02_agedpoly - IEEE Transactions on Dielectrics and...

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IEEE Transactions on Dielectrics and Elecbical Insulation Vol. 9, No. 4; August 2002 507 Dielectric Behavior of Aged Polyethylene Under UV Radiation ._ E. L. Leguenza, P. C. N. Scarpal LACTEC - COPEL/UFPR P.O. Box 19067, Curitiba-PR, 81531-970, Brazil and D. K. Das-Guptal School of Electronic Engineering and Computer Systems University of Wales, Bangor, Bangor, Gwynedd, LL57 lUT, UK ABSTRACT The present paper reports the results of a study of dielectric aging of low-density polyethylene (LDPE) hy W radiation. The extruded polymer contained carbon black particles, approximately 3% in weight. The aging studies were made for poly- mer without and with carbon black. LDPE flat specimens were aged under W ra- diation for up to 300 h, resorting to dielectric spectroscopy measurements in the frequency range from lo-' Hz lo5 Hz. The dielectric susceptibility behaviors indicate the presence of relaxation peaks obeying the asymptotic forms of Dissado and Hill susceptibility functions. As the aging progresses, Quasi-DC iQDC) and flat loss processes may be observed in the low frequency range, for the LDPE speci- mens without and with carbon black, respectively. In addition, dielectric spec- troscopy results have been compared with other results obtained with additional techniques such as Fourier transform infrared spectroscopy (ETIR) and scanning electronic microscopy (SEM). 1 INTRODUCTION OLYETHYLENE has been used as an electrical in- to its excellent electrical properties. Polyethylene filled with carbon black (CB) is an expensive material, which has found applications in UV protection and current lim- iting devices. The electrical conductivity and the anti-static properties of such typical composites have been studied in the past. However, very little work has been reported on dielectric properties of these materials [1,2]. Furthermore, it is known that on subjecting a polymer to UV radiation -C-C- and -C-H bonding breakage may occur [31. In both cases former case chain-end radicals may be pro- duced in the presence of oxygen, this phenomenon involve two competitive processes: (1) polymer and hydrogen radi- cals formation and (2) formation of cross-linking which can also occur in the absence of oxygen As a consequence, changes in the dielectric properties are expected with ag- ing time for UV radiated LDPE samples both with and without CB [3]. The present paper reports a comprehensive study of the P sulating material for almost three decades, mainly due 'Ill memoriam. Maomdpr recerwd on 7 January 2002, in find form 28 Febmav 2002 dielectric behavior of polyethylene with and without car- bon black aged under UV radiation for up to 300 h. The dielectric spectroscopy over a wide range of frequencies (lo-' Hz Hz) was carried out. In addition, these results have been compared with techniques such as: Fourier transform infrared spectroscopy (F'TIR) and scan- ning electron microscopy (SEMI.
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This note was uploaded on 06/11/2011 for the course ELECTRICAL 124 taught by Professor Ghjk during the Spring '11 term at Institute of Technology.

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02_agedpoly - IEEE Transactions on Dielectrics and...

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