The sensitisation of thermal decomposition of ammonium polyphosphate by selected metal ions and their potential for improved cotton fabric flame retardancy

A thermal analytical study of a series of metal ion-ammonium polyphosphate (APP) combinations has been undertaken to examine possible interactions that might enhance subsequent flame retardant activity. It is shown that certain metal ions, particularly Mn2+ and Zn2+, promote thermal degradation of APP at lower temperatures than in their absence, and that this enables flame retardant activity to commence at lower temperatures in the polymer matrix thereby enhancing flame retardant efficiency. This has significance where flame retardant formulations are required to become active at temperatures well below normal substrate ignition temperatures and especially in the case of back-coated, flame retardant treatments for textiles. Initial experiments show that metal ion-doped APP in the presence of cellulose not only indicates a further sensitisation of cellulose decomposition but also improved flame retardance determined by limiting oxygen index when applied as a back-coating to cotton fabric demonstrates.