Crosslinking of lignin/poly(vinyl alcohol) nanocomposite fiber webs and their antimicrobial and ultraviolet-protective properties

Lignin/poly(vinyl alcohol) (PVA) nanocomposite fibers with different lignin concentrations were developed via electrospinning to investigate further possible applications of lignin, an under-utilized renewable biomass material. The antimicrobial and ultraviolet (UV) absorption properties of lignin/PVA nanocomposite fibers were evaluated to determine whether the inherent functionalities of lignin remain in the final material. An environmentally benign crosslinking method was sought to increase the stability of lignin/PVA nanocomposite fibers in aqueous media. The crosslinking and insolubilization of the lignin/PVA nanocomposite fibers was achieved by combining several crosslinking techniques: water vapor treatment at 80℃ for 180 min, photo-irradiation for 30 min under visible light at a distance of 17 cm, and heat treatment at 200℃ for 60 min. Both lignin/PVA nanocomposite fiber webs—containing 50 and 85 wt% of lignin at a 3.0 g/m² web area density, respectively—showed a 99.9% reduction rate against Staphylococcus aureus, but no reduction against Escherichia coli. The same systems exhibited ultraviolet protection factors (UPF) of >50, indicating excellent UV protection. These findings demonstrate the potential of lignin-based composite fibers, and may widen the range of applications for this biomass material.