Epoxy nanocomposites with carbon nanotubes and montmorillonite: Mechanical properties and electrical insulation

Multiwalled carbon nanotubes have been widely used as mechanical reinforcement fillers for polymers during the past few decades. However, high electrical conductivity of raw multiwalled carbon nanotubes hampers their application in some fields demanding not only good mechanical properties and/or high thermal conductivity but also electrical insulation. In this research, carboxyl functionalized multiwalled carbon nanotubes and organically modified montmorillonite were introduced to prepare epoxy nanocomposites with anhydride as curing agent. The obtained epoxy nanocomposites possessed improved impact toughness, and the electrical insulation was maintained. Compared to the volume resistivity of the raw multiwalled carbon nanotubes (0.6 wt%)/epoxy nanocomposites, the volume resistivity of the organically modified montmorillonite/carboxyl functionalized multiwalled carbon nanotubes (0.6 wt%)/epoxy nanocomposites increased more than four order of magnitude. These excellent properties were attributed to the synergistic effect of carboxyl functionalized multiwalled carbon nanotubes and organically modified montmorillonite on toughening epoxy, as well as the suppression of electron transport by multiwalled carbon nanotubes surface modification and the organically modified montmorillonite layer in the multiwalled carbon nanotubes conductive network. The effects of adding nanofillers on the dielectric constant and dielectric loss values of epoxy nanocomposites were also studied. This work has demonstrated the feasibility of using multiwalled carbon nanotubes as mechanical reinforcement fillers, while simultaneously giving electrical insulation in the polymer nanocomposites.