Online method for characterization of the homogeneity of carbon black filled rubber compounds using electrical conductivity

The aim of this work is to develop an online method to characterize carbon black dispersion in rubber mixtures using electrical conductivity. In a HAAKE Rheomix mixing chamber a sensor was installed to measure the electrical conductivity of carbon black filled rubber compound during the mixing process. The instrument delivers characteristic curves of the electrical conductivity with a high reproducibility. However, the experimental results demonstrated that the online electrical conductivity is affected not only by carbon black dispersion but also by a lot of factors like technological ones (mixing time, chamber wall temperature, filling degree, rotor speed and kind of rotor) and material ones (rubber type). In order to get the direct correlation between carbon black dispersion and the online conductivity the technological and material effects must be eliminated. it has been empirically found, that at the BIT (black incorporation time) all the mixtures possess the same carbon black dispersion independent of the mixing parameters. This finding would be an important knowledge for the characterization of carbon black dispersion during the mixing process.