Abstract: An organopolysiloxane copolymer, comprising (i) R1SiO3/2 units, (ii) random R22SiO2/2 units, and (iii) linear (R32SiO)n units, wherein R1 is independently hydrocarbyl or halogen-substituted hydrocarbyl, R2 and R3 are independently R1 or H, n has an average value of from 5 to 500, the mole ratio of R1SiO3/2 units to R22SiO2/2 units is from 1 to 30, and the mole ratio of R1SiO3/2 units and R22SiO2/2 units combined to (R32SiO)n units is from 3 to 600 when the copolymer contains aliphatic unsaturation or from 1 to 600 when the copolymer is free of aliphatic unsaturation; and a method of preparing the organopolysiloxane copolymer.

Abstract: An organopolysiloxane copolymer, comprising (i) R1SiO3/2 units, (ii) random R22SiO2/2 units, and (iii) linear (R32SiO)n units, wherein R1 is independently hydrocarbyl or halogen-substituted hydrocarbyl, R2 and R3 are independently R1 or H, n has an average value of from 5 to 500, the mole ratio of R1SiO3/2 units to R22SiO2/2 units is from 1 to 30, and the mole ratio of R1SiO3/2 units and R22SiO2/2 units combined to (R32SiO)n units is from 3 to 600 when the copolymer contains aliphatic unsaturation or from 1 to 600 when the copolymer is free of aliphatic unsaturation; and a method of preparing the organopolysiloxane copolymer.

Abstract: Novel rubber-modified rigid silicone resins are disclosed. The novel resins are the copolymerized reaction product of (A) an organosilicon composition selected from the group consisting (I) an organosilicone resin, (II) hydrolyzable precursors of (I), and an hydrolyzate of (II), (B1) a first silicone rubber having a nonfunctional linear chain length between functional groups from 6 to 100 and (B2) a second silicone ruberr having terminal functional groups and a degree of polymerization from about 200 to 1,000. The novel rubber-modified rigid silicone resins of the invention show remarkably high fracture toughness, K.sub.Ic, and critical strain energy release rate G.sub.Ic.

Abstract: Novel rubber-modified rigid silicone resins a novel method of making the same are disclosed. The resins are the copolymerized reaction product of (A) an organosilicon composition selected from the group consisting (I) an organosilicone resin, (II) hydrolyzable precursors of (I), and an hydrolyzate of (II) and (B) an silicone rubber. In the method of the invention, the copolymerization step is carried out in an organic solvent, preferably utilizing a relatively weak condensation catalyst. Thereafter, the solution is devolatilized and the composition cured by heating.

Abstract: Novel rubber-modified rigid silicone resins are disclosed. The novel resins are the copolymerized reaction product of (A) an organosilicon composition selected from the group consisting (I) an organosilicone resin, (II) hydrolyzable precursors of (I), and an hydrolyzate of (II) and (B) an silicone rubber. The novel rubber-modified rigid silicone resins of the invention show remarkably high fracture toughness, K.sub.Ic, and critical strain energy release rate G.sub.Ic.