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The effect of functionalization of multi-walled carbon nanotubes using KMnO 4 oxidation and oxygen plasma treatment on the electrical resistance of nanotube network/polyurethane composite subjected to elongation has been studied. The layered composite is prepared by taking a non-woven polyurethane filtering membrane which is made by electrospinning, enmeshing it with carbon nanotubes and melding them into one. The testing has shown tenfold composite resistance increase for the composite prepared from KMnO 4 oxidized nanotubes in comparison to the network prepared from pristine nanotubes. The evaluated sensitivity of the treated 2 composite in terms of the gauge factor increases linearly with strain from values around 5 at the start of deformation to nearly 45 at the strain 12 %. This is a substantial increase, which put the composite prepared from KMnO 4 oxidized nanotubes among ranges the materials and strain gauges with the highest sensitivity of electrical resistance measurement.

A network of entangled multiwall carbon nanotubes is presented as a conductor whose conductivity is sensitive to compressive stress both in the course of monotonic stress growth and when loading/unloading cycles are imposed. The testing has shown as much as 100% network conductivity increase at the maximum applied stress. It indicates favorable properties of multiwall carbon nanotube networks for their use as stress-electric signal transducers. To model the conductivity-stress dependence, it is hypothesized that compression increases local contact forces between nanotubes, which results in more conductive contacts. The lack of detailed knowledge of the mechanism as well as an unclear shift from individual contacts to the whole network conductance behavior is

The effect of different chemical oxidation of multiwalled carbon nanotubes with H2O2, HNO3, and KMnO4on the change of electrical resistance of polyurethane composites with embedded oxidized nanotube networks subjected to elongation and bending has been studied. The testing has shown about twenty-fold increase in the electrical resistance for the composite prepared from KMnO4oxidized nanotubes in comparison to the composites prepared from the pristine and other oxidized nanotubes. The evaluated sensitivity of KMnO4treated composite in terms of the gauge factor increases with strain to nearly 175 at the strain 11%. This is a substantial increase, which ranks the composite prepared from KMnO4oxidized nanotubes among materials as strain gauges with the highest electromechanical sensitivity. The observed differences in electromechanical properties of the composites are discussed on basis of their structure which is examined by the measurements of Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscope. The possible practical use of the composites is demonstrated by monitoring of elbow joint flexion during two different physical exercises.