| Polymer-based dielectric materials have a wide range of applications in the fields of microelectronics and dielectric energy storage.Polymer-based dielectric materials have important significance in promoting the development of national economy and improving the national military ability.Epoxy resin?EP?has the advantages of low shrinkage and good thermal stability,but dielectric constant of EP is low.The range of applications of EP is broadened,when the dielectric constant of EP is increased.High conductivity carbon nanotubes?CNTs?can greatly increase the dielectric constant of EP.The unfunctionalized CNTs containing large amounts of impurities such as metal catalysts and amorphous carbon,etc.The effective dispersion of unfunctionalized CNTs in matrix resin is poor because the surface of CNTs lacks active functional groups.The surface of CNTs is grafted with active functional groups by chemical modification.The CNTs of core-shell structure is made by coating treatment.The dielectric constant of EP is increased by adding functionalized CNTs.The interface is the main factor of influencing electrical property of the composites.In this article,the effect of interface between CNTs and EP on dielectric properties and insulation properties of composites is analyzed,based on the theory of interface model.In this paper,EP with Bisphenol A was used as the matrix material.The carbon nanotubes of high conductivity were used to modify EP as the filler material.Carboxyl functionalized carbon nanotubes?C-CNTs?were prepared by mixed acid oxidation reaction.The surface of C-CNTs was coated SiO2,TiO2,PANI,passing sol-gel method and in-situ polymerization process,respectively.SiO2@CNTs,TiO2@CNTs,PANI@CNTs were made.C-CNTs/EP,SiO2@CNTs/EP,TiO2@CNTs/EP,PANI@CNTs/EP composites materials were prepared by solution blending.The coating effect of carbon nanotubes was characterized by Fourier Transform Infrared Spectroscopy?FT-IR?,Scanning Electron Microscope?SEM?and Transmission Electron Microscope?TEM?.The fracture structure of EP composites was observed by SEM.Dielectric constant,dielectric loss,electrical conductivity,and breakdown strength,impact strength,hot property of EP composites were tested.The results showed that the surface of C-CNTs was separately obviously coated with SiO2,TiO2,PANI after being treated and the coating effect was obvious.The dispersity of SiO2@CNTs and TiO2@CNTs was better in solution.The dielectric constant and dielectric loss of C-CNTs/EP,SiO2@CNTs/EP,TiO2@CNTs/EP,PANI@CNTs/EP composites were gradually increasing with the increase of CNTs.At 100 Hz,when the content of nanomaterials of C-CNTs/EP,SiO2@CNTs/EP,TiO2@CNTs/EP,PANI@CNTs/EP was 7.0 wt%,the dielectric constant of PANI@CNTs/EP,TiO2@CNTs/EP,SiO2@CNTs/EP,C-CNTs/EP composites was 54.8,27.3,10.3,74.2,respectively.The dielectric constant of C-CNTs/EP,SiO2@CNTs/EP,TiO2@CNTs/EP,PANI@CNTs/EP composites was severally about 14.1,7.0,2.6,19.0 times that of pure EP.The dielectric constant of epoxy resin was improved by CNTs with shell material with good conductivity and good compatibility.When the content of nanomaterials of the EP composites was large,the dielectric loss of SiO2@CNTs/EP,TiO2@CNTs/EP composites was lower than that of C-CNTs/EP,PANI@CNTs/EP composites.The dielectric loss of EP composites could be reduced by CNTs with coating insulating material.When the content of nanomaterials of SiO2@CNTs/EP composites,TiO2@CNTs/EP composites was 1.0 wt%,SiO2@CNTs,TiO2@CNTs could improve the breakdown strength of EP.In all the core-shell CNTs/EP composites,the thermal properties of EP was greatly improved by PANI@CNTs. |
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