Thermal stability and curing kinetics of polycarbosilane fibers

Thermal stability and curing kinetics of polycarbosilane (PCS) fibers were studied by thermogravimetry (TG), Fourier transform infrared spectroscopy(FT-IR). Curing is an essential step in the preparation of SiC fibers and the properties of SiC fibers are affected greatly by curing conditions. TG measurement performed in air shows that mass gain starts at approximately 200°C and PCS fibers are sensitive to oxygen. Curing with oxygen, which results in crosslinking on the surface, enabled PCS fibers to retain its shape during high-temperature pyrolysis. The curing of PCS fibers is oxidation of SiH and SiCH3, then SiOSi and SiOC bonds are formed. This is a first order reaction, with activation energy of 79.27 kJ/mol, and the pre-exponential factor is calculated as 3.07 × 106. The kinetics model was obtained and the experimental data of PCS fibers show good agreement with the kinetics model.