Yang Xulin, Li Yi, Lei Wenwu, Bai Zhongxiang, Zhan Yingqing, Li Ying, Li Kui, Wang Pan, Feng Wei, Liu Qi
School of Mechanical Engineering, Chengdu University, Chengdu 610106, China.
Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, China West Normal University, Nanchong 637009, China.
Polymers (Basel). 2023 Sep 29;15(19):3947. doi: 10.3390/polym15193947.
Polymer foam, a special form of polymer, usually demonstrates some unexpected properties that rarely prevail in the bulky polymer. Studying the thermal degradation behavior of a specific polymer foam is important for its rational design, quick identification, objective evaluation, and industrial application. The present study aimed to discover the thermal degradation mechanism of high-temperature-resistant phthalonitrile (PN) foam under an inert gas atmosphere. The macroscopic thermal decomposition of PN foam was carried out at the cost of size/weight loss, resulting in an increasing number of open cells with pyrolyzation debris. Using the TGA/DTG/FTIR/MS technique, it was found that PN foam involves a three-stage thermal degradation mechanism: (I) releasing gases such as HO, CO, and NH generated from azo-containing intermediate decomposition and these trapped in the closed cells during the foaming process; (II) backbone decomposition from C-N, C-O, and C-C cleavage in the PN aliphatic chain with the generation of HO, CO, NH, CO, CH, RNH, HCN, and aromatic gases; and (III) carbonization into a final N-hybrid graphite. The thermal degradation of PN foam was different from that of bulky PN resin. During the entire pyrolysis of PN foam, there was a gas superposition phenomenon since the release of the decomposition volatile was retarded by the closed cells in the PN foam. This research will contribute to the general understanding of the thermal degradation behavior of PN foam at the macroscopic and molecular levels and provide a reference for the identification, determination, and design of PN material.
聚合物泡沫是聚合物的一种特殊形式，通常表现出一些在块状聚合物中很少出现的意外特性。研究特定聚合物泡沫的热降解行为对于其合理设计、快速识别、客观评估和工业应用具有重要意义。本研究旨在揭示耐高温邻苯二甲腈（PN）泡沫在惰性气体气氛下的热降解机理。PN泡沫的宏观热分解是以尺寸/重量损失为代价进行的，导致开孔数量增加并伴有热解碎片。使用热重分析/微商热重分析/傅里叶变换红外光谱/质谱技术发现，PN泡沫涉及一个三阶段热降解机理：（I）释放由含偶氮中间体分解产生的HO、CO和NH等气体，这些气体在发泡过程中被困在闭孔中；（II）PN脂肪族链中的C-N、C-O和C-C键断裂导致主链分解，同时产生HO、CO、NH、CO、CH、RNH、HCN和芳香族气体；（III）碳化形成最终的N杂化石墨。PN泡沫的热降解与块状PN树脂不同。在PN泡沫的整个热解过程中，由于PN泡沫中的闭孔阻碍了分解挥发物的释放，存在气体叠加现象。本研究将有助于从宏观和分子水平上全面了解PN泡沫的热降解行为，并为PN材料的识别、测定和设计提供参考。
