Electron paramagnetic resonance studies of gamma-irradiated PVC at high pressure

PVC was compressed into discs with a pressure of 0-0.88 GPa and then irradiated with 200 kGy at room temperature and liquid nitrogen temperature, the polymeric radicals formed were studied by EPR spectroscopy. The radical concentration and its decay with temperature and time were investigated. The number of radicals increased with increase in pressure and decrease in temperature. The radicals produced by irradiation at atmospheric pressure had shorter half-lives than those formed for the compressed samples, and showed an asymmetric pattern of alkylperoxyl radicals. In the case of compressed samples, the formation of peroxyl radicals was not appreciable probably due to lack of oxygen diffusion. In all the cases three different radicals were formed and their half-lives were determined.