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This paper investigates the rheological, mechanical and electrical properties of a Ethylene-Vinyl Acetate (EVA) polymer filled with 1, 3 and 5 wt.% multi-walled carbon nanotubes (MWCNTs). The melt flow and pressure-volume-Temperature (pvT) behaviors of the EVA/MWCNT composites were investigated using a high-pressure capillary rheometer, while the electro-mechanical response was investigated on injection-molded samples. Rheological experiments showed that the melt shear viscosity of the EVA/MWCNT composite is dependent on nanotube loading and, at high shear rates, the viscosity showed temperature-dependent shear thinning behavior with a flow index n < 0.35. The specific volume of the EVA/MWCNT composite decreased with increasing pressure and MWCNT wt.%. The transition temperature, corresponding to the pvT crystallization, increased linearly with increasing pressure, i.e., about 20 to 30 °C when cooling under pressure. The elastic modulus, tensile strength and stress at break increased with increasing MWCNT wt.%, whereas the strain at break decreased, suggesting the formation of MWCNT secondary agglomerates. The electrical conductivity of the EVA/MWCNT composite increased with increasing MWCNT wt.% and melt temperature, reaching ~10−2 S/m for the composite containing 5 wt.% MWCNTs. Using the statistical percolation theory, the percolation threshold was estimated at 0.9 wt.% and the critical exponent at 4.95.

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In this paper, polypropylene (PP) filled with different levels of multiwalled carbon nanotubes (MWCNTs) manufactured by injection molding was closed-loop recycled in order to investigate the effect of recycling and reprocessing on its rheological, electrical, and mechanical properties. It was found that the PP/MWCNT composites keep the flow performance after mechanical recycling. Moreover, the stress and strain at break increase after one reprocessing cycle (mechanical recycling and injection molding), whereas no statistically significant changes in electrical conductivity, Young's modulus, and tensile strength of the PP/MWCNT composites filled with 1, 3, and 5 wt.% were observed.