软质聚氨酯泡沫阴燃前热解特性及动力学分析

Pyrolysis characteristics and kinetics of flexible polyurethane foam before smoldering

采用差示扫描量热-热重分析(DSC-TGA)同步热分析仪和中温差热分析仪(DTA)对软质聚氨酯泡沫(FPUF)在不同O2浓度下的热解特性、热解动力学及其对阴燃的影响进行研究。结果表明:聚氨酯泡沫热解主要分为2个阶段。第一阶段主要是FPUF分解产生异氰酸酯和多元醇,第二阶段主要为多元醇的分解。当O2体积分数从0增加到50%时,第一阶段热解起始温度和活化能变化很小,第二阶段最大质量分数损失速率对应温度从385℃降低到300℃,活化能从170 kJ/mo1降低到80 kJ/mo1。聚氨酯热解过程中不同类型反应的活化能大小顺序为:多元醇热解活化能>聚氨酯热解活化能>多元醇氧化活化能。多元醇氧化反应产生的热量是聚氨酯泡沫阴燃时的主要热量来源。因此,O2浓度增加通过加快热解速率、降低反应所需温度和增加放热量来促进阴燃的建立和传播。

The simultaneous differential scanning calorimeter-thermogravimetric analyzer （DSC-TGA） and differential thermal analyzer （DTA） were used to investigate the pyrolysis characteristics and kinetics of flexible polyurethane foam （FPUF） under conditions of different oxygen contents ,and their influences on smoldering were considered.Results showed that the thermal degradation of FPUF consisted of two stages. The first stage could be considered as the decomposition of FPUF, which produced isocyanate and polyol, and the second stage was associated with the decomposition of polyol.When oxygen content ranged from 0 to 50%, both the initial temperature and the activation energy of the first pyrolysis stage were little changed ,whereas in the second stage the temperature at maximum weight loss rate reduced from 385 ℃ to 300 ℃,and the activation energy reduced from 170 kJ/mol to 80 kJ/mol. The activation energies of different reactions were rated as： polyol thermolysis 〉 FPUF thermolysis 〉 polyol oxidation. The heat generated by the reaction of polyol oxidation was the main energy source to maintain the smoldering propagation of FPUF. With the increase of oxygen content the pyrolysis rates and the heat release were enhanced, the reaction temperature was reduced, and the establishment and the propagation of smoldering were thus promoted.