| 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 (R3SiO1/2)a(R2SiO2/2)b(RsiO3/2)c(SiO4/2)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'3SiO1/2, RR'2Sio1/2 or R'2SiO2/2 wherein each R' is an alkenyl group. |