Influence of “expanded clay” on the microstructure and fatigue crack growth behavior of carbon black filled NR composites

In this study, organo-montmorillonite (OMt) was treated with long alkyl chain containing docosanoic acid in order to obtain expanded organo-montmorillonite (EOMt) with increased interlayer distance. The X-ray diffraction (XRD) patterns confirmed the widening of the interlayer space of clay after intercalation of long alkyl chain docosanoic acid. The role of EOMt nanoparticles on the microstructure and fracture mechanical behavior of carbon black (CB) filled natural rubber (NR) composites was investigated. The microstructure of these clay filled NR/CB composites were revealed by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Tear Fatigue Analysis (TFA) tests were carried out using pure-shear test specimen under cyclic conditions to explicate the crack growth behavior of CB filled NR in the presence of EOMt. A significant reduction in crack growth rate was noticed in the presence of only 5 phr of EOMt. The viscoelastic properties obtained from the dynamic mechanical analysis (DMA) for different CB filled NR–clay composites were utilized to estimate the tearing energy qualitatively using the ‘Persson–Brener’ equation. The reinforcement of rubber matrix was investigated by both the static and dynamic mechanical properties. A synergy in reinforcement between clay nanoparticles and CB was attested by the marked enhancement in both mechanical properties.