Dual curing silicone, method of preparing same and dielectric soft-gel compositions thereof

A composition capable of curing by both moisture cure and UV cure mechanisms, the composition comprising:

• (a) 30-100 parts by weight of a reactive polyorganosiloxane terminated with acrylic functional dialkoxy- or diaryloxy-silyl groups and containing about 0.1-5% of a silicone moisture curing catalyst;
• (b) 0-70 parts by weight of a trimethylsilyl terminated silicone oil;
• and
• (c) an effective amount of a photosensitizer, said photosensitizer present either as photosensitive groups bound to said reactive polyorganosiloxane or as a separate ingredient in admixture with components (a) and (b) above,
• wherein the reactive polyorganosiloxane comprises the reaction product of a silanol terminated silicone represented by the formula:
• ##STR5## wherein R.sup.1 and R.sup.2 are organo groups, no more than 2% of which are crosslinkable under UV or moisture cure conditions, and n is an integer, said silanol having a viscosity of between about 600 and 20,000 cst, with an acrylic functional trialkoxy- or triaryloxysilane of the formula:
• ##STR6## wherein R.sup.3 are the same or different alkyl or aryl groups;
• R.sup.4 is H or C.sub.1-5 alkyl and R.sup.5 is alkylene, in the presence of a condensation catalyst, the mole ratio of said silane to said silanol being between 2:1 and 6:1, and the reaction including removing substantially all of the theoretical amount of R.sup.3 OH produced by the reaction.