United States	Air and Energy Engineering

Environmental Protection	Research Laboratory

Agency	Research Triangle Park, NC 27711

Research and Development	EPA/600/S2-90/019 June 1990

vvEPA Project Summary

Assessment of VOC
Emissions from Fiberglass Boat
Manufacturing

M. B. Stockton and I. R. Kuo

This report presents an
assessment of volatile organic
compound (VOC) emissions from
fiberglass* boat manufacturing. A
description of the industry structure
is presented, including estimates of
the number of facilities, their size,
and geographic distribution. The
fiberglass boat manufacturing
process is then described along with
the sources and types of VOC
emissions. Model plants
representative of typical facilities are
also described. Estimates of VOC
emissions are presented on per plant
and national bases. VOC emissions
from this industry consist mainly of
styrene emission from gel coating
and lamination, and acetone or other
solvent emissions from clean-up
activities. Potential VOC control
technologies are evaluated for this
industry, including a discussion of
technical feasibility limited cost data
are also provided.

This Project Summary was
developed by EPA's Air and Energy
Engineering Research Laboratory,
Research Triangle Park, NC, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).

"Used in this Summary, "fiberglass1' refers to
fibrous glass or fiberglass-reinforced plastic, not
necessarily Fiberglas™. trademark of Owens-
Corning Fiberglas Corporation, Toledo, Ohio.

Introduction

The purpose of this project was to
define the nature and scope of volatile
organic compound (VOC) emissions from
the manufacture of fiberglass marine
craft. This included developing a
characterization of the fiberglass boat
manufacturing industry, estimating VOC
emissions on per plant and national
bases, speciating emissions, and
identifying and evaluating potential
control options.

The fiberglass boat manufacturing and
repair industry consists of about 1,800
facilities. These facilities employ about
47,000 people and are located in 34 of
the 48 continental United States. About
88% of these establishments are small
operations, employing less than 50
people. States that have a large number
of boat manufacturing facilities include
California, Florida, Illinois, Indiana,
Michigan, North Carolina, South Carolina,
Tennessee, Texas, and Washington.

Open/Closed Contact Molding

The most common fiberglass boat
production method is open contact
molding, This method consists of laying
up plies of fiberglass reinforcement
impregnated with resin on an open male
(convex) or female (concave) mold. For
manufacturing boats, a female mold is
generally preferred since it yields a
smooth outer surface which is more
desirable for hulls and decks. The layers
are built up to the desired thickness and
allowed to cure.

The initial layer of resin is formed
without any reinforcing material by
spraying gel coat (unsaturated polyester

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resin, catalyst, and pigments) into the
empty mold to a precise thickness. After
allowing the gel coat to cure fully,
laminates of resin and fiberglass are
applied by machine lay-up, hand lay-up
or spray lay-up. Machine lay-up involves
the simultaneous mechanical application
of fiberglass reinforcement material and
is generally reserved for large huli boats;
e.g., sailboats with deep keels. In hand
lay-up, resin is brushed or sprayed on
the tacky surface of the gel coat, the
fiberglass reinforcement material is
placed into the mold, then the laminate is
completely wet out with resin and rolled
by hand to remove air pockets and other
imperfections. The spray lay-up method
uses a chopper gun .vhich
simultaneously deposits chopped strand
fiberglass and catalyzed resin on the
mold, after which rollers are used, as in
hand lay-up, to remove entrapped air.

Two alternative closed molding
methods which have been experimented
with in the fiberglass boat manufacturing
industry are bag molding and resin
transfer molding (RTM). Bag molding
uses a bag or flexible membrane to apply
vacuum or pressure during the molding
operation. Vacuum bag molding applies
pressure against the laminate by drawing
a vacuum under a cellophane, vinyl or
nylon bag which covers the laminate.
Pressure bag molding forces the bag
against the laminate using compressed
air or steam. In the RTM process,
fiberglass reinforcement consisting of
continuous or chopped strand glass fiber
mats is placed between halves of a mold.
After the mold is closed, catalyzed resin
is injected into the mold and allowed to
cure. The mold is then opened and the
finished part removed. The major
technical difficulty in using this process
for boat manufacturing is that resin void
spaces may occur, rendering the part
unusable. Also, highly skilled labor is
required for RTM to be successful.

VOC Emissions/Controls

VOC emissions from fiberglass boat
manufacturing consist mainly of acetone
and styrene. There are four areas in the
fiberglass boat production process where
VOC may be emitted to the atmosphere:
resin storage, production, assembly, and
waste disposal. The major emissions
sources are exhausts from gel coat spray
booths, room exhausts from the
lamination area, and evaporation of
acetone or other solvents during clean-
up. Emission factors for resin application
in open contact molding range from 5 to

13 lb* styrene per 100 lb of styrene used.
Emissions from gel coat application and
curing are 26 to 35 lb per lb of styrene
monomer used. Cleaning solvent
emissions, primarily acetone, can
account for 36% of the total VOC
emissions and are about equal to 56% of
the styrene emissions. Total VOC
emissions per plant are estimated to
range from 2 to 140 tons per year. Total
national VOC emissions are estimated to
be 20,150 tons per year.

The two general types of VOC
emission control techniques available are
process changes and add-on controls.
The process change offering the greatest
potential for VOC emission reductions at
low costs is the substitution of lower
VOC-containing materials. These include
vapor-suppressed resins, low styrene
resins, water-based emulsions for
cleanup, and dibasic ester compounds
for cleanup.

Vapor-suppressed resins contain
additives which reduce VOC emissions
during resin curing. The most common
vapor suppression additive is paraffin,
which migrates to the surface of the resin
layer and reduces the volatilization of free
styrene during resin curing. Styrene
emissions reductions ranging from 20 to
35 % can be achieved on a per plant
basis. Vapor-suppressed resins are not
currently being used universally in the
fiberglass boat manufacturing industry
due to problems in secondary bonding
which reduce product strength.

The emission reduction from low
styrene resins is less than that of vapor-
suppressed reins; however, low styrene
resins are currently available and being
used in the industry. Styrene emissions
can be reduced by about 14% using a
35% styrene by weight resin.
Conventional resins contain 40 to 50%
styrene by weight. A number of boat
plants have reduced the styrene content
in their resins to 38 to 40% styrene with
satisfactory results. Very few boat
manufacturers have been able to reduce
styrene content below 35% without
sacrificing some of the structural integrity
of the boat.

Water-based emulsions can be used to
replace about 50% of the solvent used
for cleanup. These emulsion cleaners
would be expected to reduce clean-up
emission by about 50%. The cleaners are
successfully being used commercially in
boat plants for resin cleanup and their

"Far readers more familiar with metric units:
I lb = O 45 kg, and I ton = 907 kg.

use has been required as a permit
restriction to reduce VOC emissions from
fiberglass boat plants in some recent
Best Available Control Technology
(BACT) decisions. These emulsions,
however, appear to be inadequate for gel
coat or cured resins cleanup.

Alternative cleaning compounds
containing dibasic esters (DBEs) are
currently being tested at a number of
fiberglass boat plants. These cleaning
solutions show great potential to replace
acetone completely for resin and gel coat
cleanup. Due to the much lower vapor
pressure of DBEs, these substitutes can
provide dramatic VOC emission
reductions. Based on preliminary tests,
an estimated reduction in VOC emissions
from clean-up activities of 75% can be
achieved if DBEs are used in place of
acetone. The DBE cleaner is currently
two to three times more expensive than
acetone; however, it lasts longer because
it evaporates at a slower rate and it can
be recycled.

Due to the high exhaust flow rates and
the low VOC concentrations characteristic
of this industry, add-on controls typically
used in other VOC-emitting industries
have not been applied to boat
manufacturing. Three add-on control
technologies were evaluated for control of
VOC emissions from fiberglass boat
manufacturing facilities: incineration,
absorption, and adsorption.

Of the add-on controls evaluated,
incineration is the only demonstrated and
readily available technology for
controlling VOC emissions from
fiberglass manufacturing facilities.
Although incineration has not been used
in a boat manufacturing facility to date, it
has been installed as a means of VOC
control in a fiberglass tub and shower
facility. Incineration can reduce VOC
emissions by 90% or more; however, the
cost per ton of VOC removed can be
quite expensive (e.g., $15,000/ton).

There are no known applications of
chemical scrubbers or absorbers to the
fiberglass boat manufacturing industry.
However, two systems could theoretically
be used for removing styrene from
exhaust air. Both Chemtact™ and the
Styrex™ scrubbers have shown the
ability to absorb styrene. Further testing
and analysis is needed to determine the
effectiveness of these systems for the
high exhaust flow rates and low VOC
concentrations that are typical of the
industry.

Use of carbon adsorption for control of
VOC emissions in the boat manufacturing

2

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industry may be limited due to the
potential for styrene to polymerize on the
carbon and deactivate the bed, and due
to the vast difference in the capacity for
carbon to adsorb styrene versus acetone.

The adsorptive capacity of styrene is 30
%, while the capacity for acetone is only
1 to 2%, making the capture of acetone
the limiting design criterion. There are no
known applications of carbon adsorption

to the fiberglass boat manufacturing
industry, however, a fiberglass horse
trailer manufacturer currently uses a
carbon adsorber to control styrene
emissions.

M. B, Stockton and I. R. Kuo are with Radian Corp., Research Triangle Park, NC
27709.

Charles Darvin is the EPA Project Officer (see below).

The complete report, entitled "Assessment of VOC Emissions from Fiberglass
Boat Manufacturing," (Order No. PB 90-216 532; Cost: $23.00, subject to
change) will be available only from:

National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-497-4650

The EPA Pro/ect Officer can be contacted at:

Air and Energy Engineering Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711

United States	Center for Environmental Research

Environmental Protection	Information

Agency	Cincinnati OH 45268

Official Business

Penalty for Private Use S300

EPA 600. S2-90/019

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