Thermal conductive silicone rubber compositions and method of making

A thermal conductive silicone rubber composition comprising

• (A) 100 parts by weight of an alkenyl-bearing organopolysiloxane having a viscosity of up to about 500,000 centistokes at 25° C.,
• (B) 300 to 1,200 parts by weight of aluminum oxide powder,
• (C) 0.05 to 10 parts by weight of an alkoxysilane of the following general formula (1):
• R1aSi(OR2)(4−a) (1)
• wherein R1 is a substituted or unsubstituted monovalent hydrocarbon group of 6 to 20 carbon atoms, R2 is an alkyl group of 1 to 6 carbon atoms, and letter a is equal to 1, 2 or 3,
• (D) a catalytic amount of a platinum group metal catalyst, and
• (E) an amount of an organohydrogenpolysiloxane containing at least two hydrogen atoms each attached to a silicon atom in a molecule, the amount of the organohydrogenpolysiloxane being such that the molar ratio of SiH groups in component (E) to alkenyl groups in component (A) may range from 0.05/1 to 3/1.