A high-efficiency and durable flame retardant for cotton fabrics: Ammonium ethyl acryloylphosphoramidate

The ammonium ethyl acryloylphosphoramidate (AEA) was synthesized by acrylamide, ethanolamine, and phosphorus oxychloride; the nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) were applied to analyze the structure of AEA molecule. Using the dip-cure process to treat raw cotton (RC) with AEA flame retardant, the finished fabric had excellent flame retardancy. The cone calorimeter, thermogravimetric, FTIR, and vertical flame tests illustrated finished fabrics underwent synergistic and condensed-phase flame retardation. The finished fabric also had excellent durability, and the higher the sealing degree of phosphorus atoms, the higher the durability. The limiting oxygen index (LOI) of RC-AEA3-20 (raw cotton finished with 20 wt% AEA3) reached 45.4 %. However, the LOI only dropped to 34.9 % after 50 laundering cycles under the AATCC 61-2013 3 A standard. The excellent durability and FTIR analyses of finished fabrics suggested that the -N-P(=O)-O-C- covalent bond was formed between flame retardant and cellulose. This covalent bond exhibited a p-π conjugation effect, enhancing the stability of -N-P(=O)-O-C- bond, improving the durability of finished fabrics. In conclusion, adding reactive groups into flame retardants, like CH₂=CH- and -N-P(=O)-O^-NH₄⁺, could increase the durability of finished cotton fabrics.