* Electrical properties: Dk, Df, volume resistivity
(p), and surface resistivity (pS)
It is said to be a reliable electrical insulator with volume resistivity
of more than 1014 ohm-cm and dielectric constant of 3.85 at 60 Hz.
The average volume resistivity
([ohm] x cm) of a sample size of 15 g, 10 sets, was measured.
Figure 1 shows the volume resistivity
in two different resin systems at various loadings of the single wdl carbon nanotubes.
Finally, we present conventional volume resistivity
measurements in the same temperature range, with the recognition that nano-dopants, microscopic structure, and environmental conditions contributed to the unique physical properties of these material systems.
The higher mold temperature can reduce the temperature gradient of the sample in the cooling process, which is conducive to the dispersion of conductive filler particles; facilitate the formation of conductive network, to reduce the volume resistivity
of the composite material.
Additionally, the electrical resistivities and respective sensitivities to variations of the applied pressure were evaluated for all obtained samples, with help of standard volume resistivity
measurements and electromechanical tests [27, 28].
In all cases, after having verified the achievement of a satisfactory dispersion of the filler in the host PBT matrix by morphological observations, effects related to filler content and type of applied particle functionalization on dielectric parameters of products such as volume resistivity
, permittivity, and dissipation factor evaluated at room temperature have been reported and discussed invoking the previous mentioned approaches.
The volume resistivity
([OMEGA] cm) of the sheets was measured by four-point probe (labsysstc-400, Nextron) using Ohm's law and a correction factor at room temperature .
The surface morphology was observed by scanning electron microscopy (SEM, S-4700 I, Hitachi, Japan) and the volume resistivity
determined from data by 4-point probe (2400-C SourceMeter, Keithley, USA) and [alpha]-step measurements.
As a dielectric material, polyimide has a few advantages over FR-4, higher dielectric strength and volume resistivity
. The dielectric strength is a measure of the electrical performance of a material as an insulator.