Patent ID: 8133949

Claim:
A separator seal for use in polymer electrolyte fuel cells which is formed of a sealing composition in the cured state, said sealing composition comprising: (A) 100 parts by weight of a liquid organopolysiloxane containing at least two alkenyl groups each attached to a silicon atom in a molecule, (B) 0.5 to 20 parts by weight of an organohydrogenpolysiloxane containing at least three hydrogen atoms each attached to a silicon atom in a molecule, (C) 10 to 30 parts by weight of fumed silica having a BET specific surface area of 50 to 400 m 2 /g, (D) 0.1 to 3 parts by weight of carbon black having a BET specific surface area of 30 to 120 m 2 /g, an iodine adsorption value of 30 to 120 mg/g, and a DBP absorption value of 100 to 200 ml/100 g, and (E) a catalytic amount of an addition reaction catalyst, said alkenyl-containing liquid organopolysiloxane (A) being a mixture of at least two liquid organopolysiloxanes having different weight average molecular weights.