Waterborne, fluorine-free self-healing superhydrophobic coating for durable oil‒water separation

Abstract

This study addresses the mechanical fragility, chemical oxidative damage, and environmental concerns of existing superhydrophobic coatings by developing a waterborne, fluorine-free, self-healing superhydrophobic coating. Biomass tannic acid (TA) and nonionic surfactant Triton X-100 are used to non-covalently modify carbon nanotubes (TCNTs), which are incorporated into a waterborne epoxy resin (WEP) matrix as reinforcing fillers to enhance the mechanical robustness of the framework. Together with a waterborne polydimethylsiloxane (PDMS) emulsion and octadecyltrimethoxysilane-modified silica (O-SiO₂), an O-SiO₂/PDMS/TWEP composite coating is constructed. The coating achieves a water contact angle of 158.6° ± 1.3° without fluorinated reagents or organic solvents in the final formulation. It maintains superhydrophobicity over at least ten damage–repair cycles and retains a contact angle of 151.1° ± 1.5° after 300 sandpaper abrasion cycles. When applied to polyurethane sponges, the resulting material exhibits an oil adsorption capacity of 47.11–86.71 g·g⁻¹, an oil–water separation efficiency above 97%, and stable performance after 20 reuse cycles. This work provides a viable strategy for developing waterborne, fluorine-free superhydrophobic materials with improved mechanical durability and repeatable self-healing for oil–water separation.

Graphical abstract

Keywords

superhydrophobic coating / self-healing / mechanical stability / oil–water separation

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