Interfacial effects in the electrical conductivity and viscous deformation of multiwall carbon nanotube–epoxy composites prepared by sonication

Abstract

Multiwall carbon nanotube composites with epoxy matrix were prepared by sonication followed by long curing. The electrical conductivity of the composite samples was measured and found to follow percolation behavior with low threshold mass fraction of multiwall carbon nanotubes and smaller value of critical exponent. The lower values of threshold and exponent are associated with higher purity and better interfacial contact between the multiwall carbon nanotubes and with the epoxy. The temperature dependence of electrical conductivity showed that both variable range hopping and fluctuation-induced tunneling mechanisms are followed. The dependence of conductivity on the width of the epoxy barrier film between multiwall carbon nanotubes is used to establish that fluctuation-induced tunneling through interfacial regions is the appropriate mechanism of conduction in the composites. The activation energy for viscous deformation of the composites was evaluated using dynamic mechanical analysis and found to increase for higher mass fraction of multiwall carbon nanotubes in the composite. These results indicate that interfacial interaction is significant in the molecular movement in the epoxy.