Preparation of superhydrophobic coating films using silica nanoparticles and trimethylethoxysilane

Superhydrophobic coating solutions were prepared using fumed silica nanoparticles and trimethylethoxysilane (TMES) as precursors. At this time, the surface of silica nanoparticles was modified by TMES from hydrophilic to hydrophobic in various types of catalysts and organic solvents. The prepared coating solutions were coated on a cold rolled steel sheet by using a spin coater, and then superhydrophobic coating films were prepared by thermal curing. In this process, the effects of the amount of silica nanoparticles added, the type of catalysts, and the type of organic solvents were observed on the hydrophobicity of the coating films. As the content of silica nanoparticles added increased from 0 g to 0.08 g, the contact angle of the coating films increased from 93 degrees to 151 degrees, and when 0.08 g of silica nanoparticle was added, it showed superhydrophobicity of 151 degrees. On the other hand, when nitric acid and hydrochloric acid, strong acids, were used as catalysts, the coating films showed low hydrophobicity of 73 degrees and 86 degrees, respectively. However, when oxalic acid, a weak acid, was used, the coating film showed superhydrophobicity of 151 degrees. In addition, with methanol as an organic solvent, the coating film showed superhydrophobicity of 151 degrees, while when i-propanol and n-butanol were used, the coating films exhibited low hydrophobicity of 97 degrees and 91 degrees.