Sustainable Water- and Oil-Repellent Coating for Disposable Meal Boxes Based on Highly Deacetylated Chitosan

To mitigate the serious environmental impact caused by the persistent accumulation of plastics, replacing conventional plastics with paper-based alternatives has emerged as a promising trend. In response to the environmental and health concerns associated with petrochemical-based plastic meal boxes and fluorinated water- and oil-repellent agents, this study proposes a sustainable, fluorine-free coating technology based on chitosan to enhance the water and oil resistance of molded-paper pulp meal boxes. By adjusting the degree of deacetylation and the solution concentration of chitosan, coated meal boxes were fabricated via a spraying method. The results demonstrate that coatings prepared with highly deacetylated (>95%) and concentrated (4% <i>w</i>/<i>v</i>) chitosan significantly improve barrier properties, achieving a water contact angle of 114.9° ± 3°, the highest oil-resistance rating (12/12) according to TAPPI standards, and stable resistance to 95 °C hot oil for up to 30 min without leakage. In addition, the coated samples exhibit enhanced mechanical strength (21.26 MPa) and excellent biodegradability. This work provides a cost-efficient and eco-friendly disposable food packaging solution, facilitating the sustainable substitution of petrochemical-based plastics.