Influence of structure on the photo-degradation of PVC: Part II—A preliminary approach to the study of photo-oxidation and of the quantum yield of dehydrochlorination

Abstract

An industrial PVC sample (IS), prepared in bulk, and its acetone soluble (S) and insoluble (I) fractions, obtained by extracting with acetone under nitrogen, were characterized by determining their molecular weights, the tacticity and the content of carbonyl groups and of unsaturation. Films, cast from tetrahydrofuran solution, were irradiated by two different irradiation systems: the one allowed for both the kinetics and the quantum yield of dehydrochlorination in the presence of oxygen, to be determined accurately; the other made it possible to follow the low rate photo-oxidation in air. The kinetic curves show an induction period followed by a stationary rate. From the extent of the former it is inferred that the initial photo-stability increases in the order S < SI < I, presumably because the content of photo-sensitive structures is higher in sample S. On the contrary, the differences found for the quantum yield values during the stationary stage and for the carbonyl built up during the photo-oxidation are tentatively explained by differences in the structures of the three samples.