Electrical conductivity effects in polyethylene terephthalate films

Abstract

Influence of the relaxation of Maxwell-Wagner-Sillars polarization and dc conductivity on the dielectric behaviors of nylon 1010Electrical conductivity effects in biaxially stretched polyethylene terephthalate ͑PET͒ films of 6 m thickness and 68% degree of crystallinity were investigated by means of dielectric relaxation spectroscopy in the frequency range 10 Ϫ2 -10 6 Hz and at temperatures higher than the glass transition temperature ͑ϳ85°C͒ up to 190°C. The formalisms of complex permittivity, electric modulus, and impedance were employed to analyze the experimental data. The results are discussed in terms of dc conductivity, conductivity current relaxation, interfacial Maxwell-Wagner-Sillars polarization, peak, space-charge polarization, and electrode polarization. They are compared with the predictions of models for the electrical and dielectric properties of ion-conducting polymers. The dc conductivity values determined from dc measurement, from ac conductivity plots and from complex impedance plots agree well with each other. Their temperature dependence is described by the Vogel-Tammann-Fulcher equation and classifies PET as a fragile system.

Evaluation of the dielectric parameters from TSDC spectra: application to polymeric systems

“…8a) and the best fit line to the data It is known that the T g of PET changes from 351 K for the amorphous material to 398 K for the biaxially stretched semi-crystalline material [19,23]. Differential Scanning Calorimetry (DSC) measurements on the same sample showed a broad and weak glass-rubber transition in the range 343-393 K, in agreement with dielectric relaxation spectroscopy (DRS) studies [16,19,24] and the present results. Taking into account these studies, the TSDC spectrum in Fig.…”

“…DRS studies, on the same material and in the same temperature range, have showed that the dielectric peak corresponding to the primary α-relaxation is very broad and can not be described by a single Debye peak [16,19,20]. The fact that the peak in Fig.…”

“…1 were fitted with equation 1 considering that the relaxation time changes with temperature following the VTF equation and using T i as a free parameter. The values obtained for the adjustable parameters are: W = 0.21 eV, A = 0.78 Am -2 and T i = 168 K. The energy barrier is considered quite low for a peak whose maximum is at 316 K. Calculation of low energies seems to be a general behavior when the VTF equation is used [16]. At the same time, T i is 148 degrees below T m .…”

Dielectric measurements in large frequency and temperature ranges of an aromatic polymer

“…The non constant part of the σ ac spectrum at LF/HT shifts towards higher frequencies with increasing the temperature, leading to an increase in the charge carrier mobility. The EP therefore tends to be superimposed on the dc bulk conductivity σ dc [21][22][23][24].…”

The analysis of isothermal current in terms of charge injection or extraction at the metal–dielectric contact

“…To have a proper assignment of the peak we have to recall that the AC dielectric measurements on the same material [15] indicate that the a relaxation appears as a weak and broad peak in imaginary part of the permittivity e 00 at a temperature around 100°C in the Hz-kHz frequency range. At room temperature, the b relaxation in the amorphous phase in observed in the kHz frequency range while the b relaxation in the crystalline phase is just entering at the lower limit of frequency range of 0.01 Hz.…”