Development of Superhydrophobic by Solgel route

A.S. Khanna, R. Grover
Indian Institute of Technology, Bombay, IN

Keywords: sol-gel coatings, inorganic-organic hybrids, hydrophobic coatings

Summary:

Generation of super-hydrophobic surfaces is one of the important requirements for many industrial applications. The effect is mimicked as lotus effect, means the surface is unable to be wetted by water. Though, there are several routes to make super-hydrophobic surfaces, the present work describes the use of waterborne inorganic-organic hybrid coatings using sol-gel route. When a simple tetra-methoxy silane was reacted with an epoxy silane, followed by its cross-linking by an amine, it resulted in a sol which when applied on a metallic/glass or plastic surface, formed a thin coating, 5-10 micron. However, such a coating was not hydrophobic. It had a contact angle of less than 70 degree. In order to make it super-hydrophobic, its contact angle was enhanced to 127 degree. The results show various methods to enhance the contact angle. Approaches used were, addition of various fluoro-silanes, nano-zinc oxide, pre-cleaning and etching and non-fluoro approach. Using these approaches, either alone in combination, helped us to achieve a contact angle of 125 degree. The studies involved the use of various analytical techniques such as FTIR, TG/DSC, SEM/EDAX, AFM and performance evaluation for Corrosion, hydro-phobicity, UV blocking etc. It was found that optimum concentration of nano-particle helps in achieving best hydro-phobicity.