Silicone rubber compositions comprising extenders/plasticisers

A method of preparing a silicone rubber composition comprising the steps of blending: a) A pre-prepared organopolysiloxane polymer of the formula R(3-n)R nSiO[(R2SiO)x(RR SiO)y]SiR(3-n)R n wherein each R is the same or different and is an alkyl group containing 1 -6 carbon atoms, a substituted alkyl group containing 1 to 6 carbon atoms or a phenyl group; R is an alkyl group an unsaturated organic group or -OH; n is zero or 1, x is an integer and y is zero or an integer and the sum of x + y is equal to a value of from 200 to 20,000; b) a filler; c) a curing component sufficient to cure the composition; d) an unreactive organic or siloxane based plasticiser and/or an unreactive organic extender. Preferred plasticisers include phosphate esters, polyisobutylenes, fatty acid esters, polyalkylbenzenes and trimethylsiloxy-terminated polydimethylsiloxanes. Suitable fillers include treated kaolin and silica.