Polymer reactions. V. Kinetics of autoxidation of polypropylene

Abstract

The rate constants for the autoxidation of polypropylene were determined by a combined ESR, volumetric, and chemical method. The values of ki, kp, and kt at 110°C. are 3 × 10−4 sec.−1, 1.9 l./mole‐sec., and 3 × 106 l./mole‐sec., respectively. The values of ki 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 kt 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.

Review on the thermo-oxidative degradation of polymers during processing and in service

“…The unimolecular decomposition has a 5 rather high activation energy, which makes this reaction less likely at low temperatures. In the oxidation of polypropylene, the propagation can take place according to an in-chain reaction [38] (Scheme 2). This reaction causes the formation of adjacent hydroperoxides.…”

ESR Spectroscopy in Polymer Research

“…A number of workers recorded the ESR studies of radiation-produced peroxy radicals of polypropylene 332,[456][457][458]603,623,683,684,838,1034,1154,1158,1159,1330,1476,1481,1591,1639,1648,1560,1651,2243) ESR spectra of peroxy radicals produced by 'Y-irradiation of polypropylene in the presence of oxygen at room temperature and at 77 K are asymmetric and do not show any distinct dependence upon temperature (Fig. 7.6).…”

“…7.7. The rate constants for the oxidation of polypropylene were also determined by ESR method458 ). The g-values are: g1 = 2.0135, g2 = 2.0245 and g3 = 2.0356 456 ).…”

Pyrolysis and Oxidative Pyrolysis of Polypropylene

“…Oxidative Pyrolysis. Autoxidation of polypropylene below its melt ing point has been investigated quite thoroughly with our own laboratory among the most active ones (21,22,23,24). This is not the proper place to discuss that topic; a chapter written by one of us dealing with the subject can be found in this volume.…”