Simple modification of phenylphosphonic acid to construct polyester-cotton fabrics with high flame retardancy

Polyester-cotton fabrics (PTCO) have excellent properties and are ubiquitous in daily life, but their serious flammability brings great safety hazards to people's lives. This study used phenylphosphonic acid (PPOA) and urea as raw materials to prepare a flame retardant named POU. PTCO/POU was prepared by the pad-dry-cure technique, and the performance was compared with that of PTCO/PPOA, revealing many interesting phenomena. Based on the gas phase and condensed phase flame-retardant mechanism brought by P/N synergy, PTCO/POU had better flame retardancy than PTCO/PPOA did. The damaged length was 6.7 cm, and the limiting oxygen index (LOI) value was 30.1%. The char residues after burning were complete and denser with a higher degree of graphitization. Thermogravimetric analysis showed that POU can significantly reduce the R_max of PTCO, and improve its thermal stability in high temperature zones. The CCT results showed that PTCO/POU had the longest time to ignition and the smallest fire growth index, which was of great significance for reducing fire risk. The TG-FTIR results showed that the volatile products of PTCO/POU were greatly reduced, and during the burning process, NH₃ was produced to dilute the concentration of combustible gases. In addition, PTCO/POU also had better whiteness performance than PTCO/PPOA did. This work greatly improved the flame retardancy of PTCO in a simple way and expanded its application prospects.