Experimental Research Of The Flowing Combustion Process Of Typically Thermoplastic Materials

Thermoplastic materials is used widely in furniture, interior decoration, heat preservation in buildings et al. because of the advantages of easy processing, low cost, water proofing, anti-corrosion et al. On the other hand, it is easily soften, even melted when suffered heating, which in turn makes a new challenge for the fire prevention and control. Specifically, when the thermoplastic materials on the wall suffered fire, the melted thermoplastic material moved around and generated pool fire on the ground, the coupling between the pool fire and the wall fire (i.e., coupling combustion) made the situation even worse.The featured fire hazard of thermoplastic materials have attracted wide attention in the world. Up to now, the related researches mainly focus on the qualitative level, the investigation concerning the mechanism of coupling combustion on the quantitative level is still scarce. So, aimed at the deep understanding of the complex combustion behavior of thermoplastic materials, the topic of this dissertation is the investigation of the mechanism of coupling combustion, which includes the related experimental setup assembly, the thermal decomposition mechanism investigation of the thermoplastic on the real scale, Specifically, the widely used polypropene (PP), polyethylene (PE) and polystyrene (PS) were selected for the investigation.The pyrolysis of the materials plays a key role on the combustion behavior. Thermo gravity analysis (TGA) was widely used for the investigation of the thermal decomposition. However, the usual TGA equipment detects the thermal decomposition of small scale materials, which is probably different from the situations of real scale. To circumvent this challenge, we designed a TGA test rig for the real scale, and investigated the related thermal decomposition kinetics and thermodynamics. The results revealed the discrepancy between TGA of small scale and real scale materials, indicates the limitation of the usual small scale TGA. The TGA results measured by our homemade test rig proved that the thermal decomposition of the thermoplastic materials mainly consists of three stages:the initial heating stage, the melting-dominated stage and the gasification-dominated stage. The gas product of the thermal decomposition supplied the fuel of the combustion, the liquid produced by melting and thermal decomposition enhanced the scope of the pool fire. The investigation is helpful for an in-depth analysis and a better understanding of the mechanism of melting dripping and flowing process of materials in fire conditions.We assembled a test rig for the investigation of the effects on the combustion by different thermal decomposition stages revealed by the former work. PP was selected for the investigation, the spread process of the hanged thermoplastic plate was investigated quantitatively, the thermo radiation from the surroundings and width of the thermoplastic plate were considered. The results indicated that the flowing combustion of the pool fire presented the highest hazard level.Based on the results of the TGA test rig, we designed a test rig for the investigation of melting dripping and flowing combustion with the aim of the dividing investigation of the coupling combustion. The experiment simulated the occurrence, advance and spread process of the overflow pool generated by the dripping of the fluid thermoplastic materials with the absent of wall fire. The results indicated that the combustion behavior of overflow pool was largely determined by the characteristics of the materials. For the external factors, the flowing material plays a key role. Based on the dividing investigation, the effects on the occurrence, advance and spread of the pool fire by different flowing materials with the absent of the wall fire were evaluated, revealed the two factors:the combustion of the pool and overflow spread of the pool, the two factors correlated with each other very weakly.