Durable tannic acid-based biological flame retardants for regenerated cellulose fabrics: Preparation, durable flame...

Lyocell fabrics, as one of regenerated cellulose fabrics, are used in clothing and home decoration due to their comfort, softness, and easy coloring. However, Lyocell fabrics are prone to be ignited, with a limiting oxygen index (LOI) of just 19.0 %. In this paper, Tannic acid, Diethylene triamine pentakis (methyl phosphonic acid) solution and urea were applied to prepare a bio-based flame retardant (named TDU). Unlike conventional halogenated flame retardants, TDU is non-toxic, biodegradable, and reduces harmful emissions during combustion, aligning with global sustainability goals. Flame-retardant Lyocell fabrics (*L-TDUud) were prepared by the pad-dry-cure finishing method. TDU can adhere to Lyocell fabrics, the LOI value of *L-TDUud rose to 47.6 %, and reduced to 27.8 % after 70 Ls, passing the vertical flame test. TDU can reduce the thermal stability of flame-retardant Lyocell fabrics in lower temperature area, while improved their thermal stability in higher temperature area. The peak heat release rate and total heat release of *L-TDUud were reduced by 94.1 % and 68.5 % compared with those of control. The air permeability of treated Lyocell fabrics was not affected, and was even enhanced in comparison with that of control. However, the whiteness and breaking strength of Lyocell fabrics after flame-retardant finishing had decreased. In this paper, the durable flame-retardant Lyocell fabrics have been successfully prepared, which had better durable flame-retardant properties.