Dispersion of entangled carbon nanotube by melt extrusion

Abstract

This paper investigates the dispersion of carbon nanotube (CNT) in a polymer melt during iterative extrusion by measuring electrical and rheological properties. 2 wt% CNT as received was mixed with polymer (low density polyethylene) through twin screw extruder. The extrusion was iteratively performed at the same process condition. At the same time, the rheological and electrical properties were measured. We expected the mixing energy applied on entangled CNT increases with process time, which improves the CNT dispersion. The electrical property of intermediate composite was effectively improved by iterative extrusion. After the fifth extrusion, CNT/LDPE composite reached to the conductive electric level (surface resistance <= E+5 Omega/sq). Also, the theological properties of composite were increased according to CNT dispersion. Especially the rheological properties over lower frequency region were significantly increased by the dispersed nanotube. This paper suggests that the dispersion by only iterative mixing process results in a disentanglement of CNT and they forms an electrically useful structure. The rheological and electrical measurements indicate that the CNT disentangled by the iterative mixing method forms a percolation structure.