Investigations on the use of nanoclay for generation of superhydrophobic coatings

• Nanoclay Cloisite® used for generation of superhydrophobic coatings
• Water contact angle of 170° achieved by heat treatment at 250 °C
• Low sliding angles obtained for nanoclay based superhydrophobic coatings
• Nanoclay based pigmented superhydrophobic coatings studied and found promising
• Environment friendly, cost-effective superhydrophobic coatings demonstrated

Organically modified layered silicate nanoclay particles were dispersed into a sol–gel silica matrix to obtain a formulation for generating a superhydrophobic coating. Dimethyldiethoxy silane, tetraethoxysilane and hexamethyldisilazane were used as precursors. Commercially available organically modified montmorillonite clay, Cloisite® 25A was used as the source of nanoclay. The loading of Cloisite® into the hybrid silica sol was varied and coatings were generated by dip coating technique on soda lime glass substrates. Heat treatment was carried out in air at 250 °C for 2 h. In some cases, spray coating was also employed and pigmented coatings were deposited on aluminum substrates and cured using the same conditions as employed for coatings generated using dip coating. Coatings were characterized for their transmittance, haze, thickness, water contact angles, surface morphology using scanning electron microscopy, atomic force microscopy and resistance to weathering. The present investigation explored for the first time, a pathway towards practical applications of nanoclay dispersion in silica matrix for generation of environmentally friendly superhydrophobic coatings in a cost effective manner. Water contact angles as high as 170 ± 2° could be generated using optimized compositions and heat treatment conditions of sol and nanoclay fillers.