34 Analytical Instrumentation


maintaining fl uid viscosities over a greater range of temperatures without losing to much viscosity over the oil service life [15]. VIIs resist thinning of lubricants. Several mechanisms have been proposed to explain how VIIs perform this function. The most widely cited mechanism is coil expansion, which states that increasing temperature increases the solubility of the polymer in the base oil, which results in expansion of the polymer coil and, in turn, increases viscosity. Many polymers used as thickeners do not follow this mechanism and are often referred to as Viscosity Modifi ers (VM). They, like all soluble polymers, impede the motion of solvent (oil) molecules and do so relatively more at high temperatures than at low temperatures. With the use of VIIs, regardless whether the engine runs at high or low temperatures, the oil can maintain a good viscosity.


Automatic transmission fl uids (ATF) are another kind of multi- grade, polymer-thickened lubricants. ATF’s are used in a closed system and are not exposed to outside elements or pollutants [16]. They are composed of base oils, anti-wear additives, corrosion inhibitors, anti-foam, detergents and seal swell additives and agents. Their features and benefi ts are enhanced, long-term frictional properties, exceptional thermal and oxidation stability, great fi lm-strength and anti-wear properties, exceptional shear stability, and low-temperature fl uidity [17]. All ATF’s contain friction modifi ers, except for those specifi ed for some Ford transmissions and the John Deere J-21A specifi cation. Dexron/ Mercon/ATF+4 and multi-vehicle synthetic are some of the various types ATF fl uids on the market. Automatic transmission fl uids have many performance-enhancing chemicals added to the fl uid to meet the demands of each transmission.


Hydraulic fl uids are another kind of multi-grade, polymer- thickened lubricants. They are primarily used as a medium to transfer energy in hydraulic systems [18]. Other uses of hydraulic fl uids include heat transfer, contamination removal, sealing, and lubrication. Hydraulic fl uids help keep proper viscosity across a wide range of temperatures. Hydraulic machines generate excess heat that can overheat the system and damage the components due to low of viscosity. Hydraulic fl uids have similar characteristics and properties as other previously mentioned lubricants such as good thermal and shear stability, low chemical corrosiveness, and high anti-wear characteristics [18]. They can be broken down into different categories such as mineral oils, fi re-resistant fl uids, water/oil emulsions, water glycol, and phosphate esters [19]. Depending on the operating hydraulic system, operating pressures, environment temperatures, and types of pumps, different kinds of hydraulic fl uids serve different systems. Mineral oils are excellent for extreme hot or cold temperatures, but they can have a low fl ash point. When a fi re risk is plausible and the system requires a lubricant to high higher fl ash points, fi re-resistant fl uids are utilized. In applications where mineral oil hydraulic fl uids are used, like excavators and back hoes, the use of single-grade fl uids is still common. Mechanical shear is much more severe in these applications than in engine oil applications, so multi-grade polymer-thickened hydraulic fl uids require much more shear stable polymers which come at an increased cost. The advantage of all-season use may not be enough to overcome these costs, but it turns out that the higher VI of the multi-grade hydraulic fl uids provide improvements in hydraulic effi ciency, which over the service life of the fl uids more than overcomes the cost difference.


Gear oils are another common type of multi-grade, polymer- thickened lubricants. Their primary usage is in transmissions, transfer cases, and differentials of automobiles [20]. Essentially gear oils can be used wherever a gearbox can be found. They are composed of a base oil, extreme pressure additives, and anti-wear additives. A good gear oil must have great thermal and oxidation stability, extreme pressure properties, and the ability to demulsify to remove water from the system. Gear oils can be made for specifi c purposes. Depending on which gears and system the lubricant will be applied onto, different additives may be more or less suitable. Various types of gear oil include rust and oxidation inhibitors (R&O), extreme pressure, compound (EP), and synthetic oil [20]. R&O gear oils are designed to reduce corrosion and oxidation in the gearbox. Extreme pressure gear oils are used to handle extreme heat and pressure and contains a few additives. Compound gear oil are formulated with fatty oils to create high viscosities which are suitable for low-speed and high-pressure applications. Synthetic gear oil is used for extreme machine conditions, vary in their viscosities, are more shear stable and can work in both extremely low and high temperatures.


In conclusion, multi-grade, polymer-thickened lubricants are essential to many mechanical systems as they prevent mechanical systems from breaking down due to high shear stress, and frictional heating. Shear stability is an important property and predictor of the performance of multi-grade, polymer-thickened lubricants and viscosity loss is the technique used to measure it. Finally, with the number and variety of multi-grade, polymer-thickened lubricants at hand, it is essential to test each of them to compare their properties and determine which kind will deliver the highest performance in automotive, hydraulic, and machinery operation.


References


[1] Armstong, Haydon, et al. “Lubricating Oil.” Lubricating Oil - Energy Education, University of Calgary, 3 Sept. 2018, energyeducation.ca/encyclopedia/Lubricating_oil.


[2] Gravitateonline. “News.” Master Muffl er, 1 Mar. 2016, mastermuffl er.net/2016/03/01/why-engine-lubrication-is- important/.


[3] Ind. Eng. Chem. Prod. Res. Dev. 1970, 9, 4, 525-529, December 1, 1970.


[4] “Multigrade Oil Defi nition and Meaning: Collins English Dictionary.” Multigrade Oil Defi nition and Meaning | Collins English Dictionary, HarperCollins Publishers Ltd, 2020, www. collinsdictionary.com/dictionary/english/multigrade-oil.


[5] “Shear Stability.” Shear Stability, Synforce Lubricants, www. synforce.com.au/shear_stability.html.


[6] Shear Stability and Viscosity Loss, Savant Labs, 2019, www. savantlab.com/testing-highlights/testing-shear-stability-and- viscosity-loss/.


[7] “Shear Rate.” Shear Rate, Schlumberger, www.glossary.oilfi eld. slb.com/en/Terms/s/shear_rate.aspx.


[8] Troyer, Drew. “Kinematic Viscosity Explained.” Machinery Lubrication, Noria Corporation, 2 Dec. 2018, www. machinerylubrication.com/Read/294/absolute-kinematic-viscosity.


[9] “Oil Viscosity - How It’s Measured and Reported.” Machinery Lubrication, Noria Corporation, 5 Jan. 2019, www. machinerylubrication.com/Read/411/oil-viscosity.


[10] ASTM D6022-19, Standard Practice for Calculation of Permanent Shear Stability Index, ASTM International, West Conshohocken, PA, 2019, www.astm.org


[11] Hydraulic Fluid Shear Stability, Exxon Mobil Corporation, 2008.


[12] “Products.” Shear Stability Tester, Koehler Instrument Company Inc, koehlerinstrument.com/products/category/tribology/ shear-stability-tester/.


[13] Sequence VIII Engine Test. Southwest Research Institute, www. swri.org/sites/default/fi les/sequence-viii-test.pdf.


[14] Selby, Theodore. Trends in Shear Stability of Automotive Engine Oils, Institute of Materials, 19 Apr. 2016, www.api.org/~/media/ Files/Certifi cation/Engine-Oil-Diesel/Publications/4-Trends-in-Shear- Stability-of-Automotive-Engine-Oils.pdf.


[15] What Is Motor Oil? Pennzoil, www.pennzoil.com/en_us/ education/know-your-oil/what-is-motor-oil.html.


[16] What Is the Difference Between Transmission Fluid and Motor Oil, Mainline Transmission, 3 Apr. 2017, mainlinetransmission.com/ what-is-the-difference-between-transmission-fl uid-and-motor-oil/.


[17] “Mobil 1™ Synthetic ATF: Mobil™ Motor Oils.” Mobil 1™ Synthetic ATF, Mobil, www.mobil.com/en/lubricants/for-personal- vehicles/our-products/products/mobil-1-synthetic-atf/.


[18] Cosford, Josh. “What Is Hydraulic Fluid?” What Is Hydraulic Fluid?, Mobile Hydraulic Tips, 6 Aug. 2014, www. mobilehydraulictips.com/what-are-hydraulic-fl uids/.


[19] Lee, Ben. Types of Hydraulic Fluid. Hydra Products, 24 Oct. 2014, www.hydraproducts.co.uk/Blog/types-of-hydraulic-fl uid.


[20] RecondOil. The Ultimate Gear Oil Guide. SKF RecondOil, 9 May 2018, recondoil.com/gear-oil-guide/.


ASTM publications are available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19482- 2959, or www.astm.org


SAE Publications are available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001 or www.sae.org


About the Authors


Dr. Raj Shah is a Director at Koehler Instrument Company in New York, where he has worked for the last 25 years. He is an elected Fellow by his peers at IChemE, STLE, AIC, NLGI, INSTMC, The Energy Institute and The Royal Society of Chemistry. A Ph.D in Chemical Engineering from the Pennsylvania state University and a Fellow from the Chartered Management Institute, London, he is also a Chartered Scientist with the Science Council, a Chartered Petroleum Engineer with the Energy Institute and a Chartered Engineer with the Engineering council, UK. An ASTM Eagle award recipient, Dr. Shah recently coedited the bestseller, “Fuels and Lubricants handbook”, details of which are available at https://www.astm.org/DIGITAL_LIBRARY/MNL/SOURCE_ PAGES/MNL37-2ND_foreword.pdf A 2020 recipient of the illustrious Tau Beta Pi eminent engineer title, he is currently on the Advisory board of Directors of several universities. More information on Raj can be found at https://www.che. psu.edu/news-archive/2018/Alumni-Spotlight-Raj-Shah.aspx


Hillary Wong is part of a thriving internship program at Koehler Instrument company and a student of chemical engineering at State University of New York, Stony Brook, where Dr. Shah is a volunteer adjunct professor and the head of the External advisory board of directors.


Dr. Alan Flamberg Dr. Alan Flamberg earned a Ph.D. in Chemistry from Stanford University in 1984. He also received an M. S. in Chemistry and a B.S. in Mathematics both from the State University of New York at Albany.He spent over 34 years as an industrial scientist working for Rohm and Haas, RohMax (a Joint Venture with the German company Rohm), Hüls, Degussa- Hüls, Degussa and Evonik from which he retired in 2018. His work involved the chemical and physical characterization of polymers and how they performed in different applications, especially in automotive and industrial lubricants. He remains an active member of ACS, SAE and ASTM International. In addition to publishing papers, articles and book chapters, he has given presentations at national and international meetings of ACS, SAE, STLE (Society of Tribologists and Lubricant Engineers), CEC (Coordinating European Council – fuels and lubricants testing) and UNITI (a German association of small- and medium-sized mineral oil companies). At ASTM he was a member of Committee D02 on Petroleum Products, Liquid Fuels and Lubricants and chaired Subcommittee D02.7.B on High Temperature Rheology of Non-Newtonian Fluids (the subcommittee where the shear tests mentioned in this article reside).


Dr. Carl F Kernizan Received his BS in 1982 from CCNY, Ph.D. in 1987 from CUNY and Post-Doctoral degree from KSU in 1989. Worked in various technical and commercial roles from 1990 to 2017 with the Timken Company, Lubrizol, Jesco Resources Inc, Axel Americas LLC, Warren Oil and Chemtool Inc. Founded KV Tech Consulting LLC in 2017.


Kunle Y Kernizan Graduated from the University of Missouri in Kansas City in 2011 with a BA in sociology. Worked in import/ export and various sales positions from 2012 to 2017 in New York City. Joined KV Tech Consulting LLC in 2018 as an account manager.


Author Contact Details Dr. Raj Shah, Koehler Instrument Company • Holtsvile, NY 11742 USA • Email: rshah@koehlerinstrument.com • Web: www.koehlerinstrument.com David Phillips, Content Editor, Petro Industry News, david@pin-pub.com


PIN April / May 2022


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