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Thermally stimulated depolarization current studies of the α-relaxation in poly(methyl methacrylate)-poly(vinyl chloride) blends and its relation to compensation laws

2000; Institute of Physics; Volume: 33; Issue: 17 Linguagem: Inglês

10.1088/0022-3727/33/17/304

1361-6463

M. D. Migahed, M. T. Ahmed, A. E. Kotp,

Photochemistry and Electron Transfer Studies

The dipolar relaxation in PVC, PMMA and their blends has been studied using the thermally stimulated depolarization current (TSDC) technique. The peak cleaning method was used. The peak associated with the glass transition temperature (α-relaxation) was obtained, the maximum temperature of which depends on the blend composition. Modification of the TSDC theory with dipole-dipole interaction effects and a relaxation time model obeying the Vogel-Fulcher-Tammann (VFT) law was carried out. Peak parameters such as the apparent activation energy (E), pre-exponential factor (τ0) and dipole-dipole interaction strength (q) were obtained. These characterize the dipolar relaxation process using Arrhenius and VFT temperature dependence for the relaxation time. Physically realistic peak parameter values were achieved when the VFT relaxation time was used. Linearity was found to exist between the activation energy and the logarithm of the pre-exponential factor and between the activation enthalpy and activation entropy of the α-relaxations, confirming the validity of the compensation laws.