UV degradation

The gradual change in the appearance and properties of a material caused by outdoor exposure to ultraviolet radiation, moisture, temperature cycling and airborne pollutants. Coating and material durability is assessed by natural exposure trials and by accelerated weathering tests in the laboratory.

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.

An additive that protects polymers, coatings and sealants against degradation by ultraviolet light, either by absorbing the radiation (ultraviolet absorbers) or by scavenging the free radicals it generates (hindered amine light stabilisers). It is used to delay chalking, colour fade and embrittlement in exterior applications.

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.