The effect of composite interface morphology on wetting states for nanocomposite superhydrophobic coating

Abstract

This paper focuses on the effect of composite interface morphology on the wetting behavior of a nanocomposite coating based on an organosilane binder. Experimental results supported by modeling demonstrated that a sharp change in contact angle hysteresis occurred at air fractions in the range of 40–60%, as controlled by particle loading. The air-liquid interface evolution with particle loading was visualized using the fluorescent dye staining method. A correlation between topography and this air-liquid-solid interface was done by overlapping the optical images and fluorescence dye stained images of the stained superhydrophobic surface, which allowed the visualization of microscale features. The results showed the structures supporting solid-liquid contacts were 20 to 40 μm in size and had an edge-to-edge spacing that decreased with increasing particle loading. In this system a critical spacing to transition from the Wenzel to the Cassie-Baxter state was found to be approximately five times the average width of these microscale structures. Identification of critical surface topography can aid in the development of coatings that provide anti-corrosive and/or anti-icing features for marine vessels, bridges, and buildings.