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 SiNSi 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 of 2. 5103 and good spinnability was successful synthesized by optimizing the mass ratio of TMDS and LPCS at 0. 08 which was suitable for preparing high-performance continuous silicon carbide fibers.