Surface tension of fresh and used marine motor oils

Abstract

It is well known that the effectiveness of lubricating oils depends on temperature. An important role in the effectiveness of lubrication is played by the sur-face tension of the oil at the interface of phase. Determination of the surface tension properties of motor oils is very desirable, since it has direct industrial significance. Although surface tension is not the most important property in determining relative lubricity, the relationship between the physical properties of used oils and surface tension has not been sufficiently studied to date. Differences in the surface tension of lubricants result in differences in their ability to maintain these thin films. It seems that in the absence of published data on the surface tension of used motor oils, the study of temperature dependences will be important for solving diagnostic problems. This article focuses on the measurement of interfacial tension and its significance when the oil is contaminated, for example, by polar organic compounds that are formed during engine operation. Interaction of oil, water and oxygen reduces oil functionality. These contaminants are attracted to the oil/air interface and, as a result, significantly reduce the interfacial tension. The temperature dependences of the density and surface tension coefficients of fresh and used marine motor oils have been measured and approximated. Correlations between these parameters have been established, which is important for the diagnostic task.