Temperature dependence of the electrical properties of the carbon nanotube/polymer composites

Abstract

Abstract. In this paper, pristine and oxidized multi-walled carbon nanotube (MWCNT)/poly(vinylidene fluoride) (PVDF) composites were prepared and the temperature dependence of some electrical properties of these composites were studied. It is found that the transition temperature (Tt), from positive temperature coefficient (PTC) to negative temperature coefficient (NTC) effect, of the oxidized MWCNT/PVDF composites shifted to a higher temperature. The shift of the Tt of the oxidized MWCNT/PVDF composites can be attributed to the chemical functionalization of the MWCNTs. The dielectric constants of these composites are enhanced remarkably, which can be understood by the interfacial polarization effect. The largest dielectric constant of 3600 is obtained in the composite with about 8 vol% oxidized MWCNTs at 1 kHz. The dielectric constants of these composites increase firstly and then decrease with increasing temperature. However, when the temperature reaches a higher value, the dielectric constants increase again with increasing temperature. The 'wave' phenomenon of the temperature dependence of the dielectric constants can be understood by the temperature dependence of the interfacial polarization.

Drastic modification of the piezoresistive behavior of polymer nanocomposites by using conductive polymer coatings

“…This behavior has been explained by the rearrangement of the percolated network that results in an increased number of interconnections. Alternatively, the increasing thermal energy may facilitate a conduction potential barrier jump [18]. PC is a polymer with T g = 420 K; the NTC behavior of CNT/PC observed in our experiments is thus consistent with the literature.…”

“…It is accepted that the main mechanism leading to resistance change with temperature is the modification of the tunneling distance caused by a mismatch in the coefficients of thermal expansion among the constituents [17,18,19,20]. The results for our M A N U S C R I P T…”

Electrically conducting polymer nanostructures confined in anodized aluminum oxide templates (AAO)

“…Moreover, in semicrystalline polymers, the volume expansion of the polymer matrix which separates the fillers is also attributed to the transformation of the crystalline phase to the amorphous phase. These results agree with others reported in the literature [50]. For instance Tao et al [51] also reported a decrease in conductivity with temperature for a composite of MWCNTs and polyethylene at higher temperatures (T > T m ) and was related to the phenomena of crystallization of polyethylene which would disconnect the conductive paths [51].…”

“…Other authors [40,52] also observed a continuous increase of conductivity with temperature below T m (positive temperature coefficient effect of the resistivity). Moreover, an effect similar was reported by Li et al [50] below a transition temperature of 80°C. This effect was explained by the fact that at higher temperatures (T > T m ), Brownian motion of the carbon nanotubes make them mobile within the melting matrix and they tend to coagulate which results in an decrease of the electrical conductivity of the composite with temperature.…”

Study of low weight percentage filler on dielectric properties of MCWNT-epoxy nanocomposites

“…The dielectric constant increases again. 39 There are two mechanisms of electrical conduction. One is when the conductors in composites connect with each other to form conductive routes, and the other is that the conductors in composites do not connect with each other, but their distances are so small that the electrons can be transmitted through electron tunnels formed among conductors nearby.…”