Inspired by sodium alginate: Amino acids cooperating with sodium ions to prepare phosphorus-free flame retardant lyocell fabric

Inspired by the intrinsically flame-retardant alginate fiber, a novel eco-friendly, biomass-based flame retardant was developed to endow lyocell fabrics with excellent flame-retardant properties by using bio-material glycine, aspartic acid as raw materials. Furthermore, glycine and aspartic acid were converted into sodium carboxylate (glycine-Na and aspartate-Na), respectively. Then, lyocell fabric was respectively modified by glycine-Na and aspartic acid-Na to prepare flame retardant lyocell fabric (G-lyocell-Na and A-lyocell-Na). The combustion test result showed that the modified fabrics exhibited self-extinguishing characteristics and high char-forming ability. In addition, compared to the control sample, the peak of heat release rate (PHRR) of G-lyocell-Na and A-lyocell-Na reduced by 36.5% and 49.9%. TG-IR and Raman spectra results indicated that both the condensed and gas phase played the flame retardant role. The electron withdrawing effect of the Na + reduced the activation energy, promoted the pyran ring-opening reaction and reduced the decomposition temperature. Therefore, the flame retardant lyocell fabric decomposed and formed more char residue containing Na 2 CO 3 . The expanded char layer formed during combustion could effectively block the release of heat and the overflow of combustible gases, so that the modified lyocell fabric showed highly flame-retardant efficiency. In this work, a novel preparation strategy that can endow lyocell fabric with good flame retardant properties without traditional flame retardant elements such as P, Cl and Br was proposed, which was green, environment-friendly and in line with sustainable development. Graphic abstract