| 摘要 |
1491782 Arc track resistant siloxane compositions DOW CORNING CORP 24 Feb 1975 [6 May 1974] 7601/75 Heading C3T A composition consists essentially of 20-50% by weight of a siloxane fluid having a viscosity of from 100-5,000 cS. at 25‹ C., the substituents on the silicon atoms in the fluid being monovalent C 1 -C 18 hydrocarbon radicals, preferably methyl and/or phenyl radicals, and from 50- 80% by weight of a mineral filler which is a clay, e.g. bentonite or a montmorillonite clay, ground quartz, gypsum, amorphous silica or aluminium oxide or a mixture thereof; and optionally up to 6% by weight of a siloxane resin composed of SiO 2 and (CH 3 ) 3 SiO 1/2 units in a ratio of from 1 : 0À6 to 1 : 1À2. Other optional additives include a dye, a curing agent, an ultraviolet light stabilizer, e.g. titanium dioxide, or a thixotroping agent, e.g. a high surface area silica. The siloxane fluids are composed predominantly of R 2 SiO units. The filler preferably has a particle size of less than 10 microns. The compositions generally have a grease-like consistency but can be diluted with an organic solvent. In the examples compositions are prepared by thoroughly mixing by roll-milling a trimethylsilyl-terminated polydimethylsiloxane fluid (1,000 cS. or a blend of 100 cS. or 350 cS.), the above siloxane resin, alumina and silica and optionally diluting with toluene. The electrical properties of the resulting compositions were determined. Uses.-Arc track resistant compositions. |
