A study of the adhesion of thiokol-epoxy hermetics to a brass and an aluminum alloy substrate

The conditions under which hermetics can be used depend largely on the nature of the bond between the polymer and the substrate. Here we have studied the thiokol-epoxy compositions and have investigated the processes taking place at the interface between the hermetic and a brass or an aluminum alloy substrate. To establish the nature of interfacial interactions electron spin resonance (ESR) spectroscopy was utilized. The ESR spectrum of the species from the interface layer is assigned to a bivalent copper ion complex, sulfur-containing fragments being the ligands. The ESR signal intensity of the complex was maximum for the case of the brass substrate and minimum for the aluminum alloy substrate; no spectrum was detected for the glass substrate or for the bulk hermetic. The dependence of the ESR signal intensity on the free sulfur content in the hermetic was found to be opposite to the dependence of the adhesion values.