Structure And Properties Of Fluorene Polyester/Silicon Oxide/Boron Nitride Nanocomposite Dielectrics

With the development of electronic technology,polymer has excellent performance in many fields,such as power equipment,aviation,communication equipment,new energy devices and so on.Fluorene polyester is a new type of dielectric material.Compared with its heteroaromatic polymer,it has excellent insulation properties and excellent thermal stability,which has become a research hotspot of scholars recently.However,in practical application,the dielectric constant of pure fluorene polyester is relatively low,which cannot satisfy some application needs.At present,adding nano inorganic fillers with high dielectric properties into polymers is a common method to prepare high dielectric composite films,but the breakdown strength is often greatly degraded,which is of great significance to further improve the dielectric constant of fluorene polyester and maintain high breakdown strength.In this thesis,two kinds of composite films with different components and doping systems based on Fluorene polyester(FPE)were prepared by solution blending method with zero dimensional SiO₂ nanoparticles and two-dimensional BN nanosheets as fillers.XRD,SEM,FTIR and SAXS were used to characterize the microstructure and interface structure of SiO₂ nanoparticles,BN nanosheets and composite films.The dielectric properties,breakdown properties and mechanical properties of the composite films were tested and studied.It is found that SiO₂ particles can be evenly dispersed in FPE matrix,the introduced SiO₂ particles do not damage the structure of FPE molecular chain,and increase the thickness of the interface layer of the filler matrix.When the filling component of silicon oxide is 9 wt%,the dielectric constant of the composite increases from 3.54 to 7.30,and the adding of SiO₂ particles has little effect on the dielectric loss and AC conductivity of FPE.At the same time,the corona resistance life of the composite is about 12 times higher than that of pure FPE matrix.Due to the introduction of SiO₂ particles,the molecular chain spacing of FPE is expanded,resulting in the increase of its free volume.At the same time,the introduction of particles produces some physical defects,resulting in the significant decline of AC breakdown performance of composite films.In order to improve the breakdown strength and obtain composite films with better comprehensive properties,SiO₂/BNNS/FPE three-phase filled composite films were prepared by solution blending.Compared with FPE/SiO₂ composite films,the three-phase filled composite films show better dielectric properties,short-time breakdown properties,tensile properties and corona aging resistance.In particular,the dielectric constant and breakdown strength of the composite films filled with 9 wt%SiO₂and 5 wt%BN are synergistically improved.By studying the interface characteristics between hexagonal boron nitride nanosheets,silica nanoparticles and fluorene polyester matrix,as well as the microstructure and properties of composite films,this paper explores the synergistic mechanism of two-dimensional boron nitride nanosheets and zero dimensional silica particles on the properties of FPE based composite films,establishes an interface model,and deeply analyzes the interface structure,dielectric properties,AC breakdown properties The variation characteristics of tensile properties and corona aging resistance,focusing on the synergistic regulation mechanism of silica nanoparticles and hexagonal boron nitride nanoparticles in FPE polymer,so as to provide corresponding theoretical basis for the study of the application of zero dimensional/two-dimensional filler in electrical engineering.