Solvent-dependent adsorption of phenolic resin onto silica substrate

The solution impregnation route is commonly exploited to prepare polymer-based composites. However, the adsorption of polymer components is complicated, which is the result of interactions between reinforcement, solvent and polymer. In this study, the adsorption of phenolic resin onto silica substrate from different solvents was investigated by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, UV-visible absorption spectroscopy and thermogravimetric analysis (TGA). Isotherms for phenolic resin adsorption from solvents onto silica substrate have been examined as a function of phenolic resin content in different solvents. The viscosity and surface tension were measured for the solution systems before and after adsorption. Hydrogen bonding interaction was considered to be operative in the resin-solvent-silica system. The adsorption of phenolic resin is dependent on its relative affinity for the solvent on one hand and for the silica surface on the other. UV-visible absorption spectroscopy results suggested that phenolic resin forms hydrogen bonds with the solvent, which competes with the hydrogen-bonding adsorption mechanism for phenolic resin occurring on silica surface. This hydrogen bonding in solution along with the competitive adsorption of solvent onto silica surface suppresses the adsorption of phenolic resin and such suppression is unfavorable in a solution impregnation process.