Improving the dielectric constants and breakdown strength of polymer composites: effects of the shape of the BaTiO3 nanoinclusions, surface modification and polymermatrix

Abstract

Flexible polymer composite films are prepared by a solution cast method with polar polyvinylidene fluoride (PVDF) or non-polar epoxy as the polymer matrix. BaTiO₃ nanoparticles and BaTiO₃ nanofibers with large aspect ratio are used as dielectric fillers after surface modification by polydopamine. The effects of filler shape, surface modification and polarity of polymer matrix on the microstructure, dielectric constants and breakdown strength of polymer composites are investigated in detail. Surface modification by polydopamine improves the compatibility between BaTiO₃ and polymer as well as passivating the surfaces of BaTiO₃. At the same volume fraction, composites filled with BaTiO₃ nanofibers exhibit greater dielectric constants than the composites filled with BaTiO₃ nanoparticles. The polydopamine layers on BaTiO₃ nanofibers give rise to stronger interfaces between the fillers and polymer matrices. Improved breakdown strengths are achieved in both composites. This work may provide a general strategy for flexible polymer nanocomposites with greatly enhanced dielectric constants and breakdown strength.