The Degradative Effect of Boiling Water on Polyester Fibres in a PVC-Coated Fabric

Polyester-fibre 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, par-ticularly in hot, moist environments. In order to elucidate fibre-breakdown pro-cesses, coated-fabric samples were subjected to accelerated weathering by boiling in distilled water. Tensile stress-strain characteristics show a progressive embrittle-ment of the polyester (poly(ethylene terephthalate)) fibres and coating, confirmed by electron micrographs of fracture morphology. A characteristic "stake-and-socket " fracture is observed after five weeks ’ exposure, which is marked by the ap-pearance of two endothermic DSC (differential scanning calorimeter) peaks. It is proposed that boiling initially increases the crystallinity and brittleness of the polyester fibres before hydrolysis/oxidation leads to disruption of the polyester molecules and a reduction in their crystallinity. 1