Mechanism of Action of Phosphorus-Based Flame Retardants in Nylon 6. II. Ammonium Polyphosphate/Talc

Abstract
Talc added to PA-6 fire retardant with APP increases the oxygen index and upgrades the UL94 ranking to class V0. A chemical reaction of APP with talc, detected in the mixtures above 350°C, prevents volatilization of poly phosphoric acid and increases the amount of thermally stable solid residue. The inorganic phosphates that are formed improve the insulating properties of the intumescent layer on the surface of burning PA-6, as compared to the use of APP alone.