Morphology development in nanoclay filled rubber compounds and rubber blends detected by online measured electrical conductance

Abstract

The online measured electrical conductance (OMEC) during the rubber mixing process has been used as a novel method to characterize the dispersion of organoclay in rubber compounds and blends. This method was also used for the investigation of morphology development and kinetics of organoclay distribution in carboxylated hydrogenated nitrile butadiene rubber (XHNBR) and hydrogenated nitrile butadiene rubber (HNBR) as well as blends of HNBR with natural rubber (NR). The synchronized increase of the OMEC measured directly in the mixing chamber of the internal mixer along with dispersion of organoclay in the rubber matrix has been observed. The conductivity signal is sensitive to the intercalation/exfoliation process of organoclay in rubber compounds. The correlation between the OMEC and intercalation/exfoliation of organoclay has been determined by various offline experimental techniques like atomic force microscopy (AFM), transmission electron microscopy (TEM), and small angle X-ray scattering (SAXS). In heterogeneous blends the organoclay not only has the tendency to localize in one specific phase, but also strongly influence the development of the blend morphology, which has been nicely correlated with the OMEC chart of HNBR/(NR–clay) blends. A deeper insight into the mixing kinetics, clay transfer as well as development of the blend morphology was achieved on the basis of OMEC chart.