Oxidative Degradation of Polymers. III.

Abstract

The rates and products of poly(vinyl alcohol) (PVA) photo oxidation were measured over a temperature range of 30°-90°C. Oxidation was initiated with 253.7-nm light, and several model compounds were included. The PVA photooxidation rate was autocatalytic and relatively insen sitive to temperature with the major products being carbon dioxide, acids, peroxides, polymeric β-hydroxyketone, and hydrogen peroxide. Acids were mostly formic acid and carboxylic acids at the polymer chain ends. Several molecule of carbon dioxide and acid were formed per statistical chain scission. The mechanism of the photooxidation of PVA is discussed.T)VA is one of the most widely used polymers with the characteristic property that it is soluble in water but insoluble in most organic solvents. PVA oxidation by molecular oxygen in aqueous solution is interesting fundamentally and practically. From a fundamental point of view, it gives information on the chemistry and reactions of oxy radicals in aqueous solution. Practically, it is important in suppressing oxidative deterioration and such ecological problems as wastewater treatment and chemical recovery.PVA oxidation has been studied by several groups, and it has been observed that the degree of polymerization decreases when PVA is oxi dized with hydrochloric acid (J), potassium permanganate (2-4) potas sium bichromate (3,5,6), hydrogen peroxide (7,8), periodic acid, and ozone (9). However, only a limited number of studies have been per formed on the oxidation of PVA by molecular oxygen. Shiraishi and Matsumoto (10) observed that it is oxidized by molecular oxygen in alkaline aqueous solution, which causes discoloration and a decrease in 0-8412-0381-4/78/33-169-078$05.00/l

Recent advances in oxidative degradation of plastics

“…Other than this previous study, more reports of photo-induced oxidative degradation with other polymers have been published. [110][111][112] Singlet O 2 can also oxidatively degrade polymers after generation via irradiation. Molecular oxygen exists in its triplet form at the ground state and is excited to a singlet state through photo-excitation or energy transfer from photocatalysts.…”

“…Other than this previous study, more reports of photo-induced oxidative degradation with other polymers have been published. 110–112…”