Study on Dielectric Behaviors of PMMA during Thermal Aging

During the accelerated thermal aging at various temperature of pure polymethyl methacrylate (PMMA) which was applied as the core material of polymer optical fiber (POP), it was found that the relative permittivity decreased at first and then increased with the aging time increasing. For explaining it, a hypothesis of unification of dipole depolarization and dipole repolarization was proposed. On the basis of relative experimental analysis of infrared spectrogram (IR), refractive index and weight loss rate, both degree of depolarization and degree of repolarization were defined to describe the novel dielectric phenomena quantificationally