Method for forming thermally conductive thermal radical cure silicone compositions

A method for forming a thermally conductive thermal radical cure silicone composition comprising (I) a clustered functional polyorganopolysiloxane;

• (II) a silicone reactive diluent;
• (III) a filler comprising a thermally conductive filler, (III′) a filler treating agent, and (IV) a radical initiator, the method comprising:
• (A) providing a clustered functional polyorganosiloxane (I) that comprises a reaction product of a reaction of:
• a) a polyorganosiloxane having an average, per molecule, of at least 2 aliphatically unsaturated organic groups,
• b) a polyorganohydrogensiloxane having an average, per molecule, of 4 to 15 silicon atoms and at least 4 silicon bonded hydrogen atoms per aliphatically unsaturated organic group in component a),
• c) a reactive species having, per molecule at least one aliphatically unsaturated organic group and one or more curable groups selected from acrylate groups and methacrylate groups, and
• in the presence of d) a hydrosilylation catalyst and e) an isomer reducing agent, wherein the isomer reducing agent is present in an amount based on the total weight of the clustered functional polyorganosiloxane (I) to produce at least a 10% reduction in beta-addition of SiH groups to the polyorganosiloxane to the aliphatically unsaturated group of the reactive species as compared to a clustered functional polyorganosiloxane formed in the absence of the isomer reducing agent;
• (B) forming a first mixture by mixing the filler (III) comprising the thermally conductive filler, the filler treating agent (III′), and at least one of the silicone reactive diluent (II) and the clustered functional polyorganosiloxane (I);
• (C) heating the first mixture to a temperature from 50° C. to 110° C. to treat the thermally conductive filler (III) with the filler treating agent (III′)
• (D) after heating in step (C), introducing the silicone reactive diluent (II), the clustered functional polyorganosiloxane (I), or neither to the first mixture as needed to obtain a final mixture that comprises both the silicone reactive diluent (II) and the clustered functional polyorganosiloxane (I);
• and then
• (E) cooling the final mixture to 30° C. or less and then blending a radical initiator (IV) with the final mixture to form a thermally conductive thermal radical cure silicone composition.