Durable Flame-Retardant, Anti-UV, Photothermal, and Antibacterial Cotton Fabrics Based on Lignin and Ammonium Polyphosphate

The demand to produce durable multifunctional cotton fabrics without detrimental effects on the environment is increasing. Herein, a durable multifunctional cotton fabric (cotton-APP/LP) is designed and prepared through covalently grafting phosphorylated lignin (LP)/ammonium polyphosphate (APP) onto the fabric surface, presenting UV protection, photothermal conversion, fire safety, and antibacterial properties. The preparation of LP adopted a green mechanochemical method, and the whole treatment process is organic solvent-free. LP possesses excellent free-radical absorption capacity, and cotton-APP/LP achieves a UV protection factor value of 421.97. Under xenon lamp simulated irradiation, cotton-APP/LP exhibits a temperature of approximately 63.4 °C at a light intensity of 150 mW cm–2, presenting a robust photothermal conversion effect. The antimicrobial properties (inhibition of Escherichia coli and Staphylococcus aureus) are also achieved for cotton-APP/LP. In addition, the limiting oxygen index (LOI) of cotton-APP/LP increases to 48.5%, and self-extinguishment is observed in the vertical burning test. After 50 washing cycles, the cotton-APP/LP self-extinguishes and the LOI value reaches 31.5%, demonstrating excellent washing durability. This work prepared a durable cotton fabric to realize multifunctionality in a cleaner and safer way, further promoting the practical application of durable multifunctional cotton fabrics.