New Low Smoke Zero Halogen Tray Cable Jacket Materials designed for Balance of Cost, Performance and Enhanced Fire Resistance

摘要

A next generation low smoke zero halogen (LSZH) tray cable jacket compound based on a unique combination of inorganic fillers has been designed, which provides enhanced flame performance. This has been accomplished by the development of a jacket compound which features enhanced char strength during the exposure to fire. An opportunity provided by this capability, is to reduce the cost of cable designs either by reducing jacket thickness (where allowed by specification), or removal of fire barrier tapes wrapped around the insulated cores. The improvement in char strength was accomplished through an appropriate combination of fillers, which act to form a partial fused ceramic char when exposed to the fire. The formulation still provides sufficient gradual water release covering temperature gradient during vertical cable flame tests such as IEEE 1202/FT4. The protective hardened char layer has been observed to form early after exposure to the flame source and acts as a barrier to propagation. The result observed is a reduction in vertical propagation in the case of a 9 conductor 14 gauge construction, to a char length of less than 1 foot (30.24 cm) with close to zero total smoke release, even with halogenated cores. The barrier effect of the char formed for this class of jacket materials prevents flame propagation not only in a vertical direction but also around the diameter and through into the core. The level of flame performance is clearly differentiated from conventional cable jacket technologies.