08_srtahi_wavelet_fractal - 178 R. Sarathi et al.:...

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R. Sarathi et al.: Understanding the Hydrophobic Characteristics of Epoxy Nanocomposites Using Wavelets and Fractal Technique 1070-9878/08/$25.00 © 2008 IEEE 178 Understanding the Hydrophobic Characteristics of Epoxy Nanocomposites Using Wavelets and Fractal Technique R. Sarathi, R.K. Sahu Department of Electrical Engineering, Indian Institute of Technology Madras Chennai- 600 036, India. and T. Tanaka Graduate School of Information, Production & System, Waseda University, Japan ABSTRACT In the present study, the influence of water ageing on the surface characteristics of epoxy nanocomposites was analyzed through Atomic Force Microscopy (AFM) studies. The hydrophobic properties of the epoxy nanocomposite material were analyzed through contact angle and diffusion coefficient measurements. Fractal dimension were calculated by adopting a Multi Resolution Signal Decomposition (MRSD) to the 1D- AFM signal through power spectral density calculations at each level of decomposition. 2D-MRSD studies were applied to AFM pictures to understand the surface characteristics of the material. The result of the study shows the presence of high and low frequency signals indicating characteristic variation in surface roughness of the material. The surface roughness parameter measured through the MRSD technique indicates that the surface roughness is lower for epoxy nanocomposites (upto 5Wt%) compared to pure epoxy resin. It is observed that the fractal dimension and the root mean square roughness values vary proportionately. Also it is realized that diffusion coefficient and surface roughness of the material shows an inverse relationship. Index Terms - Insulation, nanocomposites, surface roughness, contact angle, hydrophobicity, atomic force microscopy, wavelets, Fractals. 1 INTRODUCTION HIGH performance polymer nanocomposites are emerging as a new class of insulating materials for demanding application in all electrical equipment used in the outdoor/indoor power system network [1,2]. The major problem in insulating material is that the ingression of moisture/absorption of water leads to enhanced leakage current during operation which raises the temperature of the insulating material due to leakage current flow in the surface. This allows a chain scission/reaction to occur (changing surface hydrophobic characteristics of the material) forming carbonized surface bridging between the high voltage point and ground, which leads to catastrophic failure of the equipment [3,4]. Hence, it is essential to understand the characteristic variation in the surface properties of the epoxy nanocomposite material due to migration of water into the bulk material. Recently, epoxy resin with organically modified clay filler has been used in major applications [5-9]. The selection of clay as a reinforcing material in epoxy resin is extremely appealing because of the cost, high thermal inertness, and environmentally friendly characteristics. It is believed that consistent improvements in the properties of clay loaded polymeric systems can be achieved by minimizing clay
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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.

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08_srtahi_wavelet_fractal - 178 R. Sarathi et al.:...

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