硅橡胶/黏土可瓷化复合材料的热行为及微观结构

Thermal behavior and microstructure of ceramifiable polymer composites

添加无机填料可改善硅橡胶烧蚀陶瓷残余物的强度,从而加强其结构完整性和高温稳定性。以甲基乙烯基硅橡胶为基体,以黏土矿物为填料制备硅橡胶/黏土可瓷化高分子复合材料,利用TG/DSC等热分析技术研究该材料的热稳定性。结果表明,添加黏土矿物可以改善硅橡胶的热稳定性,使其分解温度提高100℃左右。通过XRD分析和SEM观察发现:除少量杂质相之外,硅橡胶经600℃烧蚀后的物相主要为方石英,1 200℃烧蚀后的物相为莫来石和方石英,微观形貌特征分别为不致密絮状结构(600℃烧蚀后)和液相桥连的多孔结构(1 200℃烧蚀后)。根据试验结果分析复合材料的瓷化机理。

Compared with other polymers, silicon rubbers have shown excellent thermal stability even though their high temperature strength is very low as they forming loosely compacted ceramic powders when exposed on firing. This limits their wide and due applications. Addition of some inorganic fillers into silicon rubber matrix may enhance their microstructures and increase ultimate strength of ceramic residues and maintain structural integrity upon firing. In the present paper, ceramifiable composites based on clay minerals filled silicon rubber have been prepared. Thermal stability of the ceramifiable composites were studied by thermogravimetric techniques （TG） and differential scanning calorimetry （DSC）. The results show that clay minerals can improve thermal stability of silicon rubber and increase its decomposition temperature about 100℃. In addition, XRD analysis and SEM observation reveal that, beside several impurities, the main phases are mullite and quartz with loosely masses and porous structure linked by liquid phase bridge after pyrolysed at 600 and 1 200 ℃ respectively. Ceramified mechanism of ceramifiable of silicon-based composites is proposed based upon our experiments.