Polymer reactions. V. Kinetics of autoxidation of polypropylene

The rate constants for the autoxidation of polypropylene were determined by a combined ESR, volumetric, and chemical method. The values of k_i, k_p, and k_t at 110°C. are 3 × 10^?4 sec.^?1, 1.9 l./mole-sec., and 3 × 10⁶ l./mole-sec., respectively. The values of k_i and its activation energy are the same as those for the decomposition of polypropylene hydroperoxide, thus identifying the latter as the principal initiation process. The values of the temperature-independent k_t suggest that secondary peroxy radicals are the terminating species. The rate constants are compared with rate constant ratios for initiated autoxidations of squalane and other related systems.