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Viscoelastic properties and filler dispersion in carbon black-filled and silica-filled cross-linked natural rubbers


Correspondence to: A. Kato (E-mail:


The activation energies (ΔEJ and ΔEJ) calculated from the temperature dependence of the storage compliance (J′) and the loss compliance (J″) of carbon black (CB)-filled, hydrophobic silica- and hydrophilic silica-filled cross-linked natural rubbers (NRs) were found to be less than 15 kJ mol−1, which corresponds to the physical range of van der Waals interaction. The results of three-dimensional-transmission electron microscopy measurements indicate that the closest distance (dp) between the two neighboring nanofiller aggregates centers decreased sharply with increasing nanofiller loading and tended to become constant at a nanofiller loading of around 30 phr or higher. For all samples examined, there were two regions related to the elastic deformation energy, and the critical dp value between the two regions was in the order of CB > hydrophobic silica = hydrophilic silica. Additionally, ΔEJ developed in the region of longer dp than that of ΔEJ. On the other hand, ΔEJ occurred after the formation of the filler network and was larger than ΔEJ. ΔEJ is assumed to be related to slippage of the junction and the rearrangement of the nanofiller network. Therefore, the dependence of ΔEJ and ΔEJ on dp suggests that the interaction layer between the nanofiller and NR has at least two energy levels. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2594–2602, 2013