Polypropylene-based melt mixed composites with singlewalled carbon nanotubes for thermoelectric applications: Switching from p-type to n-type by the addition of polyethylene glycol

• Published in: Polymer (Guilford) Vol. 108; pp. 513 - 520
• Main Authors: Luo, Jinji, Cerretti, Giacomo, Krause, Beate, Zhang, Long, Otto, Thomas, Jenschke, Wolfgang, Ullrich, Mathias, Tremel, Wolfgang, Voit, Brigitte, Pötschke, Petra
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 13.01.2017; Elsevier BV
• Subjects: Carbon nanotube; Carbon nanotubes; Composite; Copper; Copper oxide; Copper oxides; Melts; n-type; Nanocomposites; Nanotechnology; Nanotubes; Oxides; Polyethylene glycol; Polyethylenes; Polymer; Polymer matrix composites; Polymers; Polypropylene; Polypropylenes; Prototypes; Studies; Switching; Temperature gradients; Thermocouples; Thermoelectric; Thermoelectricity; Carbon nanotube; Polymer; Thermoelectric; Composite; Copper oxide; n-type
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2016.12.019

The thermoelectric properties of melt processed conductive nanocomposites consisting of an insulating polypropylene (PP) matrix filled with singlewalled carbon nanotubes (CNTs) and copper oxide (CuO) were evaluated. An easy and cheap route to switch p-type composites into n-type was developed by adding polyethylene glycol (PEG) during melt mixing. At the investigated CNT concentrations of 0.8 wt% and 2 wt% (each above the electrical percolation threshold of ∼0.1 wt%), and a fixed CuO content of 5 wt%, the PEG addition converted p-type composites (positive Seebeck coefficient (S)) into n-type (negative S). PEG was also found to improve the filler dispersion inside the matrix. Two composites were prepared: P-type polymer/CNT composites with high S (up to 45 μV/K), and n-type composites (with S up to −56 μV/K) through the addition of PEG. Two prototypes with 4 and 49 thermocouples of these p- and n-type composites were fabricated, and delivered an output voltage of 21 mV and 110 mV, respectively, at a temperature gradient of 70 K. [Display omitted] •Compatible p- and n-type melt mixed composites prepared with same base material.•Polypropylene composites with singlewalled carbon nanotubes at 0.8 and 2.0 wt%.•PEG addition during melt mixing switches p-type CNT composites into n-type.•PEG increases electrical conductivity due to the better dispersion of fillers.•TEG prototypes with output voltages of 21 mV (4 p/n) and 110 mV (49 p/n) @ ΔT = 70 K.