Mechanisms for Flame Retardancy and Smoke suppression -A Review

The prevailing mechanisms for halogen and phosphorus flame retardancy are reviewed. Halogens act in the vapor phase and phosphorus can act in either the vapor or condensed phase depending on the specific phos phorus compound and the chemical composition of the polymer. Halogen- antimony synergy is discussed. Convincing evidence is presented for bromine- phosphorus synergy in specific polymers. The mode of decomposition of polycarbonate is shown and the effect of salts of organic acids in changing the mode of decomposition hence producing a more flame resistant polymer is shown. Intumescence in polyolefins is discussed. Inorganic metal hydrates used in large concentration cool by endothermically releasing a large concentration of water. The effect of boron compounds is discussed. Methods of smoke suppres sion are presented as is the role of zinc borate, molybdenum and tin compounds acting as Lewis acids in PVC.