Some features of the kinetics and mechanism of polypropylene autoxidation under tensile stress

✍ Scribed by N.Ya. Rapoport; G.E. Zaikov

• Publisher: Elsevier Science
• Year: 1984
• Tongue: English
• Weight: 440 KB
• Volume: 20
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(84)90069-7

✦ Synopsis

Al~tract--The influence of tensile stress on different stages of the chain oxidation of polypropylene (PP) has been studied. The degrees of oxidation at various sites of the stressed samples, oxidized up to failure, were determined by i.r. spectroscopy using a focussed beam; the scanning was performed along the samples from the fracture site to the clamps. The change in the mechanism of initiation of oxidation with increasing stress was shown to be accompanied by a decrease in the propagation rate and an increase in the termination rate (with the participation of quickly decaying terminal radicals) and this led to a sharp decrease in the oxidation chain length. Consequently, inhibitors of chain oxidation become ineffective under high stresses and therefore do not increase polymer durability. The oxidation of stressed PP is shown to be local in nature; a defect detection process in oxidizing stressed PP is proposed based on the differences in product composition and concentration in stressed sites (matrix) and relaxed sites (near the cracks).