Hydrolysis

The tendency of a material to absorb moisture from its surroundings. Moisture uptake in polymers and composites adds weight, plasticises the matrix and lowers the glass transition temperature, which is why laminates and adhesives are conditioned or dried before critical use.

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.

Degradation caused by reaction with oxygen, which embrittles polymers and bituminous compounds and corrodes metals. Heat and sunlight accelerate oxidative ageing, so antioxidants and protective coatings are used to prolong service life.

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.