Melt flow behavior of polypropylene composites filled with multi-walled carbon nanotubes during extrusion

Polypropylene (PP) composites filled with multi-walled carbon nanotubes (MWCNTs) were prepared using a twin-screw extruder. The melt flow properties of the composites were measured with a capillary rheometer in a temperature range from 180 to 230 °C and at various apparent shear rates varying from 100 to 4000 s^?1. The results showed that the melt shear stress increased almost linearly while the melt shear viscosity decreased almost linearly with increasing shear rates in a bi-logarithmic coordinate system. The melt shear flow followed the power law relationship and the dependence of the melt shear viscosity on temperature obeyed the Arrhenius equation. The relationship between the melt shear viscosity and the MWCNT weight fraction was roughly linear under the investigated range of temperature or shear rate.