Flame-retardant, non-tracking thermoplastic resins for high-voltage cable application

Cables for luminous signs require an insulation of high dielectric strength, flame resistance, and in addition, high resistance to tracking (high surface discharge strength because the cable must operate, without protection or end reinforcement, in dirty, moist, and salt-laden atmospheres). Alternatively, an insulation of high dielectric strength, such as polyethylene, may be used (which, incidently, has also high tracking strength) but it needs covering with a flame-resistant jacket which in turn must have high tracking resistance (two-wall construction).