LAUSR

A high-efficiency, halogen-free flame retardant: ammonium salt of guanazole-penta-(methylphosphonic acid) (AGPMPA) was synthesized in water solution under a mild reaction condition. The chemical structure of AGPMPA was characterized by FT-IR, 1H NMR, 13C NMR and 31P NMR spectra. Vertical burning tests showed that cotton fabrics treated with 20%, 25% and 30% AGPMPA cannot be ignited, and the shortest carbon length reaches 2.9 cm for 30% treated cotton. The limiting oxygen indices of the treated cottons go up to 43.7–47.9% with the increases of AGPMPA concentrations and are still beyond 26.8% even after 50 laundering cycles, indicating that AGPMPA is a superior, durable flame retardant. Simultaneously, cone calorimeter data indicate that the heat release rate and the total heat release of treated cotton was remarkably decreased compared with those of control cotton. The TG-IR results indicate that the amounts of volatile products are prominently reduced, and the degradation temperature of treated cotton is lower than that of control cotton. The residual amounts of 46.1% in N2 gas and 31.6% in air for treated cotton fabric were attained, respectively. No noteworthy change for the surface of treated cotton fiber was observed by SEM. The mechanical properties of cotton fabrics before and after treatment have barely changed. These results proved that eco-friendly AGPMPA is an effective anti-flaming agent and has excellent durability.Graphical abstract