ABSTRACT
Abstract Thermally stimulated depolarization current (TSDC) technique has been recognized as a most suitable investigative tool in the realm of dielectric spectroscopy for polymeric materials. The technique provides a deep insight into the molecular dynamics associated with the different relaxation processes. In the present paper we discuss the various dielectric relaxation processes investigated in polyetherimide, a well-known member of high performance polyimide family, using this technique. The samples were polarized at various polarizing fields (Ep: 23-341 kV/cm) and polarizing temperatures Tp varying from 290 K to 573 K. The TSD currents were recorded at a linear heating rate of 2 K/min. The TSDC spectra consist of four current maxima namely γ,β,α and ρ appearing around 313 K, 383 K, 473 K and 503 K, respectively. The origin of γ - and β-peaks has been attributed to the dipolar nature of ether linkages and carbonyl groups respectively, whereas α-and ρ-maxima have been attributed to the space charge polarization process. However, in certain cases, we observe merging of β-and α-relaxation processes to become the αβ-relaxation process appearing around 413-453 K. The observed dependence of the peak temperature Tm on polarizing temperature Tp and polarizing time tp indicates a continuous distribution of relaxations. The various relaxation parameters and activation energy for different relaxations have been calculated.
