Multi-walled carbon nanotube (MWCNT)/polycarbonate (PC) nanocomposite was prepared by direct melt mixing to investigate the effect of the shear rate on the surface resistivity of the nanocomposites. In this study, an experiment was carried out to observe the shear induced orientation of the MWCNT in the polymer matrix using a very simple melt flow indexer with various loads. The compression-molded, should be eliminated. MWCNT/PC nanocomposite sample exhibited lower percolation thresholds (at 0.8 vol%) and higher electrical conductivity values than those of samples extruded by capillary and injection molding. Shear induced orientation of MWCNT was observed via scanning electron microscopy, in the direction of flow in a PC matrix during the extrusion process. The surface resistivity rose with increasing shear rate, because of the breakdown of the network junctions between MWCNTs. For real applications such as injection molding and the extrusion process, the amount of the MWCNT in the composite should be carefully selected to adjust the electrical conductivity.

Abstract
 1. Introduction
 2. Experimental
  2.1. Materials and composite preparation
  2.2. Melt extrusion
  2.3. Surface resistivity measurements
  2.4. Microscopic measurements
 3. Results and Discussion
  3.1. Dispersion of MWCNT in the PC matrix
  3.2. Electrical properties of MWCNT/PC nanocomposites
  3.3. Microscopic examination
 4. Conclusions
 References

• Young Sil Lee(ICT Convergence Research Center)
• Kwan Han Yoon(Department of Polymer Science and Engineering, Kumoh National Institute of Technology, Gumi 730-701, Korea) Corresponding author