Functionalized lignin nanoparticles prepared by high shear homogenization for all green and barrier-enhanced paper packaging

Paper-based materials made from cellulose have been sought after as a sustainable and inexpensive packaging option. However, the porous structure and high hydrophilicity of paper-based materials result in inadequate water and oil repellency, as well as a limited water vapor barrier. In this work, lignin nanoparticles (LNPs) were prepared using a high-speed homogenizer, and subsequently coated on base paper along with cationic starch to enhance its multi-barrier performance to facilitate the packaging application. The LNPs obtained through such a facile process formed stable colloidal dispersion in water, which exhibited excellent interfacial compatibility with cationic starch. During the coating process, a highly adhesive emulsion consisting of cationic starch and LNPs were coated on the surface of base paper, imparting good hydrophobic properties to the paper. The resulting paper material exhibited good water resistance (Cobb value of 37.5 g m⁻²), high oil resistance (Kit rating 9) and tensile strength (48.93 MPa). The reduction in water vapor transmission rate (WVTR) exceeds sixfold. This study provides a new avenue for the application of lignin in high-barrier, fluorine-free, water-and oil-resistant packaging materials.