Preparation and properties of BaTiO3 filled butyl rubber composites for flexible electronic circuit applications

Butyl rubber-micron barium titanate (BR/BT) and butyl rubber-nano barium titanate (BR/nBT) composites were prepared by sigma mixing followed by hot pressing. The tensile tests show that both the composites were mechanically flexible. The microwave dielectric properties of both BR/BT and BR/nBT composites were investigated as a function of ceramic loading and were found to be improved with filler content. The butyl rubber has a relative permittivity (epsilon(r)) of 2.4 and loss tangent (tan delta) of 0.0017 at 5 GHz. At a filler loading of 0.24 volume fraction (v(f)) of micron sized barium titanate (BaTiO3) powder loading, the composite attained a epsilon(r) of 7 and tan delta of 0.014 and for the same filler content of nano BaTiO3 the composite have epsilon(r) of 8.9 and tan delta of 0.019 at 5 GHz. The thermal and mechanical properties of both the composites were investigated. The experimental values of epsilon(r) of both BR/BT and BR/nBT composites for different volume fractions were compared with theoretical models.