Dielectric dispersion and AC conductivity of acrylonitrile butadiene rubber-poly(vinyl chloride)/graphite composite

摘要

Dielectric properties and ac electrical conductivity of Acrylonitrile Butadiene Rubber-poly(vinyl chloride)/Graphite Composite were studied at different frequencies (10~2-10~6 Hz) in the temperature range (298-423 K). The results show that the dielectric constant (ε′), dielectric loss (ε′), ac electrical conductivity (σ_(ac)) and, the electric modulus are strongly dependent on the frequency and temperature. The dielectric constant ε′ increases with temperature and decreases with frequency, whereas the dielectric loss ε′ displays a broad maximum peak whose position shifts with temperature to a higher frequency region. Cole-Cole diagrams have been used to investigate the frequency dependence of the complex impedance at different temperature and graphite loading. Interfacial or Maxwell-Wagner-Sillars relaxation process was revealed in the frequency range and temperature interval of the measurements, which was found to follow the Havriliak-Negami approach for the distribution of relaxation times. At constant temperature, the frequency dependence of ac conductivity was found to fit with the established equation σ_(ac)(ω) = Aω~s quite well. The values of S for the investigated samples lie between 0.88 and 0.11. The conduction mechanism of ac conduction was discussed by comparing the behavior of the frequency exponent S(T) with different theoretical models. It was found that the correlated barrier hopping (C.B.H.) is the dominant conduction mechanism.