While the incorporation of the inorganic fillers into polymers is envisioned to improve the properties of polymers, the organic-inorganic interface in the nanocomposite plays a prominent role in the modulation of the electrical, mechanical and thermal properties. Here, the epoxy chain-grafted silica nanoparticles were prepared and utilized as the fillers in epoxy matrix. The multiple physical properties such as the tensile strength, the elongation at break, the glass transition temperature, the dielectric strength of the nanocomposites with epoxy chain-grafted silica are simultaneously improved in comparison with those of the neat epoxy and the nanocomposites with unmodified silica. Moreover, substantial reductions in the water absorption ratio, dielectric loss and electric conductivity are obtained in the nanocomposites filled with epoxy-grafted silica even at relatively low filler loadings. These results verify the critical role of the chemically-bonded interface between organic and inorganic phases in determining the mechanical and dielectric strength of the polymer nanocomposites. The interaction zone models for the interface between nanoparticle and polymer matrix have been proposed to rationalize the experimental results.
As the transmission capacity of gas insulated transmission line (GIL) increases, the synergistic improvement in dielectric and mechanical strengths of GIL insulators is urgently needed for the development of advanced power systems. Mechanical defects in power equipment are prone to induce discharges during high voltage operations, which need to be mitigated. In this paper, the strains on the GIL insulator surface are measured by fiber Bragg grating (FBG) strain sensors during hydrostatic tests. An abnormal change of strain is detected near the interface between center conductor and the spacer. The numerical results of stress distributions of GIL insulator during manufacturing and high-voltage operation are calculated by the finite element method. The results indicate that the mechanical stresses are concentrated at the interface, which lead to the development of conductor-spacer interface separation. In addition, based on the hydrostatic test and the FEM calculations, the dielectric interfacial strength, including the electric field distribution, and flashover are investigated by a combination of numerical and experimental studies. The results indicate that the air gaps generated by the separated interface distort the electric field at the tip of the gap, which is likely to cause discharges and reduce the gas-solid interfacial flashover strength of the insulator, placing concerns of insulation failure and even operating failures of GIL. This work sheds light on the importance of interfacial structure of power equipment and will guide the design and the manufacture of GIL insulator.
This work was supported by the Tianjin Natural Science Foundation (19JCYBJC15700) entitled research on the design and optimization for storage mechanism in blockchain system based on redundant residual number system.
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