Thermal conductivity and dielectric properties of polypropylene-based hybrid compounds containing multiwalled carbon nanotubes

In this article, we explore the possibility to develop composites with improved thermal conductivity and electrically insulating properties. The strategy adopted is to combine a thermal and electrical conductive filler (multiwalled carbon nanotubes) with secondary dielectric (but thermally conductive) fillers. To this end, particles with different compositions, sizes, and shape were used as secondary fillers and the composites, prepared by melt compounding, are characterized in terms of thermal and dielectric properties. Results show that, in ternary formulations, an increase of thermal conductivity is always verified for all kind of secondary particles. Analogously, increments in electrical conductivity are observed for ternary compounds containing larger size secondary fillers, while a significant reduction is achieved with the addition of smaller ones. This behavior is explained in terms of mutual distribution of the fillers and is consistent with direct (scanning electron microscopy) and indirect (rheological) observations.