The Influence of Decomposition Kinetics Evolution During Burning on Peak Heat Release Rate for Typical Thermoplastics in Cone Calorimeter

ABSTRACT Thermoplastics generally produce a peak heat release rate ( PHRR ) at the end of burning in the cone calorimeter test, which has been ascribed to the heat build‐up effect at the specimen bottom surface. In this study, the decomposition kinetics evolution is proposed as another important factor influencing PHRR . HRR curves of polyethylene (PE), polypropylene (PP), high impact polystyrene (HIPS), and poly(methyl methacrylate) (PMMA) are measured by the cone calorimeter. Decomposition kinetics analyses for samples quenched during burning are conducted through the thermogravimetric technique, and the combustion process is simulated by fire dynamics simulator (FDS). For PMMA, the decomposition activation energy ( E a ) hardly changes during burning and the single‐step pyrolysis model well predicts PHRR . However, E a of PE and PP significantly decrease with the burning progress. E a of HIPS remains unchanged at 250 s and decreases at 350 s. To take the kinetics evolution into account, a multi‐step pyrolysis reaction model is developed. PHRR of PE, PP and HIPS predicted by the multi‐step model are 10%, 27%, and 30%, respectively, greater than those predicted by the single‐step model, and are closer to experimental results. The influence of decomposition kinetics evolution on PHRR is as important as the heat build‐up effect.