液态聚硅烷高温高压合成聚碳硅烷工艺研究

Synthesis of Polycarbosilane from Liquid Polysilane at the High Temperature and under High Pressure

以聚二甲基硅烷裂解制备的液态聚硅烷(LPS)为原料,在高压釜内高温高压反应制备了聚碳硅烷(PCS)先驱体,研究了合成条件对反应终压、Si H键含量、产物产率、软化点、分子量分布及可纺性的影响。研究表明,随着反应温度的提高、反应时间的延长,反应终压逐渐增大,产物的分子量与软化点增高,但同时分子量的分散性增大,使可纺性变差。当LPS在高压釜内460℃下反应3～4h,或450℃下反应6～7h时,可以制得软化点约为210～230℃的PCS,其高分子部分含量约5wt%～10wt%,Si H键含量大于0.9,可纺性较好,适合于制备SiC纤维。

The polycarbosilane (PCS), the precursor of SiC fiber, was synthesized at the high temperature and under high pressure by thermal decomposition of liquid polysilane (LPS) which was obtained by thermal decomposition of polydimethylsilane (PDMS). The influence of synthesis conditions on final pressure at the room temperature, Si-H bond content, PCS yield, softening point, the molecular weight and distributions, and spinnability were investigated. The results showed that the molecular weight and softening point of PCS increased while the reaction temperature increased. The spinnability of PCS, however, decreased gradually. Suitable reaction time for the synthesis of PCS from LPS in autoclave should be 3 to 4 hours at 460℃, or 6 to 7 hours at 450℃. The as-synthesized PCS, in which the high molecular weight content was about 5～10wt% with softening point about 210 to 230℃, Si-H bond content more than 0.9, and good spinnability, was the suitable precursor for the preparation of SiC fiber.