Abstract: Copolymeric organopolysiloxanes comprising SiO.sub.2 are prepared by forming an acidic, homogeneous mixture of a silanol-containing resinous copolymeric siloxane comprising R.sub.3 SiO.sub.1/2 siloxane units and SiO.sub.2 siloxane units, an organohydrogenpolysiloxane and an organic solvent and heating the resulting mixture to remove substantially all of the organic solvent. The copolymeric organosiloxanes contain silicon-bonded hydroxyl radicals and/or silicon-bonded hydrogen radicals in varying amounts which depends upon the acidity of the homogeneous mixture that is formed and the ratio of silicon-bonded hydrogen radicals to silicon-bonded hydroxyl radicals therein. The copolymeric organopolysiloxanes are useful as a reactive component in various types of curable silicone compositions.

Abstract: Physical properties, especially tack characteristics, of silicone adhesives comprising a silicone polymer and a silicone resin are improved by incorporation, prior to curing, of certain silicone cluster compounds. One preferred cluster compound has the formula RSi{OSi(OR').sub.3 }.sub.3 wherein R is a methyl group and R' is a secondary butyl group.

Abstract: Ceramifiable silicone adhesives having tack and green strength are provided by mixing a ceramifiable filler with certain silicone pressure-sensitive adhesives. The silicone pressure-sensitive adhesive comprises approximately equal weights, plus or minus five percent, of a polydiorganosiloxane having a viscosity of from 1 to 1000 Pa.multidot.s and a xylene-soluble resin copolymer of R.sub.3 SiO.sub.1/2 siloxane units and SiO.sub.4/2 siloxane units. High loadings (80 weight percent of the ceramifiale adhesive) of ceramifiable filler are attainable without loss of tack and green strength when the polydiorganosiloxane is a mixture of a low-viscosity fluid and a high-viscosity fluid. These ceramifiable silicone adhesives are useful for assembling and adhering a plurality of ceramifiable greenware components to form a ceramifiable composite greenware article.

Abstract: When a small amount of polytetrafluoroethylene powder is mixed with certain curable polydiorganosiloxane compositions containing a reinforcing silica and an organic peroxide curing agent and the resulting mixture is extruded and heat-cured, the resulting elastomeric article has a durometer of less than 30 and has a greatly reduced amount of porosity or bubbles.

Abstract: When a small amount of polytetrafluoroethylene powder is mixed with certain curable polydiorganosiloxane compositions containing a reinforcing silica and an organic peroxide curing agent and the resulting mixture is extruded and heat-cured, the resulting elastomeric article has a durometer of less than 30 and has a greatly reduced amount of porosity or bubbles.