Phospham—A stable phosphorus‐rich flame retardant

Abstract

Abstract Phospham is an iminophosphazene polymer of unusually high thermal stability. We have found that phospham imparts a substantial level of flame retardancy to nylon‐4,6, a high‐melting crystalline engineering thermoplastic. It did not appear to produce degradation of the polyamide in the processing temperature range. The flame retardant efficacy of phospham in nylon‐4,6 was similar to that of stabilized red phosphorus, when compared on an equal phosphorus basis. In nylon‐4,6, it did not display nitrogen–phosphorus synergism. Limited evidence from TGA suggested a condensed phase mode of action in nylon‐4,6. Phospham showed orders‐of‐magnitude better hydrolytic stability than did ammonium polyphosphate, and did not produce detectable phosphine on processing as did red phosphorus.