Development of natural wax based durable superhydrophobic coatings

In the present work, environment friendly non-fluorinated superhydrophobic composite coatings were developed using naturally available carnauba wax from palm tree, Copernicia prunifera. The hierarchically structured coating morphologies were composed of micro-scale protrusions along with submicroscopic pores (non-composite) and protrusion (composite). The hierarchically structured carnauba wax coatings showed extreme de-wetting with superhydrophobicity (θ > 150°) and low hysteresis (<5°). In contrast, the other mineral and animal waxes showed mild hydrophobic behavior with high hysteresis (>10°) owing to flat morphology. These peculiarities in morphology and hence de-wetting properties are related with the viscosity differences. Further, the composite wax coating also showed high resilience to simulated rain and weathering due to high roughness and mechanical strength. The composite wax showed high ultimate strength (14 MPa) and elastic modulus (427 MPa) than the non-reinforced wax (8.8 MPa and 97 MPa, respectively). The results showed that composite carnauba wax coatings provide an effective and environment friendly solution for developing superhydrophobic self-cleaning surfaces.