Oxidation of polyethylene,polypropylene, and copolymers

This investigation of the autoxidation of ethylene–propylene copolymers and polyethylene–polypropylene mixtures was undertaken to determine whether reactivity is a linear function of composition. The copolymers and the mixtures were autoxidized in a trichlorobenzene solution at 100°C in the presence of 1,1′-azodicyclohexanecarbonitrile, and the rates of oxygen absorption were determined. The reactivity of the copolymers and the mixtures, after the underlying absorption of oxygen by initiator radicals is accounted for, is a nearly linear function of composition; however, the polymer mixtures and copolymers oxidized somewhat less readily than predicted by a straight line relationship. Several additional oxidations were performed on solutions of polypropylene so that the effects of initiation rate and substrate concentration could be evaluated. The oxidation kinetics of polypropylene even in dilute solution, are complex; titratable hydroperoxide yields are low. Further work will be required to specify the mechanism of oxidation.