| Filling nanoparticles in polymer is an effective way to inhibit the growth of electrical tree,and the interface is the main factor affecting the properties of nanocomposite dielectric.In this paper,based on chemical grafting and plasma assisted grafting,hyperbranched polyester modified nano-SiO2/epoxy composite was obtained,and the effects of the two methods on the growth of electrical tree were studied.Firstly,the surface of nano-SiO2 was grafted with the carboxyl-terminated hyperbranched polyester(CHBP)by chemical grafting method and plasma assisted grafting method respectively.And the nano-SiO2/EP composite modified by KH550-CHBP and CHBP/DBD with different filling amount was prepared.The microstructure of composite and modified nano-SiO2 was analyzed by SEM and TEM.The activation energy of different modified composites were measured by thermally stimulated depolarization current(TSDC).And the partial discharge(PD)characteristics and electrical tree growth characteristics of nano-SiO2/epoxy composites with different interface modifications were studied.The experimental results show that the CHBP functional layer with thickness of 2.2 nm is formed on the surface of Nano-SiO2 by CHBP/DBD grafting treatment,which significantly improves the dispersion of Nano-SiO2 in epoxy resin.By filling with HBP/DBD modified nanosilica,the deep traps of 0.99～1.53 eV appear in the composite.When nano-SiO2 was filled to 3wt%,the PD initiation voltage of CHBP/DBD modified composite reached the peak value of 14.5 kV,which was 55.9%higher than that of pure EP.In addition,compared with KH550-CHBP modification method,CHBP/DBD modification can effectively improve the electrical tree resistance of nano-SiO2/EP composite.When the nano-SiO2 is filled to 5wt%,the electrical treeing performance of CHBP/DBD modified composite is the best.At this time,the extension and carbonization degree of the electrical treeing channel reach the minimum value,and the rate of the electrical treeing channel extending along the vertical electric field direction is higher,while the degradation area and the complexity of the morphology and structure of the electrical treeing are relatively highCompared with the traditional chemical grafting,a large number of short chain chbp were grafted on the surface of nano-SiO2 after plasma treatment.In this way,the bonding strength between nano-SiO2 and EP matrix is improved,and a large number of deep traps are introduced,which improves the electrical tree growth characteristics of nano-SiO2/EP composite. |
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