Surface Coating and Metal-Based Organic Additives—Approaches for FRSS PVC Cables
Polyvinyl chloride (PVC) is one of the most widely used polymers today. One of its major applications is in electrical and control cables. Although PVC is intrinsically self-extinguishing, it supports flame spread along its length because of the additives used during processing. The spread of fire along electrical cables may be alleviated either by using flame-retardant smoke-suppressant (FRSS) additives or by applying fire-retardant intumescent coatings to the surface of the cable sheath. The intumescent coating also acts as a fire-protective barrier for electrical cables. Plasticized PVC compositions incorporating a molybdenum-based organic (MBO) complex were prepared and evaluated for their fire performance. Excellent smoke suppression was observed in the specimens modified using the complex, which acts as an FRSS additive. The limiting oxygen index (LOI) was also found to be fairly high, particularly when the PVC samples were plasticized with a phosphate plasticizer. FRSS intumescent coatings were applied on PVC-sheathed electrical cables. Their fire performance was evaluated using national and international standard procedures. Significantly low levels of smoke generation was observed along with zero flame spread when the coated cables were exposed to standard test conditions. The formulations used in both the treatments — coating as well as additive — offer improved resistance to ignition, flame spread and smoke generation.