Gamma-irradiation would change the physical and mechanical properties of polymer. Discoloration is a problem in the radiation processing of polymers.
After γ-irradiation, the transmittance of poly(4-methyl-1-pentene) (TPX) decreases monotonically with increasing time. The cutoff wavelength moves to right side direction as time increases. The optical absorption of irradiated TPX follows a first-order kinetic process. The activation energy was slightly increased with the increase of dosage. Besides, the DSC measurement shows that the melting temperature (Tm) decreases with increasing dosages.
Crack can heal above the glass transition temperature (Tg). However, when it reaches a critical temperature, instead of crack healing, it will grow to cylindrical void. The spherical defect will grow to a spherical void above a critical temperature. We find that when the polycarbonate is annealed above 177℃, the voids will grow. But a period later, some voids will shrink and the final size is approached to the original size. And some voids will combine with the other voids and final disappear. This is possible due to the rotation and movement of polymer chains above Tg.

Gamma-irradiation would change the physical and mechanical properties of polymer. Discoloration is a problem in the radiation processing of polymers.
After γ-irradiation, the transmittance of poly(4-methyl-1-pentene) (TPX) decreases monotonically with increasing time. The cutoff wavelength moves to right side direction as time increases. The optical absorption of irradiated TPX follows a first-order kinetic process. The activation energy was slightly increased with the increase of dosage. Besides, the DSC measurement shows that the melting temperature (Tm) decreases with increasing dosages.
Crack can heal above the glass transition temperature (Tg). However, when it reaches a critical temperature, instead of crack healing, it will grow to cylindrical void. The spherical defect will grow to a spherical void above a critical temperature. We find that when the polycarbonate is annealed above 177℃, the voids will grow. But a period later, some voids will shrink and the final size is approached to the original size. And some voids will combine with the other voids and final disappear. This is possible due to the rotation and movement of polymer chains above Tg.

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