Pyrolysis and Combustion Characteristics of Extruded Polystyrene

Due to its effective thermal insulation properties, extruded polystyrene (XPS) is extensively used in high-rise buildings. However, it can be easily ignited, which has resulted in numerous fire incidents. Pyrolysis, the initial stage preceding combustion, has kinetic parameters that are critical for predicting fire behavior. Therefore, micro-scale pyrolysis and bench-scale cone calorimeter experiments are conducted. XPS was analyzed by thermogravimetric experiments, and its kinetic parameters were estimated by multiple isoconversion methods. Then, the endothermic properties were obtained by the differential scanning calorimetry experiments, and the pyrolysis products were analyzed using the Fourier transform infrared spectrometer. Finally, the combustion characteristics were studied based on the cone calorimeter experiments. The results showed that the pyrolysis reaction of XPS could be complete within a short temperature range, meaning a fast reaction. The average activation energy of the single-step reaction was 183 kJ/mol. The only endothermic peak centered at about 700 K, which indicated the pyrolysis mechanism was depolymerization. The main functional groups indicated that many aromatic products were produced. XPS had high heat release along with significant smoke and gas emissions. It was determined to be a thermally thin specimen property, and multiple parameters were calculated, which reflected the fire risk of XPS, including theoretical critical heat flux, ignition temperature, fire performance and fire growth indexes.