Synergistic effect of MWCNTs and graphite powder on the properties of polymer nanocomposites

• Synergistic effect of carbon nano-materials on nanocomposites was investigated.
• We proved the successful modification of carbon with the proposed method.
• Synergistic of carbon nano-materials improved the electrical conductivity greatly.
• The structure and morphology of grafted carbon were investigated.
• The mechanical properties of nanocomposites were investigated.

Multi-walled carbon nanotube/polystyrene (MWCNT/PS), graphite powder/polystyrene (GP/PS) and multi-walled carbon nanotube–graphite powder/polystyrene (M–G/PS) nanocomposites with different contents of carbon materials were prepared by bulk radical polymerization. The products were pressed into slices to prepare specimens for electrical conductivity testing. All of the nanocomposites demonstrated good electrical conductivity. Compared to MWCNTs/PS and GP/PS composites, the M–G/PS composites showed a good synergistic effect between the MWCNTs and GP, and the electrical conductivity of M–G/PS was higher than that of GP/PS. To investigate the structure and morphology of the grafted carbon nano-materials, samples were submitted to Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA) and transmission electron microscopy (TEM) after being extracted with toluene. The results show that some polystyrene was grafted onto the surfaces of the MWCNTs, GP and M–G, which is likely responsible for the increase in the electrical conductivity of the composites. Furthermore, the mechanical properties of the M–G/PS nanocomposites increased with the M/G ratio.