EFFECT OF SILANES ON THE INTERFACIAL COMPOSITIONS OF EPOXY METAL ADHESIVE BONDS - XPS AND RAIR ANALYSES

The effects of silanes on the interfacial compositions of adhesive bon ds formed by curing silanes with the epoxy/amidoamine adhesive against clean and oiled cold-rolled steel (CRS) and electrogalvanized steel ( EGS) substrates are studied using x-ray photoelectron spectroscopy (XP S) and reflection absorption infrared spectroscopy (RAIR). Silanes use d are N-(2-aminoethyl)-gamma-aminopropyltrimethoxy silane (gamma-AEAPS ), gamma-glycidoxypropyltrimethoxysilane (gamma-GPS) and gamma-mercapt opropyltrimethoxysilane (gamma-MPNIS). The XPS results show that the a ddition of silanes to the adhesive increases the number of C-O bonds a nd decreases the N/C ratios in the resins of the interfacial regions. The addition of silane could help the adhesive bond with the oiled sub strates. The RAIR results confirm that adding various silanes to the a dhesive can change the compositions in EGS/adhesive interfaces differe ntly and affect the preferential adsorption of amino groups from the a dhesive on the EGS surface. Silanes can also increase the protonation of amino groups in the adhesive on the clean and the oiled CRS surface s. However, the absence of protonated amino groups in the adhesive/EGS interfaces indicates that the protonation is metal dependent. X-ray p hotoelectron spectroscopy detects two S 2p species in the bonding inte rface of the specimen prepared using gamma-MPMS-added adhesive cured a gainst EGS substrate. The higher binding energy S 2p is attributed to the chemical reaction of mercapto groups in the gamma-MPMS with the zi nc surfaces.