Relationship between electric conductivity, thermally stimulated currents, thermoluminescence and polymer structure

In order to study the relation between polymer structure and their d.c. conductivity the measurements of current‐ voltage characteristics, thermally stimulated currents /TSC/ and thermoluminescence /TL/ measurements of poly (ethylene terephthalate) films were carried out. The PET samples were subject to different thermal treatment and deformations (unixial stretching). The degree of crystallinity of the thermally treated films was determined on the basis of density measurements and their supermolecular structure by means of light scattering technique. It was found that PET samples exhibit non ohmic behaviur and different TSC curves depending on crystallinity degree and orientation. The TSC curves analysis allowed establishing of the trap levels energy depth and trap densities. The shallow trap levels energy was also calculated from TL glow curves. The trap depth was correlated with the structure of the investigated specimen. The observed behaviour of PET films in d.c. field and the related phenomena were interpreted in terms of the injected current carrier theory.