Hollow polymeric microsphere-filled silicone-modified epoxy as an internally insulated material for composite cross-arm applications

Abstract Composite cross-arms have been developed to take place of the steel cross-arm in the power system. In order to suit the environmental impact factors in the long-term operation, superior comprehensive properties of the internally insulated materials for composite cross-arm are required. In the present study, a syntactic foam based on hollow polymer microsphere (HPM)-filled siliconized epoxy resin (SER) was prepared for satisfying these requirements. First, the SER was synthesized using poly(methylphenylsiloxane) and an epoxy resin via a graft reaction. The as-synthesized SER was characterized via Fourier transform infrared, 1H nuclear magnetic resonance (NMR), and 13C NMR spectroscopies. Subsequently, a series of SER-based syntactic foams were fabricated using HPM with five different mass fractions. According to the thermogravimetric analysis results, the thermal stability of the composites considerably improved because of the introduction of the siloxane bond. The dielectric constant and dielectric loss of the composites simultaneously decreased with increasing HPM content. The dielectric strength of the composites remained 10.08 to 21.31 kV/mm after hydrothermal treatment, indicating excellent electrical insulation reliability. Notably, after water diffusion pre-stressing, the leakage current properties of the composites only slightly differed as the HPM content increased. These results further support their application as an internally insulated material for a composite cross-arm.