Inhibited Thermooxidative Degradation of Polyesters. Oxidation of Poly(ethylene Adipate) and Poly(ethylene Sebacate)

Abstract

AbstractThe noninhibited and inhibited oxidation of poly(ethylene adipate) and poly(ethylene sebacate) polyesters was studied at temperatures of 130–200°C. Oxygen absorption curves, typical for autocatalytic processes, were obtained. Hydroperoxides formation was not confirmed even at lower temperatures. Induction periods and maximal rates of oxygen absorption were estimated. Activation energies calculated from temperature dependence of induction periods and of maximal rates were 19–22 kcal./mole. Addition of 0.5% of 2,2′‐methylene bis(4‐methyl‐6‐tert‐butylphenol), N,N′‐diphenyl‐p‐phenylene‐diamine, and tri‐octylphenyl phosphite extends induction period 5–50 times. Inhibitor concentration changes during the induction period led to the conclusion that after inhibitors' consumption the reaction is inhibited by the products of direct attack of oxygen on the inhibitor. This supposition was verified on using oxidized inhibitors and it was proved that these are more effective than the inhibitors of original structure.