Comparative study of mechanical and electrical relaxations in poly(etherimide). Part 1

Abstract

: Relaxations in poly(etherimide) PEI Ultem 1000 have been analysed by di †erential scanning calorimetry (DSC), dynamic mechanical spectroscopy (DMS), dielectric relaxation spectroscopy (DRS) and thermally stimulated depolarization current (TSDC) measurements. DMTA and DRS results show three distinct relaxations c, b and a in the temperature range [140 to 250¡C. The Ðrst one depends strongly on the water content in the sample as will be discussed in more detail in the second paper of this series. These results are in good agreement with those observed by TSDC of conventionally polarized electrets. In addition to these three relaxations, TSDC measurements show : (1) a peak (o) at which is attributed to space charge temperatures above the a relaxation, (2) indications of structure in the b relaxation zone. In the case of electrets formed by the windowing polarization method, the resulting TSDC spectra allow us to discern the Ðne structure of the b relaxation, which is formed by three subrelaxations. In this work, the activation energies calculated by the di †erent techniques are compared, and a molecular origin for each relaxation is proposed.1998 SCI. Polym. Int. 46, 11È19 (1998)

Heating Effects on Structural and Electrical Properties of Polyetherimide

“…Studies on the effects of these parameters could give information on material reliability. Numerous investigations on PEI properties have been made by researchers [1][2][3][4][5][6][7][8][9] . The relaxational behaviour of this material is one of the researched topics.…”

“…6. Each spectrum shows two peaks assigned to dipolar relaxations [5,6] . The first one is around 70°C ( 2 ) and the second one with a higher intensity appears at about 170°C ( 1 ).…”

“…The relaxational behaviour of this material is one of the researched topics. Belana et al [5] have shown different relaxations in PEI related to dipole motions, which are identified as , β and α relaxations. The influence of gamma irradiation on charge relaxations in PEI has been presented in a previous research [7] .…”

Study of relaxations in epoxy polymer by thermally stimulated depolarization current (TSDC) and dielectric relaxation spectroscopy (DRS)

“…The Vogel temperature T 0 has been found in many polymers to be in the range of about 50 K below T g [2,6,29,30], which is approximately the case of the epoxy resin studied here.…”

“…0925 Dielectric relaxation spectroscopy (DRS) and thermally stimulated depolarization currents (TSDC) are two complementary techniques which are often used to reach a most complete knowledge of the relaxation and conduction mechanisms. By coupling these two techniques many works have been carried out to study dielectric relaxations in different materials [2][3][4][5][6][7].…”