Mineral Oil‐Induced Ageing Characteristics of Aluminium Nitride‐Doped Silicone Rubber Nanocomposites

ABSTRACT Room temperature vulcanised (RTV) silicone rubber, commonly used as an external insulating coating on ceramic bushings of oil‐immersed transformers, undergoes significant degradation when exposed to mineral oil under harsh environmental conditions. Therefore, the present study investigates the ageing characteristics of aluminium nitride (AlN)‐doped silicone rubber nanocomposites subjected to mineral oil ageing at 80°C for 200 h. Nanocomposites with 0, 1 wt.%, 3 wt.% and 5 wt.% AlN were fabricated. Post‐ageing, Fourier transform infrared spectroscopy (FTIR) confirmed the scission of side chains and main backbone chains in the silicone rubber matrix. This degradation resulted in decreased surface hydrophobicity and shore hardness, along with increased surface roughness, as evidenced by contact angle measurements, shore hardness testing and 3‐D microscopy, respectively. Surface potential measurements indicated reduced surface charge dissipation capability in the aged specimens. Additionally, inclined plane tracking and erosion (IPT‐E) tests performed according to IEC 60587 revealed a significant decline in tracking and erosion resistance. Thermogravimetric analysis and IR thermography showed reduced thermal stability and increased heat accumulation in the aged samples. Overall, the 3 wt.% of AlN‐doped nanocomposite demonstrated superior resistance to degradation, suggesting its potential for improved performance under mineral oil ageing conditions for transformer bushing applications.