ATR ANALYSIS OF THE OIL-ABSORPTION ABILITY OF A 2-PART EPOXY ADHESIVEON OIL-CONTAMINATED METAL SUBSTRATES

The oil absorption behavior of a room-temperature-cured, two-part epox y adhesive on three metal substrates, cold-rolled steel (CRS), 2024-al uminum, and electrogalvanized steel (EGS), was studied using attenuate d total reflection infrared spectroscopy (ATR). From relative absorban ce ratios calculated from ATR spectra taken at different penetration d epths, it was determined that the effectiveness of the adhesive in rep lacing the oil from the metal surfaces followed in the order of 2024-A l > CRS > EGS. As thick as 20 microns oil could be absorbed from the 2 024-Al and CRS surfaces, but much less oil could be absorbed from the oiled EGS substrate. However, the heat applied during cure could great ly help the adhesive absorb oil from the EGS substrate. Distributions of adhesive functional groups with respect to penetration depths were found in adhesive layers adjacent to metal surfaces. The abundance of curing agents in the adhesive/EGS interfacial region resulted in the i ncomplete oil absorption observed on the oiled EGS substrate. The resu lts from ATR also showed that the oil did not inhibit the cure of the adhesive in the bulk. (C) 1994 John Wiley & Sons, Inc.