P.1 

OAR Box 1500 

Prepped by Ollie Stewart 

Document Number: 

1) ll-C-27 

Docket Number: 

A-94-52 

Printed 8/5/2008 1:45:54 PM Sheet 1 of 343 
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1532. 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

RESEARCH TRIANGLE PARK. NC 27711 

OFFICE OF 

AIR QUALITY PLANNING 

ANU olMIVBHWS""" 

November 7, 1995 

Dear Team and/or Work Group Member: 

. *rJ&W!!<^•^4y^y?"ttK•^yf•••^'^ 

DEC 3 5 

- % > EPA /UR DOCKCT •** s 

I am forwarding a copy of a draft "Pollution Prevention/Source Reduction Measures 

Memorandum" to the trade association members and others who have volunteered to review it. 

This memorandum contains information on the various pollution prevention techniques which 

can be used to reduce emissions in the reinforced plastic composites source category. If anyone 

else would like to review this memorandum, please contact me at (919) 541-2383. 

Sincerely, 

AcMadeleine Strum 

Environmental Engineer 

Coatings and Consumer Products Group 

Enclosure 
P.3 

Addressees: 

Mark Banner, RTI, w/Enclosure 

Mohan Balagopalan, SCAQMD (Electronically sent) 

Janet Beloin, Region I (Electronically Sent) 

Bob Burmark, Washington DOE (Electronically Sent) 

Neil Carman, Sierra Club (for Ben Pamar) 

Leonardo Ceron, Region IV (Electronically Sent) 

Linda Chappell, OAQPS/AQSSD (Electronically Sent) 

Patricia Embrey, OGC (Electronically Sent) 

Bob Fegley, ORD (Electronically Sent) 

Chuck French, OAQPS/AQSSD (Electronically Sent) 

Linda Herring, OAQPS/ESD (Electronically Sent) 

Norm Kaplan, ORD (Electronically Sent) 

Emery Kong, RTI 

Karen Levy, OPAR (Electronically Sent) 

Maria Malave, OECA (Electronically Sent) 

Haile Mariam, OSW (Electronically Sent) 

Craig Matthiessen, OSWER (Electronically Sent) 

Steve McNally, Composites Fabricators Assoc, w/Enclosure 

Christine McPhee, Ohio EPA 

Arnold Medbery, OSDBU (Electronically Sent) 

Richard Nielson, Clark County, NV 

Carlos Nunez, ORD (Electronically Sent) 

Nancy Pate, OAQPS/ITPID (Electronically Sent) 

Solomon Ricks, OAQPS/EMAD (Electronically Sent) 

Ron Ryan, OAQPS/EMAD (Electronically Sent) 

John Schweitzer, Composites Institute, w/Enclosure 

Jordan Spooner, OPPT/PPD (Electronically Sent), w/Enclosure <__ 
P.4 

DRAFT 

MEMORANDUM 

TO: Madeleine Strum 

U.S. EPA/ESD/CCPG 

FROM: Greg LaFlam 

Pacific Environmental Services, Inc. (PES) 

DATE: October 23, 1995 

L:\N308 

SUBJECT: Pollution Prevention/Source Reduction Measures 

This revised memorandum on pollution prevention/source reduction measures for the 

plastic composites source category is being submitted in response to task 1 in Work 

Assignment No. IV-4. Your comments on the September 25, 1995 draft, as well as the 

suggestions you made by telephone, have been incorporated. Please notify me if you would 

like any additional changes made. [Additional changes are indicated in redline, strikeout 

or bold — M. Strum] 

4.0 POLLUTION PREVENTION/SOURCE REDUCTION MEASURES 

4.1 RESINS 

4.1.1 Low Monomer Content Resins/Gel Coats 

Traditional general purpose orthophthalic (ortho) type polyester resins have historically contained approximately 44 to 48 weight percent styrene (or styrene and other HAP 

monomer) content by weight. By the mid-1980's dicyclopentadiene (DCPD) resins with a 

lower monomer content were in use for certain applications, but generally produced 

products that were more brittle and lower in strength. In 1988 the South Coast Air Quality 

Management District (SCAQMD) in California issued Rule 1162, which provides a number 

of control options including an upper limit on the monomer content (after fillers and 

additives are taken into account). Several other areas have implemented regulations since 
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Madeleine Strum DRAFT 

October 23, 1995 

Page 2 

the SCAQMD rule was issued (see industry description memorandum1), some of which 

provide similar options or restrictions on the monomer content of the resin on an "as 

applied" (i.e. after filler and additional styrene have been added) basis. While the great 

majority of applications use large quantities of inorganic solid filler material, eliminating the 

need for these lower monomer content resins, low styrene (less than 35 percent or less) 

resins are available and in use in California and in many other areas. These resins typically 

have a higher viscosity, so it may be more difficult for the resin to wet a surface and 

saturate glass fiber.2 

Limited studies provide indications that low-styrene resins can reduce emissions 

when comparted to regular general-purpose resins, however, they do not allow a definite or 

precise prediction of the quantity of emission reduction in actual production scenarios. A 

demonstration project entitled Reducing Styrene Emissions in Fiber Reinforced Plastics 

Operations6 conducted by the Minnesota Technical Assistance Program found that styrene 

emissions from low-styrene resins were reduced by 25 to 45 percent compared to a conven* 

tional Ortho-based general purpose resin. However^ the emissions measured from the 

simulated production trials were not a typical open molding process, and the emissions 

quantifiesd may not directly apply to actual operations. A Finnish study reported that lowstyrene resins reduced total styrene evaporation by 30 to 60 percent compared to a standard 

resin. In this test, a hand lay up operation was conducted under a laboratory hood. (REFER? 

ENCE: AJ. Saamamen> R.X. Mlemela, T.K. Blotnquist, and E.M. Kikander, Emission of 

Strying During the Hand Lay-Up Molding of Reinforced Polyester, Applied Occupation 

Environmental Hygiene, 6(9):790-793, September 1991.) 

In a study performed by a major resin supplier, of seven resins of different types 

ranging in styrene content from 32.5 to 48 percent; were compared. The two low styrene 

(32.5 and 34 percent) vinyl ester resins lost an average of 20 to 40 percent less styrene as 

emissions than the standard resins. The process tested was a laboratory simulation of a hand 

layup process in which a tongue blade, but no roller as would normally be used in produc-
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Madeleine Strum DRAFT 

October 23, 1995 

Page 3 

tion, was used to spread the resin and wet out the glass.3 Therefore, it may not represent 

emissions and emission reductions expected in an actu<al hand lay up production process. 

The EPA's Office of Research and Development (ORD) carried out a detailed test 

program in mid-1995 to evaluate the emission reduction potential of several pollution 

prevention measures.4 Gel coats containing 25.4 and 38.7 percent styrene and an MEKP 

catalyst were sprayed onto a male FRP mold using three types of spray guns. In nine runs 

with each-resin gelcoat, the low-VOC gel coat reduced total emissions when compared to 

the regular gel coat. When measured in units of grams emitted per square meter of mold 

surface, the reduction was 28 percent (170 to 122 g/m2). (The SCAQMD Rule 1162 static 

emission test, which determines only curing emissions, indicates a 37 percent reduction.) In 

terms of percentage of available styrene (AS) emitted, the reduction was only 3.2 percent 

(56.0 to 54.2 percent AS). This indicates that the emission rate had little dependence on 

monomer content, and that styrene content was the controlling factor in the weight of 

styrene evaporated. 

In the same test program, a series of five resins including a DCPD-based-iow=styrene 

resin two DCPD-based resins containing 3$. 3 and 35.3 percent styrene catalyzed with 

MEKP were applied to a mold with the same three spray guns. Emissions from the lowVOC (35.3 percent styrene) resin were reduced by 11 percent (195 to 173 g/m2

)-when 

eomparcd to controlled resin sprayup, or 38 percent (278 to 173 g/m2)-^en-compared-to 

normal resin sprayup (see Section 4.5.4) of a low-profile DCPD-based resin (3873-percent 

styrene). 

[NOTE: WHEN CFA results are available, they will also be included in this section] 

4.1.2 Vapor Suppressants 

In the late 1970's, a new generation of resins, sometimes termed "low styrene 
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Madeleine Strum DRAFT 

October 23, 1995 

Page 4 

emission" (LSE) resins, was introduced. These LSE resins contain a small quantity of wax 

or paraffin, or some other additive, that is dissolved in the resin. Typically, the additive is 

1 to 2 percent of the resin formulation. As curing begins, the wax migrates to the surface 

and reduces evaporative losses of styrene and other volatiles. These LSE resins are 

presumed effective at reducing emissions only in the curing or static stage. In the preceding 

dynamic phase of resin application (spraying and rollout), the barrier paraffin film is 

continuously disrupted and thus essentially inactive. 

Both resins and gel coats can be formulated with vapor-suppressing additives. In 

EPA's 1993 screening survey ofthe industry, suppressants were reported for the resins used 

in most molding processes, with the exception of continuous lamination and 

pultrusion. By far the most prevalent usage was in sprayup operations (about 22 percent of 

all sprayup operations). An early problem with vapor-suppressed resins involved their 

negative effects on interkiminar adhesion (i.e., laminate layers would show a tendency to 

split or separate under stress due to the presence of the suppressant additive). These 

problems were largely overcome in later generations of LSE resins. A study reported in 

19795 indicated that secondary bonding problems may occur when the resin, glass, or molds 

are at low temperatures (below 65 °F) or when the initial laminate has been allowed to cure 

more than 16 hours before secondary lamination is carried out. High concentrations of 

suppressant (beyond recommended levels) will also cause poor bonding. 

The use of a suppressed resin, even though the resin itself may be more expensive, 

can result in a cost savings with respect to non-suppressed resins. One estimate is that a 

savings of at least $100 per 40,000 lb of suppressed resin could be realized due to about 

1,400 fewer pounds of styrene lost from the resin.5 Additional cost savings may be realized 

through a reduction in air ventilation costs necessary to meet OSHA workplace styrene 

concentration limits.6 

A recent development in LSE gel coats is a gel coat with a 25 percent styrene content 

as well as a vapor-suppressing wax additive. While not yet fully commercially available, 
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Madeleine Strum DRAFT 

October 23, 1995 

Page 5 

this product is undergoing laboratory trials and testing at a number of facilities, and is being 

used at one or two facilities on an ongoing basis. The properties of this product are claimed 

to be comparable, and in some cases superior, to those of currently available gel coats.7,8 

The emission reduction achieved by the use of suppressants is a function of the type 

and amount ol* supressent and tbe type of resin used with the suppressant. This further 

complicates our ability to compute or predict the qu^tity of emission reduction afforded by 

vapor suppressed resins in actual production scenarios. The following describes various 

tests which have been performed to study the reduction of emissions achieved by the use of 

vapor suppressed resins. 

In the study referred to previously in this section5, static emission tests were 

performed to examine the effectiveness of suppressants on curing emissions. Unfilled, 

catalyzed resin was weighed into a 1-gallon can lid and weight readings were taken every 5 

minutes over a 30-minute period. Styrene losses were found to be as much as 50 percent 

lower for resins containing a suppressant. A stondard catalyzed sprayup resin applied to a 

glass mat was also tested, and the suppressant was found to reduce the weight loss by 57 to 

80 percent. An isophthalic, filament winding resin subjected to the same "can lid" test 

showed a 76 to 81 percent reduction in styrene monomer loss when a suppressant was used. 

Finally, in an evaluation of filled resins containing high levels of the fire retardant alumina 

trihydrate (such as used in the tub/shower industry), styrene losses were reduced by about 

70 percent through the use of a suppressed resin. In addition, it was found that the 

suppressant acted as a wetting agent, providing faster glass wetout and necessitating less 

rollout. 

In another test program, styrene-emissions were compared between-two-conventional 

(38.0 and 33.1 percent styrene content). The two conventional resins-were-catalyzed-with 

rron^TiT4)7-^oth-the 
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Madeleine Strum DRAFT 

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Page 6 

static "can lid" test and a process that simulated a sprayup and cure operation were-carried 

out on the samples. In the static tests, the emissions from the LSE resins were 24 to 30 

percent less than the emissions from the conventional resins. Overall emissions in the 

sprayup/curc process ranged from 25 to 36 percent less when using the LSE resinsr6 [This 

emission study tested LOW styrene resins, not vapor suppressed resins. It does not 

belong in the vapor suppressed section. This section can, however, be moved to the 

previous section regarding lower styrene content resins.] 

In the same EPA testing mentioned above in Section 4.1.1, vapor suppressants 

(including the addition of extra wax additive) were found to reduce styrene emissions during 

curing as compared to non-suppressed resins.4 One ortho styrene-suppressed resin catalyzed 

with MEKP and the same suppressed resin with an additional 0.1 percent wax were 

compared with the DCPD-based low-profile resin. The suppressed resin reduced emissions 

by 55 35 percent (278 195 to 126 g/m2), or by 61 |§fpercent hi units of percent available 

styrene (27ri 17.5 to 10.6 percent AS). Total emissions from the resin containing additional wax (suppressant) were not significantly different from the "normal" suppressed resin. 

However, prerelease of the part from the mold was observed for parts made from the resin 

with additional wax. 

4.1.3 Dynamic Phase Suppression > 

As discussed above, the vapor suppressing additives used in LSE resins arei!||||||mi| 

effective only in the curing or static stage. A new line of resins, incorporating a proprietary 

concept termed "intrinsic styrene emission reduction technology" (INSERT), has been 

developed which the manufacturer claims also exhibit reduced styrene evaporation and loss 

in the dynamic phases of the process. These resins contain only 25 percent styrene by 

weight. The first of the new resins include a pre-accelerated general purpose laminating 

resin and an LSE version containing a vapor-suppressing additive. The manufacturer claims 

that mechanical properties of these resins are comparable to conventional general purpose 

resins, and the volume shrinkage is 1.5 to 2 percent less than that of conventional resins. In 
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Madeleine Strum DRAFT 

October 23, 1995 

Page 7 

tests at the manufacturer's facility, the INSERT resin emitted 50 percent less styrene than 

both the standard and the LSE (conventional) resin in the dynamic phase of the sprayup 

9 10 

process. ' 

4.1.4 Catalyst/Initiator Substitution 

Testing has indicated that substitution of benzoyl peroxide (BPO) for the catalyst (or 

initiator) methyl ethyl ketone peroxide (MEKP) may dramatically reduce the emissions that 

occur during the curing process. Part of this effect has been attributed to a reduction in gel 

time and a lower peak exotherm (temperature) while curing at room temperature. In one 

test, the same amount of material was sprayed onto two molds, using the same spray booth 

and the same cpncentration of initiator. During the curing process, the styrene emitted from 

the laminate containing BPO was determined to be two-thirds less than the styrene emitted 

from the laminate containing MEKP as a catalyst. The mechanism thought to be responsible 

for this difference concerns the gel times of the two resin formulations, about 1 hour for the 

BPO catalyzed resin and about 48 hours for the MEKP catalyzed resin.11 In another study6, 

BPO-catalyzed resin outperformed the ability of MEKP-catalyzed resin to reduce emissions 

in both static cure and sprayup/cure simulated production trials. In the static cure ("can 

lid") tests, emissions from the BPO resin (43.9 percent styrene) were 50.9 g/m2, versus 

69.6 g/m2 for the MEKP resin (46.0 percent styrene), or 27 percent lower. In the 

sprayup/cure trials, BPO resin showed 49 percent less emissions in the spray phase and 35 

percent less emissions in the curing phase as compared to the MEKP resin. 

In EPA's recent evaluation test program, emissions were not significantly different 

between resins catalyzed with BPO versus MEKP.4 One DCPD-based resin catalyzed with 

BPO was used in the test series to verify whether the use of BPO in place of MEKP would 

be an effective emission reduction measure. Two versions, a neat resin with 2.1 percent 

BPO catalyst (slow gel time) and a fiime silica thickened resin with 3.1 percent BPO catalyst 

(fast gel time), were tested. The results showed that for both BPO resins the emissions were 

higher than for the low-profile resin catalyzed with MEKP. The neat BPO resin showed an 

/ 
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Madeleine Strum DRAFT 

October 23, 1995 

Page 8 

increase of 69 percent (195 to 330 g/m2), or 50 percent in terms of percent AS (17.5 to 26.2 

percent AS). The modified BPO resin showed increases of 15 percent (195 to 225 g/m2) 

and 22 percent (17.5 to 21.3 percent AS). These results contradict the earlier testing 

results. It should be noted that styrene contents ofthe BPO resins were 46% as compared to 

38% for the DCPD "baseline" resin. Additional information documenting the mechanisms 

affecting emissions when using these two catalysts need to be collected before their effects 

can be positively determined. 

4.1.5 Alternative Monomers and Resin Formulations 

A number of volatile monomer components can be used as a cross-linking 

agent/solvent in the resins, the most common of these being styrene, methyl methacrylate, 

and vinyl toluene. Of these, styrene is by far the most prevalent. Both styrene and methyl 

methacrylate occur on the Clean Air Act's list of hazardous air pollutants (HAP). For most 

purposes, styrene is typically the monomer of choice and is not likely to be replaced to any 

great extent in the foreseeable future. 

Epoxy resin systems are available as direct replacements for polyester or vinyl ester 

resins used in sprayup and hand layup processes. Some manufacturers claim several 

advantages for epoxies, including resistance to blistering, superior fatigue and impact 

resistance and fracture toughness, and outstanding adhesion in secondary bonding applications. These resins also have a longer shelf life and low flammability. Most significantly, 

epoxies contain little or no volatile organic compounds or HAP. Therefore, their contribution to the HAP emissions from a composites facility is often negligible. Epoxy resin 

systems are more expensive that styrenated polyester or vinyl ester resins on a per-pound 

basis, but the advantages cited above may often compensate for this disadvantage.12 

Light-cured or photo-cured resin is another material that has had some application in 

the composites industry. The EPA's 1993 screening survey identified one facility manufacturing chemical resistant laminates using photo-cured resins in a continuous lamination 

process. In processes using photo-cured resins, an additive with sensitivity to ultraviolet 

C 
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Madeleine Strum DRAFT 

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(UV) light is mixed into a standard resin, the resin is applied, the product is exposed to light 

with a specific UV wavelength, and the product cures usually within 10 seconds. This 

curing process involves the decomposition of the photoinitiator by exposure to a particular 

wavelength of light. Once exposed to UV lighting or direct sunlight, the decomposition 

produces free radicals which trigger the polymerization reaction of the resin. The curing 

agent or initiator can be used in either polyester or vinyl ester resins. The composite can 

usually be removed from the mold within 10 minutes. Within 10 seconds of the initial light 

application, the styrene is "locked" inside the part and emissions cease. These photo-curing 

additives have no effect in reducing emissions during spraying or other application methods, 

but only during curing. 

Photo-cured resins have several advantages: they require no mixing with catalysts or 

promoters; there are no limits on processing time, so layup can proceed in stages; the resin 

exhibits fast gelling and short curing times. Also, unused resin that is not exposed to UV 

radiation can be returned to storage. Since resin does not need to be mixed with a catalyst, 

it can be applied directly with a flow coater or roller (see Section 4.2.2) without a mixing 

and metering system. Finally, since cure begins at the surface and moves inward, evaporation of styrene from the surface during cure is reduced.13 

A relatively new resin formulation (Water Emulsified Technology, or W.E.T. resin) 

consists of a water emulsion that contains 40 percent less styrene than standard polyester 

resins.14 This resin is produced by adding proprietary agents to the resin and water 

components, and then blending them together. The water emerges from the resin during the 

curing process, and a high density cellular structure is produced. No post curing is 

required. Secondary bonding may be enhanced due to the properties of the agents that are 

added to emulsify the resin. While no formal emission tests have been performed, the 

developer of the resin constructed a fishing boat using the W.E.T. resin and claimed that 

workers were able to continue to work in a closed building without special ventilation or 

respiratory protection, but needed to frequently leave the building when the same process 
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Madeleine Strum DRAFT 

October 23, 1995 

Page 10 

was performed with a standard resin system. Further, the quality of the finished product 

made from W.E.T. resin was claimed to be excellent. 

The water emulsified resin can be used with either MEKP or BPO catalysts and 

standard spray equipment. In EPA's 1993 screening survey, one facility was using a water= 

based resin for part of its production, and expressed satisfaction with the results. Atthat 

facility, heat was bemg applied to the parts to cure the resrn. Additiond testing by means-of 

formal test methods will be necessary before the merits of water-based resin systems cairbe 

properly evaluated. [Ohio confirmed that this facility was using an epoxy water-based 

system, not a polyester waterbased system] 

4.2 EQUIPMENT CHANGES 

4.2.1 Improved Spraying Equipment 

The three principal types of spray guns used in the industry are airless, air-assisted 

airless, and high volume low pressure (HVLP) guns. Airless guns rely on high fluid 

pressures in the range of 1,000 to 3,000 psi to deliver resin to the mold in resin application 

and resin/chop sprayup operations. These high pressures, while necessary for atomization 

and spray pattern development, may contribute to excessive fogging, overspray, and 

bounce-back during resin application. The consequence is that excess use of resin and 

subsequent evaporation and loss of the volatile monomer component prior to curing 

contributes to emissions, excess waste, and added material expense. ||||B||||l||i||iiii 

industry believe that airless guns are being phased out in this industry, and their use is not 

common. 

Like airless guns, air-assisted airless guns use fluid pressure to atomize resins, but 

the pressures are considerably lower (400 to 1,000 psi). For this reason, pressurized air at 3 

to 30 psi is introduced into the resin spray pattern as it exits the pressure nozzle. While 

these guns cannot match the high volumes of material transfer of conventional air spray and 

airless guns, ^^t^S^BER|the y appear to reduce the excessive resin use that accompanies use of these other guns. This makes for a cleaner work environment and, conse-
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Madeleine Strum DRAFT 

October 23, 1995 

Page 11 

quently, less overspray and less monomer emissions. This spraying equipment can be 

adapted to existing resin delivery systems at a relatively low cost. 

A more recent development is the introduction of HVLP spray equipment similar to 

that in use in many painting operations. These guns utilize low pressure air spray (10 psi or 

less) delivered to the gun at high volumes (10 to 20 cfm). Material (hydraulic) pressure 

ranges between 200 and 2,000 psi. Once the gel coat or resin leaves the orifice, the low 

pressure air completes the atomization and encapsulates the resin fan on its way to the mold 

surface. This creates a soft, low velocity spray which reduces the level of overspray. 

Transfer efficiencies in the range of 65 percent (versus about 40 percent for conventional air 

spray guns) have been reported by one manufacturer for HVLP equipment. In one comparison of airless and HVLP spray at a boat building facility, the HVLP spray equipment 

reduced the overspray by an estimated 25 percent.15 The EPA's 1993 screening survey 

indicated that 11 gel coating operations (7.2 percent) and 7 sprayup operations (4.4 percent) 

were using HVLP. No data were provided in the survey on the use of airless or air-assisted 

airless equipment. 

In EPA's recent test program, in which significant efforts were taken to keep 

operator spray techniques the same, three gun types were tested: air-assisted 

airless/external mix (AAA), HVLP/external mix, and HVLP/internal mix.4 In an experiment in which two gel coat formulations were spray applied, the AAA gun was considered 

the baseline case and was compared to the HVLP spray guns. The effects of internal and 

external catalyst mixing were evaluated for the HVLP spray guns. The measured total 

emissions for the regular gel coat were 373, 387, and 400 grams for the AAA, 

HVLP/internal, and HVLP/external spray guns, respectively. For the low-VOC gel coat, 

emissions were 272, 278, and 284 grams for the three guns. The conclusion from the 18 

test runs was that there was no difference in emissions when using these particular gun 

types; i.e., the transfer efficiency of each of the guns was similar. Additional information 

will have to be collected to properly evaluate the efficiencies of the available spray guns. 
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Madeleine Strum DRAFT 

October 23, 1995 

Page 12 

Transfer efficiency (the amount of sprayed material actually accumulating on the 

mold expressed as a percentage of the total amount of material leaving the spray gun) is a 

function not only of the specific application equipment but also of the mold shape and size, 

air flow through the work area, and the technique of the operator, which is -(probably the 

largest impact)-(this is discussed in more detail in section 4.5.4). 

4.2.2 Substitution for Spray Equipment7,8 

Pressure-fed roller dispensing of resin is being fairly widely used as an alternative to 

spray application. Like spraying systems, resin roller dispenser units utilize a low-pressure 

fluid pumping system to draw resin from drums or bulk distribution lines. This pumping 

system also includes a separate, adjustable catalyst pump. Delivery rates for catalyzed 

resins may be as high as 20 pounds per minute. As the operator rolls out the reinforcing 

materials in the mold, the flow of resin can be applied and controlled as needed through a 

trigger mechanism. 

Resin roller dispensers can transfer catalyzed resins to the molding surface while 

totally eliminating the dynamic material losses inherent in the spraying process. Installation 

of this equipment does not require major modifications to the production facility or the 

tooling already in place. The protective clothing and respiratory protection needed in 

spraying is also eliminated. Resin rollers are available through most companies that 

manufacture spray equipment. Manufacturers claim that a resin roller will save a laminator 

5 to 10 percent in resin usage compared to spray application. Figure 4-1 shows a schematic diagram of a resin roller dispenser.16 

Another technology being used to reduce the styrene emissions associated with 

spraying is the flow coater. This system makes use of a special gun (either resin/chopper 

or straight resin) that dispenses resin in narrow, nonatomized streams, rather than in a mist 

as from regular spray guns. 

In EPA's recent evaluation test program, emissions from the use of pressure-fed 

resin rollers and flow coaters were compared to emissions from spraying with AAA guns. 
P.16 

Madeleine Strum DRAFT 

October 23, 1995 

Page 13 

The nonspraying equipment reduced total emissions by 31 to 33 percent when compared to 

controlled spraying (i.e., extra effort was expended to minimize overspray), and by 52 to 53 

percent when compared to normal (ie. t effort was made to simulate production line 

|||||p|||resin spray application. The difference in total emissions between the flow coater 

and the pressure-fed roller was not statistically significant.4 

In EPA's 1993 screening survey, one facility reported that they were applying gel 

coat using brushes (bathtubs and spas) and three reported the use of rollers (swimming 

pools, bus bodies, Md chemical storage tanks). 

4.2.3 Fabric Impregnators 

Reinforcing fabrics pre-saturated with resin (and then cooled after reaching a state of 

partial curing), known as "prepreg," are used in certain lamination operations because ofthe 

advantages they offer in product quality control, production efficiency, and cost effectiveness. A primary use for prepregs is in the advanced composites market, such as the 

aerospace/defense industry. Fabric impregnator equipment is available that provides some 

of the advantages offered by prepregs while using lower cost polyester resins and glass 

reinforcements. Impregnators can be installed so as to feed resin saturated reinforcing 

materials directly to the molding operation. Woven glass rovings are impregnated as they 

pass through a reservoir system containing catalyzed resin. Figure 4-2 shows a 

/ < ^ 
Madeleine Strum DRAFT 

October 23, 1995 

Page 14 

P.17 
P.18 

Madeleine Strum DRAFT 

October 23, 1995 

Page 15 

Figure 4-1. Pressure-fed resin roller dispenser.16 
Madeleine Strum DRAFT 

October 23, 1995 

Page 16 

Figure 4-2. Resin/fabric impregnator system.17 

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rz 
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Madeleine Strum DRAFT 

October 23, 1995 

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schematic of a resin/fabric impregnator system.17 

Fabric impregnation clearly has emission reduction advantages when compared to 

spray operations by eliminating atomization and wasted resin. For many fabricators, 

installation of impregnator systems may require extensive modification in the plant layout 

and production techniques. The potential for savings is greatest where operations demand 

the production of large volumes or resin saturated roll stock.17 

4.3 OPERATIONAL PARAMETER CHANGES 

4.3.1 Covered Resin Baths for Pultrusion Operations 

Covering or partially covering the resin bath or reducing the size of the bath in an 

attempt to reduce evaporation of monomer from the resin has been tried to a limited extent 

at pultrusion facilities. Tests at facilities with covered baths indicate that this measure may 

have an emission reduction impact, but this impact has not been quantified. [Results from 

recent Pultrusion Industry Council testing of a laboratory pultrusion process at Reichhold 

Chemicals will be added when available.] 

4.3.2 Air Flow Effects 

The Pultrusion Industry Council, an activity of the Society of the Plastics Industry 

Composites Institute, conducted an initial (Phase I) series of experiments to characterize the 

effect of key operating variables on styrene emissions from the pultrusion process.18 Among 

the variables studied, air flow tiirough the test chamber (and past the open resin bath) had by 

far the largest effect on emissions. One conclusion from this study is that any open resin 

bath surfaces should be shielded from moving air streams in order to reduce emissions. 

This could include either rigid or curtain-type barriers placed between the bath and the 

source of air flow. The magnitude of the effect of air flow on emissions was One of the 

main goals of the pultrusion experiment conducted September 1995 on a full scale pultrusion 

inachine set up to manufacture ladder rails. [ Results will be added when available.] 

In EPA's recent emission test program, a pilot experiment involving the spray lay up 

pjillll was conducted to evaluate the effects on styrene emissions of changes in air flow 
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Madeleine Strum DRAFT 

October 23, 1995 

Page 18 

velocity in the spray zone. A regular isophthalic (iso) gel coat catalyzed with MEKP was 

sprayed using an AAA gun in a low (30 to 50 ft/min) and a high (90 to 120 ft/min) room air 

flow velocity representing the range of velocities found in an open molding process area or 

in a spray booth. In these tests, the effect of air velocity on emissions was found to be 

statistically insignificant at the air velocities tested.4 

4.3.3 Temperature Control 

The Phase I pultrusion study referred to above indicated that a lowered resin mix 

temperature could have the effect of reducing emissions, at least for the pultrusion process. 

This parameter change has not been studied for the other fabrication processes. It is 

expected that a significant cooling of the resin could have a negative impact on processability or gel time, and thus could affect product properties or production rates. 

Another approach taken by a few pultrusion facilities is to air condition (cool and 

dehumidify) the entire plant production area. Besides providing a more comfortable yearround working environment for employees and cooling the resin materials, this measure 

should reduce or eliminate the need for high speed ventilation fans on the plant floor. This 

in turn would lead to a further reduction in emissions, as discussed above in Section 4.3.2. 

4.3.4 Underwater Curing 

Two facilities responding to EPA's 1993 screening survey reported the use of 

underwater curing as an emission reduction measure. One facility, a manufacturer of 

automotive parts, used this technique for uncured scrap only. The other facility manufactured buttons from resin cylinders. These cylinders are submerged in water at some point in 

the curing cycle. 

4.4 PROCESS CHANGES 

4.4.1 Vacuum Bagging 

4.4.1.1 Traditional bag molding19 

Vacuum bag molding is a technology that has been in existence since the late 1940's. 

In this process, gel coat, reinforcing materials, and catalyzed resin are applied to an open 

-- c! 
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Page 19 

mold, and then the exposed area is covered by special layers of plastic sheet which are 

sealed to the edges of the mold. Before the resin begins to cure, a vacuum is drawn through 

one or more strategically located ports in the mold or the plastic cover. Vacuum molding 

works with flat, female, and male molded parts. The quality of the finished pjuts is 

typically very good. Product with a controlled resin-to-fiber ratio can be produced to be 

virtually porosity-free. Small parts can be made, and epoxies, phenolics, polyesters, and 

vinyl esters can be used with the system. 

Vacuum bag molding processes can be set up to replace or supplement many 

conventional (hand layup or sprayup) open molding operations. Molds are built from the 

same materials and using the same techniques as required for creating open molds. 

Conventional gel coats, resins, and reinforcing materials can be used, and resin delivery can 

be accomplished without atomization. The labor involved in distributing the resin and 

rolling out air bubbles is reduced because the vacuum creates a distribution and compaction 

of the laminate. 

To the extent that resin application using spray techniques may be reduced or 

4 

eliminated, monomer emissions can be reduced. Vacuum bag molding does not reduce 

emissions associated with the application of the resin to the mold, or from any other 

operation that occurs before the bag is placed on the mold. It is presumed to eliminate the 

emissions that would occur during the curing process. The emissions that occur during 

curing on an open mold can be dramatically reduced due to the presence of the plastic sheet 

covering the laminate during most of the curing cycle. Since a more precise part can be 

produced, the trimoff and grinding operations are reduced so that less dust is created. 

Vacuum bag molding appears to be best suited for intermediate volume production of small 

to midsize components. The EPA's 1993 screening survey indicated that vacuum bagging 

(usually in combination with sprayup) is being used at about six facilities to manufacture 

items such as trailer panels, tubs and showers, missile parts, and miscellaneous other 

products. 
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Page 20 

AAA.2 Infusion molding 

Infusion shares many of the characteristics of vacuum bag molding and resin transfer 

molding (see Sections 4.4.1.1 and 4.4.2). Figure 4-3 shows a comparison of the vacuum 

bagging and infusion processes.20 Like RTM (Section 4.4.2), infusion reduces styrene 

emissions by wetting out and curing the laminate in a closed system. 

One form of the infusion process, known as SCRIMP (Seeman Composite Resin 

Infusion Molding Process), provides many emission reduction and product quality benefits 

that its developers claim rival the material and mechanical properties obtained for advanced 

composites (such as epoxy parts made in the aerospace industry that are cured in a 
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October 23, 1995 

Page 21 
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Madeleine Strum DRAFT 

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Page 22 

Figure 4-3. Comparison of vacuum bagging and infusion processes 20 
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Madeleine Strum DRAFT 

October 23, 1995 

Page 23 

temperature-controlled autoclave).7 While the developers claim that almost any part can be 

manufactured using SCRIMP technology, the process is especially suited to large, complex 

parts that have a medium production rate, such as boat hulls and decks. As of October 

1995, the process has been used to produce the following on a production scale: windmill 

blades, larger satellite dishes, rail cars, bridge pilings, amusement rides, shuttle bus bodies, 

and assorted parts for the military. It has also been used to make a number of other parts 

such as swimming pools. SCRIMP produces composites of up to 70-75 percent fiber 

content by volume, and is effective with 50-100 oz. cloth reinforcements (up to 200 oz. 

cloths are anticipated in the future).8 

A typical production process utilizing SCRIMP technology involves the following 

steps: 1) gel coat is applied to the mold normally using spray guns, 2) a stabilizing skin 

coat is applied to the mold (also usually sprayed on), 3) the outer fiberglass fabrics used as 

the outer skin and structural reinforcements are placed against the mold surface with the aid 

of a resin soluble contact adhesive, 4) the core is trimmed and placed in the mold, 

5) the balance of the laminate is placed in the mold including the transverse and longitudinal 

stringers, 6) bagging materials are placed and sealed over the mold, 7) a vacuum of 

approximately 30 inches Hg is applied and maintained, 8) the resin is drawn into the 

evacuated laminate (approximately 45 minutes for a 60-foot boat hull, and 9) the hull is 

ready for demolding the following morning or as soon as the resin cures. Steps 3 through 9 

are considered the SCRIMP process. Step 1 (and sometimes step 2) is typically done as a 

separate process in conjunction with sprayup or hand layup molding processes. 

Advantages claimed for the SCRIMP process are numerous. Compared to prepreg 

(see Section 4.2.3), SCRIMP eliminates the need for refrigerated storage and the processing 

steps needed to prepare prepreg for fabrication. Less material is needed to achieve the same 

results. Better surface quality eliminates rework to correct pinholing and other surface 

faults. A SCRIMP shop is a cleaner operation than the traditional composites shop, with 

very little need for cleaning solvents. 

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Madeleine Strum DRAFT 

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To use the SCRIMP process, laminators must pay a one-time fee in addition to a 

royalty based on the cost of the manufacture of the composite part (labor, materials, 

manufacturing overhead). These costs are for the use of the patent and to pay for training 

covering some proprietary techniques. As of 1995 the fee structure is as follows: 

One-time fee 

$25,000 

$25,000 

$100,000 

Royalty1 

5% 

7% 

5% 

Application 

Boat builder only 

All industrial end-use 

All industrial end-use 

According to the developers, this cost is offset by savings in personnel health and 

safety equipment, plant maintenance and utilities, tools and equipment, and solvent costs. 

For one licensee, there was a return on the investment in less than 1 year.21 

One of the issues facing SCRIMP (and other reinforced plastic molding processes) is 

of a cosmetic nature and is loiown in the industry as "print through." According to the 

developers, the print through profile on SCRIMP parts is somewhat different from that seen 

on hand laid parts; however, it is a function of the same phenomenon (resin shrinkage 

during the cure cycle). One solution has been to paint those products that require a high 

gloss finish. Another solution is the use of a print through skin coat (see step 2 in the 

process summary above). 

SCRIMP continues to undergo new developments. One recent development is the 

use of reusable bags. Experiments have shown that using the correct silicone material will 

result in over 250 cycles with the reusable bags. These bags reduce solid waste and also 

(through a snap-on system) can be used to reduce production time. 

Another variation of the infusion method is called the resin infusion recirculation 

'In cases where production volumes are large, royalty rates have been contractually 

reduced. 

7L 
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Madeleine Strum DRAFT 

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method (RIRM). Tiiis process utilizes a semi-rigid cover that can be reused, and provides 

a middle ground between vacuum bagging and RTM. 

Dramatic emission reduction benefits are claimed for infusion processes. One 

company was able to reduce its styrene emissions to less than 20 percent of previous levels 

through adoption of this process.8 In order to estimate emissions from the SCRIMP 

process, one operator installed activated carbon filters in the line to the vacuum pump. 

Measurements were made by weighing a carbon filter (before and after the SCRIMP) 

process) that was plumbed parallel to the 30-inch Hg vacuum line used for infusion. Results 

indicated that only 0.0091 percent of the available styrene monomer was emitted.21 

4.4.2 Other closed molding fabrication processes 

Closed mold technologies may offer a practical alternative to open mold processes 

for reducing curing emissions and the costs associated with open molding. Closed molding 

eliminates requirements for atomization of resins and may offer a number of production 

advantages over other fabrication processes. The closed molding technologies most 

frequently applied to production of reinforced plastic composites are resin transfer molding 

and compression molding. 

Resin transfer molding (RTM) is considered a direct replacement for traditional open 

mold hand layup and sprayup lamination processes. Since resin is transferred directly into a 

closed mold containing dry reinforcement, the emissions associated with exposure of 

wet resin surfaces to the air are essentially eliminated. RTM applications are best suited for 

intermediate volume production of small to midsize components. This would include items 

such as restaurant seats, doors, covers, recycling bins, automotive parts, and bath/shower 

components. In comparison to open molding, potential savings are greatest when production rates are moderately high and both sides of the part must be finished.22 

Compression molding, another closed process, utilizes premanufactured, ready to 

mold materials, such as bulk molding compound (BMC) and sheet molding compound 

(SMC), rather than liquid resins and reinforcements. Therefore, this process is not 
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Madeleine Strum DRAFT 

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Page 26 

considered a direct replacement for open molding. In addition, the cost of the matched 

metal dies is considerably higher than for traditional open molds. However, it is one option 

in cases where the solid molding compounds can be used and the production volume is high 

enough to make the investment in the dies worthwhile. 

Injection molding (most often used in conjunction with thermoplastics) is another 

closed process reported by a few composites facilities on EPA's 1993 screening survey. 

Thermoset products made by this process include bowling balls, reflectors, and circuit 

breakers. 

The benefits of closed molding processes in reducing emissions are similar to those 

discussed for vacuum bagging. However, reductions from closed molding are likely to be 

greater because bag molding usually involves applying the resin to the open mold surface 

before the bag is installed on the mold. 

4.4.3 Process Elimination/Substitution 

The sanitary product market (bathtubs, showers, tub/showers, spas/hot tubs) 

typically manufactures its products using open molding processes. Gel coat spraying 

followed by resin/chop sprayup is the typical process. However, certain products (especially spas/hot tubs) are also produced by substituting a thermoformed acrylic sheet for the 

gel coat layer. This alternative produces a more expensive product, but a very smooth and 

durable finish is produced. Through the elimination of the spraying process, this process 

substitution eliminates the emissions associated with gel coating. 

Another process substitution involves replacing the thermoset resin with a thermoplastic material. The plastics industry as a whole uses far more thermoplastics than 

thermosetting resins. Thermoplastics processing offers faster curing cycles, lower costs per 

pound or raw material, ease of recycling, lower labor intensity, and lower VOC and HAP 

emissions during processing. New engineering grades of thermoplastics can be reinforced 

with glass or other fibers, and these materials can rival the strength of many of the strongest 

thermosets. One company producing fan blades for cooling tower fans replaced the hand 

or. t 
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Madeleine Strum DRAFT 

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layup thermoset blades with injection-molded nylon (thermoplastic) reinforced with long 

glass fibers. Costs for the nylon version were reported to be about 30 percent less than for 

the thermoset product. The new fans showed good impact resistance and rigidity, and were 

easier to balance due to more consistent weight uniformity.23 

4.4.4 Resin Injection in Pultrusion 

The principal source of monomer vapor emissions in pultrusion operations is the 

fiber wet-out area, including the resin bath and other areas of the machine in which wetted 

fibers are exposed to the open air. In addition to covering the resin bath (see Section 

4.3.1), another approach being used at some facilities to reduce these emissions is to 

directly inject resin into the fiber preforming station or directly into the forming die itself. 

In resin injection, the resin can be stored in a closed drum and pumped up onto the production line to directly wet the fibers. In the preform injection process, resin is pumped into a 

preform box as the fiber roving is fed through the box, so that the resin saturated fibers only 

have to travel the distance between the preform stage and the die. Preform injection cannot 

be used for certain composites with complex shapes because a large amount of space is 

necessary to form the fibers. Direct die injection involves the injection of resin directly into 

the heated forming die. Insufficient wet-out of the roving, and consequent poor product 

quality, is one of the chief problems to be overcome in the use of resin injection for pultrusion operations. 

The EPA's 1993 screening survey showed that resin injection is being used at two 

facilities in the manufacture of beams, booms, channels, tubes, rods, and door panels. 

4.4.5 Substitution of Cleaning Materials 

The liquid cleaners used to clean tools, spray guns, hands, and work surfaces in the 

fabrication area often contain or consist entirely of VOC and/or HAP. The traditional 

solvent in the industry has been acetone, which, until recently, was considered by EPA to be 

a VOC (but not a HAP). However, on June 16, 1995 (60 FR 31633), EPA formally 

removed acetone from the VOC list and classified it as an exempt compound. In the last 

.y 
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several years a number of non-VOC or low-VOC replacements for acetone have been 

introduced and are in use in this industry. The status of these substitutes that contain low 

levels of VOC may have to be reevaluated with respect to the use of acetone. 

Another fairly common cleaning solvent is methylene chloride, which is included on 

the Clean Air Act's HAP list. Several facilities reported on EPA's screening survey that 

they have reduced or eliminated their use of this chemical. 

4.4.6 Mixing Operations 

Closed mixing systems are available for preparing bulk molding compound (BMC), a 

paste-like mixture of resins, fillers, pigments, catalysts, modifiers, and chopped strand glass 

fibers. An example is the Littleford 600 liter BMC mixer. These systems have covers 

which remain closed except when ingredients are being added or final BMC paste is being 

removed. 

4.5 WORK PRACTICES 

Work practices are a category of pollution prevention measures consisting of 

improved ways of handling or tracking materials containing pollutants that lead to a 

reduction in emissions. These practices are carried out without making any significant 

changes to existing processes, so they are typically very cost-effective or may provide a cost 

savings. Since work practices depend on the behavior of the employees who are actually 

performing the fabrication operations, and who may not normally be associated with 

pollution control activities, the practices are inseparably linked with employee education and 

training. In order for these measures to be effective, employees must be trained in the 

proper 

procedures and then given incentives to carry them out on an ongoing basis. 

The following are suggested pollution prevention work practices based on a policy 

statement issued by the Composites Fabricators Association.24 It is difficult to associate a 

specific emission reduction with each measure; in practice, the reductions achieved by any 

measure would be widely variable depending on the specific nature of the practice and the 
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Madeleine Strum DRAFT 

October 23, 1995 

Page 29 

diligence with which it was carried out. 

4.5.1 Material Storage and Handling 

The principal work practice involves maintaining covered containers for all resin 

materials (resins and gel coats) while they are being stored prior to use. Drums of material 

should be opened immediately before use, and reclosed as soon as practicable. Care should 

be taken to avoid spills. Any spills should be cleaned up immediately and the soiled mops, 

rags, etc. placed in vapor-proof bags or cans until curing is complete, or disposed of 

properly in the case of uncatalyzed resins. 

4.5.2 Fluid Handling Equipment 

Many operations utilize resin and gel coat transfer systems to pump resin from a 

storage vessel or container to mixing vessels or directly to the fabrication process. During 

all phases of fluid handling, covers should be mauuained on vessels as much as possible and 

spills should be avoided. Fittings and pump packings should be maintained so as to avoid 

leaks. Resin lines and spray guns should be purged into approved, sealed containers after 

use. 

4.5.3 Mixing Operations 

Prior to application, neat (unfilled) resin is mixed with promoters, catalysts, 

additives, and sometimes solid inorganic fillers, often in automated (powered) mixing 

vessels. Covers on these containers should be left fully in place except when adding or 

removing materials. As discussed above for other operations, spills should be avoided and 

cleaned up immediately when they do occur. 

4.5.4 Spraying Operations 

Certain work practices can be applied to reduce emissions in gel coating, resin spray 

application, or resin chop (laminate) sprayup operations. Spray application technique is a 

critical factor in increasing transfer efficiency and thus reducing resin use and subsequent 

emissions. Generally, those procedures that reduce fogging and overspray, and ensure that 

the maximum amount of resin is deposited on the mold, will be effective in minimizing 

__> 
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Madeleine Strum DRAFT 

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emissions. This includes operating the spray gun at the lowest recommended pressure, 

spraying close to and perpendicular to the mold, and maintaining the spray fan pattern 

within the mold perimeter. 

In EPA's recent evaluation test program, a pilot experiment was conducted to 

evaluate the effect of operator spraying technique on styrene emissions from gel coat spray 

application. This was done by asking the operator to spray a normal (uncontrolled) pattern 

and a controlled pattern. The norm<al technique represented no special control of the 

overspray past the flange of the mold, while controlled spraying was carried out with a 

conscious effort to minimize overshooting of the atomized gel coat beyond the flange. Total 

normal spraying emissions averaged 513 grams, while total controlled spraying emissions 

averaged 391 grams, representing a 24 percent reduction when the controlled technique was 

used.4 

One facility reporting in EPA's 1993 screening survey established a standard weight 

for each of its products (bathtubs, showers, .and tub/showers), then generated a weekly 

computer report showing predicted versus actual material usage. The production department 

used this report as a tool to work with the sprayers to reduce overspray, material waste, and 

emissions. 

4.5.5 Cleanup Operations 

Cleanup materials (rags, etc.) saturated with HAP-containing cleanup solvents should 

be deposited in vapor-proof bags or storage cans. Containers of such solvents should be 

kept closed, and spills should be avoided and cleaned up as they may occur. The minimum 

amount of solvent needed to perform a job should be used. Leftover solvent should be 

returned to storage and spent solvent should be recycled or disposed of using a method 

approved by the local agency. 

~i Z 
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4.6 REFERENCES 

1. Memorandum. LaFlam, G. and Proctor, M., Pacific Environmental Services, to 

Strum, M., U.S. EPA. September 21, 1995. Description of Plastic Composites 

Fabrication Industry. 

2. Hillis, David R. and Davis, A. Darryl. Wasted Reduction Strategies for Fiberglass 

Fabricators. East Carolina University. Greenville, NC. 1995. p. 73. 

3. Adkins, L.M., Kitchen, K.E., and Landes, D.S., Ashland Chemical, Inc. The 

Determination of Styrene Emissions During the Hand Lay-up and Spray-up 

Processes. 48th Annual Conference, Composites Institute, The Society of the Plastic 

Industry. February 8-11, 1993. 

4. Kong, E.J., Banner, M.A., Wright, R.S., and Clayton, A.C., Research Triangle 

Institute. Evaluation of Pollution Prevention Techniques to Reduce Styrene Emissions from Open Contact Molding Processes. Draft Report. Prepared for U.S. 

EPA, National Risk Management Research Laboratory. Research Triangle Park, 

NC. September 1995. 

5. Duffy, M.J., Ashland Chemical Company. Styrene Emissions - How Effective are 

Suppressed Polyester Resins? 34th Annual Technical Conference, Reinforced 

Plastics/Composites Institute, The Society of the Plastics Industry. 1979. 

6. Reducing Styrene Emissions in Fiber Reinforced Plastic Operations. Minnesota 

Technical Assistance Program, Minnesota Office of Waste Management. March 

1993. 

7. Memorandum. Strum, M., U.S. EPA, to Pre-MACT Team/Work Group Members. 

July 21, 1995. Reminder of upcoming pre-MACT teleconference. Enclosure: 

Cook Composites and Polymers, 962-WA-196 Low VOC/Buffback White Gel Coat. 

8. Memorandum. Strum, M., U.S. EPA, to Pre-MACT Team/Work Group Members. 

September 15, 1995. Summary of July 31, 1995 teleconference. 

9. De Koning, A.J. 'INSERT' Resins; A Break-through in the Reduction of Styrene 

Emission During Open-Mould Processing. DSM Resins BV, Zwolle, The Netherlands. April 1995. 

10. DSM Halves Styrene Emissions with Insert. Reinforced Plastics. June 1995. p. 14. 

3> 
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Madeleine Strum DRAFT 

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11. Reinforced Plastic Composites Pollution Prevention Focus Group Meeting (meeting 

summary). Organized by Organics Control Branch, Air & Energy Engineering 

Research Laboratory, U.S. EPA. Research Triangle Park, NC. September 13, 

1993. p. 10. 

12. Hovan, G.R., GLS Corporation. The Epoxy Alternative. Composites Fabrication. 

February 1995. p. 9-10. 

13. Reference 11, p. 10-12. 

14. Reference 11, p. 12-13. 

15. Reference 2, p. 40. 

16. Reference 2, p. 48. 

17. Reference 2, p. 44. 

18. Phase I Emission Study. Pultrusion Industry Council, SPI Composites Institute. 

May 3, 1993. 

19. Reference 2, p. 51-54. 

20. Reference 2, p. 56. 

21. Letter and enclosures from Tunis, George C, Hardcore DuPont Composites, 

L.L.C., New Castle, DE, to Strum, Madeleine, U.S. Environmental Protection 

Agency, Research Triangle Park, NC. October 11, 1995. 

22. Reference 2, p. 62. 

23. Open-Molded Thermoset Composites are Replaced. Plastics Brief - Reinforced 

Plastics Newsletter. Vol. XIX, No. 16. Market Search Inc. August 7, 1995. 

24. Policy Statement on Reducing Air Emissions from Open Molding Composites 

Fabrication. Composites Fabricators Association. September 1993. 

3H