Electrical and physical properties of magnetite-filled NBR

In this work, the effect of different contents of Fe₃O ₄ and temperature variation on the electrical conductivity (σ) in the polar acrylonitrile butadiene rubber (NBR)/Fe₃O₄ (magnetite) mixture system was investigated. It was found that the percolation threshold concept holds true for the conductive particle-filled composites where σ indicates a nearly sharp increase when the concentration of magnetite in the mixture exceeds 22%. The temperature dependence of σ was thermally activated below and at the percolation threshold (P_c). Magnetite acted as reinforcing and conductive filler for NBR. At room temperature and higher voltages, the electrical current was proportional to the square of voltage (I∝V²) for the composites which contain 30 phr of magnetite. Moreover, it was shown that the composites with magnetite of 50 phr showed the highest tensile strength and elongation at break, which was due to the formation of optimal physical interlock and crosslinking. The results of 100%, 200%, and 300% Young moduli said that the moduli are largely correlated with reinforcement effect of magnetite and viscosity of the blends from torque curve.