Open AccessInverse effect in simultaneous thermal and radiation aging of EVA insulation
Author(s) -
G. Przybytniak,
Jacek Boguski,
V. Plaček,
Luca Verardi,
Davide Fabiani,
Erik Linde,
Ulf W. Gedde
Publication year - 2015
Publication title -
express polymer letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.695
H-Index - 72
ISSN - 1788-618X
DOI - 10.3144/expresspolymlett.2015.36
Subject(s) - materials science , inverse , composite material , radiation , thermal , polymer science , thermodynamics , mathematics , optics , physics , geometry
Poly(ethylene-co-vinyl acetate) (EVA) insulation of the cable applied in nuclear power plants was accelerated aged by gamma-rays at two various temperatures, namely 55 and 85°C. Radiation degradation in the dose range of 0–1500 kGy was monitored using a Differential Scanning Calorimetry method by measuring oxidative induction temperature (OITp), gel fraction, mechanical and electrical tests. It was confirmed that a dose rate effect in the range of 420–1500 Gy/h was negligible whereas progress of degradation with increasing dose was strongly temperature dependent. For the insulation accelerated aged at 85°C the OITp and permittivity measurements confirmed lower degradation than for the specimens radiation treated at 55°C at the same dose rates. It was postulated that an inverse thermal effect resulted from radiation induced cross-linking facilitated by melting of EVA crystallites at 85°C