Comparing the rheological behavior and the electrical properties of CNT-PP copolymer composites obtained by two compounding methods: direct addition and dilution of a masterbatch

Abstract

Composites of multiwall carbon nanotubes (CNT) at 1, 2, and 3 wt.% on a propylene-ethylene random copolymer matrix were prepared by melt compounding CNT powder and by dilution of a commercial polypropylene masterbatch. While the shear viscosity shows similar behavior for both dilution modes, the differences in their elastic properties clearly show the addition method's effect, and the masterbatch's presence. This also indicates the relevance of having a difficult to mix masterbatch to enhance the elongational viscosity of the composites for free wall applications such as fiber spinning and blown film. On the other hand, the 2 and 3 wt.% CNT composites from both addition modes have similar electrically conductive behavior, with values near the semiconductors' range. TEM and SEM images show different states of dispersion for each source of CNT. The morphology observed in those images is the simplest explanation for the differences in the elastic properties of the molten composites due to the filler incorporation processes used.