High char yield silazane derived preceramic polymers and cured

Abstract

Novel polysiloxane-silazane preceramic polymer compositions are prepared by the controlled hydrolysis polymerization of a trimer or tetramer of a monomer of the structure ##STR1## wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are independently alkyl groups containing from 1 to 4 carbon atoms R.sup.a, R.sup.b, R.sup.c, and R.sup.d are independently alkenyl or alkyl groups containing from 2 to 6 carbon atoms with the proviso that at least one of R.sup.a, R.sup.b, R.sup.c, or R.sup.d group is an alkenyl group. Another useful composition is made by reacting the above mentioned monomers with alkoxide or aryloxide compounds of the elements Al, B, Zr, Ti, Si, Hf, and Y in the presence of water to make polysilazoxane polymers modified with said alkoxides or aryloxide compounds. Another useful composition is made by reacting the polysiloxane-silazane polymer with vinyl or allyl substituted compounds of boron or silicon or both. These modified polysiloxane-silazane polymers have increased char yields and can develop other refractory phases due to the presence of other metals. Another useful composition is made by reacting substituted phenols or compounds containing substituted phenols with the above mentioned monomers. All of the above mentioned reaction products are useful as high temperature resins, fibers, etc., and as preceramic polymers to be made into ceramics by high temperature.