Low smoke and fume cables with enhanced fire performance, resistance to moisture and mechanical properties

PVC (the traditional general purpose oversheathing material used in cables), when burnt emits large quantities of dense black smoke and hydrochloric acid gas arising from its decomposition mechanism in fire. Attempts to incorporate flame retardant fillers into PVC have been successful in limiting fire propagation but do little to minimise the problems of smoke and acid gas. As a result low smoke and fume (LSF) compounds were developed in the early 1970´s. These compounds, however, have two major drawbacks: (1) poor mechanical strength; and (2) poor performance in water. In order to address these two limitations of LSF an intensive development programme was initiated, the results of which are discussed in this paper