Prebreakdown current and dc breakdown strength of alumina-filled poly(ethylene-co-butyl acrylate) nanocomposites: Part I - breakdown strength

Abstract

Dielectric breakdown strength of poly (ethylene-co-butyl acrylate) (EBA)nanocomposites filled with spherical alumina particles was studied as a function of particle coating, moisture content and the effective specific surface area. Two kinds of alumina nanoparticles were used: NA (25 nm in diameter) or ND (45 nm in diameter). The particles were either unmodified or surface-treated with aminopropyltriethoxy silane or octyltriethoxy silane. Two different relative humidities of air were used for conditioning the samples prior to testing: 0 % RH (dry case) and 86 % RH (samples were saturated with moisture). The dielectric breakdown strength measurements were performed with a DC ramp of 1.2 kV/s. Twenty samples were tested for each material formulation -ten of which were tested in dry conditions and ten were tested after conditioning in humid environment. Results were compared to the reference unfilled EBA samples. Applying Weibull analysis to the measured breakdown voltages indicated that the material filled with amino-coated ND particles exhibited the highest breakdown strength under dry conditions. As expected, conditioning materials in a humid environment had a negative impact on breakdown strength. This effect was more pronounced for nanocomposite materials, compared to the unfilled reference material.

The Effects of Water on the Dielectric Properties of Aluminum-Based Nanocomposites

“…3) show disrupted spherulitic textures, which are suggestive of enhanced polymer nucleation, and contain Al2O3 inclusions ranging in size from ~50 nm to 5 μm. In thermosetting epoxy/alumina systems, both good [14,16] and poor [17] alumina particle dispersions have been reported, whilst another study using the more relevant thermoplastic host polymer ethylene-co-butyl acrylate [22] indicated very similar aggregated morphologies to those reported here.…”

“…Previously, silica based systems were studied by the authors [37] and it was found that the dielectric properties were highly sensitive to conditioning and several papers indicate that this may also be the case for alumina [22,23]. Drying the nanocomposites led to electrical properties similar to that of the host polymer, whereas absorbed water always had a detrimental effect.…”

“…The consequence of the local interactions, particularly hydrogen bonding with silanol groups, was markedly retarded dynamics, such that the water relaxation peak was seen to vary from below 1 Hz to above 10 5 Hz, depending on the local, conditions. Elsewhere, ethylene-co-butyl acrylate was used as a matrix together with spherical alumina particles [22]. Under dry conditions, there was little difference in breakdown strength compared to the host material, whereas wet conditioning caused a fall in breakdown strength in the nanocomposite systems -this effect was attributed to water shells surrounding the nanoparticles.…”

The effects of hydration on the DC breakdown strength of polyethylene composites employing oxide and nitride fillers

“…Similarly, increases in AC breakdown strength in epoxy/alumina systems have been reported [16,17] while, in another study [18], absorbed water was reported to reduce the electrical breakdown strength of a series of alumina/ethylene-co-butene acrylate composites. Other notable papers on alumina [19,20] and aluminum nitride [21,22] focus on their improved thermal conductivity, which could potentially increase short term overload ratings if such composites were to be employed in a high voltage cable system [23].…”

On the effect of functionalizer chain length and water content in polyethylene/silica nanocomposites: Part I — Dielectric properties and breakdown strength

“…Hui et al [34] considered the effect of moisture on a series of XLPE/silica nanocomposites and showed a progressive reduction in breakdown strength with increasing moisture content. Finally, Jaeverberg et al [35] compared the breakdown strength of epoxy/alumina nanocomposites exposed to dry and humid conditions and found that humid conditions significantly reduced the breakdown strength. Thus, all the available work seems to indicate a reduction in the breakdown strength of nanocomposites that contain water, in agreement with our findings.…”