Abstract

The dielectric properties of flaxseed, sunflower, mustard, rapeseed, and olive oils were studied in the temperature range 25–70˚C and in the frequency range of the electric field 25 Hz–1 MHz. A mechanism for the hardening of vegetable oils is proposed according to temperature-dielectric spectroscopy. The hardening of oils is interpreted as a combination of crystallization processes of triglycerides of saturated fatty acids and glass transition processes of triglycerides of unsaturated fatty acids. The glass transition temperature should be considered the true pour point, which allows setting the low temperature limit of the operability of vegetable oils as insulating liquids. Linear correlations between physicochemical, dielectric properties, and fatty acid composition of oils were established. The data presented can be used to assess the quality of vegetable oils, identify falsifications and to obtain oils with a balanced composition of fatty acids. The data derived can also be utilized in the selection of oils as oleochemical raw materials and for the development of compositions of electrical insulating liquids.

中文翻译：

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植物油的介电谱

摘要

研究了亚麻籽油，葵花籽油，芥菜油，菜籽油和橄榄油在25–70°C的温度范围和25 Hz–1 MHz的电场频率下的介电性能。根据温度-介电谱，提出了一种植物油的硬化机理。油的硬化被解释为饱和脂肪酸的甘油三酯的结晶过程和不饱和脂肪酸的甘油三酯的玻璃化转变过程的组合。玻璃化转变温度应被视为真正的倾点，这可以设定植物油作为绝缘液体的可操作性的低温极限。建立了油的物理化学，介电性能和脂肪酸组成之间的线性关系。所提供的数据可用于评估植物油的质量，识别伪造并获得具有均衡脂肪酸组成的油。导出的数据还可用于选择油类作为油脂化学原料，以及用于开发电绝缘液体的成分。