Yang Ming, Zhu Xiao-ling, Liang Guo=zheng
Guang Pu Xue Yu Guang Pu Fen Xi. 2016 May;36(5):1374-7.
Modern industrial application and technologies require materials with superior mechanical and thermal properties. Kevlar fibers have been known as fibrous materials with good properties of high strength and high decomposition temperature which have become a hot research field in recent years. The properties of fibrous materials depend on their structures and compositions. Thermal decomposition processing of the materials is of great significance for their structures and thermal properties. As a new technique, thermogravimetric (TG) analysis coupled with Fourier transform infrared spectroscopy(FTIR), are able to analyze materials not only qualitatively but also quantitatively. This method has obvious advantages in researching the thermal decomposition of many materials. However, the thermal decomposition processing of Kevlar fibers is rarely reported in the literature, therefore, we firstly studied the pyrolysis behavior of Kevlar fibers with thermogravimetric analysis coupled with Fourier transform infrared spectroscopy at the temperature of 30800 ℃. We not only obtained the processing of the Kevlar fibers’ thermal decomposition with great details but also the products of every stage. Experimental results exhibited that the decomposition of Kevlar fibers has experienced three stages： 100240, 240420 and 420800 ℃. The weight loss of Kevlar fibers was quite slow before 500 ℃. The third stage was the main stage of the decomposition, and the amount of residue finally reached to a mass percent of 56.21%. FTIR analysis illustrated that free water released from Kevlar fibers at the first stage, followed by the dehydration and depolymerization which made polymer chains short. Finally the fiber fragments further reacted and produced the gases of small molecular mass, and the main products were water, ammonia, carbon monoxide and carbon dioxide. Generation rate of water was increased; the emission of ammonia was at the same rate; carbon monoxide was only produced at the temperature of 515~630 ℃, then turned into carbon dioxide. The release of carbon dioxide was on rise because of the conversion process of carbon monoxide, and then dropped to a certain value.
现代工业应用和技术需要具有卓越机械性能和热性能的材料。凯夫拉纤维是一种具有高强度和高分解温度等优良性能的纤维材料，近年来已成为一个热门研究领域。纤维材料的性能取决于其结构和组成。材料的热分解过程对其结构和热性能具有重要意义。作为一种新技术，热重（TG）分析与傅里叶变换红外光谱（FTIR）联用，不仅能够对材料进行定性分析，还能进行定量分析。该方法在研究多种材料的热分解方面具有明显优势。然而，凯夫拉纤维的热分解过程在文献中鲜有报道，因此，我们首先采用热重分析与傅里叶变换红外光谱联用的方法，研究了凯夫拉纤维在30800℃温度范围内的热解行为。我们不仅详细获得了凯夫拉纤维热分解的过程，还得到了每个阶段的产物。实验结果表明，凯夫拉纤维的分解经历了三个阶段：100240℃、240420℃和420800℃。在500℃之前，凯夫拉纤维的失重相当缓慢。第三阶段是分解的主要阶段，最终残余物的质量百分比达到56.21%。FTIR分析表明，凯夫拉纤维在第一阶段释放出游离水，随后发生脱水和解聚，使聚合物链变短。最后，纤维碎片进一步反应并产生小分子质量的气体，主要产物为水、氨、一氧化碳和二氧化碳。水的生成速率增加；氨的排放速率保持不变；一氧化碳仅在515~630℃的温度下产生，然后转化为二氧化碳。由于一氧化碳的转化过程，二氧化碳的释放量不断增加，随后降至一定值。
