Kinetic model of the mechanism of high-temperature inhibited oxidation of polymers

Abstract

A kinetic model has been presented for the mechanism of the inhibited autooxidation of polymers. In addition to the reaction of the peroxide radical RO 2 • with the radical In • (stage 8) and the molecule InH (stage 7) of the inhibitor, which are typical of this process, the model also involves kinetic chain propagation by the radical In • (stage 10). Theoretical analysis of the model has been performed, which shows the basic difference between the model and the conventional kinetic schemes of inhibited oxidation in which the RO 2 • + InH reaction (stage 7) is considered to be the kinetic chain termination step. The model allows the quantitative description of the inhibited autooxidation in general, viz. the kinetic curves of oxygen absorption and hydroperoxide accumulation during induction, inhibitor consumption and the concentration dependence of induction. The fact that the model fits the real process adequately is corroborated by the quantitative and qualitative agreement between calculations and experimental data on the oxidation of polyethylene in the presence of various spatially-hindered phenols and that of polypropylene in the presence of Nonox WSP. Application of the model for interpreting experimental data provides information on the mechanism of inhibited oxidation of polymer and quantitative criteria of antioxidant efficiency in the systems under study.