软质聚氨酯泡沫阴燃前期热解特性研究

On the particular features of the pyrolysis prior to the smoldering of the flexible polyurethane foam

采用DSC-TGA（差示扫描量热-热重分析）同步热分析仪对软质聚氨酯泡沫（聚氨酯软泡）在不同氧气体积分数（0、10%、30%、50%）和不同加热速率（10 K/min、20 K/min、50 K/min）下热解到800℃的过程及其对阴燃的影响进行了研究。结果表明,当氧气体积分数介于10%~50%时,聚氨酯软泡热失重DTG曲线只有1个峰;当氧气体积分数降低到10%时,DTG曲线开始逐渐分离为2个峰;当氧气体积分数降为0（即氮气气氛）时,DTG曲线已经明显分为2个峰。这表明氧气体积分数对聚氨酯软泡热解特性具有重要作用。氧气体积分数和加热速率降低均对聚氨酯软泡的热解有抑制作用,均能减小阴燃传播速率和向明火转化的可能性。加热速率降低主要是延长了聚氨酯软泡的热解周期,从而减小了热解可燃气体积分数和放热速率。氧气体积分数降低对聚氨酯软泡热解的影响相对复杂的多：当氧气体积分数从10%降低到0时,主要提高了聚氨酯软泡的分解温度,而对热解速率影响不大;当氧气体积分数介于10%~50%时,氧气体积分数减小主要会降低聚氨酯软泡的热解速率、放热速率和放热量而对热解温度影响相对不大。氧气体积分数和加热速率降低抑制了多元醇的分解,而多元醇是聚氨酯软泡维持阴燃或向明火转化的主要物质及能量来源。

The paper is inclined to introduce the results of the two series of experiments we have carried out on the particular features of the pyrolysis prior to the smoldering of the flexible polyurethane foam at the temperature rising rates of 10 K / min,20 K /min,and 50 K / min under different oxygen contents（ 0,10%,30%,50%）. At the same time,we have explored the effects of different oxygen contents and heating rates on the properties of pyrolysis phase（ from the room temperature to 800 ℃） prior to smoldering establishment of flexible polyurethane foam by using the differential scanning calorimeter-thermogravimetric analysis（ DSC- TGA） apparatus. As the result,we have found that there exists only one DTG peak for the flexible polyurethane foam when the oxygen content is kept in a range from 10% to 50%. There would gradually appear two DTG peaks when the oxygen content is reduced to 10%. And,next,when the oxygen content is reduced to zero,there would be appearing two obvious peaks of the DTGcurve. This may indicate that the constituent components of the atmosphere tends to play an important role in the thermal degradation of the flexible polyurethane foam. In addition,the reduction both of the oxygen content and heating rates tend to inhibit the effects of the pyrolysis on the formation of the flexible polyurethane foam,that is to say,both the propagation rate of smoldering and the possibility of its transition to flaming cases have been reduced or suppressed. And all this helps to prolong the pyrolysis cycle,with the concentrations of produced volatiles and heat release rates being lowered. Nevertheless,it remains a rather complicated problem to study the effect of the oxygen content on the polyurethane pyrolysis. For example,when the said oxygen content is reduced from 10%（ volume ratio in mixed nitrogen-oxygen atmosphere） to zero,little effect of the decomposition temperature of flexible polyurethane foam can be found on the promotion of the pyrolysis rates. On the contrary,when the oxygen contents stay between 10% and 50%,it can be found that the pyrolysis rate,the heat release rate and the amount of the heat released have all been greatly reduced,whereas little effect has been noticed on the decomposition temperature of the flexible polyurethane foam. In contrast,the reduction of the oxygen content and the heating rates help to inhibit the decomposition of polyol,which serves as the main material and energy source for keeping the smoldering process or its transition to flaming of the flexible polyurethane foam on.