A novel durable and soft cotton flame retardant containing phosphonamide phosphate ester with ammonium phosphonate group

A novel type of durable flame retardant applied to cotton fabrics, phosphoacetamide phosphate ammonium phosphate (PAPAP), was synthesized. The PAPAP structure characterization was determined via nuclear magnetism resonance, X-ray photoelectron spectroscopy and Fourier transform infrared (FTIR). Scanning electron microscopy and X-ray diffraction revealed that PAPAP diffused into fibers and did not significantly influence their morphology and crystal structure. The FTIR analysis and wash fastness of samples suggested that PAPAP was bound to cellulose through N–(P = O)–O–C and O–(P = O)–O–C covalent bonds. The presence of p-π conjugated effect in the (P = O)–N group of PAPAP strengthen the stability of the N–(P = O)–O–C bond, resulting in highly durable flame resistance in the finished cotton fabrics, which is supported by the fact that the treatment of cotton with 30 wt% PAPAP (30%FRC) exhibited an LOI value of 54.7%. Even after undergoing 50 washing cycles based on the AATCC 61–2013 3A standard, 30%FRC maintained an LOI value of 44.1%. Thermogravimetry (TG), TG–FTIR, cone calorimetry, and char residue analyses indicated that PAPAP modified the thermal decomposition pathway of cellulose, reduced the generation of flammable gases and promoted char formation, effectively resisting fabric fires. The whiteness, breaking strength and comfortability of the treated cotton fabrics were well sustained, and their softness was very well, even softer than that of control cotton. In conclusion, the introduction of N-P(= O) group and phosphate ester groups into a flame-retardant molecule effectively improved the durability and softness of finished cotton fabrics.

Graphical Abstract