AN XPS STUDY OF THE STEEL-AROMATIC MOISTURE-CURED URETHANE INTERFACE

The surface of an aromatic moisture-cured urethane (ArMCU) and the steel-ArMCU interface have been studied using XPS. Study of the interface after failure showed that iron was present in the polymer and nitrogen from the ArMCU was detected on the steel surface after failure. This suggests a failure within a chemical interphase formed at the steel-ArMCU boundary, the -N = C = O group from ArMCU reacting with the hydroxylated metal surface to yield a surface carbamate (-NH-CO-OFe). Another possible interaction between steel and ArMCU is via the C-O and C-N carbon types, but this is unlikely on the basis of the XPS evidence presented. On the other hand, although no modification of the ArMCU surface on cure by moisture was detected by XPS, this technique is useful for studying the ageing of the material. In this case, decarboxylation of the urethane group was shown to be a possible reaction at the surface.