The thermal decomposition of cured polyaluminocarbosilane (PACS) fiber was studied by using a thermogravimetric analyzer (TGA) under non-isothermal condition. The improved Coats-Redfern method was used to determine the kinetic parameters and Doyle method was used to calculate the decomposition data. The mechanism of thermal decomposition was studied by using FT-IR, XRD and SEM. It was found that the active energy of the cured PACS fiber is lower than that of the PACS fiber in the main stage of thermal decomposition. Introducing oxygen and increasing the heating rate were found to promote the thermal decomposition. The thermal decomposition of the cured PACS fiber occurred via dehydrogenation and dehydrocarbonation condensation with the evolution of low molecular species and water during the initial stage of heating. The fiber was converted into an inorganic structure through the decomposition of the side chains of the polymer at elevated temperatures. When the temperature was further increased, SiC nanocrystals were formed and the fiber was transformed to inorganic compound completely. At 1300 ℃, the SiC fiber exhibited a good property with the crystal size of β-SiC being 2～4 nm.

Key words: polyaluminocarbosilane, thermal decomposition, kinetics, improved Coats-Redfern method