A robust, fluorine-free and economical superhydrophobic coating based on rosin, shellac, and calcium carbonate nanoparticles

Fluorides and long-chain aliphatic hydrocarbons are commonly used low surface energy compounds in superhydrophobic coatings. However, the potential toxicity of the former and the instability of the latter restrict the practical application of superhydrophobic coatings. In this study, a sustainable and environmentally friendly natural superhydrophobic coating was developed. This coating incorporates natural shellac and rosin to reduce surface energy and enhance adhesion, followed by the application of calcium carbonate nanoparticles (CaCO₃ nanoparticles) to modify white cardboard (WCB). Superhydrophobic white cardboard (SWCB) was successfully prepared. The water contact angle (WCA) of the coating is 155.3 ± 2°. SWCB exhibits excellent durability, retaining superhydrophobicity after 50 abrasion cycles, 45 tape stripping cycles, 30 min water impact, 30 knife strokes, and 7 days of outdoor exposure. It also demonstrates excellent self-cleaning properties, effectively repelling powders that mimic contaminants. In addition, when the coating is applied to paper cups, the paper cups exhibit excellent anti-adhesion properties. Therefore, this environmentally friendly superhydrophobic coating could offer a potential new approach to paper antifouling and food packaging.