Electro-mechanical properties of thermoplastic polyurethane films and tubes modified by hybrid carbon nanostructures for pressure sensing

Abstract

Electrical and piezoresistive properties of hybrid nanocomposite films and tubes made of a segmented aliphatic polyurethane modified with multilayer graphene sheets (MLGSs), multiwall carbon nanotubes (MWCNTs), and hybrid mixtures of both, were investigated.Hybrid nanocomposites were fabricated at a total weight concentration ( ) of 5 wt.%, with relative weight concentration of MLGSs with respect to MWCNTs ( ) of 25%, 50% and 75%. The electrical conductivity of these films is dominated by the MWCNT network, observing electrical MLGS-MWCNT collaborative effects only for = 25%. Dielectric impedance spectroscopy indicates that the nanocomposites display capacitive effects at frequencies higher than tens of Hz, which is explained by interfacial polarization. The burst pressure and circumferential stiffness of internally pressurized tubes fabricated from these films is slightly higher for tubes containing only MWCNTs. The strain fields in the pressurized tubes, determined by digital image correlation, showed localized strain gradients, and the piezoresistive response of the electro-conductive tubes was nonlinear. The highest pressure-sensing factor (4.59 kPa -1 ) was obtained for hybrid nanocomposite tubes with = 25%.

Effect of temperature on the electrical and electromechanical properties of carbon nanotube/polypropylene composites

“…%) indicates the increasing influence of interfacial polarization, due to the differences between the conductivities and permittivities of the polymer and CNTs [42]. The transition frequency where the frequency-independent zone changes to a frequency-dependent one has been named 'critical frequency' ( f c ) [43,44]. Herein, such a critical frequency was calculated from the intersection of straight lines corresponding to fittings of the frequency-dependent and frequency-independent regions in the BDS spectrum.…”

“…Higher number of micro-capacitors increases the susceptibility of the material to polarization effects with increasing temperature [45,48], causing a decrease in the critical frequency for higher temperatures, as seen in figure 3(a). For frequencies lower than f c , polarization effects are still incipient so the majority of the micro-capacitors may behave like open circuits [42,44,48]. In this sense, it has been reported that MWCNT/PP nanocomposites below the electrical percolation threshold behave as highly polar dielectrics at temperatures below 80 • C, and present dielectric relaxation effects for f > 1 MHz [13].…”

Mono‐filler and bi‐filler composites based on thermoplastic polyurethane, carbon fibers and carbon nanotubes with improved physicomechanical and engineering properties

“…They reported that with the addition of 1 wt% CNT/GNP bifiller, the tensile strength and toughness became 1.9 and 2.9 times those of neat TPU, which was attributed to homogeneously distributed fillers and their unique energy dissipations. Pérez-Aranda et al 27 prepared bi-filler composite films of TPU containing multiwalled CNTs (MWCNTs) and multilayer graphene sheets at a total weight concentration of 5 wt% and investigated their electrical and piezoresistive properties. They reported that the electrical conductivity and pressure sensitivity factor of composites are dominated by the MWCNT network.…”

Giant Piezoresistive Effect of CdS@C Hybrid Nanobelts for Volatile Real-Time Sensor and Erasable Nonvolatile Memory to Stress

“…It can be expected that a strong interface coupling effect can take place between two nanostructures owing to the existence of affluent surface states. , In addition, QDs can form effective trap centers, and the filling of trap level is tunable. Therefore, some novel properties are likely to appear. , For carbon materials, they can generally show superior conductive properties, and furthermore, they can show a PZR effect as well. − Therefore, it is more suitable as a matrix of a hybrid composite structure to build high-performance GPZR materials. For the nanostructure with one-dimension (1D), in addition, it is extremely beneficial to build a single nanostructure-based two-terminal device, and thus, it is very easy for the actual physical mechanism to be well-identified by the simple configuration in comparison with nanostructure assemblies. − Accordingly, it is more appropriate for an individual 1D nanostructure to serve as a building block to directly construct a nanodevice.…”