INFLUENCE OF THE EXPERIMENTAL CONDITIONS ON THE PHOTOOXIDATION OF POLY(VINYL CHLORIDE)

The photooxidation of poly(vinyl chloride) involves complex reactions in which photooxidation and photodiscoloration by the formation of polyenes compete. These reactions are now fairly well understood, and on the basis of the mechanisms formerly reported, it appears possible to investigate the influence of irradiation parameters such as the thickness of the samples, the temperature, or the external pressure of oxygen. This objective requires the distribution of the photoproducts through the irradiated polymer matrix to be analyzed at the microscopic level. The shapes of the profiles that are determined show that the overall behavior of the polymer results from oxygen-starvation effects. The diffusion of oxygen controls the rate of the photooxidation of the matrix, the rate of the photooxidative bleaching of the polyenes, and the rate of absorption of the light by the residual polyenes that have not been oxidized.