A synthetic bis-triazine ring derivative based on ammonium phosphonate towards durable flame-retardant modification of cotton fabrics

•The flame retardant prepared has no formaldehyde release and has excellent flame retardant properties (LOI:41.8).•Excellent durability, after 50 times of washing, still have considerable flame retardant effect (LOI:30.3).•Smoke suppression effect is remarkable.•ASBSMP/cotton exhibited outstanding mechanical integrity for a wide range of applications. Cotton is widely used in daily life. However, its flammability limits its application in certain areas. In this study, a novel formaldehyde-free reactive flame retardant, ASBSMP, derived from a bis-triazine ring ammonium phosphonate, was successfully synthesized. The ASBSMP/cotton exhibited excellent flame-retardant properties, with self-extinguishing characteristics and a LIMITING OXYGEN INDEX (LOI) of 41.8 %. Even after 50 washing cycles, the LOI remained at a high level of 30.3 %, indicating outstanding durability. Thermogravimetric analysis (TGA) revealed its superior thermal stability. Cone calorimeter tests further confirmed the superior flame retardancy of the treated cotton, showing a 44.6 % reduction in total heat release (THR) and a 90.1 % reduction in peak heat release rate (PHRR) compared to pure cotton. Results from Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), and char residue analyses demonstrated that ASBSMP exhibited flame-retardant activity in both the gas and condensed phases. ASBSMP/cotton exhibited outstanding mechanical integrity for a wide range of applications. [Display omitted]