Facile, one–pot, formaldehyde-free synthesis of reactive N[sbnd]P flame retardant for a biomolecule of cotton

Abstract

The NP flame retardant ammonium salt of hydroxyethyl hexahydrotristriazine˗triphosphoric acid (AHTTPA) was prepared by a one–pot synthesis method under formaldehyde-free and solvent-free conditions. The AHTTPA was finished on the biomolecule of cotton by using the dip-roll-bake method. Nuclear magnetic resonance (NMR 1H, 13C, and 31P) demonstrated that AHTTPA was successfully synthesized. The flame retardancy of AHTTPA-treated cotton was studied by limiting oxygen index (LOI), vertical flaming test (VFT), scanning electron microscopy (SEM), and cone calorimetry (CC). The results from these tests indicate that AHTTPA-treated cotton exhibited favorable flame retardancy and durability (the LOI value of 40%-treated cotton after 50 laundering cycles (LCs) was 29.8%), the flame was immediately extinguished after removal from the treated cotton, no smoldering or continued burning, the burned part formed a complete carbon frame and generally maintained its original morphology, the peak heat release rate (PHRR) and total heat release (THR) of AHTTPA-treated cotton fabric were significantly lower than pure cotton. Thermogravimetric analysis (TGA) results showed that AHTTPA improved the thermal stability of cotton. The breaking strength and softness of AHTTPA-treated cotton was also retained.