Fabrication of multifunctional lignin-based composite coatings for enhanced strength, barrier properties and UV protection of cellulosic paper

The ultraviolet (UV) shielding properties of food packaging materials have garnered significant attention for mitigating issues such as off-flavors, discoloration, and nutrient degradation. However, achieving effective UV protection while maintaining sustainability and performance in packaging materials remains a challenge. Herein, a novel multifunctional composite coating with UV-shielding properties was prepared using cellulose nanocrystals (CNCs) and sodium lignosulfonate (SL) as functional components and polyvinyl alcohol (PVA) as a cross-linking agent. Notably, the SL-4/C/P coated paper prepared using the coating with an SL/CNCs mass ratio of 4:1, exhibited excellent UV-shielding efficiencies (98 % shielding in the UVA region and almost completely block the whole UVB region), enhanced mechanical properties (126 % increase in tensile index and 308 % improvement in folding endurance), lower Cobb 30 value (decreased from 66 g/m 2 to 56 g/m 2 ), and reduced air permeability (decreased from 124 mm/s to 52 mm/s) compared to uncoated paper. This work offers a sustainable and promising strategy for balancing UV-shielding performance with the functional properties of food packaging paper, opening new avenues for the high-value application of CNCs and SL in the papermaking industry.