Evolution of morphology and electrical properties under controlled flow in polypropylene/polystyrene co-continuous blends containing interfacially localized carbonaceous nanoparticles

This study investigates the evolution of morphology and electrical properties of polypropylene (PP)/polystyrene (PS) blend nanocomposites under controlled steady shear flow. These nanocomposites contain either few-layer graphene (FLG) or a mixture of FLG and multi-walled carbon nanotubes (MWCNT), prepared via a conventional melt-mixing. Composites were created by premixing FLG or FLG/MWCNT with either PP [PP/PS/FLG or PP/PS/(FLG+MWCNT)] or PS [PS/PP/FLG or PS/PP/(FLG+MWCNT)] at a PP/PS ratio inducing co-continuous morphology. Results showed a significant reduction in the percolation threshold (PT) for PS/PP/FLG composites, with an 81% decrease compared to PS/FLG. When FLG was premixed with PS, PT required only 2 wt. % FLG, compared to 5.9 wt. % in PP/PS/FLG. Steady shear deformation disrupted the electrical network in both PP/PS/FLG and PS/PP/FLG composites. However, the PS/PP/FLG composites exhibited greater stability in electrical conductivity at lower FLG concentrations (above 3 wt. %) compared to the PP/PS/FLG composites (above 6 wt. %). The applied shear did not affect the co-continuous morphology of the blend-based composites containing 1 wt. % or more of FLG. Additionally, the synergistic effects of the hybrid FLG/MWCNT mixture on the electrical conductivity and rheological properties of both PP/PS/(FLG+MWCNT) and PS/PP/(FLG+MWCNT) composites were evaluated. The incorporation of MWCNT into both PP/PS/FLG and PS/PP/FLG composites significantly enhanced the formation of a hybrid electrical network structure, leading to a further reduction in the percolation threshold concentration of FLG. Specifically, in PP/PS/FLG composites, PT decreased from 5.9 to 1–3 wt. % of FLG, while in PS/PP/FLG composites, PT dropped from 2 to 1 wt. % of FLG.