DIELECTRIC AND MECHANICAL-PROPERTIES IN THE PHOTODEGRADATION OF POLY(VINYL BUTYRAL) FILMS

The dielectric behaviour of unirradiated and irradiated PVB films, usi ng UV radiation, was investigated as a function of temperature and fre quency. The results obtained are discussed in terms of the dielectric parameters epsilon('') (max,) Delta epsilon, beta and Delta E. These e xperimental results, in combination with the temperature dependence of dynamic mechanical measurements in the tensile mode and with d.s.c me asurements, show that during UV irradiation of PVB, besides other chan ges, cross-linking predominates. A mechanism of photodegradation has b een proposed and is supported by gel content determination and IR spec tra.