The Photooxidation of Isotactic Polypropylene as a Nonhomogeneous Process

Abstract

Abstract The experimental data on the photooxidation of isotactic polypropylene (PP) have been reviewed. The photooxidation of PP has three main features. Firstly the process proceeds with different rates in different regions of polymer volume. Secondly the reactivity of peroxyl macroradicals of solid PP strongly depends on the spectral distribution of incident light, duration of irradiation and the mechanism of the photoinitiator action. Thirdly, the photooxidation occupies only a small part of amorphous phase of the solid polymer. The proposed mechanism of photooxidation includes nonuniform distribution of free radicals and hydroperoxides in the popolymer volume, photobranching of the oxidation chains and the termination via reactions of first and second orders. The nonhomogeneous kinetic model based on the proposed mechanism is in good agreement with the different kinds of oxidation kinetics observed with, during and after irradiation.