resin. VS • vapor-suppressed resin. 

bFactors are 30-70% of those for nonvapor-suppressed resins. 

CGel coat Is not normally used in this process. 

dResin factors for the continuous lamination process are assumed to apply. 

aResln factors for the hand layup process are assumed to apply. 

fFactors unavailable. However, when cast parts are subsequently sprayed 

with gel coat, hand and spray layup gel coat factors are assumed to apply. 

gResin factors for marble casting, a semiclosed process, are assumed to 

apply. 

TABLE 4.12-3. TYPICAL RESIN STYRENE- PERCENTAGES 

Resin Application 

Resin Styrene Contents 

(wgt. X) 

Hand layup 

Spray layup 

Continuous lamination 

Filament winding 

Marble casting 

Closed molding 

Gel coat 

43 

43 

40 

40 

32 

35 

35 

*May vary by at least +5 percentage points. 

X2-8 EMISSION FACTORS 9/J8 
P.10 

. • .. V. ' 

Emissions from use of gel coat would be calculated in the same manner. 

If the monomer content of the resins were unknown, a representative value 

of 43 percent could be selected from Table 4.12-3 for this process combination. It should be noted that these emissions represent evaporation of 

styrene monomer only, and not of acetone or other solvents used for cleanup. 

In addition to process changes and materials substitution, add-on control equipment can be used to reduce vapor emissions from styrene resins. 

However, control equipment is infrequently used at RP/C fabrication facilities, due to low exhaust VOC concentrations and the potential for contamination of adsorbent materials. Most plants use forced ventilation techniques to reduce worker exposure to styrene vapors, but vent the vapors 

directly to the atmosphere with no attempt at collection. At one continuous lamination facility where incineration was applied to vapors vented 

from the impregnation table, a 98.6 percent control efficiency was measured.1 Carbon adsorption, absorption and condensation also have been 

considered for recovering styrene and other organic vapors, but these techniques have not been applied to any significant extent in this industry. 

Emissions from cleanup solvents can be controlled through good housekeeping and use practices, reclamation of spent solvent, and substitution 

with water based solvent substitutes. 

References for Section 4.12 

1. M. B. Rogozen, Control Techniques for Organic Gas Emissions from Fiberglass Impregnation and Fabrication Processes, ARB/R-82/165, California 

Air Resources Board, Sacramento, CA, (NTIS PB82-251109), June 1982. 

2. Modern Plastics Encyclopedia, 1986-1987, 63 (10A), October 1986. 

3. C. A. Brighton, G. Pritchard and G. A. Skinner, Styrene Polymers: 

Technology and Environmental Aspects, Applied Science Publishers, Ltd., 

London, 1979. 

4. M. Elsherif, Staff Report, Proposed Rule 1162 - Polyester Resin 

Operations, South Coast Air Quality Management District, Rule Development Division, El Monte, CA, January 23, 1987. 

5. M. S. Crandall, Extent of Exposure to Styrene ln the Reinforced Plastic 

Boat Making Industry, Publication No. 82-110, National Institute For 

Occupational Safety And Health, Cincinnati, OH, March 1982. 

6. Written communication from R. C. Lepple, Arlstech Chemical Corporation, 

Polyester Unit, Linden, NJ, to A. A. MacQueen, U.S. Environmental Protection Agency, Research Triangle Park, NC, September 16, 1987. 

7. L. Walewski and S. Stockton, "Low-Styrene-Emlsslon Laminating Resins 

Prove It in the Workplace", Modern Plastics, 62(8):78-80, August 1985. 

J/88 Evaporation Loss Sources 4.12-9 
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M. J. Duffy, "Styrene Emissions - How Effective Are Suppressed 

Polyester Resins?", Ashland Chemical Company, Dublin, OH, presented 

at 34th Annual Technical Conference, Reinforced Plastics/Composites 

Institute, The Society Of The Plastics Industry, 1979. 

G. A. LaFlam, Emission Factor Documentation for AP-42 Section 4.12; 

Polyester Resin Plastics Product Fabrication, Pacific Environmental 

Services, Inc., Durham, NC, November 1987. 

4.12-10 EMISSION FACTORS 9/88