Silicone compositions for high voltage insulator

1 . A composition comprising:

(a) from about 15% to about 50%, by weight of the total composition, of a silicone polymer;

(b) from about 5% to about 30% by weight of the total composition of a reinforcing filler;

(c) from about 20% to about 70% by weight of the total composition of an anti-tracking agent and a flame retardant;

(d) from about 0.01% to about 1% by weight of the total composition of a coupling agent;

(e) from about 0.1% to about 5% by weight of the total composition of a curing agent;

(f) up to about 20% by weight of the total composition of an extending filler; and

(g) from about 0.1% to about 5% by weight of the total composition of at least one processing fluid.

2 . A composition of claim 1 wherein:

(a) the silicone polymer comprises from about 25% to about 40%;

(b) the reinforcing filler comprises from about 8% to about 20%; and

(c) the anti-tracking and the flame retardant comprises from about 25% to about 60%.

3 . A composition of claim 2 wherein the silicone polymer is represented by recurring units of Formula I

wherein:

R 1 independently at each occurrence represents C 1-4 alkyl, or C 2-4 alkylene;

R 2 independently at each occurrence represents C 1-4 alkyl, C 1 -C 4 haloalkyl, or C 2-4 alkylene;

R 3 independently at each occurrence represents H, C 1-10 alkyl, C 2-4 alkylene, C 4-6 cycloalkyl, C1-C4 haloalkyl, OH; and

n represents an integer from 1,000 to 20,000

4 . A composition of claim 3 wherein

R 1 independently at each occurrence represents, CH 3 or CH═CH 2 ;

R 2 independently at each occurrence represents CH 3 , CH 2 CH 2 CF 3 , or CH═CH 2 ;

R 3 at each occurrence represents CH 3 , CH═CH 2 , OH, or CH 2 CH 2 CF 3 ; and

n represents an integer from about 4,000 to about 10,000.

5 . A composition of claim 3 wherein the vinyl content of the silicone polymer ranges from about 0.05% to about 0.5% by weight of the silicone polymer.

6 . A composition of claim 5 wherein the reinforcing filler is fumed silica, precipitated silica, or carbon black having a surface area of from about 50 to about 400 m 2 /g.

7 . A composition of claim 5 wherein the coupling agent is vinyltriethoxysilane (VTES), or vinyltrimethoxysilane, methacrylpropyltrimethoxy silane.

8 . A composition of claim 5 wherein the curing agent is a peroxide based curing agent.

9 . A composition of claim 8 wherein the curing agent is a diacylperoxide, ketone peroxide, and dialkyl peroxide.

10 . A composition of claim 5 wherein the extending filler is ground quartz, calcium carbonate, magnesium silicate, or magnesium aluminum silicate.

11 . A process of claim 5 wherein the processing fluid is a methyl or hydroxy terminated polydimethyl siloxane.

12 . A composition of claim 5 further comprising a mold release agent, a coloring agent, or a heat resistive agent.

13 . A composition of claim 12 wherein the mold release agent is a silicone fluid, magnesium, aluminum, or cerium stearate.

14 . A composition of claim 13 wherein the heat resistive agent is a cerium octoate, cerium hydroxide, magnesium oxide, cerium oxide, or magnesium hydroxide.

15 . A composition of claim 1 wherein upon heat curing the composition, the heat cured composition comprises a high voltage insulating composition.

16 . A process for making a high voltage insulating composition, the process comprising heat curing the composition of claim 1.