Effects of UV radiation on the charge trapping capability of PET

• Published in: arXiv.org
• Main Authors: Cañadas, J C, Diego, J A, Mudarra, M, Parsa, S E, Sellarès, J
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 19.09.2018
• Subjects: Activation energy; Charge materials; Depolarization; Dielectrics; Electric fields; Energy distribution; Irradiation; Physics - Materials Science; Polyethylene terephthalate; Space charge; Trapping; Ultraviolet radiation
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1809.07129

Poly(ethylene terephthalate) (PET), as most dielectric materials, is able to retain space charge in traps. This allows the material to attain an almost-permanent polarization when space charge is displaced by an external electric field or it is injected from an electrode. We have studied the influence of UV irradiation on the charge trapping capability of PET in samples exposed for different periods of time, up to 10 weeks. The pulsed electro-acoustic technique (PEA) has been used to determine the charge profile. The injected charge that the material is able to retain on the irradiated surface increases with irradiation time. This indicates the formation of new traps. An extensive characterization of these localized states has been performed by thermally stimulated depolarization currents (TSDC) technique. Parameters of charge relaxation kinetics have been obtained fitting spectra of the \(\rho_c\) peak, related to injected charge, to the general order kinetics model. A relaxation map analysis shows that relaxation times become more distributed and the activation energy decreases as irradiation time is increased. The activation energy decreases approximately by 10% after 10 weeks of exposition. These results show that UV irradiation creates additional traps on the treated surface, which agrees with PEA results, and that these traps are shallower and their energy depth distribution is wider than in the case of pre-existing traps.