Curable compsns for encapsulating electronic appts - comprising monophenylsiloxy-dimethylvinylsiloxy copolymer-hydrogen functional siloxane compsns, with platinum catalyst

摘要

Curable compsns. comprise a mixture of (a) an organopolysiloxane with an av. of >=8 Si atoms per molecule, contg. 75-85 mol.% C6H5SIO3/2 units and 15-25 mol.% CH2=CH(CH3)2SiO1/2 units; (b) an organopolysiloxane for formula: in an amt. sufficient to provide 0.9-1.1 mol = SiH per mol. vinyl substituent in (a), and (c) a Pt catalyst in an amt. sufficient to catalyse the addn. reaction of = SiH with CH2=CHSi=. Cured products have excellent strength, flexibility, thermal shock resistance and low temp. cure capability. The compsns. are esp. useful as encapsulating agents for heat sensitive electronic items.