Kinetics of sensitised photo-oxidation of polyvinyl chloride

Abstract

The quantum yields of accumulation of oxygen-containing groups, formation of free radicals and consumption of sensitisers were determined during irradiation of rigid polyvinyl chloride (PVC) films in air at room temperature. Sensitised oxidation of the polymer was shown to be characterised by the following features: (1) linear dependence of oxidation rate on light intensity; (2) insignificant hydroperoxide yield in comparison with carbonyl compound yield; (3) linear dependence of carbonyl group accumulation from the very start of the process; (4) short length (2–4) links of the polymer oxidation chain; (5) decay of peroxide radicals in air in accord with first-order reaction; (6) low (⋍0·5) yield of alkyl radicals from thermal transformation of peroxide radicals in vacuum; and (7) valency migration to considerable distances. A kinetic scheme for the process of sensitised oxidation has been suggested. The constants of the individual stages of the process have been estimated on the basis of experimental data.