Cone calorimetry studies of polymer systems flame retarded by chemically bonded phosphorus

The combustion behaviour of polystyrene flame retarded by the incorporation of phosphorus-containing compounds has been studied by LOI and cone calorimetry. Both 'reactive' and 'additive' approaches to the incorporation of the phosphorus have been applied and assessed. The data obtained show that the reactive approach results in enhanced char formation during combustion due to a condensed phase mechanism. Flame retardation by the additive systems occurred exclusively in the vapour phase via both chemical and physical interactions. The main advantage of the reactive approach was the maintenance of the physical and chemical properties similar to those of the homopolymer. The phosphorus environment was also a significant factor in terms of the level of flame retardance achieved. Phosphonate species were more effective than were phosphate species.