Waterproof and wet-strong cellulose paper via synergistic maleic anhydride/epoxidized soybean oil modification

Developing cellulose paper that is both waterproof and mechanically robust under wet conditions remains a key challenge for sustainable packaging. Herein, a green and synergistic modification strategy is proposed to simultaneously enhance the water resistance and wet mechanical strength of cellulose paper via a solvent- and catalyst-free two-step process. Maleic anhydride (MAH) is first grafted onto cellulose fibers, followed by in situ ring-opening crosslinking of epoxidized soybean oil (ESO), constructing a dense covalently bonded hydrophobic network within the fiber matrix. As a result, the modified paper exhibits excellent waterproof performance, with a high water contact angle of 118° and a low Cobb value of 30.8 g/m 2 after 1 h. Notably, it retains a high dry tensile strength of 49.6 MPa and achieves a wet tensile strength of 20.8 MPa, approximately 30 times higher than that of untreated paper. In addition, the paper demonstrates enhanced thermal stability, nearly complete biodegradation within 100 days in soil burial tests, and confirmed safety based on residual MAH analysis. This work provides an effective and sustainable strategy for developing high-performance, fully biodegradable cellulose-based alternatives to conventional plastics.