Magdalena Żółty

This article presents studies on the degradation susceptibility of two commercially available gear oils used in electric passenger vehicle transmissions. A series of aging tests were conducted using selected research methods. Due to the lack of a recommended methodology for testing the thermal oxidation stability of such oils, standardized methods were applied: ASTM D5704, ASTM D8206, ASTM D2272, PN-EN 16091, and PN-C-04080. To determine the degree of degradation, changes in physicochemical parameters (kinematic viscosity at 40 °C and 100 °C and acid number) and changes in the chemical character of oil components, based on FTIR spectra, were evaluated. Significant changes in properties were found in the tested oils, which were confirmed by spectral analysis. It was found that all the mentioned methods for assessing thermal oxidation stability are suitable for evaluating such oils, but they differ in the aggressiveness of the method towards the tested oil. These methods can be ranked according to their impact on the degradation of the tested oil.

The European Union requirements related to the quality parameters for fatty acid methyl esters (FAMEs) are gathered in the standard EN 14214:2012 + A2:2019 that also includes reference to low-temperature properties. This paper presents studies on the obtaining of modified FAMEs, featuring improved low-temperature properties. Investigated fatty acid methyl esters (FAMEs) were subjected to a solvent dewaxing process with a methyl ethyl ketone and the mixture of methyl ethyl ketone—Toluene. It was found that the application of a process carried out under conditions similar to solvent dewaxing, used as a standard procedure for oils dewaxing and slack waxes of petroleum origin deoiling usually used in refinery industrial installations, allows us to achieve the intended goal. The modification of three different types of FAME by the dewaxing process with MEK-TOL and MEK solvents allows for the improvement of low-temperature properties of the obtained modified FAME, consistent in obtaining reduced cloud points, flow points and CFPP. The tests of fatty acid profiles show a clear increase in the content of glycerides of saturated acids in the separated sludge, as compared to the charges from the dewaxing process, which confirms that the selectivity of the dewaxing process is maintained for the atypical raw material, which are fatty acid methyl esters.

Four base oils of different chemical nature were subjected to an oxidation processes using the ASTM D 8206-18 method. On the basis of these oils, three different types of lubricating greases were manufactured: lithium, silica and polyurea lubricating greases. Samples of the lubricating greases...