Space charge, conduction and photoluminescence measurements in gamma irradiated poly (ethylene-2,6-naphthalate)

• We investigate space charge build up in irradiated PEN under high DC electric field.
• We show the increase in conductivity and charge storage after irradiation.
• Mild chemical ageing occurs for irradiation dose up to 1 MGy.
• We conclude on the high radiation resistance of the dielectric properties of PEN films.

Polyethylene naphthalate (PEN) thin films were subjected to gamma rays at different doses and changes in both the dielectric and photophysical properties were investigated. Samples were irradiated in air at room temperature by means of a 60Co gamma source at a dose rate of approximately 31 Gy/min. Total doses of 650 kGy (344 h) and 1023 kGy (550 h) were adopted in this work. The space charge profiles and residual electric field of virgin material and material exposed to these representative doses, obtained after 30 min of depolarization following field application in the range 40–200 kV/mm, have been examined by Focused Laser-Intensity Modulation Method (FLIMM). The dependence of space charge density with electric field values and irradiation dose is analyzed. Under high DC voltages and after irradiation, PEN tends to accumulate space charge. Space charge versus electric field and current-field characteristics issued from FLIMM method and conduction measurements exhibit good agreement. The high radiation resistance of PEN film is highlighted.