Abstract: Improved heat-curable organopolysiloxane compositions, easily vulcanizable into silicone elastomers, are comprised of (A) a major amount of a diorganopolysiloxane gum, (B) a reinforcing filler therefor, (C) optionally, a diorganopolysiloxane oil, (D) an organic peroxide catalyst, and minor amounts of at least three of the following four additives: (E) an organohydrogenopolysiloxane, (F) an organofluorinated polymer, (G) an organosilonxane irgabcompound bearing at least one acroyloxyalkyl or methacroyloxyalkyl substituent covalently bonded to a silicon atom thereof, and (H) a boron compound.

Abstract: Pasty organopolysiloxane compositions are facilely injection-molded into elastomeric shaped articles at low pressures, at a temperature ranging from about 125.degree. C. to about 225.degree. C., and in a molding cycle of less than about 25 seconds, said pasty organopolysiloxane compositions comprising an intimate admixture of:(A.sub.1) 100 parts by weight of a diorganopolysiloxane oil having a viscosity of 500 to 300,000 mPa.s at 25.degree. C., consisting essentially of recurring units of the formula R.sub.2 SiO and blocked at each end of the chain by units of the formula R.sub.2 R'SiO.sub.0.5, in which formulae the symbols R, which are identical or different, represent hydrocarbon radicals which are unsubstituted or substituted by halogen atoms or cyano groups and which have 1 to 8 carbon atoms, and the symbol R' represents the same radicals as the symbols R and also a hydroxyl radical, an alkoxy radical having from 1 to 4 carbon atoms or a .beta.-methoxyethoxy radical;(B.sub.

Abstract: Pasty organopolysiloxane compositions having a penetration of from 80 to 400 and which can be thermoset into elastomers having good mechanical properties, are comprised of an intimate admixture of (i) 100 parts by weight of a diorganopolysiloxane oil having a viscosity of from 500 to 300,000 mPa.multidot.s at 25.degree. C., (ii) 7 to 85 parts by weight of reinforcing silicas having a specific surface area of at least 50 m.sup.2 /g, said reinforcing silicas comprising from 55 to 95% precipitated silica and 5 to 45% pyrogenic silica, (iii) 1 to 20 parts by weight of a structuring inhibitor, and (iv) 0.1 to 4 parts by weight of an organic peroxide cross-linking agent.