UNCORRECTED PROOF 2 Synergistic effects of EB irradiation and heat on EVA 3 electrical insulators 4 S. Jipa a,b , T. Zaharescu b, * , M. Ma ˇrcut ßa ˇ c , R. Setnescu a , 5 L.M. Gorghiu a , C. Dumitrescu a 6 a ‘‘Valachia’’ University of Ta ˆrgovis ßte, Faculty of Sciences, 1 Carol I Av., Ta ˆrgovis ßte, Romania 7 b Advanced Research Institute for Electrical Engineering, 313 Splaiul Unirii, Bucharest 030138, Romania 8 c ICPE ELECTROSTATICA, 313 Splaiul Unirii, Bucharest 030138, Romania Available online 10 Abstract 11 Radiation/thermaldegradationisdiscussedasasuccessfulendurancecheck.EVAsamplesweresubjectedtoelectron 12 beam irradiation at 12, 30, 60 and 90 kGy. Heat treatment was performed in air at 120 °Cfor72hand120h.Chemi- 13 luminescence(CL)investigationsonEVAspecimenswerecarriedoutat200,210and220 °C.Severalkineticparameters 14 such as oxidation induction time (t i ), half-oxidation time (t 1/2 ), maximum oxidation rate (v max ox ), maximum time of ther- 15 mal oxidation (t max ) and other chemiluminescence features were obtained from the time dependencies of the CL inten- 16 sity. While the ageing factors of processed EVA samples reveal a constant value for two testing temperatures (200 and 17 210 °C), the co-operative factors that describe a combined (synergistic) degradation present higher than unity values, 18 eitherfortheoxidationratesorforthemaximumCLintensitymeasuredforallirradiationdoses.Theyincreaselinearly 19 with dose. 20 Ó 2005 Published by Elsevier B.V. 21 PACS: 61.82.Pv; 68.60.Dv 22 Keywords: Ethylene–vinyl acetate; Thermal degradation; Gamma irradiation; Chemiluminescence 23 24 1. Introduction 25 The commercial and scientific interest in study- 26 ing polymer systems with desirable applications 27 has led to significant information in the field of 28 electrical insulators as several papers have proved 29 [1–8]. The service time of any equipment depends 0168-583X/$ - see front matter Ó 2005 Published by Elsevier B.V. doi:10.1016/j.nimb.2005.04.044 * Corresponding author. Tel.: +40 21 346 7231; fax: +40 21 346 8299. E-mail addresses: zaharescut@icpe-ca.ro, zaharescut@gw- chimie-math.unibuc.ro (T. Zaharescu). Nuclear Instruments and Methods in Physics Research B xxx (2005) xxx–xxx www.elsevier.com/locate/nimb NIMB 51020 No. of Pages 8, DTD = 5.0.1 21 April 2005 Disk Used ARTICLE IN PRESS