Studies on Trapping Phenomena of PEN γ-Irradiated at High Doses

The γ-irradiation effect on the structure of molecular chains and supermolecular structure of polyethylene naphthalate (PEN) was investigated. The tolal dose was ranged over 500Mrad. No γ-irradiation induced crystallization was observed in the amorphous PEN, while the crystallinity of biaxial stretched one decreases with increment of doses.
The weight average and number average moleculer weight determination indicated the degradation of molecular chains at dose below 400Mrad. Further increment of MW images molecular rearrangment strenghting of intermolecular action at higher doses.
It was observed that the mean trap level obtained by means of short-circuit Thermally Stimulated Current measurements at two heating rates, considerably sensitive to γ-irradiation. Experimental results clearly show that the degradation of molecular chains causes shallowing of trap levels, while factors strenghting the intermolecular action including increment of relative content of crystalline region and closslinking provide deeper one.