Benzoylation strategy for enhancing the light stability of kenaf fibers through lignin removal and radical scavenging

Enhancing photostability of lignocellulosic fibers is essential for their long-term use in light exposure applications. In this study, benzoylation was applied to kenaf fibers to suppress ultraviolet (UV)-induced yellowing and improve their light fastness. Structural analyses confirmed that esterification of hydroxyl groups and partial removal of lignin were successfully achieved during the benzoylation reaction. After 500 h of UV irradiation, benzoylated kenaf (BKF) showed a distinct whitening phenomenon, in contrast to the gradual yellowing of unmodified kenaf. This whitening effect was attributed to the initial photostabilization, and the discoloration was characterized by a plateau after the initial 48 h. The results confirmed that BKF effectively inhibited the formation of light-induced free radicals and mitigated subsequent surface oxidation. In the component-specific study, lignin was identified as the primary contributor to yellowing. In addition, the photobleaching behavior of benzoylated hemicellulose closely mirrored that of BKF, suggesting its pivotal role in the whitening effect observed in BKF. These results demonstrated that the photostability of natural fibers can be effectively improved through benzoylation by removing chromophore-forming lignin and introducing aromatic ester groups that mitigate radical propagation and oxidative degradation.