XPS analysis of the interphase between an anaerobic adhesive and metal substrates

Abstract

AbstractX‐ray photoelectron spectroscopy (XPS) has been used to study the interphase between a model anaerobic adhesive system composed of triethylene glycol dimethacrylate monomer (TRIEGMA) and a curing system consisting of cumene hydroperoxide (CHP), acetylphenyl hydrazine (APH) and saccharin (BS), and the substrates copper, iron, zinc and aluminum. Miniature cantilever beam specimens were prepared by curing beams of the adhesive against beams of the metal substrates. The specimens were then immersed in liquid nitrogen, causing the adhesive to delaminate from the substrate. XPS spectra obtained from the adhesive failure surfaces were very similar to spectra obtained from the bulk adhesive, containing peaks corresponding to carbon, oxygen and trace amounts of sulfur and nitrogen. However, the spectra also contained peaks due to trace amounts of metal or metal ions from the substrate. Spectra obtained from the substrate failure surfaces were very different from those of the corresponding adhesive failure surfaces and contained peaks due to higher concentrations of metal or metal ions and higher concentrations of nitrogen and sulfur, indicating that failure was near the interface and that both BS and APH segregated to the interface. C 1s multiplex spectra obtained from thin films of BS spin‐coated from dilute solutions onto iron, copper and zinc contained a weak component shifted from the main hydrocarbon peak to higher binding energy by ∼3.1 eV. This was more similar to the shift observed from the hydrated sodium salt of BS (Δ2.9 eV) than neat BS (δ3.7 eV), indicating that BS readily forms a complex with these substrates. When a copper foil was placed in a solution of BS and analyzed periodically in XPS, peaks due to Cu(I) were initially observed in the Cu 2p spectra, but peaks due to Cu(II) appeared after ∼110 h. The Cu(II) BS complex was also observed when a blue powder, which precipitated when a copper foil was placed in a solution of BS in methanol, was analyzed. Spectra obtained from aluminum (which does not catalyze the polymerization of the anaerobic adhesive as well as copper or iron) did not show the formation of a BS‐metal complex in any of the samples studied.