Evaluating the fire resistance and durability of cotton textiles treated with a phosphoramide phosphorus ester phosphate ammonium flame retardant

The phosphoramide phosphorus ester phosphate ammonium (PPEPA) flame retardant was synthesized by phosphorus oxychloride and ethanolamine, and its structure was characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy (FTIR). Cotton textiles treated with 20 wt% PPEPA (CT-PPEPA3) would have high durability and flame retardance. The limiting oxygen index (LOI) of CT-PPEPA3 was found to be 46.5 %, while after undergoing 50 laundering cycles (LCs) following the AATCC 61-2013 3 A standard, the LOI only decreased to 31.4 %. Scanning electron microscopy and X-ray diffraction analyses suggested the penetration of PPEPA molecules into the interior of cotton fibers, resulting in a minor alteration of the cellulose crystal structure. The excellent durability, FTIR, and energy-dispersive X-ray of CT-PPEPA3 provided evidence for the formation of -N-P(=O)-O-C- and -O-P(=O)-O-C- covalent bonds between the PPEPA molecules and cellulose. The -N-P(=O)-O-C- bond exhibited a p-pi conjugation effect, leading to enhanced stability and improved durability of the flame-retardant cotton textiles. Vertical flame, thermogravimetric, and cone calorimetry tests demonstrated that the CT-PPEPA3 underwent condensed-phase and synergistic flame retardation. Additionally, these finished cotton textiles retained adequate breaking strength and softness, making them suitable for various applications. In conclusion, the incorporation of the -N-P(=O)-ONH4 group into the phosphorus ester phosphate ammonium flame retardant demonstrated effective enhancement of the fire resistance and durability of treated cotton textiles.