典型热塑性材料竖直逆向火蔓延研究

Study on downward reverse flame spread over typical thermoplastic materials

以典型的热塑性材料聚丙烯(PP)和聚甲基丙烯酸甲酯(PMMA)为研究对象,实验分析了不同宽度的试样竖直贴壁向下燃烧的温度、火蔓延速率等参数,并给出火蔓延速率、未燃区表面接收的对流传热和辐射传热的计算公式。试样长度为20cm,厚度为3 mm,宽度分别为1、2、3、4、5cm。实验表明:燃烧中PP材料会受热熔融生成液滴并发生卷落现象,火焰主要呈蓝色且温度较低,卷落时出现火焰高度和温度增加。PMMA材料流动性差,不产生熔融液滴并在试样上方有稳定的黄色火焰。火蔓延速率受试样宽度与流动性的综合影响。在实验范围内,随着宽度的增加,PP的火蔓延速率呈先减小后增大的趋势,PMMA的火蔓延速率呈单调递增的趋势。

The combustion temperature and combustion spread velocity and the effect of width on the downward flame spread of polypropylene （PP） and polymethyl methacrylate （PMMA） were researched. The formulas to calculate the fire spread ve- locity and convective heat transfer or radiation heat transfer to the un-ignited surface were put forward. The length of samples was 20 cm, the thickness of samples was 3 ram, the width of samples was 1,2,3,4,5 cm. The results showed that in the combustion process, droplets were generated after the PP was heated, and the samples fell off the board sometimes with the higher temperature and flame. The flame was blue and the tem- perature was not high. Due to the poor liquidity, there were no droplets during the combustion of PMMA, and a steady yellow flame above the sample was observed. The flame spread rate was influenced by the width and liquidity. With the expansion of width in the experiments, flame spread rate of PP decreased first and then increased, but that of PMMA increased only.