Dielectric behaviour and conductivity of high-filled BaTiO3–PMMA composites and the facile route of emulsion polymerization in synthesizing the same

Poly(methyl methacrylate)–BaTiO3 composites were prepared by a combined process of free radical emulsion polymerization and hot pressing. Using a cationic surfactant, emulsion polymerization was proven to be an easy and fast method to synthesize core–shell hybrid particles. By subsequent hot pressing of powders with different amounts of polymers, composites with barium titanate filler contents up to 65 vol% with uniform microstructures could be achieved, as determined by thermogravimetric analysis and scanning electron microscopy. The dielectric properties were characterized for frequencies and temperatures ranging from 100 Hz to 1 MHz and −30 to 80 °C, respectively. Composites exhibited a significant increase in dielectric constant up to 85 with BaTiO3 content and low loss tangents of 0.06 at 1 kHz. Dc conductivity measurements reveal increasing leakage currents with BaTiO3 contents, enhanced by cationic surfactant influences.