Preparation of New Nitrogen–Phosphorus Flame Retardants and Their Application in Polyester

Polyester is easily flammable, generating melting droplets and dense smoke, resulting in secondary hazards. In this paper, utilizing phosphoric acid, pentaerythritol, phosphorus pentachloride ([Formula: see text]) and ethanolamine as raw materials, a novel nitrogen–phosphorus flame retardant is synthesized for the flame-retardant treatment of polyester fibers. The flame-retardant polyester treated is characterized in terms of performance by means of TG-DSC, SEM, limiting oxygen index (LOI) testing, vertical burning testing and tensile testing. With a flame-retardant additive amount of 100[Formula: see text]g/L, the damage length of the polyester sample strand is merely 4[Formula: see text]cm, exhibiting no continuous burning or afterglow time, with an LOI value reaching 30.3%. This value surpasses that of untreated polyester by 11.2%. Furthermore, even after undergoing 50 cycles of water washing treatment, the LOI value remains above 30.0%. The polyester treated with the nitrogen–phosphorus flame retardant demonstrates reduced smoke, nearly no melting droplets and flame retardancy characterized by both gas-phase and condensed-phase mechanisms.