Thermal conductivity and rheological measurements on hybrid polypropylene-based systems

Polypropylene (PP) resins, widely used in several industrial applications, are still the object of research interests with the aim to improve specific functional properties. As a well-known weakness of plastics is their low thermal conductivity, a great deal of attention is paid to explore the possibility to enhance thermal conductivity of polymers through the addition of conductive particles. Although particle composites suffer the limitation that high filler loadings can give rise to high viscosities and poor processability, recent studies have shown that hybrid systems developed by using different (in shape and nature) particles can give rise to specific conductive paths with limited particle concentrations. In this view - and with the aim of improving thermal conductivity of a commercial polypropylene without sacrificing its extrudability - we have prepared binary, containing up to 2.5% in vol. of multiwalled carbon nanotubes (MWNT), and ternary nanocomposites, containing 1.5% in vol. of the same carbon nanotubes and 10% in vol. of an additional filler (boron nitride, calcium carbonate, zinc oxide, talc, respectively). The hybrid ternary systems (PP/MWNT/secondary filler) show a remarkable enhancement of thermal conductivities with respect to binary ones (PP/MWNT) while rheological tests demonstrated that their extrudability remain acceptable.