MICROSCOPIC FT-IR STUDIES OF EPOXY ADHESIVE FILMS ON CHEMICALLY TREATED ALUMINUM

Microscopic reflection-absorption FT-IR spectra were obtained on epoxy adhesive films on treated and untreated aluminum. Compositional differences were observed across the interphase. The epoxy on the untreated Al showed a large amount of the curing agent and its salt form near the surface relative to the bulk. In the case of the anodized Al surfaces, less curing agent was found, along with a relatively large amount of unreacted epoxy. An additional carbonyl band was found in the untreated Al sample, probably due to reaction of the curing agent with surface water. These results indicate that the surfaces are inducing selective adsorption, leading to differences in the composition of the cured adhesive bond.