Flame-Retardant, Antimicrobial, and UV-Protective Lignin-Based Multilayer Nanocoating

Creating multifunctional textiles using chemicals from renewable sources is challenging. In an effort to develop a sustainable and efficient multifunctional cotton treatment, a lignin-based multilayer nanocoating comprising magnesium lignosulfonate, chitosan, and monoammonium phosphate (MAP) was deposited using layer-by-layer assembly. A five bilayer coating adds 15.5 wt % to cotton and imparts fire extinguishing behavior and excellent UV and antimicrobial protection to the fabric. Just a two bilayer coating imparts sufficient self-extinguishing behavior to pass the standard vertical flame test. The combined influence of lignin as a char-forming and UV-protective macromolecule, chitosan as a char-forming biopolymer, and MAP acting as an antimicrobial agent (and a blowing agent and an acid source in an intumescent flame retardant system) results in a very powerful multifunctional textile treatment with very few layers of deposition.