Effect of Gamma Irradiation Dose on Space Charge in e-Beam Irradiated PET Films

Investigating radiation-induced effects in synthetic polymers makes sense for nuclear power and aerospace industries. We propose in this work to investigate the effect of the dose pre-deposited by gamma rays on the behavior of the charges implanted by electron beam in PET (polyethylene terephthalate) samples. The samples used in this study are PET films of 25 μm in thickness. The samples were first irradiated by gamma rays, at different doses (0.1 to 2 MGy). Then, they were exposed to 20 keV energy electron beam, during 5 min, with the purpose to implant electrons near the surface. Materials were characterized by different techniques, notably Light Intensity Modulation Method (LIMM) for space charge measurements and FTIR as physicochemical analysis. The results show that the electrons implanted in the PET irradiated at high dose do not stay close to the surface for a long time, which could be associated with significant material modifications at the scale of the molecules.