Preceramic polysilazane compositions
AssigneeEthyl Corporation
InventorsYuan-Fu Yu, Eric W. Liimatta
Life of this patent
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Abstract
A crosslinkable composition suitable for use as an infiltrant or as a binder for ceramic powders, such as silicon carbide and/or silicon nitride, in a formulation intended to be injection molded or extruded comprises about 40-70% by weight of a low molecular weight polysilazane, about 15-35% by weight of a medium molecular weight polysilazane, and about 5-30% by weight of an unsaturated organic or organosilicon compound containing at least two alkenyl groups. A preferred unsaturated compound is methylvinylcyclosilazane.
Claims17
A crosslinkable preceramic composition comprising about 40-70% by weight of a low molecular weight polysilazane having a relative viscosity of 1.12-1.16, measured as a solution of 5% by weight of the polymer in tetrahydrofuran, about 15-35% by weight of a medium molecular weight polysilazane having a relative viscosity of 1.3-1.4, measured as a solution of 5% by weight of the polymer in tetrahydrofuran, and about 5-30% by weight of an unsaturated organic or organosilicon compound containing at least two alkenyl groups.
A process which comprises (A) injecting into a mold a crosslinkable injection molding composition comprising (1) about 70-85% by weight of a ceramic powder selected from silicon carbide, silicon nitride, and mixtures thereof and (2) about 30-15% by weight of a preceramic composition comprising about 40-70% by weight of a low molecular weight polysilazane having a relative viscosity of 1.12-1.16, measured as a solution of 5% by weight of the polymer in tetrahydrofuran, about 15-35% by weight of a medium molecular weight polysilazane having a relative viscosity of 1.3-1.4, measured as a solution of 5% by weight of the polymer in tetrahydrofuran, and about 5-30% by weight of an unsaturated organic or organosilicon compound containing at least two alkenyl groups and (B) heating the molding composition at a temperature sufficient to effect crosslinking.
Dependencies are inferred from the claim text.