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The specific component of the free energy of adsorption, ÀÁG SP A , of untreated crystalline and fused silica, and four types of silane coupling agents-treated fused silicas, were estimated by the inverse gas chromatography (IGC) method, using the adsorption of several polar and nonpolar probes on their surfaces at various measuring temperatures. The acid-base properties of the untreated and surface-treated silicas were quantified by their K A and K D parameters, reflecting the ability of the surface to act as an electron acceptor and donor, respectively. Acidic components were detected on the untreated crystalline and fused silica surfaces, but the surface properties of the fused silicas surface-treated with -glycidoxy propyl trimethoxy silane (GMS) and -amino propyl triethoxy silane (AES) were slightly basic, and those of the fused silicas surface-treated with -methacryloxy propyl trimethoxy silane (MTMS) and -mercapto propyl trimethoxy silane (MCMS) were amphoteric.

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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 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 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 -methacryloxy propyl trimethoxy silane (MTMS) shows a relatively high D S value(42.75 mJÁm À2 at 160 C). This means that this sample should be compatible with polyester(27 AE 3 mJÁm À2 at 290 C) at high temperature. The silicas that were surface-treated with -glycidoxy propyl trimethoxy silane (GMS) and -mercapto propyl trimethoxy silane (MCMS) exhibit IntroductionSilica has a broad variety of applications in industry. Silica has been treated with surface-modifying agents to obtain improved dispersibility, mechanical and electrical properties, water resistance and reinforcement in plastics systems.1) In this study, we used silane coupling agents as surfacemodifying agents for silica.The mechanical performance of a composite material strongly depends on the properties of the filler-matrix interface and, in particular, on the level of adhesion between the matrix and the reinforcing filler. The level of adhesion is determined by the surface energies of both adherents. The surface free energy, which describes the interaction potential of a given surface, has two components: the dispersive component originating from dispersive or London interactions, and the specific component due to all other types of interactions.Inverse gas chromatography (IGC) at infinite dilution conditions may be successfully applied to the determination of the surface properties of various solids.2) IGC allows the detection of the solid surface properties, using molecules of known properties, or probes, which are injected into a chromatographic column filled with the solid of interest.In this study, we chose IGC for the detection of the possible differences in the D S values of untreated crystalline and fused silica and silicas surface-treated with silane coupling agents. The IGC results are reported in this paper. Theory of inverse gas chromatography (IGC) atinfinite dilution In IGC under infinite dilution conditions, the retention volume V N is computed from the following expression (1):where t R is the retention time of the probes, t 0 the zero retention time measured with a nonadsorbing probe such a...