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Source Reduction and Recycling Opportunities for a Fiberglass Reinforced Plastics Shop
Astoria Industries employs approximately
45 people and manufactures fiberglass reinforced plastic (FRP)
components for truck utility bodies and livestock trailers.
The manufacturing process uses an open-mold, spray lay-up
process, which involves applying a fiberglass and catalyzed
polyester resin mixture onto open molds.
A large quantity of solid waste is generated during the fabrication process, which must be disposed of in a landfill. The three primary types of wastes include:
- Overspray Waste. This waste consists of over-sprayed resin and glass that misses the mold during the spray-up operation and lands on the spray-booth floor. It also includes cardboard, which is used to cover the spray-booth floor.
- Trim Waste. Trimmings are over-sprayed FRP trimmed off the edges of both the product and the open mold. This waste also includes a small quantity of paper used for masking.
- Cut-out and Grinding Waste. This consists of solid FRP laminate cut out or ground away from a product to make openings for doors, wheel wells and trim. It also includes excess solid laminate that remains after a door has been cut out.
Incentives For Change
In 1993, Astoria disposed of approximately 176,200 pounds of solid waste. Approximately 60 percent of this total was cured FRP waste. Astoria wanted to reduce the amount of FRP waste it generated for two primary reasons:
- Disposal Costs: In 1993, Astoria spent approximately $11,000 on landfill disposal fees. Astoria anticipated that landfill disposal costs would continue to increase in the future.
- Limited Landfill Space. Local landfill space was becoming increasingly limited, causing Astoria to send its solid waste out of state for disposal. In addition, Astoria was concerned that strict regulations imposed by recent federal legislation could make siting future local landfills difficult.
Intern
Activities
During the summer of 1994, a MnTAP Intern worked at Astoria
to help find ways to reduce the FRP waste. The goals of the
intern project were to: 1) identify and evaluate solid waste
reduction opportunities in Astoria's FRP fabrication processes;
and 2) evaluate the feasibility of processing cured FRP waste
into a board-like product, which could be substituted for
the particleboard used as reinforcing material in Astoria's
products.
Waste Assessment. The
intern identified the manufacturing processes that produce
the majority of FRP solid waste, determined the composition
of each waste stream, and measured their respective amounts
generated (in pounds). These wastes were periodically collected
and weighed at each process area. Weights of the raw material
used and products made were also measured during this period.
The results are listed in Tables 1 and 2 below:
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General Information
2008 Summer Projects
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| Table 1. Composition
of FRP Wastes |
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Component
Material
|
Composition of Wastes
(percentages)
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Over-spray Wastes
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Trim Wastes
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Grinding/
Cut-out Wastes
|
|
Resin
|
40
|
45
|
43
|
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Filler
|
30
|
33
|
32
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Fiberglass
|
20
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22
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21
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Cardboard
|
10
|
--
|
--
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Particleboard
|
--
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--
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2
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Gelcoat
|
--
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--
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2
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Table 2.
Percentage of FRP Waste in Total Raw Material
Used and Waste Generated
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Type of Waste
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% of Total Raw Material
Used
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% of FRP Wastes Generated
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Over-spray Waste
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7
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27
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Trim Waste
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2.5
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10
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Grindings/Cut-out Waste
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15.8
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63
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Source Reduction Opportunities. While evaluating the current practices that generate FRP waste, the intern gathered information on best operating practices that can reduce the amount of cured FRP waste generated. Processes reviewed by the intern included the spray booth; trimmings from open molds and utility body modules; and cut-outs and grindings. Based on his findings, the intern made the following suggestions to the company supervisor:
- Substitute lightweight tar paper for the cardboard sheets used to line the spray booth. This reduces the total volume and weight of over-spray waste (overspray and liner). In addition, the cost of the tar paper is about half that of the cardboard.
- Properly maintain and periodically clean the spray lay-up equipment. Poor equipment maintenance leads to glass jamming in the spray gun chopper mechanism, which then must be cleaned. Each time the spray lay-up gun is cleaned and checked for proper operation, resin and glass are sprayed onto cardboard lying on the booth floor, creating additional over-spray waste.
- Train spray booth operators to aim the spray lay-up gun perpendicular to the open mold to increase the FRP transfer efficiency.
- Redesign open molds to reduce the quantity of cut-out and grinding waste generated. A new mold design currently used to produce a standard model incorporates the door opening into the mold. This new design has resulted in an 88 percent reduction in cut-out waste over the previous mold, saving 15 pounds of FRP from going to a landfill each time it is used. Currently, this idea applies only to one product line because of the variability of the customized utility body designs.
Complete elimination of FRP
waste through source reduction methods was not
feasible at the time of this project because of
the nature of the open mold spray-up method and
the need to make the cut-outs for doors.
Recycling.
The technical and economic feasibility of recycling
cured FRP was evaluated. The goal was to determine
if the FRP scrap waste could be reused to make
a substitute for the particleboard currently used
to reinforce and divide product modules into compartments.
Astoria was looking for a testable recycled product
that: 1) could easily incorporate scrap FRP, 2)
was adequately cured and void-free, and 3) could
match the mechanical and physical properties of
the product currently made with raw materials.
To incorporate
the scrap FRP into its product lines, the scrap
needed to consist of free glass fibers and granulated
resin. The scrap FRP was ground to reduce its
size and used as a filler material mixed with
new resin and fiberglass.
Samples of the
over-spray and cut-out wastes, in quantities representative
of their composition in Astoria's overall waste
stream, were ground by 12 different grinding-equipment
suppliers to reduce the size of the scrap to very
fine particles.
The appearance
and characteristics of the ground FRP samples
returned from the different companies varied greatly
in particle size—from a very fine powder
up to 3/4-inch pieces. Jacobson Companies (Minneapolis,
Minnesota) and Rapid Granulator (Rockford, Illinois)
ground the scrap FRP into a finely divided resin,
which maintained a good glass fiber retention.
Using the finely
ground scrap samples provided by the two companies
(Jacobson and Rapid Granulator), the intern developed
a filler-to-resin mixture of 1:1 for making test
panels. This ratio allowed the resin to adequately
contact glass fibers and filler throughout the
mixture.
The intern made
FRP scrap panels in thicknesses of 1/4 and 7/16
inches, which were compared against those standard
thicknesses of particleboard. To make the panels,
a combination of FRP scrap, resin, and methyl
ethyl ketone peroxide (MEKP) catalyst were added
to a bucket and hand-mixed for one minute. The
mixture was poured into a 16 x 21 x 0.5-inch open
mold and the mold top was fixed in place. Then
a pressure of 25 pounds per square inch (psi)
was applied to the mold using a 10-ton hydraulic
press.
The sample panels
were allowed to cure for a minimum of two hours
and were then subjected to the following tests
performed at the Composite Materials Technology
Center [COMTEC] in Winona, Minnesota:
Mechanical Properties
- Flexural test: Tests how much a material can bend before it breaks.
- Tensile test: Tests how much a material can stretch before it breaks.
- Izod impact test: Tests how much energy a material can absorb before it breaks.
- Lap shear test: Tests how strong the bond is between the resin and the material.
Physical Properties
- Specific gravity: Determines the density of a material relative to water.
- Fiber volume fraction: Determines the glass content of a material (fiberglass adds strength).
- Water absorption: Determines how much water a sample can absorb.
The results from
the above tests were compared against particleboard
and are detailed in Tables 3 and 4 below.
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| Table
3. Mechanical Properties |
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Material (thickness)
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Flexural Stress (psi)
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Tensile Stress (psi)
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Tensile Strain(in/in)
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Izod Impact (lb-ft/in)
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Lap Shear (psi)
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Jacobson
(1/4")
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4,625
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2,278
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0.0038
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1.87
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235.6
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Rapid
(1/4")
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5,200
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2,619
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0.0042
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1.5
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205.4
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Particleboard (1/4")
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3,106
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2,009
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0.0357
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1.47
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--
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Particleboard (7/16")
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1,944
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1,138
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0.0296
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--
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298.4
150.2
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'Odd-Lot' Resin (1/4")
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10,780
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6,457
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0.0245
|
--
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--
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| Table 4. Physical Properties |
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Material (thickness)
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Specific Gravity
|
% Glass Fiber Volume
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24 hr. Water
Absorption
(% wt. included)
|
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Jacobson (1/4")
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1.33
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3.6
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0.43
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Rapid (1/4")
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1.35
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4.2
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0.26
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Particleboard (1/4")
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0.78
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--
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39.9
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Particleboard (7/16")
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0.65
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--
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39
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Odd Lot Resin (1/4")
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1.17
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--
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--
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|
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Summary
The intern successfully demonstrated that Astoria's
FRP scrap waste could be ground and reused to make panels
that generally meet or exceed the required mechanical
and physical properties of the particleboard currently
used to divide and reinforce module compartments. Only
the lap-shear strength of the panels showed to be slightly
weaker than the bond between the smooth side of the
particleboard and the resin (see Table
3).
The cost per square foot
of each panel made with recycled FRP was determined
to be about five cents less than that of particleboard,
when savings from diverted FRP landfilling costs were
considered.
Currently only about
25 percent of the total cured FRP waste generated by
Astoria is needed to generate enough FRP waste boards
to replace the amount of particleboard used. In order
to recycle all of its cured FRP waste, Astoria needs
to produce a marketable product.
The estimated cost savings
from substituting FRP waste boards for particleboards
would be approximately $2,300 annually, and would reduce
the amount of solid waste going to the landfill by approximately
33,000 pounds annually.
Capital costs for purchasing
the grinding equipment necessary for manufacturing FRP
waste boards ranges from $30,000 for one grinder to
$180,000 for two grinders (Note: the second, more expensive
grinder may be needed to reduce the particle size).
Because of these high costs, recycling cured FRP waste
was not found to be economically feasible at this time.
Future
Goals
Since the conclusion of the project, the intern's project
supervisor at Astoria has met with representatives from
other FRP manufacturers to determine if a joint FRP
scrap recycling venture was feasible. They are interested
in pursuing options that may: 1) improve the economic
feasibility of recycling, 2) prevent landfilling the
scrap by reusing it in their own shops, and 3) develop
a new marketable product from the excess waste.
Though Astoria and the
other companies do not want to develop a new product
line themselves, they felt it may be a feasible business
opportunity for entrepreneurs. Important technical,
financial, marketing and liability issues will need
to be resolved before a significant amount of FRP waste
can be recycled.
More
Information
MnTAP has variety of technical assistance services available
to help Minnesota companies manage and reduce their
industrial waste. If you would like assistance or more
information about MnTAP's Intern Program, call 612.624.1300
or 800.247.0015 in greater Minnesota.
This project
was conducted in 1994 by MnTAP intern Nate
Gruber, a composite materials
engineering student at Winona
State University.
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