X-RAY PHOTOELECTRON MICROSCOPY APPLIED TO METAL EPOXY LAMINATES

In this article we describe the application of x-ray photoelectron microscopy to an industrial epoxy laminate. Cold rolled steel and galvanized steel bonds of an epoxy/dicyandiamide adhesive were studied by lap-shear strength measurements; the fracture surfaces of the sheared coupons were subsequently examined by x-ray photoelectron microscopy and x-ray photoelectron spectroscopy. X-ray photoelectron microscopy allows one to identify the lateral distribution of chemical elements and to distinguish between particulates (silicate filler), adhesively failed regions, and bulk epoxy material with a resolution of 10-mu-m. Areas selected in the microscopy mode were then analyzed by x-ray photoelectron spectroscopy to get information on the local interfacial composition. We find that a reaction between dicyandiamide and the zinc-oxide surface leads to diffusion of molecular zinc complexes into the polymer matrix when the bonds are aged for 14 days in a saturated water vapor environment at 70-degrees-C. No significant decrease in bond strength is induced by the aging process.