Improved dielectric performance of polypropylene/multiwalled carbon nanotube nanocomposites by solid-phase orientation

Abstract

By means of die drawing technique at rubber-state, effect of the orientation of microstructure on dielectric properties of polypropylene/multi-walled carbon nanotubes nanocomposites (PP/MWCNTs) was emphasized in this work. Viscoelasticity behavior of PP/MWCNTs with MWCNTs weight loadings from 0.25 to 5 wt% and dielectric performance of the stretched PP/MWCNTs under different drawing speeds and drawing ratios were studied for seeking an insight of the influences of dispersion and orientation state of MWCNTs and matrix molecular chains. A viscosity decrease (ca. 30%) of the PP/MWCNTs-0.25wt% melt was obviously observed owing to the free volume effect. Differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD) were adopted to detect the orientation structure and the variation of crystal morphology of PP/MWCNTs. Melting plateau regions, which indicated the mixed crystallization morphology for the stretched samples, were found in the DSC patterns instead of a single-peak for the unstretched samples. It was found that the uniaxial stretching process broke the conductive MWCNTs networks and consequently increased the orientation of MWCNTs as well as molecular chains along the tensile force direction, leading to an improvement of the dielectric performance.