Unsaturated polyester resinUPR

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.

A reactive monomer that acts as both diluent and crosslinking agent in unsaturated polyester and vinyl ester resins, copolymerising into the cured network rather than evaporating like a true solvent. Styrene content influences viscosity and shrinkage, and workplace exposure to styrene vapour is subject to occupational limits.

An organic peroxide used as the initiator, commonly called the catalyst, for curing unsaturated polyester and vinyl ester resins at room temperature. It is corrosive and a strong oxidiser, requiring careful handling, storage away from accelerators, and accurate dosing to control gel time.

A pigmented, resin-rich surface coat applied to the mould face before laminating, which cures to form the smooth, weather-resistant outer surface of a GRP moulding. It protects the underlying laminate from moisture and UV exposure and provides the colour and gloss of the finished part.

A composite of glass fibre reinforcement in a polymer matrix, most commonly polyester or vinyl ester resin. GRP is widely specified for boat hulls, tanks, enclosures, cladding and cold-applied flat roofing thanks to its corrosion resistance, mouldability and moderate cost.