Electrical properties and morphology of carbon black filled PP/EPDM blends: effect of selective distribution of fillers induced by dynamic vulcanization

The roles of dynamic vulcanization process in the electrical properties, morphology, and rheology of carbon black (CB)-filled polypropylene (PP)/ethylene–propylene-diene rubber (EPDM) blends have been investigated. With the addition of CB, the uncross-linked (TPE) and dynamically vulcanized (TPV) composites showed a notable difference in the electrical properties, which is mainly caused by different distributions of CB particles resulting from the dynamic vulcanization process. Particularly, it was found that the CB particles in the TPE composites tended to distribute in EPDM phase, whereas the CB particles in the TPV composites were almost located in the PP matrix. The rheological behavior of the TPE and TPV composites was significantly changed with the incorporation of CB particles. Due to the selective distribution caused by the dynamic vulcanization process, the formation of the conductive network for the TPE composites is caused by the double percolation effect, while for the TPV composite, the formation of the conductive network is caused by the excluded volume effect.