Non-Destructive Testing of Silicone Rubber Formulations for Composite Insulators Based on Terahertz Spectral Analysis

The silicone rubber formulation of composite insulators directly determines their hydrophobic characteristics, anti-aging properties, electrical and mechanical performance, etc. Currently, there are numerous insulator manufacturers and there is a lack of a non-destructive, rapid testing method for silicone rubber formulations. This leads to the fact that some silicone rubber products fail to meet grid requirements due to cost, technical, or other reasons, resulting in issues such as aging and heating. Based on terahertz spectroscopy, this paper proposes a new non-destructive, rapid method for testing silicone rubber formulations. First, a terahertz spectroscopy testing platform was built, silicone rubber samples with different formulations were prepared, and the absorption spectrums of the samples in the 0-3 THz frequency range were tested. Then, the molecular models of main components in high-temperature vulcanized silicone rubber (HTV) were established, and the calculated spectra of different fillers in the 0-3 THz range were obtained. The origin of terahertz absorption peaks in silicone rubber were analyzed, and the vibration modes of the filler molecules at corresponding frequencies were studied and verified by experiments. Next, based on theoretical predictions and elemental component test results, a characteristic frequency range for characterizing silicone rubber formulations was proposed. Finally, using successive projection algorithms (SPA), the characteristic frequencies of the silicone rubber’s spectral absorption spectrums were determined, and the multivariable linear regression (MLR) method was applied for regression calculation, establishing the relationship between absorption spectrum of silicone rubber and filler content. The results showed that this method could rapidly and non-destructively measure the content of various components, with prediction errors for ATH, PDMS, and SiO₂ of 0.2286%, 0.1751%, and 0.2400%, respectively, all superior to TGA. This approach holds promise as a technological solution for large-scale application of silicone rubber products.