Flame-retardant PVC compound for cable applications

The low-melting ternary sulfate and modified sulfate glasses based on transition metals like copper, nickel, and vanadium reduce the smoke generation during burning of the PVC compound. With increase in concentration of these glasses, the smoke-density rating values decrease without appreciably altering the oxygen index values. Although trihydrated alumina and potash alum improve flame-retarding properties, the latter cannot be used as it considerably reduces the thermal stability of the PVC compound. Formulations to meet the flame-retardant requirements of a PVC compound suitable for cable sheathing have been developed.