A study of the interaction of mechanically generated polypropylene radicals with phenolic antioxidant in the absence of oxygen using ESR spectroscopy

Polypropylene (PP) was mechanically degraded in the absence and in the presence of a phenolic antioxidant, 2,6‐di‐t‐butyl‐p‐cresol. The interaction of macroradicals of PP with the antioxidant was studied by ESR spectroscopy in the temperature region between 77 and 303 K and at antioxidant concentrations of 0.1, 0.5, and 1.5 wt % in the absence of oxygen. In the absence of the antioxidant, the end macroradicals of PP are formed which decay with increase in temperature. In the presence of antioxidant both macroradicals of PP and phenoxy radicals are generated. The PP macroradicals are very stable up to the temperature close to Tg of the polymer. Beyond this temperature they decay via bimolecular mechanism—according to the second‐order kinetics. The rate constants for PP macroradicals decay were determined, and the apparent activation energies for the regions of slow and fast decay were calculated.