Study on the effect of corona on hydrophobicity recovery performance of RTV silicone rubber and its failure criterion

Room temperature vulcanized (RTV) silicone rubber is widely used in external insulation of electrical equipment for antipollution flashover because it has many merits such as superior hydrophobicity and migration of hydrophobicity, but it also has weakness such as poor aging performance. The study on the failure criterion of RTV silicone rubber is always a concern since there has been no generally accepted method for its failure criterion. Corona has an important effect on the hydrophobicity and its recovery performance of RTV silicone rubber. In this paper, tests were conducted to reveal the effect of corona on the hydrophobicity recovery performance, and a failure criterion has been proposed. PRTV (permanent RTV) silicone rubber, a commonly used nanocomposite, was selected as the samples to study the hydrophobicity and its recovery after different corona aging time. Before the onset of aging, the factors that affect the accuracy of the contact angle measurement were studied. Fourier transform infrared spectroscopy (FTIR) was employed to find the failure criterion. The results show that, the relatively accuracy of the test data of contact angle can be obtained with 4 μL water drops and proper grounding of the test sample for 2 min. It is also found that the hydrophobicity is permanently lost when the continuous aging time is longer than 70 h under the test conditions, and compared with the virgin samples through FTIR, the peak height of CH
₃
(C-H), Si-CH
₃
and Si-O-Si in FTIR decreases by 64.9%, 47.0% and 25.9%, respectively for the aged samples. It is suggested that, the variation of peak height of CH
₃
(C-H), Si-CH
₃
and Si-O-Si in FTIR can be taken as the quantitative index of failure criterion of RTV silicone rubber.