A novel relatively high molecule durable flame retardant for cotton fabrics

A relatively high-molecule, formaldehyde-free, and halogen-free ammonium salt of tripolyphosphoric acid (ATPPA) was synthesized and characterized by nuclear magnetic resonance (NMR). The limiting oxygen index (LOI) of ATPPA treated cotton with 22.54% weight gain was 47.3%, decreasing to 33.2% after 50 laundering cycles (LCs), which still could meet the standard of flame retardancy. This showed that ATPPA could enhance the flame retardancy of cotton fabric efficaciously, and the treated cotton had excellent durability. Combining durability and Fourier transform infrared spectroscopy (FT-IR), the data suggested that the hydroxyl groups on cotton fibers reacted with ATPPA to form P-O-C covalent bonds. Surface electron morphology (SEM) and X-ray diffraction (XRD) analyses showed that ATPPA had almost no influence on the structure of the cotton fabrics. Cone calorimetry and thermogravimetry (TG) analyses indicated that ATPPA significantly reduced heat release and promoted the formation of a char layer in the cotton fabrics. The ATPPA-treated cotton fabrics also retained excellent hand feeling.