ANALIZA CONDUCTIVITĂȚII ELECTRICE A NANOCOMPOZITELOR PVC-TiO2 PRIN SPECTROSCOPIE DIELECTRICĂ

Abstract

Electrical conductivity of polyvinyl chloride (PVC) and of PVC-TiO2 nanocomposites with TiO2 nanoparticle concentration of 5% was analyzed by dielectric spectroscopy in the frequency range 10^-2 – 10^6 Hz, and for three different temperatures: 310, 320 and 340 K. Frequency variation of the imaginary part of the complex permittivity was analyzed with Havriliak-Negami (HN) model. Temperature influence on this variation was used to determine the activation energy of electric conduction in the studied materials. Frequency variation of the real part of the complex permittivity was analyzed, as well, and the temperature influence on DC conductivity (σDC) and AC conductivity (σAC) was discussed in the paper. The obtained results emphasize an important temperature influence on the dielectric response and, consequently, on the electrical conductivity, especially at low frequencies up to 10^2 Hz, for both PVC and PVC-TiO2 nanocomposites. Thus, at low frequencies in the range 10^-2 – 10^2 Hz, high frequency variations of the imaginary part of the complex permittivity can be noticed, which indicate important charge movements through the polymeric material under electric field. The increase of the temperature leads to an increase of the DC conductivity values, and to an increase of the frequency threshold up to which a frequency independent electrical conduction can be observed. The study presented in this paper shows that the dielectric spectroscopy is a performant tool that allows, besides the highlighting of dielectric relaxations corresponding to the different polarization types from polymeric materials, also to characterize these materials from the point of view of electric conduction. Thus, by dielectric spectroscopy, the electrical insulating materials from the insulations of power cables and electrical machines can be analyzed in a large range of frequencies and temperatures, which allows the understanding of the behavior of these materials in different operating conditions.