The participation of alkyl macroradicals in chain termination by reaction with inhibitors in oxidation of polypropylene

The kinetics of initiated oxidation of solid isotactic polypropylene in the presence of p-benzoquinone, anthracene and di-o-nitrophenol (DNP) have been studied. It was found that anthracene and DNP terminate chains by reaction with both alkyl and peroxide macroradicals, whereas in hydrocarbons these inhibitors terminate chains only by reaction with peroxide radicals. This difference is caused by difference in the ratio of 〈R.〉/〈RO2.〉 in the solid and liquid phases, because oxygen has lower solubility in the solid polymer than in hydrocarbons.