| Epoxy resin was widely used in many fields of electrical insulation as it hadexcellent bonding power and mechanical properties. But its poor impact resistanceand brittleness limited its use in the more demanding fields. In recent years, as thecarbon nanotubes modified epoxy resin research report more and more, it was foundthat the mechanical properties of epoxy nanocomposites showed significantimprovement with the content of MWNTs/EP nanoparticles. The results indicated,when compared to the pure epoxy resin, that the mechanical and thermal propertiesof the nanocomposite could be greatly improved by addition of MWNTs loading.When the MWNTs content increases to a certain value, the conductivity of Epoxyresin decreased, Lewis and Nelson pointed out that the interfacial action plays animportant effect to the structure and property of the composite materials. However, itwas different from zero nano materials to adhere with resin because of great length todiameter ratio, but the relationship between the microstructure and macro propertieswas still unclear. On the basis of current research status of polymer-basednanodielectric, purposed to explore the relationship between interface structure andmacroscopic properties of nanodielectric.In this paper, bisphenol A epoxy resin was modified by multi-walled carbonnanotubes (MWNTs) functionalized with carboxylic acid group(C-MWNTs) and theorganic montmorillonite(O-MMT), respectively. EP/MWNTs and EP/MWNTs/MMTnano-composites were prepared by solution blending method, and the curing agentused was methyl-hexahydro phthalic anhydride (MeHHPA). The dielectric strength,volume resistivity, dielectric contant and loss of EP/MWNTs nano-composites weretested by the breakdown voltage tester and broadband dielectric spectrometer,respectively. The “Double-layers interface model of EP/MWNTs/MMTnano- composites” was set up based on the simulation of interface structure betweenMWNTs, MMT and EP matrix, which was used to analyse the dielectric andinsulating properties of nano-composites. In this article，the content of MWNTs was0to1.5wt%, the content of O-MMT was4wt%. The result shows that the volumeresistivity of nano-composites decreased no matter how the different length todiameter ratio MWNTs were treated, but it only reduced one order of magnitudewhen the doping amount of MWNTs ranged from0.2wt%to1.5wt%. At the sametime, the dielectric strength of nano-composites increased first and then decreasedwith the increasing content of MWNTs. However, When doped O-MMT,EP/MWNTs/MMT composites specimen had lower volume resistivity decreased, theamount of carbon nanotubes doped0.2to0.6wt%, the volume of the sampleresistivity offered upgrade firstly than descending latter tendency, at the same timethe breakdown strength of specimen with O-MMT doping offered upgrade firstlythan descending latter tendency. the “Double-layers interface model ofEP/MWNTs/MMT nano-composites” not only could simulate the transformation ofinteraction regions between MWNTs, MMT and resin matrix but also could make anexplanation for the variation of the dielectric strength and volume resistivity ofEP/MWNTs/MMT composites. When the MWNTs doping amount is small, O-MMTwas EP/MWNTs/MMT composites specimen of the dielectric constant of the mainfactors. The smaller the diameter of MWNTs is, the greater the falling range ofdielectric contant of nano-compocites is. It is found that a larger doping amount ofMWNTs (1.0wt%) occurred when the dielectric contant of EP/MWNTs/MMTcomposites modified C-MWNT-1020reached to the minimum value, compared to C-MWNTs-4060with the larger diameter. |
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