ASSIMILATION OF OIL FROM METAL-SURFACES BY EPOXY ADHESIVES - XPS AND ATR ANALYSES

The oil displacing and absorbing behaviors of epoxy adhesives cured wi th amidoamine curing agents on oiled metal substrates were studied usi ng X-ray photoelectron spectroscopy (XPS) and attenuated total reflect ion infrared spectroscopy (ATR). A simple XPS experiment demonstrated that amidoamine curing agents could displace an aliphatic oil from the cold-rolled steel (CRS) and the electrogalvanized steel (EGS) surface s, but an epoxy resin based on bisphenol A could not. Results of ATR m easurements showed that the oil was effectively displaced from the CRS surface and absorbed as deep as 2 mu m into the epoxy adhesive cured with amidoamine with low amine numbers. But the oil was mostly present in the 0.3 mu m thick adhesive layer near the CRS/adhesive interface for the epoxy adhesive cured with amidoamine with high amine numbers. The oil absorbing ability of the adhesive was worse on the oiled EGS s ubstrate than on the oiled CRS substrate. It was also found that the p ressure applied during cure could greatly facilitate the absorption of oil into the adhesive. (C) 1995 John Wiley and Sons, Inc.