Degradation of poly(vinyl chloride) films by X-ray radiation

The X-ray degradation of pure poly(vinyl chloride) films has been investigated by both i.r. and u.v./visible absorption spectroscopy. The transparent films become slightly yellow during irradiation. I.r. spectra show changes in relative intensities and band position, particularly in the C-Cl stretching region indicating the occurrence of dehydrochlorination and changes in the structure and conformation of the degraded polymer. U.v./visible spectra of irradiated films show several bands associated with dienes, carbonyl and many different polyenes and polyenyl radicals. The number of bands increases in the spectra of irradiated samples stored for a long time in air, indicating post-irradiation changes. This effect suggests the formation of polyenyl radicals during irradiation and their subsequent reaction. At the same time, reaction of these radicals with atmospheric oxygen is expected forming C=O groups. (author)