A survey of recent progress in phosphorus-based flame retardants and some mode of action studies

Phosphorus-based flame retardants have diverse modes of action, Aryl phosph ates can have vapor phase action in styrenic polymers but also can contribu te to producing a barrier layer. Tris(dichloroisopropyl) phosphate in a fle xible polyurethane foam can serve as both a vapor-phase (probably physical) flame inhibitor in bottom ignition but contributes to formation of a barri er in top-down burning. Halogen/phosphorus and nitrogen/phosphorus synergis m are not general but examples are known. Red phosphorus and ammonium polyp hosphate interact with nylon 6 under burning conditions to produce phosphat e esters and eventually chars. The cyclic neopentyl ester of nitrilotris(me thylphosphonic acid) as a flame retardant in ethylene vinyl acetate copolym er can serve as a char-former and catalyst. Attempts to find synergists for phosphorus provide clues to improved combinations.