Enhanced conductivity of nanocomposite films through heterogeneous distribution of nanofillers during processing

Two different materials processing approaches were studied for an enhancement of the electrical conductivity of nanocomposite materials. Different polymer matrices, i.e., a urethane-based resin or a mixture of epoxy and polyethersulfone, were used to mix with either silver nanowires or multi-walled carbon nanotubes (MWCNTs) via different fabrication strategies with the aim of achieving highest conductivities at a given nanofiller concentration. The effects of nanofillers type and their concentrations, types of polymer matrices, and nanocomposite preparation strategies on the nanocomposites electrical properties were systematically investigated. Two design strategies were studied: the creation of a self-assembled structure in a bi-phasic polymers blend and the formation of a heterogeneous distribution of fillers upon nanocomposite thermal curing. The electrical conductivity of a 50 mu m-thick film of the nanocomposite containing 1 vol.% homogeneously distributed MWCNTs was found to be similar to 3.3 x 10(-5) S.cm(-1), which significantly increased to similar to 2.2 x 10(-3) S.cm(-1), about two orders of magnitudes improvement for the biphasic nanocomposite films representing a nanofiller heterogeneous distribution. The two promising approaches studied here might find applications where lightweight conductive materials are required. (C) 2015 Elsevier Ltd. All rights reserved.