Dielectric and morphological studies on polyester/nanosilica fume composites

Abstract

Styrenated polyester nanocomposites are a class of polymers reinforced with low quantities of welldispersed nanoparticles with the aim of offering advantages over conventional composites. Nanosilica fumes with different particle sizes were used as a filler to form polyester nanocomposites. The average particle size was detected with transmission electron microscopy. We used the electrical properties [permittivity (e 0 ), dielectric loss (e 00 ), and electrical conductivity (r)] to investigate the variation of the properties of the polyester/nanosilica fume composites by varying the filler ratio and particle size as well. The e 0 , e 00 , and r values were found to increase with increasing filler content up to a certain concentration, at which aggregation began to form and after which stability in these properties was attained. The second relaxation time (s 2 ) associated with the orientation of the aggregates caused by the movement of the main chain was found to be unchanged up to a certain concentration of filler, after which a pronouncing increase in s 2 was noticed. This result found further justification through the scanning electron micrographs. In addition, the values of r, which were of the order of 10 À11 S/cm, make the materials highly recommended for use for insulation purposes.

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

“…8c), a finding that is consistent with the water uptake data and dielectric spectroscopy, the alumina composites show a large increase in conductivity, which is again consistent with their increased dielectric loss and significant water uptake. Increased conductivity in nanocomposites relative to unfilled samples has been reported in other studies [23,51] but, here, the effect is limited to only the alumina samples; i.e. those where the nanoparticle surface chemistry means that they are capable of absorbing significant water.…”

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

“…Whilst three of these reports indicate an increase in electrical conductivity when the nanofiller is added [8,19,20], the other indicates, in better dispersed systems, a reduction [5]. Again, this apparent contradiction may be explained through variations in nanofiller dispersion; Veena et al [5] make the important point, that for high filler loadings where dispersion is poor, this leads directly to increased conductivity.…”

“…Whilst the addition of a nanofiller leads to two characteristic loss peaks and an increase in permittivity at low frequencies [8,9,12,16,18,21,22], in cases where the nanofiller is well dispersed, this is not observed. Instead, the dielectric loss increases in a similar manner to that in comparable micro-filled systems [15,[16][17]20].…”

“…Since the attractive properties of nanodielectrics have generally been ascribed to the large specific interfacial area that exists within such systems and the subsequent formation of interphases [6,7], achieving good nanoparticle dispersion and avoiding particle aggregation is generally considered to be key, but is very difficult to achieve consistently [8][9][10][11][12]. Consequently, when the breakdown strength of a nanocomposite is compared with that of an identical polymer without nanofiller, examples can be found where the addition of the nanofiller reduced the breakdown strength [13,14], where no change in breakdown strength was seen [15] or where increased breakdown strength occurred [16,17].…”

“…Only a few reports exist where the electrical conductivity of a nanosilica/polymer composite is compared with the identical polymer without nanoparticles present [5,8,19,20]. Whilst three of these reports indicate an increase in electrical conductivity when the nanofiller is added [8,19,20], the other indicates, in better dispersed systems, a reduction [5].…”