Effect of transformer oil on room temperature vulcanized silicone rubber

Concerns over the operation safety of power transformers have triggered an application of room temperature vulcanized (RTV) silicone rubber on transformer bushings. However, transformer oil may cause a severe deterioration in the performance of RTV silicone rubber coatings due to oil leakage. Little attention has been paid to the degradation of RTV silicone rubber due to transformer oil. This paper presents an experimental investigation to explore the deterioration of RTV silicone rubber in transformer oil. An oil immersion experiment is performed. Mass, hardness and hydrophobicity are analyzed to research the macro properties of RTV silicone rubbers. FTIR, XPS and SEM are employed to investigate their microstructures. TG analysis is performed to evaluate their thermostability. Besides, GC-MS method is used for the analysis of the constituents of transformer oil. The results reveal that the RTV silicone rubbers deteriorate irreversibly. After immersion, the mass of RTV silicone rubber increases and the hardness decreases significantly. The hydrophobicity of RTV silicone rubber decreases after immersion and then increases with fluctuation during the standing time, but the surfaces keep hydrophobic all the time. FTIR investigations display clearly the decrease of Si-CH
₃
, Si-O-Si, Si(CH
₃
)
₂
and Si(CH
₃
)
₃
, and the increase of C-H. Besides, the change of O-H bond is very slight. XPS verifies the broken chemical bonds. The SEM photographs describe the surface structure change from the shape of chunks and spheres to uniform wrinkles and bulges. TG curves imply that some products with poor temperature resistance are generated. GC-MS analysis shows that silicone-containing molecule appears in transformer oil after immersion, which proves the deterioration of RTV silicone rubber indirectly.