## Electronic Theses and Dissertations

1993

Dissertation

Ph.D.

#### Department

Electrical and Computer Engineering

Raju, G. R. Govinda,

#### Keywords

Engineering, Electronics and Electrical.

CC BY-NC-ND 4.0

#### Abstract

This dissertation deals with the studies of charge storage and decay in aromatic and composite polyamide materials for the first time, along with an extended study of the conduction currents in Teflon (PTFE) at higher ranges of applied electric fields and 2 temperatures, where the data obtained fills the gap in the published literature. Different experimental techniques are employed to identify the mechanisms responsible for conduction currents, charge storage, and decay in aromatic and composite polyamides. The insulating materials tested during the course of this dissertation are chosen because of their engineering importance and lack of published literature on them. Several studies reported in this dissertation on these materials are believed to have been carried out for the first time. The results of the conduction current in Teflon (PTFE) indicated that the ionic space charge mechanism is operative at temperatures $\leq$120$\sp\circ$C, while electronic space charge at temperatures $>$120$\sp\circ$C. The low frequency dielectric loss factor in aramid paper shows two relaxation peaks due to dipolar reorientation at T $\leq$ 190$\sp\circ$C, and no relaxation peak at T = 200$\sp\circ$C suggesting an interfacial polarization mechanism. A relaxation time of 6.3 $\times$ 10$\sp{\rm 4}$ s at room temperature with an activation energy of 0.84 eV was obtained from the thermally stimulated polarization (TSP) current in aramid paper with total polarization of 1.73 $\mu$Cm$\sp{-2}$ at a heating rate of 2 Kmin$\sp{-1}$. The X-ray diffraction results show an improvement in the polymer crystallization when exposed to higher annealing temperature of 300$\sp\circ$C. The results of the low frequency dielectric loss factor in composite polyamide shows one broad relaxation peak at T $\leq$ 103$\sp\circ$C which is due to the dipolar polarization, while for T $\ge$ 140 no relaxation frequency was observed and the low frequency loss factor increases rapidly with decreasing frequency suggesting an interfacial polarization mechanism. The Pool-Frenkel and ionic hopping mechanisms were responsible for the conduction current in composite polyamide. The thermally stimulated depolarization (TSD) current results show that the fast dipoles are oriented at lower poling temperature while slow dipoles are at higher poling temperatures. The windowing polarization result shows that the distribution of the relaxation time of the dipolar process for T $\le$ 130$\sp\circ$C is thermally activated with activation energies in the range of 1.01 to 1.55 eV in the temperature range of 70 to 130$\sp\circ$C. (Abstract shortened by UMI.)Dept. of Electrical and Computer Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1993 .S888. Source: Dissertation Abstracts International, Volume: 54-09, Section: B, page: 4854. Adviser: G. R. Govinda Raju. Thesis (Ph.D.)--University of Windsor (Canada), 1993.

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