Effects of graphene on thermal oxidation of isotactic polypropylene

Nanocomposites containing graphene nanoplateletes (GNP) and isotactic polypropylene (PP) were obtained by in situ polymerization. The kinetics of peroxyl radical termination in the obtained nanocomposites was measured by decay of photoinduced chemiluminescence of PP. The concentration of peroxyl radicals was found to decrease significantly, and the rate of their decay was found to increase substantially in the presence of GNP. This shows that GNP is able to inhibit radical processes. At the same time, the additives of GNP were found to act as an effective catalyst, significantly decreasing oxidation induction times and increasing the rates of nanocomposite thermal oxidation. The treatment of GNP by ultrasound can reduce the catalytic activity of GNP, as a result of which the inhibitory effect of GNP becomes predominant. Possible mechanisms of catalysis and inhibition involving GNP are discussed. (C) 2018 Elsevier Ltd. All rights reserved.