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With regards to safety, such products are able to show Flash Points of more than 300°C easily.


3.4 Pushing temperature limits on greases A high temperature chain oil as described above was thickened with both clay and silica, in order to explore the possibility of producing a high temperature grease based on neopolyol ester technology.


Whilst clay yielded a mechanically stable grease, silica, as expected, did not. However, silica proved to be more neutral towards oxidation mechanisms, whilst organically modified clay did interfere with oxidation stability.


It was however possible to obtain a grease resisting temperatures of up to 230°C, maybe more (Figure 16 and 17). Such technologies may be able to compete with some silicone based greases in a temperature area where PAO based products start being strongly unstable.


Figure 18. European Ecolabel compliant hydraulic fluid


Neopolyol ester based hydraulic fluids are high performance lubricants that also demonstrate excellent environmental profile.


Figure 16. Basic bench test results on ester based greases


In a different area, specific high viscosity synthetic esters (up to ISO VG 1,000) do exhibit high biodegradability and renewability levels, which make them excellent fluids for the formulation of greases meeting environmental standards like the European Ecolabel or the Vessel General Permit. In particular, they may be used to formulate marine greases used for bearings, wire ropes, and open gears thanks to their high degree of tackiness and excellent overall performance level.


Conclusion


It appears that synthetic esters have a lot more to offer than what they have been traditionally used for, and the current market drivers will most probably unveil unexpected, sometimes unknown, added benefits of these base fluids, and promote their use in modern, high performance lubricating applications.


Figure 17. TGA, 230C, O2


3.5 Combination of high performance and low environmental impact Hydraulics is a specific area where future fluids will have to be: • more resistant to rising temperatures, as a result of increased power density;


• robust anti-wear fluids, to protect pumps and deliver energy efficiency;


• cleaner products, to facilitate filtration on finer filters; • more consistent in viscosity over temperature for improved energy efficiency;


• fire resistant, as liability in case of fire is a growing concern; • environmentally friendly.


Suitably selected neopolyol esters do provide high performance as base fluids for hydraulic oils. They show high Viscosity Indices, without using any polymer, thus ensuring excellent shear stability


References [1] Cosmachi, E., Cottia, D., Pozzoli, L., and Leoni, R., PAH emissions of synthetic organic esters used as lubricants in two-stroke engines, J. Synth. Lubr., 3, 251 (1998)


[2] Organic Chemistry: Structure and Reactivity by Seyhan Ege, pp.30–33, 67 [3] Synthetics, Mineral Oils, And Bio-Based Lubricants: Chemistry and Technology, edited by Leslie R. Rudnick, Taylor & Francis


[4] Sniegoski, P.J., Selectivity of the oxidative attack on a model ester lubricant, ASLE Trans. 20, 4, 282-6 (1977)


[5] Martem’yanov, V.S., and Kukovitskii, M.M., Mechanism of oxidation and antioxidative stabilization of polyol esters as base fluids for high temperature lubricants, Neftekhimiya, 18, 4, 539-45 (1978)


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and hydraulic efficiency. They are resistant to oxidation and provide extended lifetime as well as superior cleanliness. They are excellent lubricity fluids, as demonstrated by wear test results on vane pumps. They also show high flash points, for improved fire safety. Seal compatibility and water or air separation are of a very good level. Finally, they show high levels of biodegradability and renewability, thus complying with European Ecolabel or Vessel General Permit requirements (Figure 18).


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LUBE MAGAZINE NO.131 FEBRUARY 2016 35


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