The Role of Silanization of Barium Strontium Titanate Nanopowders on the Dielectric Constant and Thermal Stability of Epoxy Nanocomposites

This paper reports polymer composites′ microstructure and dielectric properties based on an epoxy resin matrix containing different amounts (from 2–10 wt. %) of barium strontium titanate nanoparticles. (Ba,Sr)TiO 3 was prepared using the hydrothermal method, showing an average particle size of 100 nm. The composites′ thermal properties and morphology were characterized using thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. Our studies show that the (Ba,Sr)TiO 3 nanoparticles were well dispersed in the epoxy resin matrix thanks to controlled silane functionalization. Accordingly, the glass transition temperature ( T g ) value of the nanocomposites was found to be 159.0 °C at 10 wt. % (Ba,Sr)TiO 3 loading and is higher than the neat epoxy resin T g ( T g =154.7 °C). Moreover, the dielectric composite properties were investigated comprehensively via a wide range of frequencies from 10 Hz to 100 kHz. The results indicate that (Ba,Sr)TiO 3 nanopowders and the surface modifying filler play a crucial role in the significant increase of the dielectric constants, approximately 1.5 times at the optimum added amount (Ba,Sr)TiO 3 . The limited functionalization of (Ba,Sr)TiO 3 nanoparticles by the silane affords to control the nanocomposite dielectric loss. Furthermore, the nanocomposites also exhibited good thermal stability.