Evaluation of the dielectric parameters from TSDC spectra: application to polymeric systems

The Thermally Stimulated Discharge Current (TSDC) technique is widely used for the study of main and secondary dielectric relaxations in polymers. The TSD current is described by different equations that can be arranged in a unique three-parameters (the activation energy W, A and B) general form. Th e physical meaning of A and B depends on the origin of the discharge curren ts. In this paper a method is proposed to obtain these parameters by fittin g the experimental data with the analytical expression of the current, in t he range around the maximum. Simulations were carried out to underline the relative importance of the parameters. A method is proposed for the decompo sition of experimentally determined complex bands into a limited number of elementary peaks, each of them characterized by average values for W and B. The errors resulting from different approximations used in the analytical current expression or by the utilization of various expressions for the rel axation time are analyzed. The method is applied for the analysis of the TS DC spectra in the glass-rubber transition temperature regions of PET and PM MA, yielding several peaks characterized by narrow distributions of W (Delt aW approximate to +/- 0.06 eV).