Effect of aspect ratio,bulk density,and production date of multi-walled carbon nanotubes on the electrical conductivity of polypropylene and polycarbonate/multi-walled carbon nanotube nanocomposites

Effects of aspect ratio (AR), bulk density (BD), and fabrication date of multi-walled carbon nanotubes (MWCNTs) on the dispersion quality, electrical properties, and rheological properties were investigated for the nanocomposites of polypropylene and polycarbonate matrix. Six different MWCNTs with various AR and BD were adopted. Among six MWCNTs, two pairs have the same grade names but were produced on different dates. They are two Nanocyl NC7000s and two Hanwha CM130s. The two Nanocyl NC7000s produced on different dates showed different dispersion states and electrical resistivity for both PC and PP based nanocomposites. Characterizations of MWCNTs reveal that the length and diameter of two Nanocyl NC7000s are almost the same regardless of the production date, but the BD values of the two MWCNTs are significantly different. The same is noted for the two Hanwha CM130s. Therefore, the different electrical resistivity of the two nanocomposites using two MWCNTs of the same grade name but different production dates was attributed to the different BD. When comparing two nanocomposites with two MWCNTs (one has slightly higher AR and BD than the other), the nanocomposites with MWCNTs of lower AR and lower BD showed better dispersion and higher electrical conductivity. By various investigations with six MWCNTs, we concluded that BD is a very crucial factor in determining the electrical properties of polymer/MWCNT nanocomposites.