A series of poly(ethvlene terephfhalate) (PET) films with different degrees of planar orien-tation [△(xy)z]

crystallinity and molecular weight were obtained by biaxial stretching

annealing and γ-irradiation on respectively. In oriented PET electrets

the mean depth of trap level was increased with increasing of △(xy)z and the ability to trap charge carriers was raised in the structural traps formed from orientation. 60Co γ-iiradiation of a large dose (0.5-5 MGy) led to the breaking of macromolecular chain and the increasing of group density of benzyl with oxygen. Though the mean depth of trap level was deepened

the ability of detrapp-ing change carriers was increased for γ-irradiated PET electrets. Crystallization by annealing made the depth of trap level deep too

but the ability to trap charge carriers showed a maximum at crystallinity of 20%. The three kinds of trap models were proposed corresponing to the three methods of sample treatment on the basis of the depth of trap level

the current maximum of detrapping charge carriers and the initial density of charge carriers.