STABILIZED HEAT CURABLE SILICONE ELASTOMERS

摘要

1449341 Organopolysiloxane compositions SWS SILICONES CORP 2 Jan 1974 [2 Jan 1973] 26/74 Heading C3T A heat-curable organopolysiloxane composition suitable for the manufacture of a silicone elastomer, comprises a diorganopolysiloxane, a filler and at least 0À1% wt. preferably up to 10% wt., relative to the weight of the diorganopolysiloxane, of a stannate of a metal of Group II or Group VIII of the Periodic Table, e.g. Ca, Ba, Mg, Sr, Cd, Co, Ni or Fe, or of a rare earth metal, i.e. the elements of At. No. 57 to 71 and yttrium. The diorganopolysiloxane generally has a Williams plasticity of from 50-250 mm. and a R/Si ratio of 1À9 to 2À2 where R is a monovalent hydrocarbon radical such as an alkyl, aralkyl, alkaryl, alkenyl or aryl group, in which any aryl moiety may be optionally substituted with one or more halogen atoms and/or cyano groups. Optional ingredients include anti-structuring agents generally in an amount of 2-30% wt. based on the diorganopolysiloxane such as water, OH-terminated silanes and siloxanes, trimethylsilyl end blocked dimethylpolysiloxane fluids, alkoxylated siloxanes, organophosphates, glycols, esters and anhydrides; fillers generally in an amount of 10-300% wt. based on the organopolysiloxane, e.g. asbestos, clay, hydrated calcium silicate, ZnS, silica aerogel, barium titanate, glass fibres, floe, iron oxide, bentonite, ZnO, nickel oxide, MgO, micronized graphate, slate or mica, PbO 2 , PbO, blue lead, Al 2 O 3 , TiO 2 and CaCO 3 ; vulcanizing agents, e.g. organo-peroxy compounds. In the examples compositions are prepared from a polydimethylsiloxane gum containing a minor amount of methylvinylsiloxane units, an OH-terminated polydimethylsiloxane (50 cSt), fumed silica filler, bis-(2,4- dichlorobenzoyl peroxide) catalyst and either cerium stannate or barium stannate, and additionally in another example fumed TiO 2 and iron oxide. The compositions were press-cured, post-cured and heat-aged and their tensile strength, elongation and hardness determined. Uses.-Electrical insulation, tubing, hoses, sheeting and gaskets.