Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
and seal materials and should be applied carefully depending on the application.
Polyglycols, like polyalkylene glycols (PAGs), are one of the earliest synthetic lubricants created from ratios of ethylene oxide and propylene oxide. They possess exceptional viscosity and thermal properties for applications in hydrocarbon gas compressors from -40°C to 204°C as well as excellent anti-sludging properties.
Phosphate esters, typically found in brake fluids and aircraft hydraulic systems, are characterised by their fire resistance properties. However, they are prone to hydrolytic degradation which could result in the formation of corrosive phosphoric acid that could damage paint and seal materials.
Silicones are chemically inert, providing them with excellent heat resistance and oxidative stability. Despite this, they present insufficient lubricity that limits their applications to only vacuum greases. Alkylated naphthalene displays oxidative and hydrolytic stability in high-moisture environments, seal capability, and improved additive effectiveness in food production, wind turbine, and transmission oil applications. Additionally, it can be blended with other base oils to enhance their overall solubility, cleanliness, and durability. [5]
Blends of SBFs within these categories or with petroleum lubricants are often found in gearboxes, diaphragm pumps, and compressors for effective, synergistic reactions. They can also be used in food production, wind turbines, and transmission oils.
Comparative advantages of synthetic lubricants against conventional lubricants Conventional lubricants developed by mineral oil refinement have been the mainstream lubricant to combat frictional barriers since the nineteenth century. Conventional mineral base oils for lubricants
32 LUBE MAGAZINE NO.185 FEBRUARY 2025
No.156 page 2
originate from vacuum distilled crude oil fractions that undergo sequential refining processes: solvent extraction, dewaxing, and hydrocracking. Firstly, solvent extraction removes aromatics from vacuum distillates, enhancing oil viscosity, oxidation resistance, and sludge-forming resistance. Next, dewaxing processes filter wax crystal formations at low temperatures, resulting in increased turbidity and viscosity. Lastly, hydrocracking exposes mineral base oil to extreme pressures exceeding 100 bar and temperatures ranging from 200°C to 350°C, improving ultraviolet stability and acidity through desulphurisation. [6]
Despite their low prices, conventional lubricants offer many drawbacks compared to synthetic lubricants. Problems linked to conventional lubricants include combustions by low temperature solidifications, oxidation, and viscosity loss caused by extended exposure to high temperature applications. According to Tribology International, mineral oil consists of intricate structures of hydrocarbon compounds with around 30 carbon atoms in each molecule. Moreover, as many as 125 different compounds were found in mineral oil and only 45 of them were precisely analysed, leading to uncertain understandings of the chemical properties in conventional lubricants. Additional inconsistencies in conventional lubricants stem from mineral oil base stocks being solely manufactured based on viscosity, leading to varying chemical compositions obtained from different crude oil and refineries. [7]
On the other hand, synthetic lubricants derived from specific man-made or biological compounds contribute to their well-defined chemical structures and properties. In general, synthetic lubricants are 2-3 times costlier than their conventional counterparts. However, they perform overall better than conventional lubricants with better oxidation resistance, high-temperature stability, low-temperature viscosity, and lower coefficients
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