Molecular Understanding of the Adhesive Force between a Metal Oxide Surface and an Epoxy Resin: Effects of Surface Water

Abstract

A mechanism of the adhesion interaction between an aluminum oxide surface and an epoxy resin is investigated by using density-functional-theory (DFT) calculations. To understand effects of adsorbed water molecules on the adhesion interaction, hydroxylated aluminum oxide surfaces with adsorbed water molecules are prepared. Geometry optimization is performed for a model of adhesiveadherend complex, which is comprised of a fragment of epoxy resin and a wateradsorbed aluminum oxide surface. DFT calculations demonstrate that hydroxy groups and ether groups of epoxy resin can interact with the adherend surface via a hydrogen-bond network of adsorbed water molecules, which leads to a critical factor in the adhesion interaction. 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 forcedistance curve, which is obtained from the derivative of the potential energy curve. Obtained results demonstrate that the hydrogen-bond network via adsorbed water molecules significantly affects the adhesion mechanism. The adsorbed water molecules provide a long-distance adhesion interaction but exert little influence over the maximum value of the adhesion force.

One-dimensional nanowires of pseudoboehmite (aluminum oxyhydroxide γ-AlOOH)

“…The water molecules can act as adhesive agents for connecting Al-O octahedral double-sheet layers of the PB nanoribbon as shown in Fig. 1 B and E. Similar adhesion effects of water molecules between a γ-alumina surface and an epoxy resin were also found (20). The DFT results clearly indicate the influence of intercalated water molecules in enhancing interlayer spacings of PB nanoribbons, which provide a hint to understand the splitting observed in the TEM results.…”

Molecular understanding of the adhesive interactions between silica surface and epoxy resin: Effects of interfacial water

“…Computational simulations at the molecular level will provide a better insight into the intermolecular forces acting at the adhesion interface. Recent computational studies have revealed the importance of hydrogen bonding in the adhesion of polymer–metal (metal oxide) interfaces and polymer–graphite interfaces under atmospheric or wet conditions . We have theoretically investigated adhesion interactions in the epoxy resin–aluminum oxide interface and the epoxy resin–graphite interface, [22,23] both of which are important from the viewpoint of industrial applications and surface science .…”

“…For a better modeling of the interfacial adhesion between polymer adhesives and hydrophilic adherend surfaces, it is essential to consider water molecules located in the adhesion interface under atmospheric conditions. There are quite limited computational studies that treated the moisture‐induced weakening of adhesion at the molecular level . Ogata and Takahashi have analyzed the moist‐induced reduction of adhesion strength between hydroxylated aluminum oxide surface and polymer of epoxy resin in the presence of interfacial water molecules using the hybrid quantum‐classical method .…”

“…Their large‐scale calculations reasonably reproduced that the shear strength of the interfacial adhesion is significantly reduced as a degree of moisture content increases. We previously performed periodic DFT calculations to shed light on the molecular mechanism of the adhesion between epoxy resin and aluminum surface, where the surface was modeled by aluminum oxide covered with OH groups . Calculated adhesion energies and forces suggest that water molecules adsorbed on hydrophilic aluminum oxide surface have significant effects on the interactions at the adhesion interface.…”

Nature of the adhesion bond between epoxy adhesive and titanium

“…The generally accepted standpoint is that the oxide on a metal sur face forms chemical or hydrogen bonds with adhesive molecules [1][2][3]. In this case, the thickness of the boundary layer between the adhesive and the oxide should be about 1 nm.…”