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Unformatted text preview: G. Bánhegyi et al.: Estimation of Thermal Acceleration Factors of Ageing Epoxy Insulation using Thermogravimetry 1070-9878/09/$25.00 © 2009 IEEE 1420 Estimation of Thermal Acceleration Factors of Ageing Epoxy Insulation using Thermogravimetry and Intuitive Kinetic Model G. Bánhegyi Polygon Consulting, H-1153, Budapest, Arany János u. 28, Hungary V. Vargha , P. Müller , Budapest University of Technology and Economics, Department of Physical Chemistry and Material Science, Laboratory of Plastics and Rubber Technology, H-1111, Budapest, M ű egyetem rkp. 3., Hungary and E. Zelenyánszki VISOLA Electric Insulation Technology, H-2097 Pilisborosjen ő , Budai út 28, HUNGARY ABSTRACT The long term performance of epoxy resin compounds intended to be applied as electric insulating materials in nuclear equipment has been assessed using an accelerated thermal ageing technique. Conventional Bisphenol-A-diglycidyl ether- and cycloaliphatic epoxy resin-based formulations (both crosslinked by anhydrides) have been compared using dynamic and isothermal thermogravimetry. Tests were performed on both virgin samples and on samples exposed to γ-irradiation. A simple intuitive consecutive thermal decomposition model was suggested and fitted to the isothermal decomposition data. Using the fitted parameters the thermal acceleration factor was established for both kinds of materials. Under practically available thermal conditions radiation ageing had a negligible effect on the decomposition. The Bisphenol-A-diglycidyl ether type material proved to be more stable under thermal ageing conditions. Index Terms - Life estimation, epoxy resins, nuclear radiation effects, numerical analysis. 1 INTRODUCTION 1.1 SCOPE OF THE WORK POLYMERIC insulation materials have been widely used recently in nuclear power plants (NPP). They should maintain their excellent electrical and mechanical properties even under severe service conditions for many decades. The main environmental effects limiting the service time of electric insulating material in an NPP are the simultaneous exposure to increased temperature and γ- irradiation. VISOLA Electric Insulation Technology Ltd. as a manufacturer of nuclear equipments investigated the suitability of epoxy resin compounds, in order to select a reliable candidate for electrical insulation in a new product. It had to be evaluated according to the IEEE 317- 1983 standard . Annex D of the standard describes the method to be used when evaluating thermal acceleration tests using a simple Arrhenius approximation (i.e. assuming a simple rate controlling process described by a single activation energy), but it does not prescribe the experimental method to be used to determine the activation energy. Manuscript received on 27 December 2008, in final form 3 June 2009....
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This note was uploaded on 06/08/2011 for the course ELECTRICAL 124 taught by Professor Ghjk during the Spring '11 term at Institute of Technology.
- Spring '11