| Epoxy resin (EP) cured by anhydride is the thermoset resin widely used inelectrical insulation application areas. EP modified by nano-materials receives moreand more attention with the improvement of perfomence requirements for EPmaterials in electrical insulation. Different kinds of interface regions will beformed among different types or shapes nano-particles and resin matrix. As abond between organic and inorganic components, the influence of interface onperformance of epoxy nanocomposites in many aspects has gained widely focuse.In this paper, bisphenol A epoxy resin was modified by multi-walled carbonnanotubes (MWNTs) functionalized with carboxylic acid group(C-MWNTs) andepoxy functionalized carbon nanotubes (E-MWNTs), respectively. EP/MWNTsnano-composites were prepared by solution blending method, and the curingagent used was methyl-hexahydro phthalic anhydride (MeHHPA). ScanningElectric Microscopy (SEM) was employed to investigate the microscopicstructure of MWNTs in acetone solvent. The changes of groups on the surface ofMWNTs were characterized by means of Fourier transform infrared spectroscopy(FTIR). The dielectric strength, volume resistivity, dielectric contant and loss ofEP/MWNTs nano-composites were tested by the breakdown voltage tester andbroadband dielectric spectrometer, respectively. The “Double-layers interfacemodel of EP/MWNTs nano-composites” was set up based on the simulation ofinterface structure between MWNTs and EP matrix, which was used to analysethe dielectric and insulating properties of nano-composites.The result shows that the “Double-layers interface model of EP/MWNTsnano-composites” not only could sumalate the transformation of interactionregions between MWNTs and resin matrix but also could make an explainationfor the variation of the dielectric strength and volume resistivity of EP/MWNTsnano-composites. The volume resistivity of nano-composites decreased no matter how the MWNTs were treated, but it only reduced one order of magnitude whenthe doping amount of MWNTs ranged from0.2wt%to1.5wt%. At the sametime, the dielectric strength of nano-composites increased first and thendecreased with the increasing content of MWNTs. The functionalization methodshave the major impact on the dielectric contant of nano-compocites when thedoping amount of MWNTs was smaller, but the diameter of MWNTs turn to bethe main influence factors of the dielectric contant of nano-compocites with thedoping amount of MWNTs increased. The smaller the diameter of MWNTs is, thegreater the falling range of dielectric contant of nano-compocites is. It is foundthat a larger doping amount of MWNTs (1.2wt%) occurred when the dielectriccontant of EP/MWNTs nano-composites modified C-MWNT-1020reached to theminimum value (is2.53in power frequency), compared to C-MWNTs-4060withthe larger diameter. Larger interface regions and stronger bonding formedbetween E-MWNTs and EP matrix rather than the C-MWNTs. It could beconcluded that the interface can limit the movement of intrinsic dipoles under theeffect of electric field, which may be the dominant factor to affect the dielectricproperties of EP/MWNTs nano-composites. |
PDF Full Text Request