Zinc oxide-filled addition-curable silicone rubber compositions

A zinc oxide-filled addition-curable silicone rubber composition comprises (A) a diorganopolysiloxane containing at least two alkenyl groups in its molecule, (B) an organohy-drogenpolysiloxane containing at least two hydrogen atoms bonded to silicon atoms in its molecule, (C) a platinum family metal catalyst, and (D) a zinc oxide powder surface treated with a tetraalkoxy silane and/or a partial hydrolysis-condensation product thereof. The composition can further comprise (E) a high thermal-conductive filler. The composition scarcely generates hydrogen gas during storage so as to have an excellent storage stability and provides a cured product excellent in heat resistance, electrical insulating properties, and adhesion to various metals, semiconductors, etc. while keeping good physical properties as a rubber. Further, the composition is easy to deal with and provides a cured product with a high thermal-conductivity and also excellent mechanical properties without lowering adhesion and requiring redispersia compoundven when filled with a high thermal-conductive filler.