Monomer

A large molecule built from many repeating chemical units joined into long chains. Polymers include thermoplastics, thermosets and elastomers, and form the matrices, adhesives, coatings and membranes used throughout the materials industry.

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 formation of chemical bonds between polymer chains, tying them into a three-dimensional network. It is the reaction underlying thermoset cure and determines rigidity, chemical resistance and the inability of cured resins to be re-melted.

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.