Synthesis of Cobalt Adhesion Promoters and Their Evaluation in a Passenger Radial-Belt Skim Compound

Cobalt adhesion promoters have gained considerable acceptance in the rubber industry during the past two decades and are considered the most important tool for the promotion of adhesion between the rubber compound and the brass-plated steel cord in the manufacture of steel-cord-reinforced radial tires. Most of the commercially available cobalt compounds are either higher fatty acid salts or cobalt–chelate complexes, e.g., cobalt octanoate, napthenate, stearate, and cobalt–boron complexes. Of the various cobalt salts and chelate complexes, cobalt–boron complexes are the most popular, and they form good bonding. Considering the availability, economics, and performance of this material, an attempt has been made in this study to synthesize different cobalt–chelate complexes, make a comparative evaluation of rubber compounds, and simulate field performance with laboratory tests.