The reaction process of polycarbosilane (PCS) fiber cured by cyclohexene vapor has been studied and compared with that of PCS fiber cured by air. The influence of curing temperature on SiÀ ÀH bond reaction degree and gel content, the structure and composition of PCS were investigated by FTIR, EA, TGA, NMR, and GC-MS. The results showed that, SiÀ ÀH bond in the molecular structure of PCS reacted during cyclohexene curing process and the reaction degree increased when the curing temperature increases. Simultaneously, gel content of PCS fiber rapidly increased till PCS fiber became infusible. SiÀ ÀH radical and SiÀ ÀCH 2 radicals formed SiÀ ÀCH 2 À ÀSi crosslinking of PCS molecules through the agency of cyclohexene. Some cyclohexyls linked to principal chain of PCS, which was proven by 13 C-CPMAS-NMR, and broke off, and cyclohexane and some monosilane are generated as byproducts when temperature increased.

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