Enhancing the Adhesion Retention by Controlling the Structure of the Adhesion Interphase Between Rubber Compound and Metal. Part I. Effect of Cobalt Salt

Abstract The adhesion between cobalt salt-containing rubber compounds and brass-plated steel cords was studied to understand the role of cobalt salt as an adhesion promoter. An improvement in adhesion was shown with the low loading of cobalt salt in the range 0.5–1 phr, while a significant decline in adhesion was observed with high loading at 2 phr and a long aging time of 15 days under humidity aging. The adhesion interphase between the rubber compound and the brass-plated steel cord studied using Auger electron spectroscopy (AES) showed stable depth profile by cobalt salt incorporation at low loading, resulting in the enhancement of the adhesion retention. For the high loading of cobalt salt, adhesion interphase grew excessively, especially ZnO layer formed under humidity aging, which resulted in reduced adhesion. Keywords: COBALT SALTADHESION PROMOTERRUBBER-TO-BRASS BONDINGADHESION INTERPHASEAESDEPTH PROFILEDEZINCIFICATIONCOPPER SULFIDEZINC OXIDEHUMIDITY AGINGADHESION STABILITY