Chapter 35. Optimization of New Precursor Systems for Continuous Fluid Carbon Fiber Coating

Summary

Carbon fibers are found today in a wide range of applications as reinforcing component in ceramic and metal matrix composites. In spite of the exellent mechanical properties at high temperatures a drawback is their sensitivity against oxidation and chemically active environment. Various coating technologies have been applied to build protective and adhesion controlling surface layers. The best prospects for new high temperature stable protective coating materials are shown by SiBCN and SiCN compounds. The realization is carried out by a liquid polymer coating and impregnation with polyorganoborosilazanes in a continuous fiber coating process. The precursors are optimized in flow behavior and characterized by detailed rheological investigations. The wetting behavior on the carbon fiber surface is depending on the visco-elastic properties of the precursors. Therefore one can influence the wetting properties by adjustment of the ratio between loss modulus and storage modulus. With these data the result is an optimized pass through velocity, that is inverse proportional to the thickness of the coating film.