ELECTRICAL-PROPERTIES OF POLY(BUTYLENE TEREPHTHALATE)

Direct current (dc) and alternating current (ac) electrical properties of semicrystalline poly(butylene terephthalate) (PBT) are investigated as a function of temperature and frequency. Dc electrical conductivity measurements have been performed over the temperature range -75-degrees-C to 130-degrees-C and point out an essentially ionic mechanism of charge transport. Charge carriers are identified in protons supplied by ionization of carboxyl end-groups after dissociation of the existing hydrogen bonds. Dielectric constant and loss factor have been measured over the temperature range -100-degrees-C to 130-degrees-C and over the frequency range 10(-6) to 10(6) Hz. Together with dc measurements, they allow the detection of the alpha-glass-rubber and the beta-subglass relaxation processes, as well as an interfacial polarization of the Maxwell-Wagner-Sillars type. Finally, the contour map of loss factor, summarizing the overall dielectric behavior of the polymer, is reported and discussed for electrical applications of PBT.