Rubber-to-metal bonding by silanes

This paper deals with the bonding of sulfur-vulcanized rubber compounds to metals. It had previously been reported that bis-(triethoxysilyl)ethane and vinyltriethoxysilane were found to work for bonding peroxide-cured rubber compounds to metals. These silanes were found not to work with sulfur-cured rubber compounds. In this case, a mixture of bis-(trimethoxysilylpropyl)amine and bis-(triethoxysilylpropyl) tetrasulfide was found to work and results are presented of experiments in which brass, steel, and electrogalvanized steel were bonded to a typical tire cord skim compound with and without a cobalt additive. This new silane treatment was found to be as effective as or better than brass adhesion to cobalt-containing rubber compounds. The superior corrosion protection offered by the silanes was also demonstrated using DC corrosion and polarization resistance measurements. The silane process reported in this paper behaves almost similarly with all metal substrates. In this paper, the structure of the silane film on a metal substrate is studied and a model is proposed for a possible mechanism of the adhesion of rubber compounds with silane-coated metals.