Organopolysiloxane composition for electrical insulation

An essentially unfoamable fluid organopolysiloxane composition for electrical insulation, consisting essentially of a homogeneous mixture of

• (A) a fluid organopolysiloxane represented by the general formula (1):
• (R.sup.1).sub.a (R.sup.2).sub.b SiO.sub.(4-a-b)/2 ( 1)
• wherein R.sup.1 's each independently represent an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, R.sup.2 represents an alkenyl group, a is a number of 1.5 to 2.0, and b is a number of 0.003 to 0.5, provided that a+b=2.00 to 2.07, having 30 to 600 silicon atoms on the average in the molecule, and containing at least two alkenyl groups each bonded to a silicon atom,
• (B) a fluid organohydrogenpolysiloxane represented by the general formula (2):
• (R.sup.3).sub.c H.sub.d SiO.sub.(4-c-d)/2 ( 2)
• wherein R.sup.3 's each independently represent an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, c is a number of 1.0 to 2.0, and d is a number of 0.04 to 1.0, provided that c+d=1.1 to 2.5, having 4 to 120 silicon atoms on the average in the molecule, and containing at least two hydrogen atoms each bonded to a silicon atom;
• the organohydrogenpolysiloxane (B) being contained in such an amount that the number of the hydrogen atoms each bonded to a silicon atom contained in the organohydrogenpolysiloxane (B) is 0.5 to 5 per alkenyl group in the organopolysiloxane (A),
• (C) a fluid organopolysiloxane represented by the general formula (3):
• (R.sup.4).sub.e (OH).sub.f SiO.sub.(4-e-f)2 ( 3)
• wherein R.sup.4 's each independently represent a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group, e is a number of 1.0 to 2.5, and f is a positive number of 1.0 or less, having 2 to 300 silicon atoms on the average in the molecule, and containing at least one hydroxyl group bonded to a silicon atom;
• the organopolysiloxane (C) being contained in an amount of 0.01 to 15 parts by weight per 100 parts by weight of the sum of the component (A) and the component (B),
• (D) an inorganic filler having an average particle diameter of 1 to 50 .mu.m in an amount of 30 to 350 parts by weight per 100 parts by weight of the sum of the components (A), (B), and (C),
• (E) platinum or a platinum compound in a catalytic amount, and
• (F) a member selected from the group consisting of a reinforcing filler, a pigment, a heat resistance improver, a flame retardancy improver, a reaction controlling agent, and a plasticizer,
• wherein the substituents of said substituted monovalent hydrocarbon are halogen or nitrile.