Thermal oxidative degradation kinetics of flame-retarded polypropylene with intumescent flame-retardant master batches in situ prepared in twin-screw extruder

Abstract

Abstract The thermal oxidative degradation kinetics of pure PP and the flame-retarded (FR) PP materials with intumescent flame-retardant (IFR) master batches in situ prepared in twin-screw extruder were investigated using Kissinger method, Flynn–Wall–Ozawa method and Coats–Redfern method. The results showed that the activation energy order of PP and FR PP samples with different blowing agent/char former ratios obtained by Kissinger method agrees well with that obtained by Coats–Redfern one, which well illustrates the relationship between the composition of IFRs and their flame-retardancy, i.e. FR material with richer carbonization agent has higher activation energy for thermal oxidative degradation, hence leading to a better flame-retardancy. For Flynn–Wall–Ozawa method, due to its adoption of Doyle approximation, the obtained activation energy and its order of samples are very different from those of both Kissinger and Coats–Redfern methods. Criado method was finally used to determine the degradation reaction mechanism of various samples.