Manifestation of Interactions of Nano-Silica in Silicone Rubber Investigated by Low-Frequency Dielectric Spectroscopy and Mechanical Tests

Abstract

Silicone rubber composites filled with nano-silica are currently widely used as high voltage insulating materials in power transmission and substation systems. We present a systematic study on the dielectric and mechanical performance of silicone rubber filled with surface modified and unmodified fumed nano-silica. The results indicate that the different interfaces between the silicone rubber and the two types of nano-silica introduce changes in their dielectric response when electrically stressed by a sinusoidal excitation in the frequency range of 10−4–1 Hz. The responses of pure silicone rubber and the composite filled with modified silica can be characterized by a paralleled combination of Maxwell-Wagner-Sillars interface polarization and DC conduction. In contrast, the silicone rubber composite with the unmodified nano-silica exhibits a quasi-DC (Q-DC) transport process. The mechanical properties of the composites (represented by their stress-strain characteristics) reveal an improvement in the mechanical strength with increasing filler content. Moreover, the strain level of the composite with a modified filler is improved.

Silicone Rubber Composites with High Breakdown Strength and Low Dielectric Loss Based on Polydopamine Coated Mica

“…Silicone rubber (SR) has been widely used in high-voltage outdoor insulation due to the excellent hydrophobicity and weather-resistance [1][2][3]. Fillers are added into the pure SR to improve specific properties as well as to reduce cost [4][5][6].…”

Effects of alkyl/vinyl‐modified nanosilicas on negative or positive high voltage direct current breakdown strength and tensile properties in silicone rubber nanocomposites

“…[9][10][11] In general, electrical, mechanical and physical properties of silicone rubbers are greatly improved by incorporating 20-30 wt% of nanosilica. 12,13 However, since the affinity between hydrophobic silicone rubber and hydrophilic nanosilica is low, it is very difficult to disperse uniformly the nano-sized fumed silica in the silicone rubber, so the nanosilica particles exist in agglomerated state in the silicone rubber. Therefore, electrical, physical, and mechanical properties are affected negatively by the bad interfacial characteristics.…”

“…[14][15][16] When external stress such as electrical, mechanical and heat stress are applied to a nanocomposite, micro-cracks are generated at weak interfaces, propagated and fractured. 12,17 To modify the interfacial characteristics, the nanosilica surface should be treated with hydrophobic alkyl or vinyl groups using coupling agents. 18 In liquid silicone rubber (LSR) systems, vinyl groups of polysiloxanes react with silicon-hydrogen bonds (Si-H) of poly hydrogen siloxanes via the hydrosilylation reaction catalyzed by a platinum complex.…”

“…Therefore, electrical, physical, and mechanical properties are affected negatively by the bad interfacial characteristics 14–16 . When external stress such as electrical, mechanical and heat stress are applied to a nanocomposite, micro‐cracks are generated at weak interfaces, propagated and fractured 12,17 . To modify the interfacial characteristics, the nanosilica surface should be treated with hydrophobic alkyl or vinyl groups using coupling agents 18 …”

Silicon-Containing Polymeric Materials

“…During the evaluation of silicone composites they observed modifications in the dielectric response with both of the two type of silica used: a paralleled combination of Maxwell-Wagner-Sillars interface polarization and DC conduction by using the modified silica; a quasi-DC transport process by using the unmodified nano-silica. They also observed an improvement in the mechanical strength with increasing silica content [ 7 ].…”