Aldehyde-free and ultra wash-resistant Lyocell fabrics with high flame retardancy, ultraviolet resistance and wearing performance via multi-level bonds

Developing durable and aldehyde-free flame-retardant Lyocell fabrics remains a daunting task. Here, the multi-level bonding strategy was employed to fabricate multifunctional and durable Lyocell fabrics (Lyocell-APP-TATE). A covalent P-O-C bonding formed in the inner layer from ammonium polyphosphate (APP) and Lyocell fibers, together with the hydrogen bond in outer layer via complexation of tannic acid (TA) with potassium antimony tartrate (TE), empowered Lyocell fabrics with high flame retardancy, ultraviolet resistance and wearing performance. The resulting Lyocell-APP-TATE fabrics exhibited high limiting oxygen index (LOI) of 33.5%, significantly reduced the peak heat release rate (PHRR) by 92.9% and total heat release (THR) by 73.6% compared to pristine Lyocell. Remarkably, the Lyocell-APP-TATE fabrics demonstrated outstanding washing durability, maintaining an LOI value above 30.0% and self-extinguishing performance even after 300 washing cycles due to the synergistic effects of covalent bonding and metal-phenolic network complexation. Moreover, the high ultraviolet protection factor (UPF) of 288.8 was achieved, while the air permeability and handle properties of Lyocell-APP-TATE were well preserved. The multi-level bonding method paved for high-efficiency and durable flame-retardant coatings for cellulosic textiles with aldehyde-free approach.