A reactive flame retardant ammonium salt of diethylenetriaminepenta(methylene-phosphonic acid) for enhancing flame retardancy of cotton fabrics

In this study, a novel flame retardant (FR) for cotton fabrics was synthesized, namely, ammonium salt of diethylenetriaminepenta(methylene-phosphonic acid) (ADTPMPA), using diethylenetriaminepenta(methylene-phosphonic acid) (DTPMPA) and urea, and its structure was comfirmed by ¹H NMR, ¹³C NMR and ³¹P NMR. The ADTPMPA reacted with the –OH groups of cellulose macro molecules to form P–O–C covalent bonds. LOIs of cotton fabrics finished with 70 and 90 g/L ADTPMPA reached to 40.0 and 41.5% respectively; after 40 laundering cycles, their LOIs were 26.5 and 26.7% respectively. The treated cotton fabrics still kept soft. FTIR spectroscopy confirmed –P–O–C bonds between ADTPMPA and cellulose, and X-ray diffraction revealed the formation of cellulose II structures in the finishing process. SEM suggested that ADTPMPA molecule permeates the inner space of the cotton fibers. TG result indicated that the treated cotton fibers retain more residue than the original fibers. Cone calorimetry test result showed that the treated cotton fabric had lower PHRR and THR than that of original cotton fabric. The results suggested that the ADTPMPA treated cotton fabrics had condense phase flame retardant mechanism.