| In the power industry,as the transmission capacity continues to increase,the voltage level gradually increases,and the requirements for the safety and reliability of various power equipment operations are also increasing.To enhance the bond strength of the nanosized silica/epoxy interface and modify dielectric properties of nanocomposites,a plasma-assisted surface modification method is proposed for inorganic nanofillers.A gas-liquid two-phase dielectric barrier discharge at the room temperature is initially used to graft the hyperbranched polyester(HBP)with 12 terminal carboxyl radicals onto the nanosilica surface.Then,epoxy resin composites filled with 1-7 wt%of nanosilica are prepared.Moreover,effects of the plasma-treated nanosilica on dielectric properties of epoxy resins are analyzed.Experimental results show that a HBP film of 2nm thickness can be successfully deposited onto the nanosilica surface by the bridging effect of NH2 radicals.Compared with that of pristine epoxy resins at the room temperature,the permittivity constant of the proposed nanocomposites decreases from 4.2 to 3.3,their AC breakdown strength increased by 38%,Moreover,the dielectric loss factor and DC conductivity decreases by 40.7%and 48.4%,respectively.Furthermore,deep traps of 0.99-1.53eV are observed in the nanocomposites.It is concluded that the HBP/plasma processing creates strong chemical bonds and compact-volume nanofiller/polymer interfacial regions.In addition,the HBP/plasma processing modifies dielectric properties of nanocomposites.This study indicates that the HBP/plasma treatment is an effective method for surface modification of inorganic nanofillers and modification of dielectric properties of polymer nanocomposites. |
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