Mississippi State University,
Keywords: metal ion modification, Hydrophobic, Paper, Tableware, Packaging
Summary:Lignocellulosic paper is a crucial solution for preventing the increase in plastic packaging wastes; however, the inherent hydrophilicity and poor water resistance impede its practical applications. Here, we report a facile metal-ion-modification approach (i.e., metal cation solution swelling and drying) for converting conventional hydrophilic, low-wet-strength lignocellulosic paper to hydrophobic and water-resistant paper with high wet strength. During this process, metal cations (i.e., Fe3+, Al3+, and Zr4+) coordinate with pulp fibers’ polar groups (i.e., -OH, C=O, and COOH) that induce self-assembly of their surface “hairy” cellulose nanofibrils to form a more compact structure with less available –OH groups, thereby decreasing their surface energy and increasing their hydrophobicity and water resistance. The resulting hydrophobic paper exhibit a water contact angle of up to 140°, good wet tensile strength of up to 9.5MPa, and a low water absorptiveness of < 10 g/m2, which are comparable to synthetic polymer films. Only 0.4 wt% of Fe3+ or Zr4+ cations are needed to endow the conventional unsized Kraft packaging paper with hydrophobic properties. Because of the low metal content and the stable metal-lignocellulose coordination interactions, the metal cation leaching from hydrophobic paper during solvent washing is neglectable. And the paper remains hydrophobic after long-term ambient condition storage and solvent wash. Furthermore, the hydrophobic paper is biodegradability. Additionally, the metal-cation-modification approach also can be used for pulp modification for preparing hydrophobic tableware.