Einfluss der Verfahrenstechnik eines Planetwalzenextruders auf die elektrische Leitfähigkeit rußgefüllter Polyolefine

To convert electrically isolating polymers into conductive materials, conductive fillers are mixed into the polymer matrix by melt compounding. Carbon black is the filler of choice due to easy handling and low costs, provided that the resulting black colour of the compound is acceptable. The biggest challenge for the compounding process is setting the optimal conditions. In order to obtain a conductive compound, the carbon black must be distributed homogeneously in the polymer matrix without losing its shear-sensitive structure during this process, so that a continu-ous, electrically conductive network of carbon black is achieved at a low percolation threshold. This work examines the influence of the process technology of planetary roller extruders (PWE) on the electrical conductivity of carbon black-filled polyolefins. Compounds are manufactured on the basis of polyethylene and polypropylene under different process conditions and with different contents of carbon black. The electrical conductivity of both injection molded and pressed specimens is measured. In addition to the electrical properties, the morphological and mechanical properties are also investigated. In the case of injection molded samples, feeding the carbon black directly into the melt zone of the PWE leads to the highest electrical conductivity, while for samples produced by pressing the lowest electrical conductivity is obtained. Another finding of this work is that the electrical conductivity of carbon black-filled polyolefins is less affected by the process technology of the planetary roller extruder than by the type of carbon black, the carbon black content, and the processing method. When considering the mechanical properties of the specimen it is found that as expected, impact strength and elongation at break decrease with increasing carbon black content, while tensile modulus and fracture stress are improved.