Construction and application of B/P/N durable flame retardant crosslinking system on cotton fabric

The inherent flammability of cotton fabrics necessitates the implementation of flame retardancy to prevent fires. In this study, a B/P/N cross-linking flame retardant system was developed using phosphoric acid, boric acid, and glycerol. The cross-linking system was ammoniated and catalyzed by urea and dicyandiamide to enhance water solubility and fiber bonding strength. Following treatment, the limiting oxygen index of the cotton fabric increased from 18.0 % to 40.5 %, while the damage length in vertical flammability testing decreased from 30.0 cm to 4.8 cm. Thermogravimetric testing revealed an increase in residual char content at 750 °C in a nitrogen atmosphere from 9.7 % to 31.9 %, proving improved thermal stability. Furthermore, the maximum heat release rate and total heat release of the treated samples decreased by 86.7 % and 36.5 %, respectively, compared with pure cotton fabrics. Finally, possible flame retardant mechanisms were inferred from XPS and TG-IR data, demonstrating efficacy in both solid phase and gas phase.