Temperature dependent dielectric constant/loss investigations in annealed polyetherimide

Temperature dependent dielectric constant/loss behavior has been investigated for annealed Polyetherimide. For investigating the effect of annealing, the samples were kept at desired temperature (100 degrees C) for a predetermined time (varying from 2-10 hrs). The samples were then cooled to room temperature and stored in a desicator. The dielectric constant/loss were measured in the temperature region varying from 30 -250 degrees C using a precision LCZ meter, Keith ley 3321 at different frequencies 120 Hz, 1 kHz, 10 kHz and 100 kHz. A significant decrease in dielectric constant epsilon' in annealed samples below 120 degrees C, is due to the suppression of dipolar relaxation process lying in this temperature region due to annealing. The enhancement in epsilon' above 120 degrees C, is due to the dominance of a-relaxation process. The dielectric behaviour of Polyetherimide in the temperature region below 120 degrees C is mainly governed by the dipolar relaxation processes owing either to ether linkages or to >C=O groups. Annealing has resulted in a loss of dipolar relaxation processes which is further confirmed from the fact that epsilon' varies scarcely with temperature.