Preparation and application of biomimetic superhydrophobic silica and polyurethane composite coating

A nanosilica (SiO2)/polyurethane (PU) micro-nanocomposite coating with similar surface structure as a lotus leaf was prepared using a simple spraying process via a biomimetic method. In this process, SiO2 and organosilicon-modified PU were used as raw materials, and ethyl acetate was used as a dispersing agent. The formation mechanism and structural characteristics of the coating were analysed. The coating surface was also characterised via scanning electron microscopy. The influence of the contents of SiO2, PU, organosilicon on the coating surface structure and contact angle (CA) was studied and the coating was applied to the surface of different materials. The results showed that the coating surface had a similar micro-nanostructure as the lotus leaf surface. The mass ratio of SiO2 and PU was between 4:5 and 3:5. When the content of organosilicon was greater than 15%, the water CA of the coating and sliding angles were 158 degrees and 3 degrees, respectively. The prepared SiO2/PU micro-nanocomposite coating had superhydrophobic properties.