Action of phosphorus compounds on fire-retardancy of cellulosic materials: a review

Abstract

Owing to their low cost phosphorus fire-retardants find vast application in making fire-retardant cellulosic compostions. They have been used both as a physical additive as well as part of the polymer structure. Acid forming phosphorus compounds are generally effective in cotton and other cellulosic. Acidic retardants produce char via a dehydration process and this brings about the final fire-retardancy in phosphate-containing composition. High efficiency of phosphorus fire retardants in polyurethane foam has also been suggested to be the result of stable char formation. The char affects the flammability in the three following ways: reduction of flammable fuel, insulation by the char and coating by the non-volatile thermally stable phosphorous acids which screen the hot carbon from the oxygen. Nitrogen-phosphorus synergism in cellulose in controversial and evidence indicates that it is non existent in polymers.