Mercaptoorganopolysiloxanes cured to elastomers with peroxides and nitrogen compounds

A composition curable to an elastomer comprising a material prepared by mixing

• A. a mercaptoorganopolysiloxane consisting essentially of a combination of units selected from dimethylsiloxane units, trimethylsiloxane units, units of the formula ##STR10## units of the formula ##STR11## units of the formula ##STR12## units of the formula ##STR13## units of the formula ##STR14## and units of the formula ##STR15## wherein R is a monovalent radical selected from the group consisting of alkyl radicals of from 1 to 3 carbon atoms inclusive and phenyl radicals, R' is methyl or ethyl and n has a value of from 1 to 4 inclusive, there being in said mercaptoorganopolysiloxane an average of more than two sulfur containing siloxane units per molecule and no more than 10 mol percent --SH containing siloxane units based on the total number of siloxane units in the mercaptoorganopolysiloxane, there being at least 10 siloxane units per molecule in said mercaptoorganopolysiloxane,
• B. organic hydroperoxide in an amount of from 1 to 6 parts by weight based on 100 parts by weight of (A),
• C. a nitrogen compound selected from the group consisting of N,N'-tetramethylguanidine, piperidine, cyclohexylamine and triethylamine in amounts of 0.05 to 1 part by weight based on 100 parts by weight of (A), and
• D. a filler in an amount of from 0 to 100 parts by weight per 100 parts by weight of (A).