Electromechanical response of multilayer graphene sheet/polypropylene nanocomposites and its relationship with the graphene sheet physicochemical properties

The mechanical, electrical, and piezoresistive responses of multilayer graphene sheet (GS)/polypropylene (PP) nanocomposites are investigated using four GSs of distinctive physicochemical properties. It is found that the morphology of the interconnected network of GS agglomerates at the mesoscale governs the mechanical, electrical, and electro-mechanical (piezoresistive) properties of the PP nanocomposites. The morphology of the mesoscale network of electroconductive fillers governs the effective properties of the nanocomposite. This network morphology strongly depends on the GS lateral size, dispersion, agglomeration, and, to a lesser extent, the specific surface area of the GSs. Within the range of lateral sizes investigated herein (1-21 μm), larger GSs yields nanocomposites with higher electrical conductivity. On the other hand, GSs of moderate lateral size (∼6.5 μm) and specific surface area of ∼141 m² g⁻¹ render GS/PP nanocomposites with a more dispersed and more sparsely interconnected network. This better dispersed network with agglomerates of smaller dimensions is concomitant with improved stiffness and strength, and higher gauge factors (∼18.2) for this GS/PP nanocomposites. Excellent capabilities for detection of human motion were proved for these nanocomposites.