The omission of Modaflow moves the dipole relaxation to higher frequencies and produces a broadening of the relaxation reflected in an increase in the distribution parameter (Table 4).
4c, 4d) show clearly the space charge and dipole relaxation features.
A shift of the dipole relaxation to lower frequency is indicative of the dipole reorientation process being slowed down and the [T.sub.g] of the material being increased.
Plots of the variation of the dipole relaxation peaks against reciprocal temperature yield an activation energy of 173 kJ [mol.sup.-1] which is lower than that for the unpigmented resin and indicates that the ability for the dipole relaxation to occur is slightly easier than in the unfilled cured matrix.
The imaginary modulus at the highest temperature shows clear evidence of multiple relaxation features; a dipole relaxation plus space charge being clearly evident.
A relationship between the shrinkage mechanism and the dipole relaxation was proposed.
A lower [I.sub.m] signifies fewer dipole relaxations during the discharge, which may be due to the higher crystallinity of the bottles manufactured at the higher blowing and heat-set temperatures.
where [DELTA][E.sub.a], [k.sub.B], h, and R are activation energy for dipole relaxation
, Boltzmann constant, Planck's constant and gas constant, respectively.
The unfilled polyester--epoxy resin system exhibits a simple TSD profile indicative of a combination of space charge and dipole relaxation processes.
The observed two [T.sub.g] peaks correspond to the onset of dipole relaxation in the less restricted and more restricted regions.
This plot yields an activation energy of 222 kJ [mol.sub.-1], which is consistent with the dipole relaxation being associated with a cooperative relaxation of the polymer chain designated the [T.sub.g].
Thus, the time-dependent loss of dipole orientations upon removal of the electric field is defined by dipole relaxation
. In this context, this is a great interest concerning the fundamental aspects of dielectric spectroscopy of polyimide materials (19), (20) for knowledge of various molecular motions and relaxation processes, and also the applicability domain in electronic interconnected devices, optoelectronic switches, printed board circuitry, etc.