Abstract
To enhance the bond strength of the nanosized silica/epoxy interface and modify the dielectric properties of nanocomposites, a plasma-assisted surface modification method is proposed for inorganic nanofillers. A gas–liquid two-phase dielectric barrier discharge at room temperature was initially used to graft the terminal carboxyl hyperbranched polyester onto the nanosilica surface. Then, epoxy resin composites filled with 1–7 wt. % nanosilica were prepared. The effects of the plasma-treated nanosilica on the dielectric properties of the epoxy resins were analyzed. The experimental results demonstrated that a 2 nm-thick film of hyperbranched polyester (HBP) was successfully deposited onto the nanosilica surface via the HBP/plasma treatment. Compared with the pristine epoxy resins at room temperature, the permittivity constant of the proposed nanocomposites decreased from 4.2 to 3.3 and their AC breakdown strength increased by 38%. Moreover, the dielectric loss factor and DC conductivity decreased by 40.7% and 48.4%, respectively. Additionally, deep traps of 0.99–1.53 eV were observed in the nanocomposites. It can be concluded that HBP/plasma processing creates strong chemical bonds and compact nanofiller/polymer interfacial regions. In addition, HBP/plasma processing modified the dielectric properties of the nanocomposites. The results of this study indicate that HBP/plasma treatment is an effective method for the surface modification of inorganic nanofillers and for the modification of the dielectric properties of polymer nanocomposites.
Highlights
Nanofilled polymers exhibit good mechanical,1,2 thermal,3 anti-corrosion,4,5 flame retardant,6 and insulating1,7 performance.8,9 Because of their good thermal resistance and insulating properties, inorganic nanofillers, such as silica and zinc oxide, are often used as insulating polymer materials
It was found that after completion of the hyperbranched polyester (HBP)/plasma treatments, the thickness of the carboxyl hyperbranched polyester (CHBP) layer grafted on the nanosilica surface was 2 nm smaller than that with the silane-HBP modifier
In the silane-HBP method, silane is used as the coupling agent for the nanosilica, while no such coupling agents were used for the HBP/plasma processing method; the bonds in the nanosilica and CHBP matrix were still significantly enhanced by plasma exposure, and this can be ascribed to the modification of the nanosilica surface by the plasma
Summary
Nanofilled polymers exhibit good mechanical, thermal, anti-corrosion, flame retardant, and insulating performance. Because of their good thermal resistance and insulating properties, inorganic nanofillers, such as silica and zinc oxide, are often used as insulating polymer materials. Nanofilled polymers exhibit good mechanical, thermal, anti-corrosion, flame retardant, and insulating performance.. Nanofilled polymers exhibit good mechanical, thermal, anti-corrosion, flame retardant, and insulating performance.8,9 Because of their good thermal resistance and insulating properties, inorganic nanofillers, such as silica and zinc oxide, are often used as insulating polymer materials. Because the surface activity of the inorganic nanofiller is usually insufficient in its original state, surface modification must be carried out before application. HBP modified nanofiller surfaces that exhibit improved bonding with polymer molecules have been introduced.. HBP modified nanofiller surfaces that exhibit improved bonding with polymer molecules have been introduced.13–15 This has enabled remarkable enhancement of the bending/tensile strength, glass transition temperature (Tg), and insulating behavior of polymers filled with the HBP-treated nanofillers.. The removal of these accelerants is of importance for the optimal performance of HBP as a nanofiller
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