Polyurethane (PU) and PU/multiwalled carbon nanotube (MWCNT) nanocomposite nanofibers, both with diameters of 350 nm, were prepared by an electrospinning process from PU dimethylformamide solutions. The appearance of nanowebs in PU/MWCNT nanofiber structures containing PU fibers with diameters of 20-40 nm was observed. The existence of these structures could have been based on the occurrence of strong secondary electric fields, which were created between individual conducting MWCNTs (distributed in the PU/MWCNT nanocomposites), which started to behave as the local moving nanoelectrodes promoting the creation of additional very fine nanowebs during the electrospinning processes. To our knowledge, this is the first report describing nanowebs from synthetic polymers prepared by an electrospinning process.

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.

Flexible and stretchable polyurethane/carbon nanotube composite with strain detection ability was used for human breath monitoring. The composite material consisted of a network of multiwalled carbon nanotubes and thermoplastic high elastic polyurethane. It was found that elongation of the composite led to a macroscopic increase in electrical resistance, which can be used as a principle for applied strain detection. This detection was reversible, durable, and sensitive with gauge factor reaching very promising value, as, for example, ~46 at applied deformation of 8.7%. Further, the composite could be elongated to very large extend of deformation without discontinuity in measured resistance change reaching gauge factor ~ 450 at composite mechanical break at ~300% of strain. Sensor durability was also confirmed by sine wave deformation cycling when any decrease in the sensor properties for more than 103 cycles was observed. Simultaneously, the prepared composite possessed other utility properties also and was considered as multifunctional when it was tested as an organic solvent vapor sensor, an element for Joule heating and finally as a microstrip antenna.

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The high sensitivity in response, selectivity and reversibility was achieved on a carbon nanowall-based sensor for the vapor detection of volatile organic compounds, which were tested by an electrical resistance method during adsorption and desorption cycles.