Adhesion Between Rubber Compounds Containing Various Adhesion Promoters and Brass-Plated Steel Cords. Part II. Effect of Accelerator Loading in Rubber Compounds

Abstract

The adhesion property between rubber compounds containing different types of adhesion promoters (resinous adhesion promoter (methylene donor/acceptor), cobalt salt and zinc borate) and loading amounts of accelerator and brass-plated steel cord was investigated to understand the effect of accelerator loading in rubber compounds on their adhesion characteristics to the brass-plated steel cords. The adhesion property of the rubber compounds to brass-plated steel cord was largely dependent on the type of adhesion promoter and the loading amount of accelerator in the rubber compounds. Among the various adhesion promoters incorporated, zinc borate showed the largest enhancement of adhesion properties after cure. For the rubber compounds containing zinc borate, pull-out force increased two times with increasing loading amount of accelerator from 0.4 to 1.6 phr. But for the rubber compounds containing either resinous adhesion promoter or cobalt salt, pull-out force decreased slightly with increasing loading amount of accelerator. For cobalt salt incorporated, interfacial failure between adhesion interphase and rubber compound after humidity aging occurs dominantly, whereas a cohesive failure occurs dominantly in the weak boundary layer closely adjacent to the adhesion interphase for both resinous adhesion promoter and zinc borate. Adhesion property was interpreted in terms of the interphases between the rubber compounds and the brass-plated steel cords studied using Auger electron spectroscopy. Suppression of dezincification was observed for a high loading of the accelerator in the rubber compounds.