Preparation And Performance Studies Of PVDF Dielectric Functional Composites

As the electronic information technology has developed rapidly,in order to satisfy the requirements of modern industrial development,high-performance dielectric materials have gradually replaced traditional single dielectric materials.Polyvinylidene fluoride(PVDF)is the most universal dielectric polymer matrix.Although it shows prominent dielectric properties in polymers,high energy storage density,good processability and chemical resistance,it has been unable to adapt to the higher performance requirements in practical applications.Therefore,the preparation of PVDF dielectric functional composites by combining different dielectrics with PVDF has gradually become a research trend.In this paper,halloysite nanotubes(HNTs)were added into PVDF matrix and HNT/PVDF composites with different doping contents were prepared,then HNTs was modified through ATRP grafting with poly(methyl methacrylate)(PMMA)on the surface.At the same time,Si02@rG0@CS three-layer core-shell nanoparticles were prepared and doped into PVDF matrix.The influence of several different dopants on the dielectric properties of PVDF and the mechanism of dielectric variation were researched systematically.The study on HNT/PVDF composites with different doping contents has shown that HNTs can induce and promote the formation of the PVDF electroactive phases(?-phase,?-phase).With the increase of the content of HNTs,the dielectric constant of the system gradually increased,but the breakdown strength decreased significantly.The dispersion of HNTs in the PVDF matrix and interface bonding were not satisfactory.Through the summary of the dielectric properties and mechanical properties of HNT/PVDF composite,it was found when the doping content of HNTs was 10wt%,the performance of the system was more excellent.The surface grafted PMMA was modified by ATRP on HNTs.It was found that the surface-modified HNTs effectively improved the adhesion with the PVDF matrix and the breakdown strength of the material system,reaching 287.1 kV/mm.And the high theoretical energy density was abtained,which made the modified HNT/PVDF composites having more excellent dielectric properties.The influence of the addition of SiO2@rGO@CS core-shell nanoparticles on the dielectric properties of PVDF was investigated.It was found when the added amount of the fillers was low,the dielectric constant of the system increased significantly,and the dielectric loss remained at a very low level.Especially when the SiO2@rGO@CS/PVDF composite system was in the adjacent percolation threshold,the dielectric constant reached 72.2.And the dielectric loss was effectively suppressed,compared with the same mass content of rGO/PVDF composite material,it decreased from 0.897 to 0.219.The SiO2 core and chitosan outer layer in SiO2@rGO@CS nanoparticle acted as barriers and insulators at the same time,which destroyed the formation of the conductive network and together suppressed conduction of carriers in the system.It made SiO2@rGO@CS/PVDF composites having a high dielectric constant and low dielectric loss near the percolation threshold,exhibiting excellent dielectric properties.