FLUOROSILICONE ELASTOMERS AND THEIR USE IN FLUOROHYDROCARBON ELASTOMERS

摘要

1351144 Depolymerizing fluorosilicone polymers; curing fluoroelastomer compositions DEFENCE SECRETARY OF STATE FOR 19 Nov 1971 [27 Nov 1970] 56400/70 Headings C3T and C3P A fluorosilicone polymer is modified by heating it at 150‹ C.-200‹ C. under pressure with an amine H 2 N(-R-NH-) n H, wherein R is a C 1-8 alkylene radical and n is 1-5, and a free radical source, until its specific viscosity falls within the range 0À03-0À06. The product may be incorporated into a composition containing a fluorohydrocarbon rubber, a magnesia filler and a curing agent for the rubber: the preferred proportions are 5-30 p.b.w. MgO, 10-40 p.b.w. modified polysiloxane and 0À5-5 p.b.w. catalyst per 100 p.b.w. of rubber. The preferred polysiloxanes are polymethyl trifluoropropyl siloxanes containing 0À1-0À2 mol. per cent of vinyl siloxane units. In Example 1 such a polysiloxane is heated under pressure at 160‹ C. for 1 hr. with 5 pphr of 2 : 5-dimethyl-2 : 5-dit-butylperoxy hexane and 0À5 pphr of triethylene tetramine. In Examples 2-4 30 p.b.w. of the product are incorporated into 100 p.b.w. of a vinylidene fluoride/hexafluoropropylene copolymer, with 15 p.b.w. MgO, optionally 20 p.b.w. carbon black, and 1À5 p.b.w. dicinnamylidene-1 : 6-hexane diamine or 3À0 p.b.w. hexane diamine carbamate.