A Fully Plant-Based Water- and Oil-Resistant Paper Composite

Disposable tableware commonly used at gatherings and for takeout has switched from plastic to paper due to concerns about micro- and nanoplastic pollution. Their water and oil resistance are typically achieved by using either per- and polyfluoroalkyl substances (PFAS), which are harmful and persistent in the environment, or plastic coatings, which exacerbate the plastic pollution issue. Hence, safe and ecofriendly water- and oil-resistant materials are a crucial need. Emulating natural plant properties, we applied a seamless lignin film on paper via the hot-pressing method. By varying parameters such as lignin coating weight (10–40 g/m2), hot-pressing pressure (1–5 MPa), temperature (120–180 °C), and moisture content (10–50 wt %) of lignin micro and nanoparticles (LMNP) suspension before hot-pressing, we determined that 40 g/m2 of lignin coating weight applied at 3 MPa pressure, 160 °C temperature, and 30 wt % moisture content are the optimal condition. This yielded a lignin layer with exceptional waterproofing (100 min) and oil resistance (25 min). The paper composite board biodegraded within 56 days in garden soil, thereby providing a promising eco-friendly alternative to nonbiodegradable plastics and PFAS.