Abstract: A rubber formulation including (a) a hydrogenated nitrile rubber, (b) an organopolysiloxane, (c) a cross-linking controller selected from (i) an ester or polyester of acrylic or methacrylic acid with a polyhydric alcohol, (ii) an amide or polyamide of acrylic or methacrylic acid with a polyamine, (iii) an alkoxysilane having a C.dbd.C double bond, an amino group or a mercapto group and (iv) triallyl isocyanate, (d) an optional filler, and (e) a peroxide crosslinking agent. The rubber formulation is prepared by mixing together (a') a hydrogenated nitrile rubber composition having added therein an optional filler, (b') an organopolysiloxane composition having added therein an optional filler, and (c) the crosslinking controller, and thereafter adding (e) the peroxide crosslinking agent.

Abstract: EPDM and/or EPR rubber/silicone compositions having improved thermal properties, well adapted for the production of a wide variety of useful shaped articles, e.g., automotive seals, gaskets and belts, include a 2-mercapto-benzimidazole or salt thereof, preferably the zinc salt, an antioxidant comprising a secondary amine function, a diorganopolysiloxane oil, appropriate filler material and a peroxide crosslinking catalyst.