Jk. Quamara et al., THERMALLY STIMULATED POLARIZATION CURRENTS IN POLY (P-HYDROXYBENZOIC ACID-CO-ETHYLENE TEREPHTHALATE), LIQUID-CRYSTAL POLYMER, Indian Journal of Pure & Applied Physics, 36(7), 1998, pp. 374-379
Thermally stimulated polarization currents (TSPC) in various samples o
f poly{p-hydroxybenzoic acid-co-ethylene terephthalate (PET/x PHB)} wi
th different values of x (molar concentration) have been investigated
in the temperature range (30 - 250 degrees C) under polarizing fields
in the range 6.6 - 133 kV/cm. The low temperature region of TSPC spect
ra exhibits a peak (a-relaxation) between 40 and 65 degrees C dependin
g on x. This peak has been attributed to polar nature of both PET and
PHB, confirmed by the activation energy values (0.14-0.3eV) estimated
using initial rise method. A phenomenal rise of several orders of magn
itude in the current after a-relaxation seems to be dominated by condu
cted currents followed by a peak P-2(termed delta-relaxation) in the t
emperature range 160 degrees-210 degrees C. This peak may be ascribed
to die melting crystals, i.e. movement of large segments characterizin
g a smectic-E like phase. The activation energy values (0.14-0.03 eV)
computed from the spectra are consistent with the ones estimated from
side group orientation method. The calculated values of dielectric con
stant at different temperatures are in good agreement with the results
obtained by other methods.