THE EFFECT OF SOME FLUOROPOLYMERS STRUCTURES ON THEIR RESPONSE TO UV IRRADIATION

The response of three commercial fluoropolymer films, untreated and ga mma-irradiated poly(vinyl fluoride) (PVF), poly(vinylidene fluoride) ( PVDF), and poly(ethylene-co-tetrafluoroethylene) (ETFE), to ultraviole t (UV) irradiation was studied. The changes in tensile properties, the rmal behavior, and chemical structure were investigated. The UV resist ance of the PVF film is the lowest, and that of ETFE is the highest am ong the studied films. The biaxially oriented PVF films undergo massiv e chain scission under the UV irradiation. The chain scission process in both oriented PVF and PVDF films, although at different levels, is accompanied by increased solubility, increased upper glass transition temperatures, and decreased elevated temperature shrinkage. The UV exp osure at 50 degrees C, above the polymers' T-g has annealing effects, mainly reflected by a shift to higher temperatures of their upper glas s transition. PVF films are unaffected by a low-dose ionizing radiatio n. However, the gamma-irradiated films show reduction of their UV resi stance. PVDF films undergo both chain scission and crosslinking by gam ma radiation, and the addition of UV exposure mainly causes further ch ain scission. (C) 1998 John Wiley & Sons, Inc.