Patent ID: 8071697

Claim:
A composition comprising: (A) 100 parts by weight of an organopolysiloxane resin represented by average compositional formula R 1 a R 2 b SiO (4-a-b)/2 (1) where each R 1 is independently an alkenyl group having 2 to 10 carbon atoms, each R 2 is independently a substituted or unsubstituted monovalent hydrocarbon group other than R 1 , with the proviso that at least 50 mole % of R 2 comprise phenyl groups, subscript â€œaâ€ has a value ranging from 0.09 to 0.16, and subscript â€œbâ€ has a value ranging from 1.00 to 1.20; with the provisos that (i) the organopolysiloxane resin comprises alkenyl groups and phenyl groups and (ii) the organopolysiloxane resin has a weight-average molecular weight equal to or exceeding 3000 with polystyrene as reference and determined by gel chromatography; (B) 10 to 50 parts by weight of an organooligosiloxane represented by average compositional formula R 3 c R 4 d SiO (4-c-d)/2 (2) where each R 3 is independently an alkenyl group having 2 to 10 carbon atoms, each R 4 is independently a substituted or unsubstituted monovalent hydrocarbon group other than R 3 , with the proviso that at least 10 mole % of R 4 comprise phenyl groups; subscript â€œcâ€ has a value ranging from 0.60 to 0.80, and subscript â€œdâ€ has a value ranging from 1.50 to 2.10; with the proviso that the organooligosiloxane comprises alkenyl groups and phenyl groups; (C) 20 to 100 parts by weight of an organohydrogenoligosiloxane or organohydrogenpolysiloxane represented by average compositional formula H e R 5 f SiO (4-e-f)/2 (3) where each R 5 is independently a substituted or unsubstituted monovalent or non-substituted monovalent hydrocarbon group other than alkenyl groups, with the proviso that at least 20 mole % of R 5 comprise phenyl groups; subscript â€œeâ€ has a value ranging from 0.35 to 0.65, and subscript â€œfâ€ has a value ranging from 0.90 to 1.70; (D) a catalytic quantity of an addition-reaction catalyst; and (E) 0.2 to 2 weight % of a mold release agent; where the composition is curable to form an article having a hardness of 60 to 100 at 25Â° C. and 40 to 100 at 150Â° C. as measured by ASTM D2240-86.