Outdoor durability of a common type (tetrachlorophthalic acid-based) fire retardant glass fiber reinforced polyester (GRP) sheet

Fire retardant GRP sheets based on tetrachlorophthalic acid-modified polyester resin subjected to either artificial or natural weathering undergo two types of surface deterioration (breakdown at the glass-resin interface resulting in fibre prominence and surface microcracking) 2.5 to 3 times faster than conventional sheets. Exposure to humidity-temperature cycles produces fibre prominence at comparable rates for both types of GRP sheets, but does not induce formation of surface microcracking.