A curable organopolysiloxane composition, comprising:
- A) an organopolysiloxane component having at least two radical reactive groups and/or reactive groups that can be cross-linked by a hydrosilylation reaction within the molecule, where less than 10 to 0 mol % of total organic groups bonded to silicon atoms within the molecule are aryl groups
- B) one or more inorganic fillers;
- and
- C) an organosilicon compound that differs from component A);
- wherein component A) comprises A1) and A2) as follows:
- A1) a straight chain or branched chain organopolysiloxane different from component A2);
- A2) an organopolysiloxane comprising i) and ii) as follows:
- i) a resin structural block having R1SiO3/2 units and optionally SiO4/2 units, where R1 represents a group selected from the group consisting of a monovalent organic group, a hydroxyl group, and an alkoxy group having 1 to 6 carbon atoms, and
- ii) a straight chain diorganopolysiloxane structural block represented by (R22SiO2/2)n where each R2 independently represents an alkyl group having 1 to 20 carbons or a substituted or unsubstituted aryl group having 6 to 14 carbons, optionally substituted with a halogen atom, and n represents a number within a range of 3 to 1000,
- wherein at least a portion of R1 and R2 are reactive groups that can be cross-linked by a radical reaction and/or a hydrosilylation reaction, and the ratio of aryl groups with 6 to 14 carbon atoms included in the total number of moles of the R1 and R2 groups, but excluding hydroxyl groups, is less than 10 to 0 mols;
- wherein the mass of the component B) is 30 to 95% relative to the mass of the overall composition;
- and
- wherein component C) is a straight chain or branched organosilicon compound expressed by the following general formula:
- (RaRb2SiO)p—K—(SiRb2—Y—Si(Rb)q(ORc)3-q)r
- where each Ra independently represents an alkenyl group;
- each Rb independently represents a group selected from the group consisting of monovalent hydrocarbon groups, halogenated hydrocarbon groups, and cyanoalkyl groups;
- each RC independently represents a group selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 10 carbons, and an alkoxyalkyl group having a total of 2 to 10 carbon atoms;
- and K represents a silicone resin structural block or a group selected from the group consisting of the average composition formula:
- (Rb3SiO1/2)s(Rb2SiO2/2)t(RbSiO3/2)u(SiO4/2)v(ORC)w
- where each of Rb and Rc are as defined above, s, t, u, v and w each represent the number of each unit, and each independently represents a number from 0 to 500, provided that all of t, u, and v are not 0, and the value of (s+w) is less than (u+2v);
- and Y represents an oxygen atom, a divalent hydrocarbon group, or a group expressed by the general formula:
- where Rb is as defined above, and each Z is a divalent hydrocarbon group;
- and p represents a number from 1 to 10, r represents a number from 1 to 10, and q represents a number from 0 to 2;
- and
- wherein the resin structural block i) of component A2) has both R SiQ3/2 units and SiO4/2 units.