The influence of ZnO nanoparticles on the dielectric properties of epoxy resin

Abstract

Interesting electrical properties represent the epoxy nanocomposites, because the addition of nanofillers to a pure epoxy resin demonstrate several advantages opposite to pure epoxy resin without nanofillers. In the last 20 years, the dielectric properties (the complex permittivity and dissipation factor) of epoxy nanocomposites had been evaluated and the results clearly show that they are lower than that of base epoxy and microcomposites when insulating oxides were used as the fillers. Nowadays the epoxy and epoxy based composites are preferred insulating materials for many electrical applications. The influence of the various concentrations of ZnO nanoparticles in epoxy resin Vukol 022 on the changes of the complex permittivity and dissipation factor has been measured at the temperature range from 20 °C to 120 °C by a capacitance method in the frequency ranges from 1 mHz to 1 MHz. In this contribution, we present a study of the influence of 1,0 wt.% and 5,0 wt. % concentrations of ZnO nanofillers on the dielectric properties of the epoxy resin. From the frequency dependence of dissipation factor, α-relaxation process and its shift to lower frequencies with ZnO fillers were observed.

Dielectric Responses of Polyurethane/Zinc Oxide Blends for Dry-Type Cast Cold-Curing Resin Transformers

“…For lower frequencies, higher values are observed due to IP. This effect was also observed in other works [ 27 , 54 , 55 ]. In the case of 2.0 wt.% ZnO, the real permittivity is higher than for pure PU for frequencies above 1 Hz.…”

“…From these measurements can be seen that relative permittivity for ZnO filler with concentration 0.5 and 1.0 wt.%, was smaller as for pure PU. Similar observations have been reported for polymer-based nanocomposites [ 27 , 28 , 54 , 56 ]. The decrease of relative permittivity can be attributed to the effect of the interaction zone between the polymer matrix and the nanoparticles.…”

“…The same relaxation modes are observed in other nanocomposites with ZnO filler, not presented here for reasons of brevity. The frequency dependence of complex permittivity and dissipation factor of the PU with different amount of ZnO were presented in work [ 54 ].…”

“…Their positions were dependent on the temperature ( Figure 4 and Figure 6 ) and with increasing temperature, they moved to higher frequencies. On the base of the Cole-Cole model, which is widely used by other authors [ 15 , 27 , 54 , 56 , 57 ], we can determine characteristic parameters of the dielectrics. The parameters in Equation ( 1 ) can be estimated parameters using means of the least-squares techniques to obtain the best fit for dielectric responses of complex permittivities and they are listed in Table 3 only for temperature 80 °C (2.83 ).…”

“… The frequency dependence of ( a ) the real [ 54 ] and ( b ) imaginary parts of the complex permittivity for the PU + 0.5 wt.% ZnO at various temperatures. …”