The electrical, thermal, and morphological properties of microinjection-molded polypropylene nanocomposites

Microinjection molding (µIM) exhibits significantly higher shear rates and faster cooling rates, as compared to conventional injection molding, which affect the characteristics of its final products. The effect of carbon black (CB), carbon nanotubes (CNT), and graphene nanoplatelet (GNP) fillers on the electrical conductivity properties of microinjection-molded polypropylene (PP) nanocomposites was systematically studied. Results showed the electrical conductivity properties of PP/CNT and PP/CB microparts were significantly influenced by mold geometry. PP/CNT/CB hybrid filler microparts demonstrated synergistic increases in electrical conductivity and crystallization temperature with higher CNT loading. Morphological observations indicated significant CB and CNT phase separation. Powder-PP/GNP composites exhibited higher electrical conductivity compared to pellet-PP/GNP due to the similar particle size between PP powder and GNP flakes promoting more uniform microscopic dispersion. Moreover, ‘precoated’ samples exhibited smaller GNP flake size, better microscopic dispersion and exfoliation of GNP fillers