Facts about Styrene Exposure
Styrene, a chemical used in the manufacture of composite parts made of polyester and vinylester, has been getting a bad name as of late. There has been much debate as to how carcinogenic this chemical is to humans.
From the video description:
This video is part of ACMA’s Risk Communication Program. ACMA’s Risk Communication Program is designed to give owners and managers the tools they need to inform and reassure their employees and plant neighbors about chemical health risks.
The ACMA is the American Composites Manufacturer’s Association is the world’s largest trade organization serving the composites industry.
Styrene is an important component of many products used in the world around us to make strong, lightweight, composite materials. There are many wonderful uses of this chemical and it is an important ingredient in many raw materials. It can be safely used with proper precautions to protect human health.
Liquid now, Hard later
Most of the traditional Thermoset Unsaturated Polyesters, Thermoset Unsaturated Vinylesters, and Epoxies arrive at the fabrication shop as liquids in buckets, drums, totes, or tankers. They require liquid hardeners to be mixed in at specific ratios in order to transform into a solid physical state. The esters use peroxide catalysts in the 1% to 3% range, and the epoxies use a specifically formulated part B designed in tandem with the part A manufacturer. The esters also can come prepromoted or unpromoted, which basically is another part of the chemistry package typically containing a cobalt-based mixture that promotes the curing process. Where this is added depends upon several variables, and can also affect the shelflife of the product.
Nontraditionally the Epoxies and esters can come into the fabrication shop as prepregs. These are resin and glass mixtures that are formable to shape but have all of the chemicals and glass mixed in, and are activated by heat (ovens). This of course requires that they be transported and stored in refrigerated containers. There are several tradoffs for prepregs including cost, delivery, process control, shelflife, etc.
Role of Gelcoat
Gelcoat is the decorative surface found on fiberglass parts such as boats, bathtubs, and restaurant seats. This outer layer is needed for aesthetics and protection of the underlying laminate structure. Chemically it is unsaturated polyester/vinylester resin that is unreinforced but heavily filled with a complex variety of additives. These additives are used to determine its color, UV stability, and chemical resistance.
The manufacture of fiberglass parts typically requires a gelcoat layer to aid in the release of the parts from the mold. The parts that will be painted also are manufactured with gelcoat but it is a “sandable” variety. These parts are often automotive-related, and may include pickuptruck toppers, fiberglass kitcar bodies, and other aftermarket add-ons such as running boards or hood scoops.
The unsaturated polyester/vinylester gelcoat is directly compatible with resins and laminate of the same chemistry. Gelcoat can be used with epoxy resins but requires a tiecoat for adhesion because of the chemistry difference.
Gelcoat is applied at 18 to 25 mils (thousandths) and will lose thickness as it cures. Typically when it is dry on the part, it can be down to 12 to 18 mils. This is a lot thicker than a painted surface. One of the disadvantages of gelcoat is that it can be more difficult to repair, especially with color matching. The thickness typically allows for sanding out scratches and blemishes, but going through can be painful and will require a respray. The outer layers of gelcoat will likely discolor over time due to UV degradation, and sanding and buffing into the underlying gelcoat may cause discoloration as the layers are different colors depending upon the depth.
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