05_poly_nano - IEEE Transactions on Dielectrics and Electrical Insulation Vol 12 No 4 August 2005 629 Polymer Nanocomposite Dielectrics The Role of

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IEEE Transactions on Dielectrics and Electrical Insulation Vol. 12, No. 4; August 2005 1070-9878/05/$20.00 © 2005 IEEE 629 Polymer Nanocomposite Dielectrics – The Role of the Interface M. Roy, J.K. Nelson, R.K. MacCrone, L.S. Schadler Rensselaer Polytechnic Institute 110 8 th Street, Troy, NY 12180, USA C.W. Reed 116 Woodhaven Dr., Scotia, NY 12302, USA R. Keefe and W. Zenger Electric Power Research Institute 3412 Hillview Ave, Palo Alto, CA 94303, USA ABSTRACT The incorporation of silica nanoparticles into polyethylene increased the breakdown strength and voltage endurance significantly compared to the incorporation of micron scale fillers. In addition, dielectric spectroscopy showed a decrease in dielectric permittivity for the nanocomposite over the base polymer, and changes in the space charge distribution and dynamics have been documented. The most significant difference between micron scale and nanoscale fillers is the tremendous increase in interfacial area in nanocomposites. Because the interfacial region (interaction zone) is likely to be pivotal in controlling properties, the bonding between the silica and polyethylene was characterized using Fourier Transformed Infra-red (FTIR) spectroscopy, Electron Paramagnetic Resonance (EPR), and X-ray Photoelectron Spectroscopy (XPS) The picture which is emerging suggests that the enhanced interfacial zone, in addition to particle-polymer bonding, plays a very important role in determining the dielectric behavior of nanocomposites. Index Terms Nanodielectrics, polyethylene, interface, dielectric strength, polymer nanocomposites, advanced materials, electrical insulation. 1 INTRODUCTION NANOPARTICLE-FILLED polymers provide advantages over micron-filled polymers because they provide resistance to degradation [1], and improvement in thermo- mechanical properties without causing a reduction in dielectric strength [2]. For example, an increase in dielectric strength and a reduction in space charge has been documented for the case of nano-TiO2 filled epoxy resin over micron size TiO2 filled epoxy composites [3]. Also, recently published results for electrical voltage endurance in these new materials indicate that very substantial (3 orders of magnitude) improvements in voltage endurance can be demonstrated. These improvements in dielectric properties observed for nano-filled polymers could be due to several factors: (i) the large surface area of nanoparticles which creates a large ‘interaction zone’ or region of altered polymer behavior [4], (ii) changes in the polymer morphology due to the surfaces of particles [5], (iii) a reduction in the internal field caused by the decrease in size of the particles, (iv) changes in the space charge distribution [6, 7], and (v) a scattering mechanism. It should also be recognized that this technology also results in characteristic changes in non-electrical properties that have been found beneficial as detailed in references from a recent review paper [8].
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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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05_poly_nano - IEEE Transactions on Dielectrics and Electrical Insulation Vol 12 No 4 August 2005 629 Polymer Nanocomposite Dielectrics The Role of

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