Nanoclay exfoliation in rubber compounds characterized by online measurements of electrical conductance

A new method based on the online measured electrical conductance is presented for the characterization of the kinetics of dispersion of organoclay in a polar rubber matrix during melt mixing. The charge carriers available in the clay galleries become released as a result of the dispersion processes; thus, the conductance of the nanocomposites is altering during mixing. A coupled conductance/temperature sensor installed inside the mixing chamber enables the online measurement of the electrical conductance during mixing. The online measured conductance shows a characteristic chart correlating to the nanoclay dispersion process. To clarify the structural background of the conductance curve the kinetics of macro‐ and microdispersion of nanoclay have been investigated with the use of optical microscopy, small‐angle X‐ray diffraction (SAXS), and atomic force microscopy (AFM), as well as bound rubber measurements. A close correlation was found between the online conductance chart and the development of the clay dispersion. In the first mixing step, breakdown of agglomerates, diffusion of polymer chains into the galleries of the clay, wetting, and intercalation processes take place simultaneously. As a result, a significant increase of conductance is observed during this period. Subsequently, the intercalated structures undergo the exfoliation process, which causes a further but moderate increase of the electrical conductance. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009