Steel Cord Skim Compound for Radial Tyre Based on Natural Rubber-Carbon Black-Organoclay Nanocomposites

Abstract

A novel carbon black (CB) and nanoclay (NC) filled system in Natural rubber (NR) matrix has been developed for steel cord tyre ply compound with optimized performance properties. The effect of partial replacement of CB (N-220) by two different kinds of nanoclay (Cloisite-20A and Cloisite-30B) on the adhesion properties has been extensively investigated. The nanocomposites have shown improved adhesion properties between steel cord and rubber (aged and unaged) i.e. pull out force and rubber coverage (%), for relatively lower loading of both Cloisite 20A and Cloisite 30B (3 phr). The addition of nanoclay at lower loading (upto 3 phr) leads to an increase in the overall performance of the rubber compound. Due to nano filler reinforcement, the cohesive strength of the nanocomposites increases, but it is still lower than the adhesive force between steel cord and rubber. As a result the failure is mostly cohesive with higher pull out force. The adhesion improvement is more significant in case of 3phr Cloisite 30B. Cloisite 30B contains polar modified quaternary alkyl ammonium ions as intercalants in its gallery spacing, which may form hydrogen bonding with the resin network available near the copper sulphide bonding layer and leads to better rubber reinforcement and higher pull out force. Dynamic contact angle measurement, transmission electron microscopy (TEM) and low angle X-ray diffraction (XRD) studies have been carried out to explain these phenomena.