Use of a Silicone Rubber Composition for The Manufacture of an Insulator for High Voltage Direct Current Applications

A silicone composition, obtained by curing a composition comprising:

• a) 100 pt·wt. of at least one polyorganopolysiloxane having alkenyl groups,
• b) 0-100 pt·wt. of a crosslinker component comprising one or more polyorganohydrogensiloxanes,
• c) 0-100 pt·wt. of a filler component comprising one or more reinforcing silicas or resins,
• d) >0.1-2 pt·wt. of at least one dielectric active compound selected from the group consisting of oxides, carbides, ferrites or spinels of Ti, Al, Zn, Fe, Mn, Mo, Ag, Bi, Zr, Ta, B, Sr, Ba, Ca, Mg, Na, K, and Si, and inorganic salts including chlorides, sulfates thereof,
• e) a curing catalyst selected from the group consisting of 0-1000 ppm of a compound enabling hydrosilylation and 0.1 to 2 wt.-% of an organic peroxide each related to the sum of the amounts of the components a) to d), and
• f) 0-50 pt·wt. of one or more auxiliary additives,
• said silicone composition having
• a temperature dependency of the volume resistivity in the range of 25 to 90° C. at an electric field of 10 kV/mm to 30 kV/mm, such that the ratio of the maximum volume resistivity and the minimum volume resistivity is <10, and
• the volume resistivity in the range of 25 to 90° C. at an electric field of 10 kV/mm to 30 kV/mm is between 1*1011 and 1*1016 Ohm*cm.