Flame retardant polyester fabric from nitrogen-rich low molecular weight additives within intumescent nanocoating

An intumescent nanocoating composed of chitosan (CH) and ammonium polyphosphate (APP), with and without low-molecular weight nitrogen and nitrogen/sulphur based derivatives, was deposited on polyester fabric using the layer-by-layer technique. Guanidine sulfamate (GSM), urea and thiourea were added to the aqueous chitosan deposition solution in an effort to improve flame retardancy. Exceptional self-extinguishing behavior is observed with a 10 bilayer (BL) CH:GSM/APP coated fabric. This water-based coating added 19.6 wt% to the polyester and reduced peak heat release rate by 61.7%, relative to uncoated fabric. Furthermore, the polyester is not fully ignitable because of earlier decomposition of GSM that helps to generate a thicker sponge-like char that acts as a physical barrier. This unique addition of low-molecular weight molecules in traditional intumescent polyelectrolyte pairs is a new opportunity for imparting flame retardancy to highly flammable synthetic fibers used in clothing and home furnishing.