Investigation of vulcanization reactions by means of electrical current measurements

An electrochemical method for the characterization of vulcanization reactio ns is described. A direct-current voltage is applied to a rubber mixture in a two-part mold which is between the platens of a heating press. The elect rical current, e.g. in the nA range, is registered on-line with a sensitive ammeter as a function of the reaction time, The measured curves are charac teristic of the vulcanization reaction and can be seen as a kind of "finger print" of the rubber mixture. The equipment required for such measurements is described in this publication. The example investigated is the vulcaniza tion of natural rubber with tetraethylthiuram disulfide in the presence of zinc oxide.