Epoxy resin

The component of a two-part resin or adhesive system that reacts chemically with the base resin to build the cured polymer network. Unlike a catalyst it is consumed in the reaction and must be dosed at the manufacturer's stated mix ratio; amines and anhydrides are common hardeners for epoxies.

A greasy or waxy film that can form on the surface of curing epoxy when amine hardeners react with carbon dioxide and moisture in the air, particularly in cool, damp conditions. It must be removed, usually by washing with water, before overcoating or bonding, as it destroys intercoat adhesion.

An adhesive designed to carry significant service loads as part of an engineered joint, transferring stress between substrates over the whole bonded area rather than at discrete fasteners. Epoxies, polyurethanes and methacrylates are the main chemistries, used in applications from aircraft assemblies to wind turbine blade bonding.

The temperature region over which an amorphous or partly amorphous polymer changes from a rigid, glassy state to a softer, rubbery one. It sets a practical upper service temperature for resins and adhesives and can be reduced by absorbed moisture or incomplete cure.

A thermosetting resin made by reacting an epoxy resin with an unsaturated acid and dissolving the product in styrene; it processes like a polyester but offers better toughness, chemical resistance and resistance to hydrolysis. Commonly specified for boat hulls, chemical plant, tank linings and as a barrier layer against osmosis.