Dielectric properties of SBR vulcanizates loaded with HAF carbon black and BaTiO3 ceramics

The influence of HAF carbon black and BaTiO3 ceramic powder contents in SBR vulcanizates on the dielectric constant (epsilon') at different frequencies and at fixed temperature of 303 K is studied well in this article. The temperature dependence of the ac conductivity (sigma(ac)) was also studied. epsilon' appreciably decreases as frequency increased for both filled and unfilled SBR vulcanizates. At each frequency, epsilon' gradually decreased with BaTiO3 loading, but its change at any fixed frequency with BaTiO3 filler loading is not uniform. For HAF group epsilon' (at loading >= 40 phr), drops rapidly with frequency. Meanwhile, it increased appreciably beyond a certain HAF filler loading (approximate to 20 phr). Experimental values of the dielectric constant of both BaTiO3 and HAF contents were compared with those calculated by using Tsangaris, Clausius and Bruggman models. Tsangaris model with simple modifications was applied and a fairly good agreement was obtained. The HAF particles or aggregates was found to take the shape of oblate ellipsoids with the minor axes parallel to the applied frequency as detected from the decreasing behavior of the depolarizing factor (Y) with HAF contents. (c) 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2227-2234,2007