【摘要】 采用适当分子量的低软化点聚碳硅烷(LPCS)和四甲基二乙烯基二硅氮烷(TMDS)为原料,利用硅氢加成反应合成了高软化点聚碳硅烷(HPCS).研究了该反应的过程与特点,探讨了TMDS加入比例对产物特性的影响及其结构变化与可纺性的关系.结果表明,反应初期首先形成含乙烯基侧基的悬挂式结构,并随着硅氢加成反应完成,在LPCS分子间形成Si—N—Si桥联式结构.通过控制TMDS的加入比例,可以调控桥联反应程度从而控制产物的分子量及软化点.控制TMDS/LPCS质量比为0.08,得到了软化点为244~278℃,Mn=2.5×103,分子量呈双峰分布且具有良好可纺性的聚碳硅烷,适用于制备高性能连续Si C纤维.更多还原

【Abstract】 High softening point polycarbosilane( HPCS) was synthesized via hydrosilylation reaction by using low softening point polycarbosilane( LPCS) with an appropriate molecular weight distribution and tetramethyldivinyldisilazane( TMDS) as starting materials.The progress and characteristics of the hydrosilylation reaction were investigated,and the impact of mass ratio of TMDS on the properties of the production,as well as the relationship between structure and spinnability of HPCS were also discussed.The results show that the hydrosilylation reaction of LPCS and TMDS was in a stepwise manner.The low molecular weight part of LPCS reacted with one vinyl of TMDS to form a hanging structure in the initial stage of the reaction.Subsequently,another LPCS molecule coupled with the product of the first step to form a Si—N—Si bridged structure until the hydrosilylation reaction was completed.The increase of molecular weight and softening-point of HPCS can be adjusted by controlling the content of bridged structure in HPCS,which can be tuned by changing the mass ratio of TMDS.HPCS( 244 ~ 278 ℃) with a number average molecular weight of2.5 × 103 and good spinnability was successful synthesized by optimizing the mass ratio of TMDS and LPCS at0.08 which was suitable for preparing high-performance continuous silicon carbide fibers.更多还原