The Influence of Surface Chemical Modifications on the Hydrophobicity of Chinese HTV Rubber

The Influence of Surface Chemical Modifications on the Hydrophobicity of Chinese HTV Rubber

Chinese htv rubber is an important material for composite insulators used in high-voltage transmission lines. However, it is vulnerable to many environmental stresses, such as pollution, ultraviolet radiation, heat, and salt-fog. These stressors cause the long chain structure of silicone rubber to be broken and to decrease its hydrophobicity, leading to poor insulating properties. Hence, it is necessary to develop a new type of silicone rubber with good hydrophobicity.

The current study investigates the influence of surface chemical modifications on the hydrophobicity of a chinese htv rubber. Firstly, the hydrophobicity of a htv silicone rubber was measured by the contact angle test. Secondly, the surface modification of the silicone rubber was evaluated by two-dimensional MRSD. Finally, the aging performance of the modified silicone rubber was tested in a salt-fog environment. The results showed that the degradation of the silicone rubber led to a reduction in the DC insulating performance and salt-fog resistance.

Various liquids such as water, salt, and nitric acid could permeate into the HTV silicone rubber. These liquids can cause corrosion and damage to the high-voltage composite insulator. Therefore, it is very important to understand how these liquids affect the surface chemical properties of HTV silicone rubber. Previous studies [12, 13] have shown that these liquids can permeate into the HTV silicone rubber through a diffusion process accompanied by chemical interaction and physical dissolution processes. These liquids can also interact with and dissolve the inorganic filler (mainly the ATH filler) beneath and/or on the HTV silicone rubber surface and change its surface chemical properties.

For this purpose, the HTV silicone rubber samples were immersed in deionised water, NaCl solutions (0.1, 0.5, and 1 mol/l), and nitric acid solution (0.001, 0.01, and 0.1 mol/l) for different durations and then dried in a desiccator. During the immersion and drying process, the temperature was kept in the range of 30 +- 1degC.

After the immersion and drying processes, the MRSD of the HTV silicone rubber samples was performed using a 2D MRSD system. The Daubechies wavelet of order 4 was chosen as the basis function in this analysis. The results of the MRSD were hierarchically plotted at different resolutions, as illustrated in Fig. 7. As expected, the original HTV silicone rubber surface was more hydrophobic than the surface after nitric acid solution immersion and drying.

This article presents a systematic research on the hydrophobicity of chinese htv rubber through the use of two-dimensional MRSD and three-dimensional fractal dimension. The results indicate that the fractal dimension of the original HTV silicone rubber was 2.19, which is higher than that of the silica with the smallest particle size. The higher fractal dimension of the original HTV silicon rubber may be related to its lower intermolecular force between methyl groups. In addition, the higher fractal dimension of the sample after nitric acid immersion and drying probably indicates its stronger ability to resist corrosion by nitric acid. This result supports the hypothesis that the hydrophobicity of chinese HTV rubber is mainly due to its low intermolecular force and its unique flexibility of the siloxane backbone of PDMS.

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