Electrical and Mechanical Properties of Some Composites with Polymeric Matrix

Abstract

The present study aims to investigate the dielectric properties as well as the mechanical properties of polymethyl methacrylate-carbon black and polyester-carbon black composites using semi-reinforcing furnace (SRF) and high abrasion furnace (HAF) carbon blacks. The permittivity ϵ' was found to increase by increasing carbon black content and showed anomalous dispersion. The absorption spectra (ϵ'' vs. frequency) from 100 Hz to 10 MHz were analyzed using a computer program based on Fröhlich terms. Four absorption regions were obtained for either the polymer matrix or loaded samples. The first region in the lower frequency range could be attributed to Maxwell-Wagner effect resulting from the differences in the conductivities of the ingredients of the composite. The second and third regions in the higher frequency range could be attributed to the large and small aggregates caused by movements of the main chain. The fourth region may occur due to segmental rotation (ester group or carbonyl group) or local twisting motion of the main chain. At higher carbon black concentration, the relaxation time for different regions except that for Maxwell-Wagner effect became higher and carbon black seems to interact with the polymer matrix giving rise to large aggregates resulting high relaxation times. The mechanical properties for the investigated samples were also examined, the results showed that the tensile strength is higher in the case of smaller particle size carbon black HAF. This could be attributed to a good incorporation of carbon black of small particle size into the polymer matrix. Also, the morphology study indicates the presence of aggregates and some arrangements on adding carbon black.