Structure-property-processing investigation of electrically conductive polypropylene nanocomposites

This paper investigates the structure-property-processing correlations of electrically conductive polypropylene (PP) nanocomposites. The process parameters and fabrication techniques of PP-based composite materials were studied. Various structures of carbon allotrope-based materials, including synthetic graphite (SG), exfoliated graphene nanoplatelets (xGnP), multi-walled carbon nanotubes (MWCNTs) and carbon black (CB), were used to fabricate the PP-based nanocomposites. The nanocomposites were prepared by either direct melt mixing using an internal mixer or by ball milling of components before the melt mixing process. The electrical and flexural properties were measured. In order to understand the conductivity behavior, both in-plane and through-plane electrical conductivities were measured. The results showed that the incorporation of the xGnP into PP/60 wt.% SG composites resulted in a slight increase of the in-plane conductivities and had a minimal effect on the through-plane conductivities. The addition of MWCNTs and CB to the PP/SG/xGnP composites had a significant effect on the electrical properties and was more pronounced in the case of MWCNTs. The flexural properties of all samples were much lower than those of pure PP. The interface between the filler and the PP matrix and the morphology of the composite materials were observed from the fracture surfaces of the composites using scanning electron microscopy (SEM). In addition, SEM was employed to observe adhesion, microstructural homogeneity, orientation of the xGnP platelets and agglomeration in the composites