Accelerated Laboratory Aging of Synthetic Ester Dielectric Liquid

Synthetic esters are liquids used in the lubricant industry, but also in the electrical industry for insulation and heat transfer. In this work, the synthetic ester is exposed to high temperatures to initiate and propagate the degradation reactions, study the degradation process, and investigate the effect of paper and water on thermal degradation. After 672 h of thermal exposure, there is no sludge, but the color of the samples is significantly changed. Fourier transform infrared spectroscopy (FTIR) is used to assess the occurrence of degradation products, the neutralization value is used to determine the total acidity, and the relative permittivity is used to correlate the influence of degradation products on the dielectric properties of the synthetic ester. Nuclear magnetic resonance (NMR) and color analysis are used to investigate the appearance and composition of the degradation products of seven selected samples. The NMR study shows that the change observed in the FTIR spectra, the neutralization value, and the relative permittivity as a function of aging conditions correspond very well with the size and shape of the 1 H NMR peak of 3.51 ppm, confirming that the formation of alcohols, ethers, and cross-links is responsible for the aging of the ester. It is found that the color change is misleading when it comes to the degradation of the synthetic ester dielectric liquid.