Carbon nanotube based polymeric thermoelectrics and stretchable sensory conductors

P. Riha, P. Slobodian
Academy of Sciences of the Czech Republic, CZ

Keywords: carbon nanotubes, polymer composites, deformation, electrical conductivity, electric power

Summary:

The composite composed of two different brands of multi-walled carbon nanotubes (MWCNT) or carbon nanofibers (CF) and ethylene-octene copolymer (EOC) matrix was prepared by ultrasonication of dispersion of nanotubes or CF in toluene solution of EOC and subsequently by dispersion precipitation in acetone. The composites exhibit a thermoelectric effect, that is, they convert thermal to electrical energy. The thermo power for MWCNT/EOC composite and CF/EOC composite is 13.3 microV/K and 14.2 microV/K, respectively. The measured values are lower in respect to current semiconductor materials but the composite flexibility and lightweight may offer a suitable alternative in a number of applications. A stretchable sensory conductor is composed of a network of electrically-conductive entangled carbon nanotubes embedded in elastic polyurethane. Testing has shown the material can be extended as much as 400% during which the resistance increases more than 270 times. The evaluated sensitivity of the composite in terms of the gauge factor increases linearly with strain from values around 4 at the start of deformation to nearly 69 at the strain 403%. This is a substantial increase, which put the composite among the materials and strain gauges with the highest sensitivity of electrical resistance measurement.