Time-Dependent Charging Current Study in Polyimide Film

Abstract

This article investigates charging current behavior of thermoplastic heat-resistant polyimide (PI) sample under electric fields from 25 to 200 kV/cm, at different temperatures. The charging current was recorded as a function of time in 25 µm PI thin film supplied by DuPont India Limited. The PI has different aromatic structures and various hinge-type groups in polymer macromolecules due to which, charging current was found to decay faster at shorter times whereas it shows slower decay at longer times. These characteristics agree with the Curie—Von Schweidner law. The charging current versus polarizing temperature curves at constant time is generally characterized by a broad peak. The appearance of this peak at certain charging conditions is correlated with the dipolar peak observed in thermally stimulated discharge current thermograms. The log Ic versus electric field curve suggests that electronic conduction has occurred due to the field assisted electron hopping.