Dielectric and morphological studies on polyester/nanosilica fume composites

Styrenated polyester nanocomposites are a class of polymers reinforced with low quantities of well‐dispersed 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 (ϵ′), dielectric loss (ϵ″), and electrical conductivity (σ)] to investigate the variation of the properties of the polyester/nanosilica fume composites by varying the filler ratio and particle size as well. The ϵ′, ϵ″, and σ 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 (τ 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 τ 2 was noticed. This result found further justification through the scanning electron micrographs. In addition, the values of σ, which were of the order of 10 −11 S/cm, make the materials highly recommended for use for insulation purposes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011