Surface OH group governing wettability of commercial glasses

X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and c ontact angle measurements are applied to investigate the relationship betwe en the wettability and the surface OH group density of various commercial g lasses. The contact angle of water droplets has been measured for the glass as a function of elapsed time. The hydrophobicity, resulting from the adso rption of organic substances in the atmosphere, is different among the glas ses and is dependent on the surface OH group density of the glass. These fa cts indicate that the surface OH group density is a major factor governing the wettability of the glass surface. Furthermore, there is a linear correl ation between the OH group density and silicon concentration at the surface except for the bottom face of float glass. This fact indicates that the fo rmation ability of the surface OH group depends on the surface silicon conc entration, and the majority of the surface OH groups consist of SiOH groups . For the bottom face of float glass, the formation ability of the surface OH group is affected by the tin which penetrates into the surface as a resu lt of direct contact with the molten tin bath. (C) 1999 Elsevier Science B. V. All rights reserved.