Investigation of the rubber-metal bonding system by means of analytical electron microscopy and comparison with results of technical tear strength measurements

During vulcanization of sulfur-cure mixtures in contact with brass, a bonding layer consisting of sublayers of copper and zinc sulfides and oxides is formed. As the chemical composition and structure of the layer are decisive for good adhesion. the rubber to brass bonding was investigated using an analytical electron microscope (AEM) coupled with an energy dispersive X-ray (EDX) detector. Sublayers were found in the bonding layer between rubber and brass. Different crystallographic phases were identified in an etched bonding layer by electron diffraction. Technical tear strength measurements were carried out using rubber-brass-rubber samples, showing correlations with the electron microscopic investigations. This method is a new approach to the rubber-metal bonding (adhesion) problem.