Lube-Tech PUBLISHED BY LUBE: THE EUROPEAN LUBRICANTS INDUSTRY MAGAZINE
Siegfried Lucazeau, Product Manager Industry & Automotive NYCO, Paris, France
Introduction
Synthetic esters have been used for over 60 years now in various lubricating applications. Their use is well known, for instance, in aviation turbine oils, air compressor oils, high temperature chain oils, 2-stroke and racing engine oils, or even ultra-low temperature hydraulic oils. However, such uses of esters have been limited to specific areas where cleanliness, resistance to high temperatures, good lubricity and added solvency are required.
Rapid, recent legislation changes on exhaust gas emissions, and subsequent new technologies and equipment, the quest for higher power density, improved energy efficiency, extended durability, as well as the growing concern over environmental impacts of lubrication are clearly paving the way towards higher performance and better sustainability for lubricants.
1 Traditional uses of synthetic esters The use of synthetic esters is well known in a number of specific applications where their high thermal stability, superior cleanliness, natural lubricity, and polarity have long been exploited.
1.1 Polar agents
One of the most traditional uses of esters is probably as a polar additive in non-polar hydrocarbons, such as Poly Alpha Olefins. In such base fluids, diesters in particular have been used as: • seal swell agents to mitigate seal shrinkage normally observed in such formulations;
• dispersing agents in fluids that generate sludge; • additive solubility auxiliaries in viscous non-polar media.
1.2 Aviation gas turbines In aircraft or ground gas turbines, neopolyol esters have been used almost exclusively for decades, for their ability to sustain temperatures of up to 220°C in bulk, with excellent deposit control on hot metal parts (up to 375°C), either in liquid or in vapour phase. In addition, excellent low temperature behaviour is also required (pour point is typically lower than -54°C), which neopolyol esters also deliver.
30 LUBE MAGAZINE NO.131 FEBRUARY 2016 1.3 Air compressors
In a number of volumetric air compressors, compression chambers are lubricated (piston, vane and screw compressors), thus submitting the oil to elevated temperatures of up to 230°C typically. Esters, particularly diesters (phthalates), have been used for their low volatility, delivering cleaner air, and their low coking propensity, thus protecting the equipment against possible auto-ignition of carbonaceous deposits or valve-sticking issues leading to possible explosions.
1.4 High temperature chains The low volatility features of esters, along with their high resistance to thermo-oxidation and low deposit formation properties, have long been taken advantage of in high temperature chain oils to minimize formation of gummy and carbonaceous residues and preserve lubricity over time. In addition, high flash points delivered by synthetic esters (up to 325°C) bring additional safety features to such products. Diesters and triesters (trimellitates) in particular have been used in such formulations.
1.5 Two-stroke engine oils
In such applications, the cleanliness of the oil in operation, its ability to decrease smoke formation, and its lubricity are key features. Diesters, thanks to their clean burning properties, natural detergency, and good lubricity, are excellent base fluid for 2-stroke engine oils. Since a portion of the fuel/oil/air mix is released unburnt to the environment (total loss lubrication), the good environmental profile of synthetic esters is also of great value.
Compared to mineral oils, synthetic esters will typically reduce wear, deposit and varnish formation, and exhaust smoke. Moreover, a reduction of up to 25% Polycyclic Aromatic Hydrocarbons content in exhaust gases has been reported [1].
1.6 Refrigeration compressors
This is a major outlet for neopolyol esters. The switch to non-ozone depleting refrigerant fluids (HFC) has generated the need for highly polar lubricants, showing good miscibility and chemical compatibility features with HFC. Neopolyol esters also show good cold flow properties, high thermal stability, and excellent lubricity.
No.102 page 1
New insight into the benefits of synthetic esters in challenging lubricating applications
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65
