Fabrication and properties of composites from BST and polypropylene-graft-poly(styrene-stat-divinylbenzene)

In this work, ceramic–polymer composites were fabricated from barium strontium titanate powder (BST) and polypropylene-graft-poly(styrene-stat-divinylbenzene) (ER) using a twin-screw extruder. The compounding process was characterized by rheological measurements. The effects of volume loading of BST on dielectric and mechanical properties were investigated. The dielectric properties were measured as a function of frequency and BST loading. For example, the relative permittivity and loss tangent (tan δ) of the BST–ER composites at 1 GHz were gradually increased from 2.4 and 0.0001 to 28.5 and 0.0085, respectively, as the loading was increased from 0 to 50.5 vol.%. Stearic acid (StA) was used as a surface-modifier of the BST. With an approximate surface coverage of 83%, an improvement in processability and a slight increase of the permittivity was observed, while tan δ remained low. The excellent dielectric characteristics of these composites, with high permittivity and low tan δ, make them attractive novel electronic materials for high frequency applications.