Construction of biological flame retardant layer on cotton fabric via photografting of nucleotide/amino acid monomers

The adenine nucleotide (AMP-Na₂) was modified to introduce unsaturated double bonds for photografting onto cotton fabrics together with l-Cysteine (l-Cys) monomer to prepare synergistic bio-based flame retardant cotton fabrics. The chemical structure of AMP-Na₂/ l-Cys monomers, surface morphology, residual carbon morphology, thermal properties and flame retardant properties of photografted flame retardant cotton fabrics were analyzed. FT-IR and ¹H NMR spectra verified the AMP-Na₂ and l-Cys monomers with unsaturated double bonds. Scanning electron micrographs revealed the carbon residue of photografted fiber maintained a natural curled and fiber shape. TGA showed that the major pyrolysis temperature of cotton fabric declined by 51 °C and the weight loss reduced by 20.5%, proving good charring effect of flame retardant layer via photografting of AMP-Na₂/l-Cys monomers. The afterflame and afterflow time of photografted cotton fabric were nearly decreased to 0 s. The LOI value of photografted cotton fabric was 27.34% and decreased by 7.9% after 20 washing times. The peak heat release rate and total heat release decreased from 198.05 kW/m² and 9.94 MJ/m² to 34.49 kW/m² and 4.47 MJ/m², respectively. The experimental results indicated that durable flame retardancy of cotton fabrics was achieved via facile photografting of AMP-Na₂/l-Cys monomers.