Electrical resistivity of polycarbonate/multiwalled carbon nanotube composites under varying injection molding conditions

Multiwalled carbon nanotube (MWCNT)-filled polycarbonate composites were prepared by a corotating intermeshing twin-screw extruder. The surface resistivities of compression- and injection-molded specimens were quite different, the difference ranging from 103 to 107 Ω/sq at varying MWCNT concentrations. The surface resistivity of the injection-molded specimen at 2 wt % loading varied up to 105 Ω/sq in the specimen thickness direction and up 104 Ω/sq in the polymer flow direction with respect to the gate. The difference in surface resistivity with the positions of injection-molded specimen was confirmed with the morphology, which showed the difference in MWCNT number density (numbers/surface area). There was no significant effect on surface resistivity with injection pressure, holding pressure, and molding temperature. The specimens prepared at the injection speed of 13 mm/s showed surface resistivities 103–104 Ω/sq depending on the positions, which was comparable with the compression-molded specimens, which had a surface resistivity of 103 Ω/sq. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009