Study Of High Dielectric Poly (Vinylidene Fluoride) Composite Materials

With the rapid development of electronic integrated technology and the huge demand in the field of electronic industry,the requirement of the dielectric material is higher and higher.This not only requires better dielectric properties,but also has a good processing performance and light characteristics.How to prepare high performance dielectric materials with excellent performance and simple process has become the focus of the research of dielectric materials.Traditional ferroelectric ceramics and single polymer materials cannot meet the requirements.Therefore,the high dielectric composite materials of polymer matrix have gradually become the focus of research.A series of polyvinylidene fluoride-based composites were prepared by solution blending method in this paper.The effects of the surface structure,dispersion properties and polymer interface compatibility on the dielectric properties of the composites were studied.Through the surface modification of barium strontium titanate and graphite filler,the dispersion and interfacial structure of the materials were improved.At the same time,carbon nanotubes and graphene were added to improve the dielectric properties of the composites.The main research contents and results are as follows.(1)PVDF thin films were prepared by solution mixing method,and the optimal mass ratio of PVDF and DMF was investigated.It was found that when the PVDF:DMF mass ratio is 1:10,the dielectric constant of the films is about 10 and the dielectric loss is the lowest,which is about 0.018.(2)The BST/PVDF binary composite films with a volume fraction of 30% were prepared to investigate the effect of the film thickness on the dielectric properties of the composite thin films.It was found that when the film thickness is 0.070 mm,the dielectric constant is 35.When the film thickness is 0.176 mm,the dielectric loss is 0.026.(3)The barium strontium titanate and graphene were surface modified with silane coupling agent(KH550)and grafted onto the surface.On the basis of this,the three element composite material was prepared by adding modified graphene and modified barium strontium titanate.It was found that the dielectric constant and the dielectric loss of the composite film were abruptly changed when the graphene content reached near 4.0wt% of the permeation threshold,which caused the seepage effect.When the amount of modified graphene was 4.06wt%,the dielectric constant of the composites was 502,and the dielectric loss was 0.506 under the condition of 100 Hz.(4)The dopamine coated with a layer of uniform coating layer is formed on the surface of graphene,improve its compatibility with the PVDF matrix interface,and an insulating layer is formed on the surface of graphene,to prevent direct contact between lamellae,effectively reduce the leakage current.It was found that the dispersion of graphite coated graphene dopamine in DMF solution has been greatly improved,the dielectric loss of three yuan of composite material is prepared based on the reduced graphene when doping amount is 9.08wt%,the dielectric constant of 100 Hz thin film is 494,the dielectric loss is 0.321.(5)In order to obtain the dielectric composite films with more excellent properties,more stable performance,the carboxylated multi walled carbon nanotubes and two modified graphene composite doping,by controlling the doping ratio between them,the obtained composite film materials with more excellent dielectric properties.The doping of the two kinds of particles greatly reduced the amount of the conductive phase and improved the preparation of the slurry,and the synergistic effect of the two particles also improved the dielectric properties of the composites.The addition of carbon nanotubes and silane coupling agent modified graphene was 0.8wt% and 0.2 wt%,the dielectric constant of the composite was 427,and the dielectric loss was about 0.395;When the addition amount of carbon nanotubes and dopamine coated graphene was 0.8 wt% and 0.4 wt%,the dielectric constant of the composites was 457 and the dielectric loss was 0.323.