A comparative study of polycarbonate nanocomposites respectively containing graphene nanoplatelets, carbon nanotubes and carbon nanofibers

In industrial settings, thermoplastics are frequently employed as the base materials for composites and often enhanced with micron-sized additives such as glass fibers for improved performance. This study employed twin-screw extrusion as the processing method to compound a common thermoplastic – polycarbonate (PC) with one dimensional (1D) multi-walled carbon nanotubes (MWCNTs), carbon nanofibers (CNFs) and two dimensional (2D) graphene nanoplatelets (GNPs). In the PC matrix, GNPs were found to relatively uniformly dispersed, MWCNTs were seen to have two states of dispersion, and CNFs were much shortened with many defects caused by the extrusion. At 10.0 wt%, MWCNTs reduced the electrical resistivity of PC from 4.2 × 10¹⁵ to 4.6 × 10⁷ Ω·cm, and GNPs improved the thermal conductivity from 0.13 to 0.38 W·m⁻¹·K⁻¹. GNPs, MWCNTs and CNFs at 1.0 wt% all improved the mechanical properties of PC, i.e. increments of 13.8%, 5.7% and 13.8% for Young's modulus, 6.2%, 11.7% and 21.2% for tensile strength, and 9.6%, 10.2% and 5.7% for impact strength. At 10.0 wt%, the PC/GNP nanocomposite displayed the least reduction of tensile strength of PC whilst the PC/CNF nanocomposite slightly increased the un-notched Charpy impact strength from 161 to 186 kJ/m². The structure-property relationship of these nanocompsoites was analysed, with the relavent mechanisms proposed. Overall, twin-screw extrusion proved effective for dispersing various carbon nanomaterials in PC. This work provides a guide for industry to design and manufacture thermoplastic/carbon nanomaterial composites using the extrusion method.