Method for controlling cure initiation and curing times of platinum group metal curing fluorosilicone compositions

A curable fluorosilicone composition comprising:

• (A) 100 weight parts of a fluorine-containing polydiorganosiloxane comprising at least two alkenyl radicals per molecule and repeating units described by formula R.sup.1 R.sup.f SiO and optionally R.sup.1 R.sup.2 SiO, where R.sup.1 is an alkyl radical comprising from one to about four carbon atoms, R.sup.2 is an alkenyl radical comprising from two to about 10 carbon atoms, and R.sup.f is a perfluoroalkylethyl radical comprising from three to about 12 carbon atoms,
• (B) 10 to 70 parts of a treated reinforcing silica filler,
• (C) an amount of a platinum group metal-containing hydrosilation catalyst sufficient to effect curing of the composition, and
• (D) 0.5 to 10 weight parts of a cross-linker mixture comprising an alkylhydrogensiloxane comprising at least 3 silicon-bonded hydrogen atoms per molecule with the remaining bonds of the silicon atoms being to oxygen or alkyl radicals comprising one to four carbon atoms and a dialkylhydrogen perfluoroalkylethylsiloxane at a weight ratio within a range of about 0.1:1 to 9:1.

A curable fluorosilicone composition resulting from the mixing of components comprising:

• (A) 100 weight parts of a fluorine-containing polydiorganosiloxane comprising at least two alkenyl radicals per molecule and repeating units described by formula R.sup.1 R.sup.f SiO and optionally R.sup.1 R.sup.2 SiO, where R.sup.1 is an alkyl radical comprising from one to about four carbon atoms, R.sup.2 is an alkenyl radical comprising from two to about 10 carbon atoms, and R.sup.f is a perfluoroalkyethyl radical comprising from three to about 12 carbon atoms,
• (B) 10 to 70 weight parts of a reinforcing silica filler,
• (C) 20 to 50 weight percent based on the weight of the silica reinforcing filler of a fluorine-containing treating agent described by formula HO(R.sup.1 R.sup.f SiO).sub.x H, where R.sup.1 and R.sup.f are as previously described and x is a value greater than one,
• (D) 0 to 10 weight percent based on the weight of the silica reinforcing filler of an alkenyl-containing treating agent described by formula HO(R.sup.1 R.sup.2 SiO).sub.y H, where R.sup.1 and R.sup.2 are as previously described and y has a value greater than one,
• (E) an amount of a platinum group metal-containing hydrosilation catalyst sufficient to effect curing of the composition, and
• (D) 0.5 to 10 weight parts of a cross-linker mixture comprising an alkylhydrogensiloxane comprising at least 3 silicon-bonded hydrogen atoms per molecule with the remaining bonds of the silicon atoms being to oxygen or alkyl radicals comprising one to four carbon atoms and a dialkylhydrogen perfluoroalkylethylsiloxane at a weight ratio within a range of about 0.1:1 to 9:1.