The dielectric properties of styrene butadiene rubber (SBR) loaded
with fast extrusion furnace black (FEF) samples crosslinked with sulfur via
step crosslinking process were studied. The measurements were performed in
the frequency range from 102 to 105 Hz at room temperature, and macroscopic
permittivity έ describing the dielectric properties of the samples was evaluated.
Extension of logarithmic law of mixtures enables equations to be formulated
which describe the dielectric behavior of particulate polymeric composite
containing conductive particles. These equations give the dielectric constant
and dielectric loss of the composite as a function of the dielectric constant of
the polymeric matrix, the volume fraction and the aspect ratio of the inclusions,
and the frequency of the applied field. Equations proposed by Tsangaris et al
were tested and modified with the experimental data over a wide range of
frequencies and the step crosslinking process. Satisfactory agreement was
observed taking into account the variation of the aspect ratio with the volume
fraction of the FEF black in the NR matrix and also with the partial time of
vulcanization process.