Diorganopolysiloxane elastomer loaded - with carbon black for use as ht cable

摘要

Standard diorganopolysiloxane (co)polymers, commonly used for low voltage cable insulants, have their electrical breakdown resistance improved to withstand voltages in excess of 250V, by the addition of 0.5 - 7% wt., pref. 1.5 - 3% wt. of conductive carbon black in addition to the other usual fillers. The carbon black used has a specific resistance less than 0.2 ohm/cm. under pressure of 100 - 300 kg/cm2 at room temp. The prefd. polymer quoted is dimethylsiloxane or a copolymer of 99.9 - 99.8 mol. % dimethylsilozane and 0.1 - 0.2 mol.% vinylmethylsiloxane units, having a viscosity above 104CSt/25 degrees C, with 20 - 70% wt dielectric fillers. The prepd. polymer mix. is pref. extruded onto the cable core. Under test it withstood 25 kV, 50 cycles A.C.