RHEOMETRIC AND DYNAMIC MECHANICAL ANALYSIS OF COMPLEX NATURAL RUBBER BASED COMPOSITES

Abstract

This work describes the preparation and characterization of complex natural rubber (NR) based composites containing hybrid nano- and conventional fillers intended for base seismic application. Thorough rheometric and dy-namic mechanical analyses in strain sweep mode at 2 Hz and 10 Hz (two frequencies laying in the range 0 – 15 Hz in which most of the earthquakes have the dominant frequencies) were performed on complex natural rubber (NR) based composites containing hybrid nanofiller (carbon nanotubes, expanded montmorillonite) and different amounts of con-ventional fillers like carbon black (CB) and silica. The rheometric studies showed that the influence of the combina-tion of the different fillers on curing parameters is quite complex, but mainly the introduction of the fillers reduces the scorch and optimum cure time of the compounds. The dynamic mechanical analysis showed a pronounced non-linear strain dependence of the storage modulus and a remarkable increase of the loss factor tanδ for all composites, espe-cially for those containing high CB content, compared to the NR-gum. To describe this strain-dependency of the stor-age modulus the cluster-cluster aggregation (CCA) model was used. The values of the fitting parameters ΔE’0, γc, and E’∞ calculated by this model show that they are affected by the type of the fillers present in the NR matrix and also by the applied frequency.