27—THE DEGRADATION OF POLYESTER FIBRES IN A PVC-COATED FABRIC EXPOSED TO BOILING WATER

Abstract

Polycsier-tlbre fabrics coated with PVC (poly(vinyl chloride)) are commonly used as architectural tension-structure membranes, but they have a limited lifetime of approximately ten years. Fibre and coating embrittlement occurs, particularly in hot, moist environments. In order to elucidate fibre breakdown processes. coated-fabrif samples were subjected to accelerated weathering by boiling in distilled water. Tensile stress–strain characteristics show a progressive embrittlement of the polyester (poly(ethylene terephthylate)) fibres and coating, confirmed by etectron micrographs of fracture morphology. A characteristic ‘stake-and-socket’ fracture is observed after five weeks' exposure, which is marked by the appearance of two endothermic DSC (differential scanning calorimeter) peaks. It is proposed that boiling initially increases the crysiallinity and brittleness of the polyester fibres before hydrolysis/oxidation leads to disruption of the polyester molecules and a reduction in their crystallinity.