الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Dielectric properties study, covering wide frequency range, has been used for studying the reorientational motions of molecules in polymeric materials. The dielectric properties study of the cross-linked hydroxyl-terminated poly tetrahydrofuran , HO-PTHF-OH, indicates that the dielectric constant decreases with increasing the applied frequency due to the dielectric dispersion, however, the ε increases with the temperature at all frequencies due to a decrease in enviromental effects. Also the result show that , the dielectric constant decreases with an increase in the cross-linking density due to a decrease in the mobility of segments.The dielectric loss, increases with increasing the temperatuer for most investigated samples due to the increase in the activity activity of space charges. With an increase in frequency, the dielectric loss ε , displays maximum that is representative of the σ-relaxation . from these maxima, the relaxation times, the activation energy, and the enthalpy of relaxation for all samples were calculated. As would be expected, The swelling behaviour of samples in dibutylphthalate shows that the volume fraction of swollen samples υ2 is dependent on the cross-linking density.