Nanostructured surfaces
UV stability of superhydrophobic surfaces
Baklan D.1, Myronyuk O.1, Wang W. 2, Yevpak V. 1, Raks V.3
1 Igor Sikorsky Kyiv Polytechnic Institute, Peremogy Ave., 37 b.21, Kyiv-03056, Ukraine E-mail: d.baklan@kpi.ua
2 School of Materials Science and Engineering, Ocean University of China, Qingdao 266100, China 
3 National Taras Shevchenko University of Kyiv, 60, Volodymyrska str. Kyiv-01601, Ukraine

The practical use of superhydrophobic coatings in atmospheric conditions is limited by environmental factors, particularly by the photo-oxidation. Unlike in case of usual organic and polymer materials, the substance subjected to the destruction is located at the surface of the texture-forming inorganic material [1] in thin layers. This study was focused on the determination of free surface energy change of superhydrophobic micro-nano structured surfaces under ultraviolet light irradiation.
The UV irradiation was carried out using UV(B) lamp (peak intensity - 313 nm), combined with water cooling of the surface [2]. The radiation dose was equivalent to 3-60 month range of natural conditions exposure. The surface energy determination was based on Owens-Wendt approach using testing liquids contact angles, which were determined in turn by sessile drop technique.
The aliphatic and flouoro-based hydrophobizers showed higher UV stability than those containing aromatic rings, as it was expected from absorption spectra. The same situation with the binders: aliphatic polyurethanes and acrylic resins shown better performance than aromatic PU and epoxies. It was also found that an effect of the substrate was significant: on the silica surfaces thin films were 2-2,5 times more stable than on the carbonate ones.

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2.	Yousif E., Haddad R. Photodegradation and photostabilization of polymers, especially polystyrene: review // SpringerPlus.-2013.-2(1).-P. 398.