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 degrees 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.