Research On Structure Design And Performance Of Polymer-based Composite Dielectric

With the rapid development of the electronic and electrical industry,improving the comprehensive properties of polymer-based dielectric materials has become a hot research topic.As a single polymer usually lacks excellent comprehensive properties,research on polymer-based composite materials has become the main method to improve the comprehensive properties of materials.Among the polymers,poly(vinylidene fluoride)(PVDF)is widely studied in dielectric materials because of the excellent dielectric properties,as well as outstanding advantages such as excellent flexibility,thermal stability,and mechanical strength.As a good insulating material,polystyrene(PS)is easy to process,low in price,good in chemical stability,and has a wide market supply,which has great innovative significance for dielectric research.Therefore,PVDF and PS are selected as the matrix respectively in the paper.Conductive particles and carbon-based materials with different structures and dimensions are used as fillers.PVDF-based and PS-based dielectric materials are prepared and analyzed.New methods,new processes,and new models were effectively improved the dielectric properties of PVDF-based and PS-based dielectric materials.In addition,the thermal conductivity of dielectric materials has also attracted the attention of researchers recently.For dielectric materials with high dielectric constant and low dielectric loss,high thermal conductivity can effectively reduce the thermal damage of dielectric materials caused by dielectric loss.Therefore,while studying dielectric materials with high dielectric constant and low dielectric loss,it is also necessary to study the thermal conductivity of dielectric materials.Firstly,the nickel powder(Ni)and graphite(GNS)filled PVDF composites with different filler contents were prepared by solution blending-hot pressing method in the paper.The influence of Ni and GNS for structure,morphology,dielectric properties and thermal conductivity of composites was investigated.The results showed that the polar phase content in PVDF/Ni/CNS series composites was increased significantly.At room temperature and10~2Hz,the dielectric constant of the composites(filler content 11 wt.%)could reach 65,and the dielectric loss remains at a relatively low value(?0.39).At the same time,the thermal conductivity increases to 0.534W/m K is twice of neat PVDF.In addition,the paper introduces Ni as a basic filler for composites,co-fills polymers with GNS and carbon nanotubes(CNTs)conductive fillers,and further studies the effects of magnetic materials on material structure,dielectric properties and thermal conductivity.Secondly,the Ni and CNTs as filler filled PVDF composites with different filler contents were prepared by solution blending-hot pressing in the paper.The X-ray diffractometer(XRD)results showed that the increase of Ni and CNTs promoted the transformation of?-phase structure to?-phase structure in PVDF.The increase of?-phase content is beneficial to improve the dielectric properties of the composites.The dielectric test results found that,at the room temperature and 10~2Hz,the dielectric constant of PVDF/Ni/CNTs composites increased to 38.9 and the dielectric loss increased about 5.9 at the ratio of 4.1 wt.%filler,and the dielectric properties were improved.The thermal conductivity of PVDF/Ni/CNTs composites increased to 0.801W/m K at the ratio of 4.1wt.%filler.When the filler content increased to 5.1 wt.%,the thermal conductivity of PVDF/Ni/CNTs composites continued to rise to 0.908W/m K,and has increased about twice compared with the neat PVDF(0.300W/m K).Finally,in order to further expand the scope of polymer matrix research and try to reduce the production cost of dielectric materials,the paper attempts to introduce PS which is cheap,easy to process,and has good chemical stability as the matrix material.PS/Ni/GNS,PS/Ni/CNTs and PS/Ni/GNS/CNTs were prepared by solution blending-hot pressing method to study the influence of the dielectric properties and thermal conductivity.The study found that the incresae of conductive fillers was beneficial to improve the dielectric properties and thermal conductivity of composite materials.Compared with the PS/Ni/GNS and PS/Ni/CNTs composite materials,the comprehensive performance of the PS/Ni/GNS/CNTs composite material is more excellent.At room temperature and 10~2Hz,the dielectric constant of the PS/Ni/GNS/CNTs composite material(filling amount is 11 wt.%)could reach 106,and the dielectric loss is about 5.7.The thermal conductivity rose to 0.475 W/m K,which is about five times that of the neat PS.It may be caused by the filling of multi-dimensional conductive materials,which can make up for the defects and deficiencies of single-dimensional filler filling and achieve a better filling effect.In summary,polymer-based composite dielectric materials were prepared using multi-dimensional and multi-phase filling methods in the paper,with using PVDF and PS as the matrix and Ni,GNS and CNTs as the fillers.Through structural characterization and performance testing,the relationship between the microstructure of the composite material and the dielectric properties and thermal conductivity was studied.