Preparation of silicon carbide fibers from the blend of solid and liquid polycarbosilanes

A highly branched liquid polycarbosilane (LPCS) was added into a solid polycarbosilane (PCS) to give a polymer blend. It was then melt-spun into precursor fibers, oxidation-cured in hot-air, and converted into ceramic fibers by pyrolysis under nitrogen. It was found that the addition of the LPCS resulted in a significant drop on the spinning temperature from 285 °C (without LPCS) to 225 °C (with 15% LPCS), while the spinning ability of the polymer blend was also markedly improved over the solid PCS. Furthermore, the LPCS enhanced the oxidation curing, reducing the curing temperature and hence the tendency for fiber partial melting and sticking. However, the strength of the silicon carbide fibers decreased owing to the presence of the LPCS. The effects of the LPCS addition and their mechanisms on the fiber processing and properties were studied using FTIR, NMR, GPC, XRD, SEM, and elemental analysis.