The Study of the Distribution of Carbon Black Filler in Rubber Compounds by Measuring the Electrical Conductivity

This study deals with distribution of carbon black fillers in rubber compounds using electrical conductivity measurements. Three rubber compounds samples were heated in resistive furnace in temperature interval 40-80°C and electrical current was measured, while voltage was constant. All samples showed a decrease in electrical conductivity with decreasing temperature, which is characteristic of semiconductors and insulators. On the other hand the large variance of activation energy can be seen for electric transport in different areas of the temperature dependence of the direct electrical conductivity. These quasi-linear areas were selected, linear regression was used and corresponding activation energy was calculated. The number of the identified areas was changing, and hence the number of conductivity mechanisms was changing as well. Clearly it can be concluded that all three samples show inhomogeneity of distribution of filler, which can be seen from the variance of values of the activation value of electric transport.