| abstract |
A silicone resin, curable to a resin of low coefficient of thermal expansion, high glass transition temperature and high modulus, has the empirical formula (R 3 SiO 2 ) a (R 2 SiO 2/2 ) b (RsiO 3/2 ) c (SiO 4/2 ) d wherein each R is a hydrocarbon or substituted hydrocarbon group or a hydrogen atom; and a=0.02 to 0.8; b=0 to 0.4; and c+d=0.2 to 0.98, where a+b+c+d=1.0, characterized in that at least 2 mole % of the siloxane units in the resin are of the formula R′ 3 SiO 1/2 RR′2Sio1/ 2 or R′ 2 SiO 2/2 wherein each R′ is an alkenyl group. |