Effects of calcination temperature on the microstructure and wetting behavior of superhydrophobic polydimethylsiloxane/silica coating

The superhydrophobic coating was prepared through spraying the mixture of polydimethylsiloxane (PDMS) and hydrophobic nanosilica (SiO2) on the slide glass. The surface of the as-prepared PDMS/SiO2 coating showed hierarchical roughness with a water contact angle (WCA) of 153 degrees. The resultant superhydrophobic PDMS/SiO2 coating was subsequently calcined in a muffle furnace under air atmosphere and the effects of calcination temperature on the microstructure, component, transmittance, and wetting behavior of superhydrophobic PDMS/SiO2 coating were systematically investigated. With the increase in calcination temperature from 100 degrees C to 400 degrees C, the superhydrophobic PDMS/SiO2 coating became transparent with the visible light transmittance increasing from 40% to 80%, which was ascribed to the decomposition of PDMS and the rearrangement of the hydrophobic SiO2 particles. However, when the calcination temperature was over 500 degrees C, the wetting behavior of the coating changed from superhydrophobicity to superhydrophilicity with a WCA of nearly 0 degrees, owing to the replacement of hydrophobic Si-CH3 groups with hydrophilic groups of Si-OH. Finally, the calcination mechanism of the superhydrophobic PDMS/SiO2 composite coating is proposed, which has guiding significance for the study of other composite coatings. (C) 2014 Elsevier B.V. All rights reserved.