Mechanism of adhesion of the diglycidyl ether of bisphenol A (DGEBA) to the Fe(100) surface

In this study, density functional theory (DFT) calculations were performed to analyze the mechanism of adhesion of the diglycidyl ether of bisphenol A (DGEBA) epoxy on the Fe(100) metal surface. It was found that the flat-lying orientation of the epoxy adhesive on the Fe surface (−5.47 ∼ −5.23 eV) is significantly more stable than the standing-up orientation (−3.42 eV). Through our Bader charge, charge density distribution, and local density of states (LDOS) analyses, we demonstrated that the regions between the hydroxyl group and the aromatic rings of the epoxy adhesive and the Fe surface undergo significant charge accumulation during adsorption owing to charge transfer from the d orbital of Fe to the p orbital of the O atom of the hydroxyl group and the π orbitals of the aromatic rings. Therefore, we conclude that the hydroxyl group and the aromatic ring are the crucial functional groups in the strong adhesion of epoxy adhesives to Fe metal surfaces.