Effect of Extrusion Cycles on the Dispersion and Properties of Polypropylene/Multi-Walled Carbon Nanotube Composite

Extrusion reprocessing can significantly influence the structure and properties of polymer nanocomposites. In this study, two batches of polypropylene (pp) containing 4wt% of multi -walled carbon nanotube (MCNT) loading with 4wt% of two different types of compatibilizers were prepared (one in the presence of compatibilizer at low graft level and another one with compatibilizer at high graft level). The nanocomposites were passed into the extruder for three cycles and the resultant dispersion of carbon nanotubes, mechanical, rheological, and electrical properties of the nanocomposite after each cycle were examined. For both nanocomposites, repetition of extrusion cycle improved tensile modulus, tensile strength, and flexural modulus of the nanocomposites. Rheological and electrical characterization indicated that the repetition of the extrusion cycle enhanced the dispersion of nanotubes and helped the formation of the percolation network. The electrical resistivity of the nanocomposites extruded three times was found to be up to nine orders lower than that of the first extrusion. From the morphological analyses performed by scanning electron microscopy, it was observed that the multiple extrusions assisted the homogeneous dispersion of carbon nanotubes within the polymer.