What Is In an Epoxy Resin System?
Epoxy resin systems are made up of an epoxy resin and a curing agent (also called a hardener or catalyst). Many epoxy products also contain additives such as organic solvents, fillers such as fiberglass or sand, and pigments. See the box on page 2.
When epoxy resin systems are used, single molecules (monomers) of the epoxy resin chemical and the curing agent combine to form long chains of molecules (polymers). As the mixture "cures," it becomes a hard polymer. Some epoxies cure in a few minutes at room temperature. Others need additional time or heat to harden. The characteristics of hardened epoxies (such as whether they are firm or flexible, or resistant to heat or chemicals) depend on which epoxy monomers, curing agents, solvents, and fillers are added.
The hardened, finished polymers are almost non-toxic; it is exposure to the uncured resin components that can be harmful. In a two-component epoxy product, the epoxy resin and the curing agent are packaged separately and must be mixed together just before being used. Each component can be hazardous. In a single-component product, the resin and the curing agent are supplied in a
pre-mixed form. Single-component systems are usually safer, because the
hazardous chemicals are already partly combined into less toxic polymers and because they do not evaporate into the air as easily.
Examples of Epoxy Resin System Chemicals
Epoxy Resins (monomers or oligomers) can be powders, or they can be thick, clear or yellow liquids. Some common epoxy resins are: the diglycidyl ether of bisphenol A (DGEBA), novolac resins, cycloaliphatic epoxy resins, brominated resins, epoxidized olefins, EponR and EpikoteR.
Curing Agents react with epoxy resin monomers to form epoxy products. They are usually liquids with strong, unpleasant odors. There are several categories
of curing agents. Examples include: