Thermal analysis of the styrene bulk polymerization and characterization of polystyrene initiated by two methods

Among the accidents caused by highly exothermic reactions, the proportion of polymerization thermal runaway accident accounts for about 48%. The mechanism of styrene polymerization in normal reaction process had been studied thoroughly in the literature. However, the interpretation of mechanism of runaway reactions was lacking. Based on the complicated mechanism of styrene polymerization by thermoinitiated and benzoyl peroxide (BPO) initiated. Differential scanning calorimeter and adiabatic rate calorimeter were devoted to analyze the thermal runaway processes of styrene polymerization. The initial exothermic temperature, adiabatic temperature rise, and maximum reaction temperature of BPO-initiated synthesis reaction were lower than those of thermoinitiated polymerization. Moreover, nuclear magnetic resonance imaging, gel permeation chromatography, and Fourier transform infrared spectrometry were used to characterize the polymerization products. The polystyrene initiated by the two methods had the same hydrogen structure, and BPO-initiated process included the effects of the thermoinitiated process. However, their molecular weight and distribution uniformity differed considerably. The free radicals produced by BPO decomposition participated in the chain reaction of styrene polymerization, accelerated instantaneous grain growth, and promoted the formation of short-chain polystyrene. In brief, the BPO-initiated polymerization process exhibited the desired thermal safety characteristics and gained product under thermal runaway was still polystyrene.