Structure and adsorption characteristics of silane coupling agents on silica and E-glass fiber; dependence on pH

Abstract

Fourier transform infrared spectroscopy was used to study the adsorption of silane coupling agents on silica and E-glass fiber surfaces. The structures of the adsorbed species of γ-aminopropyltriethoxysilane (γ-APS) coupling agent under various preparation conditions are postulated based on an interpretation of the NH deformation and SiOH stretching modes. The amount of γ-APS deposited on high-surface-area silica depends on the pH of the treating solution. On the contrary, the amounts of adsorption of γ-methacryloxypropyltrimethoxysilane (γ-MPS) and vinyltriethoxysilane (VS) coupling agents are independent of pH. The number of adsorbed molecules of γ-MPS and VS is comparable to that of γ-APS only at its acidic pH. The unique adsorption of γ-APS on the silica surface is partly due to the structure of the γ-APS itself in the treating solution. When E-glass fiber is used as the substrate, the amount of γ-APS adsorption in affected by pH but less than observed with silica powder. The structure of γ-APS is affected by the presence of carbon dioxide when the pH range of the silane solution is between 6 and 12. © 1984.