Influence of Nanoparticle Surfaces on the Electrical Breakdown Strength of Nanoparticle-Filled Low-Density Polyethylene
- PDF / 2,347,829 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 43 Downloads / 168 Views
Eva Mårtensson and Carina Önneby ABB AB, Department H, Västerås, S-721 78, Sweden (Received 29 September 2003; accepted 25 November 2003)
The electrical breakdown strength of TiO2 nanoparticle-filled low-density polyethylene (LDPE) nanocomposites was investigated. It was found that the surface water on the nanoparticles played a very important role in determining the breakdown strength. The breakdown strength at 63.2% cumulative failure probability (E0) for the composites filled with dried nanoscale TiO2 was similar to that of neat LDPE and 50% higher than that for the samples filled with as-received nanoscale TiO2. This increase was due to a better dispersion, a better interface, and a morphology change of the matrix. It was also found that surface modification of nanoscale TiO2 had a significant influence on the breakdown strength. N-(2-aminoethyl) 3-aminopropyl-trimethoxysilane (AEAPS)-coated TiO2-filled samples showed about 40% higher E0 than that of uncoated, as-received TiO2-filled samples. This was mainly due to enhanced electron scattering because of the presence of polar groups in AEAPS. I. INTRODUCTION
Polymers play an important role in electrical insulating technology because of their high electrical strength, ease of fabrication, low cost, and simple maintenance.1–3 Conventionally, additives have been mixed into polymer matrices to improve their resistance to degradation,4 to modify mechanical and thermomechanical properties,5 and to improve electrical properties such as high-field stability.6 One limitation of conventional additives is the negative effect they can have on breakdown strength. In the ideal case, an additive will both modify the property of interest and increase the breakdown strength or at least not degrade it. An example of an additive that can improve the breakdown strength is azocompounds.7 The azocompounds used consist of a benzene or naphthalene ring to which one or more radicals are connected. A radical is either an electron acceptor or electron donor. The increase of the breakdown strength is due to the trapping and the excitation effect of this additive. On the other hand, plasticizers tend to cause a marked reduction of the breakdown strength.8 This is because the plasticizer increases the free volume of the polymer, thus leading to an increase in the electron mean free path causing early breakdown. Both of these kinds of additives exist in polymer matrices in their molecular state. Once the additive appears as a separate phase (e.g., particles) in the polymer matrix, local field distortion becomes an important factor, and in J. Mater. Res., Vol. 19, No. 3, Mar 2004
http://journals.cambridge.org
Downloaded: 16 Mar 2015
most cases such additive particles cause a decrease in the breakdown strength of insulating materials.9–11 A second phase can also influence the breakdown strength via a tortuosity mechanism (i.e., an increase in the path length of the breakdown)12 or by changing the space charge distribution.13 Under alternating current (ac) conditions, local field distortio
Data Loading...
