Study On Shrinking And Melting Process Of A Kind Of XPS Material

As one of the most common insulation materials in current domestic market, extruded polystyrene (XPS) has the potential of fire hazard danger. In this paper, the shrinking and melting process before the material ignited in heat fluxes were studied.This paper firstly used TG-DSC thermal analysis technique to test thermal decomposition of the material. The experimental results showed that the TG, DTG and DSC curves with different heating rates during the thermal decomposition of extruded polystyrene were similar in shape. At higher heating rates, the maximum thermal decomposition shifted to a higher reaction temperature accompanied by an increase in the initial and external temperature. In air environment, the activation energy first increased in the conversion range a=0.1-0.7 and decrease when a>0.7, and the average activation energy was 141kJ/mol.Secondly, the experimental platform was applied to study the shrinking and melting behavior of XPS at different heat radiation fluxes. The results showed that the quality of sample basically remained unchanged after the experiment. With the increasing of the heat radiation flux the melt-through time of material was shortened, the shrinking rate increased, but the flow transition temperature basically unchanged. The area of melting perforation increased linearly, and the slope of fitting lines increased with the heat radiation fluxes increasing. The microstructure of the material during the experiment were observed by microscope and SEM. The results showed that the XPS material had an independent closed-cell structure, and its porosity was up to 90% while the distribution of pore size was not uniform, the diameter of bubbles increased with heating time. Finally, the heating model of XPS material was analyzed, the morphological change of material with temperature was studied. Compared with the data of the shrinking and melting experiment, the estimated results of the model could be better matched and predicted before ignited.Results obtained in this paper could be employed to predict the rate of fire growth in XPS insulation materials. These results could also provide guidance for fire hazard evaluation and lay a foundation for the fire safety of materials.