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 Na2CO3. 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