Preparation And Properties Of High Dielectric Constant And Low Dielectric Loss PVDF Hybrid Materials

With the progress and development of science and technology,and the innovation of manufacturing technology,various industries have put forward higher requirements for the comprehensive performance of the materials used.In the electronics and electrical industry,with the development of miniaturization,miniaturization and flexibility of products and equipment,traditional dielectric materials have been difficult to meet the rapid development needs in this field.In the energy industry,the efficient use of clean energy requires efficient conversion and storage devices,which are often the core components of some high-energy weapons.As an indispensable material in these fields,the research and development of dielectric materials are also very important.Therefore,the research of dielectric materials is not only a hot spot of scientific research,but also an urgent need for national economy and national security.In this paper,we use PVDF as the matrix and multi-walled carbon nanotubes as the conductive filler to prepare dielectric composites with high dielectric and low loss by adding the third component which is different from the matrix compatibility and modifying the surface of carbon nanotubes with manganese dioxide.The works are as follows:（1）PVDF/MWCNTs composites were prepared by blending PVDF with carbon nanotubes.In addition,the ternary copolymer of ethylene-methyl acrylate-propylene epoxy methacrylate（E-MA-GMA）with poor compatibility with PVDF was added to the matrix.The island-structured PVDF/E-MA-GMA/c-MWCNTs composites were prepared by melt blending.The results show that carbon nanotubes tend to be distributed in E-MA-GMA phase due to the covalent bond reaction between carbon nanotubes and E-MA-GMA.PVDF/MWCNTs composites have high dielectric constant,but their dielectric loss is also very high,while PVDF/E-MA-GMA/c-MWCNTs composites can suppress dielectric loss at relatively low values while maintaining high dielectric constant.The dielectric constant and dielectric loss of PVDF/MWCNTs and PVDF/E-MA-GMA/c-MWCNTs composites are 3570,106 and 1286,2.2 respectively when the carbon nanotube content is 2.5wt%and the electric field frequency is 1000Hz.（2）Acrylate rubber（ACM）with good compatibility with the matrix was added to the matrix as the third component.PVDF/ACM/c-MWCNTs three-phase composites were prepared by melt blending in an internal mixer.The results show that ACM is uniformly distributed in the PVDF matrix with small size.The dielectric constant and dielectric loss of the composite are 40.2 and 0.038 respectively when the electric field frequency is1000Hz and the carbon nanotube content is 5wt%.In addition,the addition of ACM has a good toughening effect on the matrix material,but the addition of carbon nanotubes greatly reduces the toughening effect of ACM on the matrix.（3）After surface modification of carbon nanotubes with manganese dioxide,PVDF/MnO₂@CNTs composites were prepared by solution blending with PVDF.The results show that the dispersibility of the modified carbon nanotubes in the matrix is poor,and a lot of agglomeration occurs.Because the existence of MnO₂ on the surface of carbon nanotubes effectively prevents the direct contact between carbon nanotubes and reduces the dielectric loss,the material can maintain a low dielectric loss while having a high dielectric constant.