Investigation On Preparation And Properties Of Polyimide/Silica Nano-Hybrid Films

Polyimide (PI), as one of the highest performance engineering plastics, exhibits excellent physical, chemical and electrical properties at a large temperature range. It was used widely in aerospace, electric and electronic industries in forms of films, fibers and separation membranes and so on, because of the multi-preparation approaches and the excellent properties, including high thermal resistance, good chemical resistance and preeminent mechanical properties as well as electrical properties at elevated temperature. Along with the development and application of the new technologies, some applications, like miniaturizing of the electrical devices and manufacturing of the frequency conversion motors, however, prefer a more rigid claim to polyimide, demand high performance and functionalized polyimide. A great many researches have been carried out, domestically and abroad, on the modification of polyimide film for preparing new kind of materials to meet the increasing demand of polyimide film caused by the increasing broadened application. Great attentions were focused, mainly, on the preparation of the polyimide/inorganic nano-hybrid films through sol-gel route and the simple analysis of influences of the nano-inorganic components on tensile strength, elongation at break and thermal decomposition temperature, as well as glass transition temperature and dielectric coefficient of PI/SiO2 hybrid films. But there were seldom deep researches on the electric properties of polyimide/inorganic nano-hybrid films which served mostly as insulating materials.In this work, polyamic acid solution was synthesized by the step-polycondensation of pyromellitic dianhydride (PMDA) and 4, 4′-oxydianilline (ODA) in the solution of N, N-dimethylacetamide (DMAc). PI/SiO2 hybrid films were prepared by the hydrolysis and condensation of tetraethoxysilane (TEOS) or methyl-triethoxysilane (MTEOS) that served as the inorganic precursor and produced the nano-particles of silica in-situ in the polyamic acid solution of...