Electrical and mechanical properties of carbon nanotube-polyimide composites

The use of carbon nanotubes (CNTs) as a conductive and high strength filler into polymer hosts has attracted great attention recently. However, in order to increase the conductivity of the polymer and to reinforce mechanically the polymer structure at low weight fraction of CNTs, the integration of the CNTs into the polymer matrix has to be effective. In this study, CNT-polyimide (CNT-Pi) composite has been fabricated by solution mixing. The electrical and mechanical properties of the composite have been investigated as a function of CNT's loading fraction as well as temperature. It has been found that the electrical and mechanical properties of the CNT-Pi can be improved by integrating the CNTs into the polymer. In particular, the presence of an ac electric field is believed to induce dielectrophoresis (DEP), hence the possible CNT's alignment inside the polyimide matrix during curing. The DEP effect can play an important role in enhancing the properties of the polymer matrix by reducing the percolation threshold. An ac electric field of 800 kV/cm at a frequency of 1 kHz has been found to be the optimal conditions for integrating the CNTs into the polymer.