Influence of screw speed on electrical and rheological percolation of melt-mixed high-impact polystyrene/MWCNT nanocomposites

Abstract

The influence of screw speed on the electrical and rheological percolation of HIPS/MWCNT composites prepared via melt mixing was investigated. Microscopic examination of these composites using POM, FESEM and HRTEM revealed optimum MWCNT dispersion was achieved at intermediate screw speeds. On addition of MWCNTs to HIPS, the electrical conductivity of HIPS increased by up to 12 orders of magnitude. At screw speeds up to 100 rpm an electrical percolation of 1-3 wt.-% was achieved. This increased to 3-5 wt.-% when the screw speed was increased to 150 rpm. The onset of a rheological percolation was detected for an MWCNT loading of 5 wt.-%, irrespective of screw speed employed. An up-shift in the Raman G-band of 24 cm-1 was observed, implying strong interfacial interaction between HIPS and MWCNTs. The screw speed employed during melt mixing has a significant effect on the level of MWCNT dispersion in the HIPS matrix. The extent of MWCNT dispersion is correlated with both electrical and rheological percolation. The electrical conductivity of HIPS was increased by up to 11 orders of magnitude. Evidence from Raman spectroscopy suggests the MWCNTs are wetted by HIPS. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.