The thermal properties (thermal conductivity, thermal diffusivity, and specific heat capacity) of nitrile rubber (NBR)/poly(vinyl chloride) (PVC) blends were measured in the temperature range of 300-425 K. The incorporation of graphite into the NBR/PVC (30/70) matrix improved its thermal properties. Moreover, these properties slightly changed with the temperature. The thermal conductivity values of the prepared samples were compared with values modeled according to the MaxwellEucken, Cheng-Vachon, Lewis-Nielsen, geometric mean, and Agari-Uno models. The Agari-Uno model best predicted the effective thermal conductivity for the whole range of blend ratios and for the whole range of graphite contents in NBR/PVC (30/70)/graphite composites.

Dielectric properties and ac electrical conductivity of Acrylonitrile Butadiene Rubber-poly(vinyl chloride)/Graphite Composite were studied at different frequencies (10 2 À10 6 Hz) in the temperature range (298-423 K). The results show that the dielectric constant (e 0 ), dielectric loss (e 00 ), ac electrical conductivity (r ac ) and, the electric modulus are strongly dependent on the frequency and temperature. The dielectric constant e 0 increases with temperature and decreases with frequency, whereas the dielectric loss e 00 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 r ac (x) ¼ Ax 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.

ABSTRACT:The current-voltage characteristics of acrylonitrile butadiene rubber (NBR)/poly(vinyl chloride) (PVC) blends are studied as a function of sample temperature and PVC content. These samples showed ohmic behavior up to (225 V), after this value the behavior become SCLC (space charge limited conduction). The results obtained show that the charge carriers are generated by Richardson-Schottky emission from the electrode as well as from trapped ionic impurities at high fields. The activation energy of the prepared samples was calculated by using Arrhenius equation.