Thermogravimetric analysis (TGA) and high-performance liquid chromatography (HPLC) have been used to investigate the adsorption behavior at an interface: between an epoxy and a silica surface. Consistent with an earlier report. the results confirm that the adsorption constant of the amine hardener (Jeffamine T-403) is greater than that of the resin (Dow DER-337). It was also found that nonpolar silica materials functionalized with C-18 groups and end-capped with alkylsilanes behave as though they have distinct regions of polar and nonpolar adsorption character. While this changes the net behavior of the surface so that it more evenly adsorbs both components of the epoxy premix, it does so by reducing the overall strength of adsorption between the components and the surface.