Analysis of thermally stimulated current and effect of rubbery annealing around glass-rubber transition temperature in polyethylene terephthalate

Thermally stimulated currents (TSC) in amorphous polyethylene terephthalate films have been investigated in the temperature range of - 180 to 140degreesC. This material shows a very weak intensity peak at approximately -95degreesC and another around 80degreesC originated from dipolar process (a-peak), as evidenced from the variation of polarizing conditions such as applied electric field and polarizing time. The effect of isochronal rubbery annealing starts to appear from a temperature of annealing of 90degreesC, it then appears in a TSC spectrum two components around 88 and 108degreesC allotted. respectively to the true and rigid amorphous phases. The first component tends to disappear in an irreversible way to the detriment of the second which implies the establishment of an order within material during annealing by the formation and growth of nodules. The thermostimulated currents technique allowed to calculate with good precision the activation parameters of each process as well as the evaluation of the crystallinity rate by an established empirical formula. (C) 2003 Elsevier B.V. All rights reserved.