Influence of Filler-Polymer Interface on Performance of Silicone Nanocomposites

The increase in voltage level and compactness of electrical equipment result in demands for electrical insulations that have high breakdown strength, high thermal conductivity, and high electrical resistivity. Use of dielectric polymer nanocomposites is a promising approach that has great advantages over the traditional materials. This article explores the influence of alumina nanofillers, both treated and untreated, on properties of silicone rubber-based nanocomposites. Composite samples made of 10 wt% and 20 wt% filler loading are prepared using high shear (HS) and electrostatic disperser (ES) techniques with the aim of achieving maximum dispersion of fillers in the silicone matrix. Effects of filler type, filler concentration and mixing method on morphological changes, thermal, erosion, and electrical properties are analyzed. Scanning electron micrographs (SEMs) showed better filler dispersion in composites prepared using ES than using HS mixer. Thermogravimetric analysis and thermal conductivity measurements revealed enhanced thermal stability and conductivity with increasing filler loadings. Additionally, ES composites showed high erosion resistance. Composites containing treated alumina performed better than those containing untreated alumina. In total, composites prepared with treated alumina using the ES method showed marked improvement in thermal properties and erosion resistance due to homogeneous filler dispersion imparting high number of filler-matrix interfaces and stronger bonding as visualized from SEMs and dielectric spectroscopy data.