Improved dielectric, tensile and energy storage properties of surface rubberized BaTiO3/polypropylene nanocomposites

The low permittivity of the polypropylene (PP) film has become a barrier for the further development of film capacitors with high energy storage density. An advanced strategy of the high-permittivity filler/polymer nanocomposite turns out to be a promising way of solving this problem. In this work, we coated ethylene propylene diene monomer (EPDM) as the shell on the surfaces of BaTiO3 successfully to fabricate core-shell structural nanoparticles. The addition of surface rubberized BaTiO3 into PP matrix promotes the permittivity to about 5.8, while the dielectric loss is barely changed as compared with PP itself. In addition, the elongation at break is as high as 364%, which is over 4 times higher than that of PP. The influences of shell thickness (3 nm, 5 nm and 7 nm) for the nanoparticles and hot-stretching process for the nanocomposite films were also carefully investigated, both of which greatly affected the properties of nanocomposites. Finally, the optimum breakdown strength as high as 370 MV/m is obtained, leading to a maximum energy density of 3.06 J/cm3, which can be attributed to both high breakdown strength and high permittivity of the core-shell structural BaTiO3/PP nanocomposites.