Abstract
Room temperature vulcanized (RTV) silicone rubber is extensively used in power system due to its hydrophobicity and hydrophobicity transfer ability. Temperature has been proven to markedly affect the performance of silicone rubbers. This research investigated the degradation of RTV silicone rubber under temperature cycling treatment. Hydrophobicity and its transfer ability, hardness, functional groups, microscopic appearance, and thermal stability were analyzed using the static contact angle method, a Shore A durometer, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetry (TG), respectively. Some significant conclusions were drawn. After the temperature was cycled between −25 °C and 70 °C, the hydrophobicity changed modestly, but its transfer ability changed remarkably, which may result from the competition between the formation of more channels for the transfer of low molecular weight (LMW) silicone fluid and the reduction of LMW silicone fluid in the bulk. A hardness analysis and FTIR analysis demonstrated that further cross-linking reactions occurred during the treatment. SEM images showed the changes in roughness of the RTV silicone rubber surfaces. TG analysis also demonstrated the degradation of RTV silicone rubber by presenting evidence that the content of organic materials decreased during the temperature cycling treatment.
Highlights
Pollution flashover accidents threaten the reliability and the safe operation of power systems, and they have been intensively studied in recent years [1,2,3]
After the aging time of 20 days, 40 days, and 60 days, the static contact angles of both Sample 1 and Sample 2 change modestly in comparison with the virgin ones. This implies that the surface of the samples always remains hydrophobic, and temperature cycling has a slight effect on the hydrophobicity of the Room temperature vulcanized (RTV) silicone rubber surface
Through measurement of the static contact angle of the pollution layers, which were formed by the drying of the suspensions, the hydrophobicity transfer ability of the samples was depicted
Summary
Pollution flashover accidents threaten the reliability and the safe operation of power systems, and they have been intensively studied in recent years [1,2,3]. Due to the promising properties, such as hydrophobicity and transfer of hydrophobicity, room temperature vulcanized (RTV) silicone rubber coatings are widely used to prevent pollution flashover, which has been proven to be effective in the presence of pollution and humidity [4,5,6]. Numerous aging problems exist in the long-term use of RTV silicone rubbers, which can cause changes in their physical and chemical properties [7,8]. Since testing methods for evaluating the long-term reliability have not been completely standardized, it becomes vitally necessary to assess the effect of environmental factors and operating conditions on the properties of RTV silicone rubbers. The degradation of silicone rubbers has been extensively studied and some valuable conclusions have been drawn. There were several factors responsible for the degradation, including corona, ultraviolet, liquid absorption, etc. [9,10,11,12], in all of which temperature was considered to be one of the Energies 2017, 10, 1054; doi:10.3390/en10071054 www.mdpi.com/journal/energies most crucial crucialfactors
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