The Vertical Ignition Process Of External Thermal Insulation System Based On Polystyrene Foam Under A Radiation Heater

Building energy efficiency is a key measure of national policy of "energy conservation and emission reduction", mainly realized through the external thermal insulation composite systems (ETICS) technology. The ETICS, especially based on polystyrene (PS) foam, has been widely used in china, which has some advantages of good thermal protection performance, light weight, convenient operation and low prices etc. However the ETICS, once on fire, can easily form a stereoscopic fire spread on the building facade, difficulty to extinguish and no effective measure to control its fire in open environment. Thus, its fire characteristics need to be studied urgently, in order to assess the fire risk of ETICS. Due to the ignition being an important stage during the fire process, a series of experiments and theoretical analysis are carried out under the radiation ignition process of the ETICS on polystyrene, in the purpose of researching its fire risk.Nowadays, researchers mainly pursue research on the material characteristics, manufacturing process, pyrolysis and burning behavior of polystyrene. There are few studies on the ignition process of XPS-ETICS in the vertical condition. Therefore a melting and dripping ignition of thermoplastics platform is designed to study the ignition process of the xps and xps-etics, and then is used to analysis the system structure effect on the fire features.In the first stage, the radiation ignition process of XPS insulation panel is taken for consideration. The burning behavior class, the radiation flux level and the way to ignite is mentioned during the experiments, and several important parameters including the time to ignition (piloted ignition and auto ignition), the mass of pyrolysis and the temperature distribution in the sample is measured. The burning process, including origin, shrinking, melting and dripping, pyrolysis and ignition phases, has been described in the experimental results. The difference of tig between the auto ignition and the piloted ignition decreases as incident heat flux increasing, and it is quite insignificant once the incident heat flux exceeds50kW/m2for B1and35kW/m2for B2. Comparing with the auto ignition process, the difference of tig between B1and B2is much smaller in piloted ignition condition. The dripping and the pyrolysis rate of the sample rise while the incident heat flux increase although the increasing rate is dropping. The highest temperature before ignitions changes more obviously during the process of auto ignition.Secondly, based on the analysis of the ignition process of XPS and theoretical derivation of heat transfer, the prediction model of tig is put forward to thermoplastic foaming material in vertical condition. On the basis of the mass change, the ignition process is divided as heating-melt and pyrolysis phase in the model. Comparing with the data of the ignition experiment, the model can better match and predict the tig for the thermoplastic foaming material in vertical condition.In the end, the fire behaviors of the ETICS are discussed and focused on the role of the rendering layer during the experiments, along with the comparison analysis of the ignition process with and without the rendering layer and with the dropped behavior of the rendering layer or not. The difference of tig between different combustion grade materials is smaller than the pure xps. The dripping rate rises while the radiation flux increases. The pyrolysis rate is quite small before the rendering layer dropped, once the rendering layer dropped that increases about two times, and the pyrolysis rate also increase two times as soon as the material be ignited. There are larger gap of the maximum temperature of rendering layer dropped comparing with that of ignition, which is decreased as the radiation flux increase, but it can be ignored when the radiation flux exceed to60kW/m2. Even higher radiation flux is needed in the ignition process under the condition of rendering layer remained. Furthermore, the fire behaviors of ETICS under comer fire are studied, and the temperature vertical along with the sample surface are investigated.