A Thermosetting resin is a prepolymer in a soft solid or viscous liquid state that changes irreversibly into an infusible, insoluble polymer network by curing.Curing is induced by the action of heat or suitable radiation often under high pressure, or by mixing with a catalyst or crosslinking agent often under atmospheric conditions at ambient temperature.
A cured thermosetting resin is called a thermoset or a thermosetting plastic/ polymer – when used as the bulk material in a polymer composite, they are referred to as the thermoset polymer matrix.
When compounded with fibres they form fibre reinforced polymer composites which are used in the fabrication of factory finished structural composite OEM or replacement parts, and as site-applied, cured and finished composite repair and protection materials. When used as the binder for aggregates and other solid fillers they form particulate reinforced polymer composites which are used for factory-applied protective coating or component manufacture, and for site-applied and cured construction, or maintenance, repair and overhaul (MRO) purposes.