THE THERMAL-OXIDATIVE DEGRADATION OF AN EPOXY ADHESIVE ON METAL SUBSTRATES - XPS AND RAIR ANALYSES

The thermal oxidative degradation of a commercial epoxy adhesive on interstitial free steel (IFS), 2024 aluminum (2024-Al), and copper (Cu) substrates has been studied using reflection absorption infrared spectroscopy (RAIR) and X-ray photoelectron spectroscopy (XPS). The epoxy films, which were spun-coated onto the metal surfaces, were exposed at 150 degrees C and analyzed periodically. From the relative intensities of the generated amide, carbonyl, and para-substituted phenolic IR bands, it was concluded that the degradation rate of the epoxy resin on metal substrates followed in the order of Cu > IFS similar to 2024-Al. From curve-fitting of the XPS C(1s) spectra, it was evident that carboxyl and carbonate species, which could not be detected in RAIR spectra, were formed on the most severely degraded epoxy surface, i.e. in the epoxy resin degraded on the Cu substrate. The loss of materials after 90 h exposure at 150 degrees C was also confirmed by both RAIR and XPS analyses.