In this article, two synthetic esters along with a natural ester are investigated to monitor the generation of colloidal and dissolved decay particles under thermal aging. The thermal aging of the oils is carried out as per a modified ASTM D1934 in the presence of cellulose and copper at elevated temperatures. Later, the colloidal and dissolved decay particles are monitored as per ASTM D1698 (centrifuge treatment) and ASTM D7150 (Fuller's earth filtration), respectively. The aged and treated dielectric liquids are characterized for the number of decay particles, oil absorbance curves, the concentration of dissolved decay content, and turbidity as per ASTM standards. The evolution of colloidal and dissolved decay contents is individually reported for ester fluids and mineral oils. The degradation in mineral oils has been witnessed by both dissolved and colloidal particles. The generation of colloidal particles following the degradation of ester fluids is almost negligible, whereas dissolved decay content is noticed with thermal degradation time. Importantly, the obtained results depict the ability of esters to dissolve more sludge. This is due to the high (oxidative) stability of ester leading to reduced radical decomposition products. Also, the temperature solvent nature of the ester group tends to dissolve sludge particles back to the liquid phase into the bulk liquid.

中文翻译：

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监测酯类介电流体中的胶体和溶解衰变粒子

在本文中，研究了两种合成酯和一种天然酯，以监测热老化下胶体和溶解衰变颗粒的产生。油的热老化根据修改后的 ASTM D1934 在纤维素和铜的存在下在升高的温度下进行。随后，分别按照 ASTM D1698（离心处理）和 ASTM D7150（富勒土过滤）对胶体和溶解的衰变颗粒进行监测。根据 ASTM 标准，老化和处理过的介电液体的特征在于衰减颗粒的数量、吸油率曲线、溶解衰减内容的浓度和浊度。酯流体和矿物油的胶体和溶解衰变含量的演变单独报告。溶解和胶体颗粒都见证了矿物油的降解。酯流体降解后胶体颗粒的产生几乎可以忽略不计，而随着热降解时间的推移，溶解的腐烂含量会被注意到。重要的是，获得的结果描述了酯溶解更多污泥的能力。这是由于酯的高（氧化）稳定性导致自由基分解产物减少。此外，酯基团的温度溶剂性质倾向于将污泥颗粒溶解回液相进入大量液体。获得的结果描述了酯溶解更多污泥的能力。这是由于酯的高（氧化）稳定性导致自由基分解产物减少。此外，酯基团的温度溶剂性质倾向于将污泥颗粒溶解回液相进入大量液体。获得的结果描述了酯溶解更多污泥的能力。这是由于酯的高（氧化）稳定性导致自由基分解产物减少。此外，酯基团的温度溶剂性质倾向于将污泥颗粒溶解回液相进入大量液体。