Dielectric property and thermal conductivity of polyvinylidene fluoride composites modified by BN and Al₂O₃@BaTiO₃ fibers

The research on dielectric energy storage materials with high dielectric constant, breakdown strength and thermal conductivity has attracted much attention. In this paper, the hydroxylated boron nitride nanosheets (BN) prepared by high-temperature calcination and the barium titanate fibers loading alumina particles (Al₂O₃@BaTiO₃) prepared by electrospinning were used to fill polyvinylidene fluoride (PVDF), and the composites were obtained by casting and hot-pressing. The synergistic effect of BN and Al₂O₃@BaTiO₃ on the structure and properties of PVDF matrix composites was investigated. The results show that the Al₂O₃@BaTiO₃ fibers can bridge the BN nanosheets, making the BN-Al₂O₃@BaTiO₃/PVDF composites exhibit improved mechanical, dielectric properties and thermal conductivity in comparison with pure PVDF and BN/PVDF composites. With the increase of Al₂O₃@BaTiO₃ fibers content, the dielectric constant and thermal conductivity of BN-Al₂O₃@BaTiO₃/PVDF material increase, while the tensile strength and breakdown strength increase first and then decrease. When the content of Al₂O₃@BaTiO₃ is 5wt%, the breakdown strength of BN-Al₂O₃@BaTiO₃/PVDF composites reaches the highest value of 253.9 kV/mm, which is 2.43 times that of pure PVDF. Meanwhile, the tensile strength, dielectric constant and thermal conductivity are raised to 41.23 MPa, 12.1@1 kHz and 0.508 W/(m·K), also 10.8%, 44.0% and 185.4% higher than those of pure PVDF, respectively.