Influence of melt-mixing processing sequence on electrical conductivity of polyethylene/polypropylene blends filled with graphene

Abstract

In this paper, we produced composites of high-density polyethylene (PE)/polypropylene (PP) filled with graphene by melt compounding. Comparing composites produced in three processing sequences, we explored whether the sequence improved the composites’ electrical conductivity. The (graphene/PE)/PP composite, prepared by simultaneous compounding, exhibited an electrical percolation threshold of 1.25 vol.%. In contrast, the (graphene/PP)/PE composite, prepared by blending the graphene with PP first and then blending the graphene/PP with PE, had a much lower electrical percolation threshold at less than 0.83 vol.%. At its percolation threshold, the (graphene/PP)/PE composite had a conductivity about two orders of magnitude higher than the (graphene/PE)/PP composite. We attribute this difference in conductivity to differences in the graphene distributions in the composites. In the (graphene/PE)/PP composite, the graphene sheets were selectively dispersed in the PE phase; in the (graphene/PP)/PE composite, some of the graphene was localized at the interface of the PE/PP blend. We also showed how the different processing sequences affected the composites’ measured rheological and mechanical properties.