Dielectric response and molecular dynamics in epoxy-BaSrTiO3 nanocomposites: Effect of nanofiller loading

Abstract

BaSrTiO3/epoxy resin nanocomposites were prepared in a wide range of filler concentrations. Electron microscopy images demonstrated fine dispersion of the nanoinclusions. Variation of glass transition temperature with particles concentration was determined via differential scanning calorimetry. Three relaxation processes were detected in the dielectric spectra, namely interfacial polarization, glass to rubber transition of the matrix (α-relaxation), and re-arrangement of polar side groups (β-relaxation). Nanofiller content affect the dielectric and thermal response of the composites via the particle-polymer and particle–particle interactions. At low filler content, reduction of the macromolecular mobility causes a decrease of permittivity and an enhancement of glass transition temperature. At intermediate filler content, interparticle interactions appear to dominate, leading to altered polymer flexibility, higher permittivity and lower glass transition temperature. At high filler loading, glass transition temperature increases in tandem with permittivity because of the limited macromolecular mobility, and the high permittivity of the particles. Systems’ performance can be interpreted by a three “filler load zones” model.