High dielectric acrylonitrile-butadiene rubber with excellent mechanical properties by filling with surface-modified barium/strontium inorganic functional powders

Acrylonitrile-butadiene rubber (NBR) filled with surface-modified barium titanate (MBT), strontium titanate (MST) and barium strontium titanate (MB_xS_1−xT) was used to prepare the polymer dielectrics. B_xS_1−xT powders (x = 0.8, 0.7, 0.5 and 0.3) were synthesized via solid-state method. The crystal structure was observed by X-ray diffraction. The morphology and particle size of different powders were characterized by scanning electron microscopy (SEM). The contact angle test verified the hydrophobicity of the inorganic functional powders modified with bis-(γ-triethoxysilylpropyl)-tetrasulfide (KH845-4) improved obviously. The ratio of the dispersive solid surface tension and polar solid surface tension between inorganic filler and NBR matrix became closer after surface modification. The NBR/MBT/MST and NBR/MB_xS_1−xT systems were designed to improve the dielectric properties and enhance the mechanical properties. The curing characteristic of all NBR gums was tested. The dispersion of surface-modified functional filler in NBR was observed great according to the images of SEM. The mechanical properties of NBR/filler composites reinforced markedly compared with the neat NBR. For dielectric properties, the NBR/MB_0.7S_0.3T composites had the highest dielectric constant and the NBR/MST composites had the lowest dielectric loss factor at room temperature. They were suitable to be applied under the different frequency in oily environment for a long time. The oil resistance of all composites was also tested.