Vinyl ester resinVE

A thermosetting resin dissolved in a reactive monomer, usually styrene, that cures by free-radical polymerisation when initiated with an organic peroxide such as MEKP. It is the workhorse matrix for glass-reinforced plastic in boat building, GRP roofing, tanks and vehicle panels, offering low cost and straightforward processing.

A thermosetting resin based on molecules containing epoxide groups, cured by reaction with a hardener such as an amine or anhydride. Valued for strong adhesion, low cure shrinkage, chemical resistance and high mechanical performance, it is widely used in structural adhesives, laminating resins, coatings and composite matrices.

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.

The movement of water through a semi-permeable layer towards a more concentrated solution. In glass fibre hulls, water diffusing through the gelcoat can react with soluble substances in the laminate to form fluid-filled blisters, a defect widely known in the marine industry as osmosis or osmotic blistering.

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.