The Influence of the Cation in Organometallic Boroacylate Adhesion Promoters on the Adhesion Between Steel Cord and Skim Rubber Compound

The influence of transition metal cations (cobalt, nickel and zinc ion) associated with organometallic boroacylate adhesion promoters on the adhesion between brass-coated steel cord and rubber skim compound under the influence of various environments, which simulate tyre service conditions, has been studied.

Incorporation of adhesion promoters individually in the steel cord-skim formulation leads to increase in crosslink density, Young's modulus and cord pull-out force. The adhesion energy is enhanced significantly with the addition of cobalt adhesion promoter. The performance of the promoter is influenced by the ease of dissociation of the transition metal ion from the promoter, its participation in the rubber curing and the modification of the interfacial film responsible for adhesion. During aerobic ageing, cobalt followed by nickel is found to be effective, whereas cobalt and, partially, zinc salts offer certain resistance to thermal ageing. Against salt and steam ageing, cobalt boroacylate is very effective followed by zinc salts. The influence of the variation of concentration of zinc ion on adhesion energy is not appreciable. The study points towards the supremacy of cobalt ion among the cations studied, considering its overall good performance and the protection offered against various hostile environments.