Influence of humidity on the tribological performance of unmodified soybean and sunflower oils

Abstract

In general, vegetable oils exhibit superior lubrication properties but lack the thermal stability of petroleum base stocks. However, vegetable oils could make an ideal candidate as a base stock for lubrication applications involving high humidity levels, such as marine and offshore applications. This study focuses on the friction and wear rate of unmodified soybean and sunflower oils in comparison with an unformulated mineral oil at various levels of relative humidity, ranging from 10% to 98% RH. It was observed that the vegetable oils retain their friction and wear reducing capabilities much better than the mineral oil at high humidity levels. This was attributed to their inherent ability to react with the metallic contacting surfaces and form multilayers of soap films. Furthermore, the soybean oil provided a superior level of wear resistance when compared with the sunflower oil at extremely high levels of relative humidity due to its lower viscosity and differences in chemical compositions.

The Effect on Diesel Injector Wear, and Exhaust Emissions by Using Ultralow Sulphur Diesel Blending with Biofuels

“…12,13) Biodiesel is a clean burning mono-alkyl ester-based oxygenated fuel made from natural, renewable sources such as new/used vegetable oils and animal fats. 14) Although biodiesel contains no petroleum products, its main characteristics are similar to those of conventional diesel. Therefore, it can be blended in any proportion with mineral diesel to create a stable biodiesel blend.…”

Dika nut oil as base oil for lubricants — effect of processing conditions on physicochemical properties

“…The need to harness all available resources for biolubricants is partly based on the rapid depletion of the world fossil fuel reserves and partly on environmental implications of mineral oil . Also, in the recent years, there have been increased considerations on the use of vegetable oils in various industries because the oils have high flash points and very high viscosity index, they are biodegradable and nontoxic to the environment.…”

“…Adhesion of the molecular layer to metal surface results in the formation of a surface film, which inhibits metal‐to‐metal contact and progression of pits and asperities on the metal surface . In addition, vegetable oils have high solubilising power for polar contaminants and additive molecules, low volatility and excellent temperature–viscosity properties …”

“…The need to harness all available resources for biolubricants is partly based on the rapid depletion of the world fossil fuel reserves and partly on environmental implications of mineral oil. [1][2][3][4][5] Also, in the recent years, there have been increased considerations on the use of vegetable oils in various industries because the oils have high flash points and very high viscosity index, they are biodegradable and nontoxic to the environment. Furthermore, the oils exhibit satisfactory lubricity because of the inherent polar ester groups that enhance adherence to metal surfaces, creating a close packed monomolecular or multimolecular layers.…”

“…3,6 In addition, vegetable oils have high solubilising power for polar contaminants and additive molecules, low volatility and excellent temperature-viscosity properties. 1,3,4,7 However, the use of vegetable oils as lubricant is dependent upon its physical, thermal and chemical properties, such as its density, viscosity, flash point, pour point, free fatty acid content, iodine value, acid value and saponification value. [8][9][10][11] It is therefore expected that the use of Dika nut oil as lubricant would depend on its physicochemical properties.…”