Alignment of MWCNTs in polymer composites by dielectrophoresis

Successful structural reinforcement of polymer matrices by carbon nanotube has been broadly applied where significant improvement of mechanical properties was achieved at a low carbon nanotube loading rate. The notion of the mechanical properties of aligned composites are better than random ones has been proofed and demonstrated whereas the concept is not easy to implement through carbon nanotube polymer composites by the conventional techniques. Here, we introduce a novel practice to actively align and network the multi-wall carbon nanotubes (MWCNTs) in hot melting high density polyester (HDPE) matrix. In this process, MWCNTs were aligned via AC electric field which induced dipolar interactions among the nanotubes in a hot melting matrix and followed by immobilization by cooling curing matrix under continued application of the anisotropic electric field. In situ SEM verified the electrostatic stabilization of the MWCNTs in the dispersion while the orientation and agglomeration are caused by the dielectrophoretic force. Alignment of MWCNTs was controlled as a function of magnitude, frequency, and application time of the applied dielectrophoresis. In the present work, MWCNTs are not only aligned along the field, but also migrate laterally to form thickness. Eventually, the actively aligned MWCNTs would amplify the hardness and wear-resisting property.