Determination of Dispersive Properties of Silicas by Inverse Gas Chromatography: Variation with Surface Treatment

Abstract

The application of inverse gas chromatography (IGC) to the examination of the surface properties of untreated crystalline and fused silica and surface-treated silicas with silane coupling agents is discussed. The carbon content of the silane coupling agents adsorbed on the surface of the silicas was determined by means of a Carbon Determinator. If the assumption is made that each silane coupling agent molecule occupies an area of 0.5∼1 nm 2 , the adsorption amounts show that multilayers are generally adsorbed onto the silica surfaces. This paper presents and discusses the dispersive properties expressed by γ D S , the dispersive component of the surface free energy, as determined at various temperatures. At the same temperature of IGC measurement, the values of γ D S determined by IGC were lower for the crystalline silica than for the fused silica. This means that crystalline silica is more stable than fused silica. The silica surface-treated with γ-methacryloxy propyl trimethoxy silane (MTMS) shows a relatively high γ D S value(42.75 mJ·m -2 at 160°C). This means that this sample should be compatible with polyester(27 ± 3 mJ·m -2 at 290°C) at high temperature. The silicas that were surface-treated with γ-glycidoxy propyl trimethoxy silane (GMS) and γ-mercapto propyl trimethoxy silane (MCMS) exhibit γ D S values that are in close agreement with those of almost all resin(30mJ·m -2 at 160°C). The γ D S value of the silica surface-treated with γ-amino propyl triethoxy silane (AES) is similar to that of epoxy resin(40mJ·m -2 at 80°C). This means that this sample is compatible with epoxy resin at relatively low temperatures.