软质聚氨酯泡沫阴燃前期热解特性和成炭形貌分析

Pyrolysis Properties and Microscopic Morphological Evolutions in Char Formation Process of Flexible Polyurethane Foam Prior to Its Smoldering

利用热重分析仪（TGA）、差热分析仪（DTA）和扫描电镜（SEM），在不同升温速率（10,℃/min、20,℃/min 和50,℃/min）加热至不同终止温度（100～700,℃）实验工况下，对开孔软质聚氨酯泡沫（FPUF）在建立阴燃过程前期的热解特性及炭化残余物微观形貌进行表征．TGA 结果表明，FPUF 热解历程分为200～340,℃和340～450,℃两个阶段，阴燃主要发生在200～300,℃和320～400,℃之间，第2阶段多元醇的分解造成阴燃过程主要的质量损失，并为阴燃建立和维持提供主要能量来源；DTA 结果表明，氮气气氛中 FPUF 在230～430,℃范围内进行吸热，阴燃波不断前移主要受第2阶段炭化物氧化放热效应驱动；SEM 结果表明，受热成炭后 FPUF 内部呈现出轮廓清晰的细削骨架，孔径尺寸增加的同时空气气流量和氧气容纳量也相应增加，便于阴燃过程建立．

Using thermal gravimetric analyzer（TGA）,differential thermal analyzer（DTA）and scanning electronic microscope（SEM）,the pyrolysis properties of open-celled flexible polyurethane foam（FPUF）and the microscopic morphology evolution features of char residues were characterized when the samples were heated to various end tem-peratures（100—700,℃）at different heating rates（10,℃/min、20,℃/min、50,℃/min）before its smoldering process was established.TGA results show that the pyrolysis of FPUF consists of two stages,i.e.,200—340, and 340℃ —450,℃;smoldering mainly occurs within the ranges of 200—300, and 320℃ —400,℃;the decomposition of polyols in the second stage contributes most to mass loss and provides most heat sources for smoldering establishment and propagation.DTA results show an endothermic process occurs within the range of 230—430,℃;the propagation of smoldering wave front is self-sustained with the driving force of heat released by the oxidation of char residues formed in the second stage.SEM results show that clear and thin frames are formed inside polyurethane foam substrate after heat release and char formation,and that with the increase of the pore sizes inside the foam,both airflow volume and oxygen accommodation capacity increase too,which promotes the establishment of a smoldering.