Polymer - Carbon Nanotube Composites for Thermoelectric Applications

The thermoelectric (TE) performance of electrically conductive thermoplastic composites prepared by melt mixing was investigated. A cost effective widely used in industry polymer, namely polypropylene (PP), was chosen as the matrix to fabricate the composites. Singlewalled carbon nanotubes (SWCNTs), the amount (2 wt%) of which was selected to be above the electrical percolation threshold (< 0.2 wt%), were used to form an electrical conducting network. Besides as-produced SWCNTs plasma modified tubes were employed to study the influence of the functionalization on the morphology, dispersion and properties of the PP composites. In addition, melt processing conditions, e.g. temperature, rotation speed, and time during mixing in a small-scale compounder were varied. Furthermore, an ionic liquid (IL, 1-methyl-3-octvlimidazolium tetrafluoroborate) was used as a processing additive during melt mixing, which was continued to improve the electrical conductivity of the composites. Simultaneous increase in the Seebeck coefficient up to a value of 64 mu V/K was recorded, leading to a much better power factor of 0.26 mu W/(m.K-2) compared to composites without IL. This melt mixing strategy opens new avenues for solvent-free, large scale fabrication of polymer based TE materials.