Rubber-metal bonding as an electrochemical process

Rubber-brass bonding during vulcanization has already been previously discussed as a result of ionic reaction mechanisms. If electrically charged species (e.g. metal and sulfide ions) are formed, the bonding process should be influenced by an electric field. An experimental set-up for the application of a voltage during vulcanization and the preparation of test specimens for bonding strength measurements is described. Electric conductivity is brought about by the carbon black component. Indeed, experiments with SBR mixtures/brass show that an electric field influences the bonding process and that under suitable conditions an improvement of the bonding strength is observed. Unexpectedly rubber-metal bonding is also observed with NR mixtures/aluminium (alloy with 5% silicon) when a voltage is applied.