Electrical and mechanical properties of manganese dioxide-magnetite-filled acrylonitrile butadiene rubber blends

Different concentrations of fillers such as manganese dioxide (MnO2) and magnetite (Fe3O4) were incorporated into acrylonitrile butadiene rubber (NBR)-interlinked composites. The prepared composite systems were irradiated by electrons at a constant dose of 50 kGy to induce radiation cross-linking under atmospheric conditions. The effect of different contents of fillers and temperature variations on direct current (DC) electrical conductivity, sigma(DC), in NBR/MnO2 and NBR/Fe3O4 mixture systems was investigated. The calculated activation energy, E-DC, from sigma(DC) was found to be highly affected by both the type and concentration of the fillers, while the dielectric properties namely dielectric constant, dielectric loss, and the alternating current (AC) electrical conductivity (sigma(AC)), were measured as functions of frequency and temperature and for different filler concentrations of MnO2 and Fe3O4. The sigma(AC) value was calculated from dielectric measurements and by employing a simple relationship. The analysis of the sigma(AC) results shows that the conductivity increases up to a temperature of about 330 K. Further increase of temperature reduces the conductivity of Fe3O4 samples, while the conductivity of MnO2 samples tends to show almost constant values after this temperature. Mechanical properties, tensile strength (TS), tensile modulus at 100% elongation, and hardness were established as a function of different concentrations of fillers MnO2 and Fe3O4. It was found that filler incorporation into the NBR matrix is one of the major factors that enhance the TS as well as hardness resistance, while the elongation at break shows an adverse behavior by increasing the content of MnO2 and Fe3O4 fillers.