Molecular processes in polymer electrets

The nature and origin of molecular motions in macromolecular polar and nonpolar polymers which can affect the operation of electrets, are dependent on their morphology including crystallinity. A qualitative theory of polymer chain dynamics is provided by the reptation model in which a polymer chain moves in a snake-like motion parallel to its own contour. Molecular motions in amorphous polymers are more well defined than those in crystalline polymers. In contrast to mechanical relaxation theories, the dielectric relaxation models are quite empirical, except in the Debye case. In addition to dipolar rotations, space charge relaxations can appear in all amorphous and semicrystalline polymers, and can be detected mostly by electrical studies. (C) 2001 Elsevier Science B.V. All rights reserved.