Molecular understanding of the adhesive force between a metal oxide surface and an epoxy resin

A mechanism of the adhesion between an aluminum oxide surface and an epoxy resin is investigated by using density functional theory (DFT) calculations. Force field simulations are carried out for a better understanding of the dynamic behavior of the resin on the surface and for constructing models for DFT calculations. Stable structures of a resinsurface complex, adhesion energies, and details about interaction sites are obtained from geometry optimizations for some models based on DFT calculations with a plane-wave basis set and periodic boundary conditions. DFT calculations reveal that hydroxyl groups of the epoxy resin interact with the surface of aluminum oxide to form hydrogen bonds, which work as a main force for the adhesion. Plots of energy versus vertical distance of the resin from the surface are nicely approximated by the Morse potential. The force required for detachment of the resin from the surface can be estimated from the maximum value of the force-distance curve, which is obtained from the derivative of the potential energy curve. Obtained results demonstrate that hydrogen bonds play a central role for the adhesion between an aluminum oxide surface and an epoxy resin.