Regenerated cellulose fibers functionalized with lignin-derived boron-containing phenolic networks for durable flame...

The inherent flammability and insufficient ultraviolet (UV) protection of regenerated cellulose fibers limit their functional applications. Inspired by the natural polyphenol-polysaccharide synergy in plants, a lignin-derived boron-containing phenolic network (Lig-BPF) was incorporated into a cellulose spinning system and then coordinated with Zn²⁺ to fabricate Cellulose/Lig-BPF@Zn fibers. Compared with pristine cellulose fibers, Cellulose/Lig-BPF@Zn increased the char residue at 800 °C from 13.72% to 30.35% under N₂ atmosphere, and reduced the peak heat release rate by 43.03%. The limiting oxygen index increased from 17.2% to 31.5%, and still remained 29.1% after 20 laundering cycles. TG-FTIR analysis showed an 88.56% reduction in total volatile release intensity, while Raman analysis confirmed an increased degree of graphitization, as evidenced by a decreased I_D/I_G value from 3.59 to 2.55. Furthermore, the UV protection factor increased from 11.42 to 128.82, and remained 109.74 after durability testing. Mechanistic analyses demonstrate that lignin-derived aromatic domains, boron-containing structures and Zn-coordinated species regulate cellulose pyrolysis and promote the char formation. This work develops a sustainable strategy for converting natural lignin into a bio-based flame retardant that simultaneously improves the flame retardancy and UV protection performance of regenerated cellulose fibers, providing a phosphorus-free and eco-friendly approach for preparing multifunctional carbohydrate-based fibers.