Epoxy/aluminum interphases

The interactions between an epoxy/dicyandiamide adhesive and chemically treated aluminum surfaces were studied using Fourier Transform Infrared Spectroscopy (FTIR) microscopy and Nuclear Magnetic Resonance Imaging (NMRI). Applying these techniques in a concerted way provided answers to several key questions related to the phenomena of adhesion.;FT-IR was used to characterize the surfaces of Al after various chemical treatments. All of the oxide surfaces were composed of anhydrous alumina, aluminum oxyhydroxide and aluminum hydroxide. The major contaminants found in the different oxides are chemisorbed CO;Microscopic reflection-absorption FTIR spectra obtained from epoxy adhesive films on treated and untreated aluminum samples showed compositional differences normal to the interphase. The results indicate the surfaces induce selective adsorption depending on the surface treatment.;NMRI was used to analyze the curing behavior of epoxy adhesives in the presence of anodized and chemically treated aluminum surfaces. The proton images of the epoxy for the untreated Al samples images are characterized by a variety of inhomogeneities (fine texture of uncured and cured domains) finely distributed throughout the sample. Large uncured domains of epoxy were found aggregated near the center of the bonded adhesive sample. Diffusion of uncured material was observed during the curing process. The anodized aluminum/epoxy samples, on the other hand, showed very small contrast and coarse texture images characteristic of phase separation phenomena. However, the onset of curing was clearly shown with increases in contrast and texture. Large amounts of uncured material were seen near the surface indicating the anodized surfaces influence the curing behavior of the adhesive near the interface. This effect was more pronounced in the CAA/epoxy samples. (Abstract shortened by UMI.).