Alignment of Multiwall Carbon Nanotubes in Polymer Composites by Dielectrophoresis

Abstract

Studies have proved that enhancing polymer matrices by adding carbon nanotubes to form structural reinforcements and to increase electrical conductivity has significantly improved mechanical and electrical properties at very low carbon nanotube loading. That mechanical and electrical properties of aligned composites are better than those of random ones has been demonstrated in past studies; however, alignment is not easy to achieve in carbon nanotube polymer composites by conventional techniques. In this report, we introduce a novel operation to actively align and network multiwall carbon nanotubes (MWCNTs) in a polymer matrix. In this process, MWCNTs were aligned using an RF electric field to elicit dipolar interactions among the nanotubes in a viscous matrix following immobilization by curing under continuous application of an anisotropic electric field. Scanning electron microscopy (SEM) images have been use to verify the electrostatic stabilization of the MWCNTs in the dispersion as well as alignment without agglomeration caused by the dielectrophoretic force. Alignment of MWCNTs was controlled as a function of magnitude, frequency, and processing time of the applied dielectrophoresis. In this work, MWCNTs are not only aligned along the field, but also migrate laterally to enhance thickness. Consequently, the actively aligned MWCNTs amplify the flexural modulus, wear resistance, and electrical conductivity.