| | Environmental aspects of lubricants and cooling liquids used in manufacturing processes. | | | |

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Contents
1. Introduction..................................................................................................... 3 1.1 Background theory....................................................................................................................3 1.2 History.......................................................................................................................................5
2. Lubricants in manufacturing processes.............................................................5 2.1 Mineral oils...............................................................................................................................5 2.2 Synthetic lubricants..................................................................................................................6 2.3 Boundary lubricants – natural oils and fats........................................................................6
3. Health issues...................................................................................................7
4. Old methods of Lubricant removal and waste treatment.................................7
5. Modern methods of Lubricant removal and waste treatment. ........................7
6. Comparison of old and new.............................................................................8
7. Environmental impact of lubricants. ...............................................................8
8. Coolants in the manufacturing process............................................................9
9. Environmental impact of coolants. .................................................................10
10. Conclusions...................................................................................................11
11. Future trends................................................................................................12
12. References....................................................................................................12

1. Introduction.

Mankind has searched for better and more efficient ways of production. Lubricants and coolants both play an important role in achieving that goal. They play today a key role in modern manufacturing, they are used in almost every major engineering sector ranging from automotive manufacturing engineering to pharmaceutical and cosmetic uses. [1]

2.1. Background theory.

A lubricant is defined as “a liquid such as oil which is used to make the parts of an engine move easily together, or a substance put on any surface to help it move more easily against another one” [5] A lubricant is basically an oil or grease that when placed between two moving objects reduces the friction between them. This ability to reduce the friction between two moving objects has many useful applications in engineering, the most prominent of which is reducing the wear between the objects and thereby improving the mechanical efficiency of the system. [6]

Other Important uses of lubricants include separation of working and tool surfaces, protection of the object, the ability to remain durable and stable when subjected to processing conditions, transfer of heat to keep the object cool, be non toxic or harmful in any way to humans and be inexpensive . [7]

Coolants are fluids designed to reduce heat effects in machine transfer, they do not have much effect on the heat energy generated but they do remove the heat generated thus reducing the temperature. The ability of a coolant to reduce temperatures will depend on the thermal properties of the coolant, the two most important properties are specific heat and thermal conductivity.

Relative to other fluids water has a high specific heat and thermal conductivity, these properties mean that water is often used as a base in coolants. Specific heat and thermal conductivity allow the coolant to draw heat away thus reducing the temperature.[10]

“What types of lubrication are there?” one might ask. There are actually four types of lubrication which have varying degrees of friction and reduction of friction.

Four ways in which lubrication works can be distinguished from this diagram (d) dry friction is where no lubricant is present.

Method (a) fluid film lubrication. When two surfaces are separated by a fluid this form of lubrication occurs. For this to be a perfect lubricant where no wear occurs the two surfaces must not touch each other, this is known as thick-film lubrication. [7] In order for thick-filmed lubrication to be maintained the conditions and properties of the lubricant must be correct and be maintained constantly. If the speed of viscosity of the lubricant decreases then the gap between the two surfaces is reduced and coefficient of friction decreases and the surfaces occasionally touch.[7]

Depending on the formulation of the lubricant thin films may form next to the surfaces which limit the contact between the actual surfaces. When these surfaces form this represents a change in the type of lubrication and it becomes boundary lubrication.

Method (b) boundary lubrication. This type of lubrication only occurs when there are boundary layers present between the two surfaces. These layers help to carry the normal force that occurs between the objects and prevents contact. The boundary layers are created from the adsorption of various kinds of lubricants, from this thin adhering films are formed.[7]

A common use of boundary lubrication is bearings which would normally operate with fluid film lubrication but it experiences boundary lubricating conditions during the starting and stopping of the equipment. Other uses are gear tooth contacts and reciprocating equipment. [8] Common boundary lubricants are oils, fats, fatty acids and soaps. They create a slippery film area on the surface, and work the most effectively at low temperatures and pressures.[7]

[16]

The Stribeck curve. Schematic dependence of coefficient of friction, µ, on lubricant viscosity, η, relative velocity N, and load, P.

Method (c) solid lubrication. This can be considered a special case of dry friction where a solid material is used to reduce the friction between two surfaces in relative motion. [7] Common solid lubricants are graphite and molybdenum disulfide. Graphite has a low friction coefficient and a high thermal stability however due to oxidisation it has a practical range of 500c to 600c. Molybdenum disulfide also has a low friction coefficient but does not need moisture, it is often used in two stroke engines. [9] The function of solid lubricants is to separate the surfaces with an interface of low shear strength and low friction coefficient, this reduces the friction and wear of the surfaces. [7]

Industrial lubricants can be divided into 2 categories; oil and grease, organizations such as SAE, AGMA, and NLGI have established standards for these categories. The oils are slippery liquids that are insoluble in water. The standard characteristics for oil are:
Viscosity - A measure of how thick the oil is.
Performance additives - The additives added to increase the performance of the oil.
Applications - Oils designed for specific applications such as gear oils.
Its origins - e.g. mineral, synthetic. [11]

Grease is an oil with a higher viscosity and performance thickeners added. The standard characteristics of a grease are:
Worked penetration – a test which determines the consistency of grease by seeing how far a standard cone will penetrate at 25°C for 5 seconds.
Base oil viscosity - A measure of the resistance to flow.
Performance additives - The additives added to increase the performance of the grease.

2. Lubricants in manufacturing processes

There are various types of lubricants used in the manufacturing industry, and with them come many issues of health, waste removal and the environmental impact of lubricants. Three common lubricants used in manufacturing are shown.

2.1. Mineral oils

Mineral oils, usually derived from hydrocarbons such as crude oil are a common type of lubricant which provides boundary lubrication (as shown in the introduction section,) their use is quite limited unless enhanced with performance additives. With the use of these additives, mineral oils become one of the most widely used lubricants in metal-working.[7] Mineral oils are in abundance and have desirable characteristics, some of the more common performance additives used to increase the lubricating qualities include, compounds of sulphur, chlorine and phosphorous. They react chemicals with the surfaces to form solid films (Extreme Pressure Lubricants), this prevents contact between the surfaces which would increase the friction.[7]

Mineral oils are generally safe for human contact and are approved by the FDA and European Commission. [13] [14] Both a short term study and a long term study [15] on rats showed that mineral oils had no effect on body weight gain, food consumption or other physical parameters.

When using mineral oils in a manufacturing process it is important to know certain relationships which will allow the manufacturer to prevent damage and increase efficiency.

Operating Temperature - The range of temperatures at which the grease is designed to work, exceeding this temperature will cause the grease to liquefy.[11]

Coolants in manufacturing are generally used as cutting fluids, they are most effective at high speeds where heat generation and the high temperature cause difficulties. The coolants are more effective on materials more susceptible to temperature failure such as high speed steels, they are used often in operations in which lots of heat is generated such as milling.[10] The coolants remove the heat generated in cutting by carrying it away thereby increasing the life of the cutting tool.[7]

1.2. History

Lubrication otherwise known scientifically as tribology has been an integral part of engineering for many centuries, the earliest recorded use of lubricants was in the Roman and Egyptian era, these lubricants were simple consisting of lime mixed with olive oil. The lime combined with the triglycerides in the olive oil to form a soap known as calcium grease.[2]
The problem with such early lubricants was their life expectancy, since most of the lubricants at that time contained some form of bio-degradable substance such as animal fat they did not last long. It was not until the middle of the 19th century and the industrial revolution that the study of tribology began to be examined in greater detail by Beauchamp Tower and Nikolay Pavlovitch Petrov.[4]

The earliest recorded examples of coolants was in 1885 when Karl Benz invented and patented the first automotive radiator which provided recirculation cooling for the water cooled engine for his first horseless carriage. [12]

Viscosity temperature relationship is an important practical aspect for commercial products, as the temperature increases the viscosity also increases. The effect of high pressures on viscosity has an importance in conventional applications when a continuous film of lubricant is needed to prevent the surfaces of the two work pieces touching. In metalworking lubrication this has an even greater significance because the viscosity is shown to increase exponentially as the pressure increases. [17]

Viscosity temperature pressure relation is a relation that occurs in cold metal deformation, significant increases in temperature arise from the friction which markedly decreases the viscosity of the fluid lubricant. Counteracting this change is the increase in viscosity with pressure because of the high load used. The relationship of these changes can be found in the equation shown.[17]

Synthetic lubricants are often formed from a base mineral oil with synthetic performance additives introduced, the increase of the chemical industry has meant that a wide range of performance additives are used for synthetic oils. [18] Some of the additives used and their effects will be described. Lots of synthetic organic esters are utilised as a base fluid for lubricants. Some examples are esters of C8–C13 monoalcohols with diacids such as adipic acid, these synthetic lubricants tend to have a good low temperature fluidity and reduce volatility when subjected to high temperatures in addition to providing some affinity for metal surfaces.[18] Hindered phenols and aromatic amines are used as antioxidants, they decrease the rate of autoxidation of the lubricant basefluids and extend the lifetime of their use. Long chain fatty acids and diacids prevent rust and corrosion on the surfaces. They adsorb to ferrous metal surfaces, displacing water and preventing corrosion. [18] 2.3. Boundary lubricants – natural oils and fats

In the background information provided it was shown that under special circumstances thin layers of lubricant may be formed creating boundary lubrication. Some of the most common boundary lubricants used in manufacturing are derived from natural oils and fats. [17] Natural oils consist of water-insoluble fats and oils derived from plant and animal sources, the major components are glyceryl esters of fatty acids. An important physical property of natural oils and fats used as lubricants is viscosity. One aspect of the viscosity of natural oils and fats is the increase with pressure and the early solidification in comparison with mineral oils.

2.2. Synthetic lubricants

Due to the demand for new lubricants to meet high performance specifications a new type of lubricant was developed, synthetic lubricants. Synthetic lubricants have many uses ranging from aircraft purposes to nuclear industries. [17]

Other chemicals that are mixed include hydroxide, carbonates, phosphates and silicates. The most effective method for removing a lubricant is emulsion cleaning, it is based on the use of common organic solvents dispersed in water with the aid of an emulsifying agent. [17]

Water use in this method varies greatly but the table below shows figures typical of steel plants [20]

Increasing the temperature has a counter effect of reducing the viscosity, this must be taken into effect in manufacturing.[17]

3. Health issues

In the 1960’s there were many cases of lubricants used in manufacturing causing diseases particularly of the skin. Bourne [19] indicated that in England 9 out of every 13 affected workers were employed in engineering and manufacturing, in the United States, almost 19% of the total incidents were because of contact with petroleum products and greases. Back in the 1960’s mineral oil presented a probable skin hazard unlike today. [17] The effects on the skin were initially irritation sometimes accompanied by redness or pimples. On exposure to soluble oil the skin could become soggy, followed by scaling and cracking. Most of the workers which came into contact showed some degree of plugging and septic pimples from which scars may develop. [17] Any oils containing sulphur or chlorine were shown to produce a skin disease known as chlorachne which results in cysts on the face, arms, forehead, neck and ears. [17] In the present day however it has been proved that treated mineral oils will not cause damage to the body and can even be consumed. [13] [14]

4. Old methods of Lubricant removal and waste treatment.

Older methods of lubricant removal generally consisted of washing away the lubricant with a mixture of water and other chemicals. Alkaline cleaning solutions were often used to clean away the lubricants, they contain a mixture of water to act as a diltuent, solvent, reaction medium and carrier.

Increasing the temperature has a counter effect of reducing the viscosity, this must be taken into effect in manufacturing.[17]

2.4. Health issues

In the 1960’s there were many cases of lubricants used in manufacturing causing diseases particularly of the skin. Bourne [19] indicated that in England 9 out of every 13 affected workers were employed in engineering and manufacturing, in the United States, almost 19% of the total incidents were because of contact with petroleum products and greases. Back in the 1960’s mineral oil presented a probable skin hazard unlike today. [17] The effects on the skin were initially irritation sometimes accompanied by redness or pimples. On exposure to soluble oil the skin could become soggy, followed by scaling and cracking. Most of the workers which came into contact showed some degree of plugging and septic pimples of which scars may develop. [17] Any oils containing sulphur or chlorine were shown to produce a skin disease known as chlorachne which results in cysts on the face, arms, forehead, neck and ears. [17] In the present day however is has been proved that treated mineral oils will not cause damage to the body and can even be consumed. [13] [14]
These Figures show that these old methods of washing away lubricants with large amounts of water were wasteful and the chemicals being washed into the environment would be damaging to forms of sea life and nature.

2.6. Modern methods of Lubricant removal and waste treatment.

New landfill regulations do not permit the disposal of wastes that are both hazardous and biodegradable. [21] The more modern method of disposal is to recycle and reuse as much as possible whilst using biodegradable lubricants. [22]

Waste oil disposal in the EU is regulated according to Directive 75/439/EEC. According to this directive there is a hierarchy of waste oils management and preference goes to regeneration or refining, however it accepts burning under environmentally acceptable conditions. [22]

These Figures show that these old methods of washing away lubricants with large amounts of water were wasteful and the chemicals being washed into the environment would be damaging to forms of sea life and nature.

2.6. Modern methods of Lubricant removal and waste treatment.

New landfill regulations do not permit the disposal of wastes that are both hazardous and biodegradable. [21] The more modern method of disposal is to recycle and reuse as much as possible whilst using biodegradable lubricants. [22]

Waste oil disposal in the EU is regulated according to Directive 75/439/EEC. According to this directive there is a hierarchy of waste oils management and preference goes to regeneration or refining, however it accepts burning under environmentally acceptable conditions. [22]

These Figures show that these old methods of washing away lubricants with large amounts of water were wasteful. Further the chemicals being washed into the environment would be damaging to forms of sea life and nature.

5. Modern methods of Lubricant removal and waste treatment.

New landfill regulations do not permit the disposal of wastes that are both hazardous and non-biodegradable. [21] The more modern method of disposal is to recycle and reuse as much as possible whilst using biodegradable lubricants. [22]

Waste oil disposal in the EU is regulated according to Directive 75/439/EEC. According to this directive there is a hierarchy of waste oils management and preference goes to regeneration or refining, however it accepts burning under environmentally acceptable conditions. [22]

6. Comparison of old and new.

If the modern and old methods of lubricant removal are compared then there are clear advantages of the modern techniques against the old techniques. The use of recycling lubricants provides an economical and environmentally friendly use. The use of re-using 36% and using 48% as fuel saves on costs and has a good environmental impact. Another advantage of modern lubricants is that they optimise energy efficiency, minimise wear in the machinery and have maximised service lifetimes in order to reduce the lubricant needed.

7. Environmental impact of lubricants.

The annual global production of lubricants and other related functional fluids is approximately 38 Mtes, the lubricant additives account for 1.5–2 Mtes pa., the synthetic lubricant basefluids are approximately 0.7 Mtes pa. [18] The manufacture and disposal of this large volume of material obviously represents an environmental burden. This is why the environmental aspect of lubricant continues to be an area of active investigation.

The natural oils and fats were the first lubricants and they still can be used as a source of renewable raw materials. As shown earlier in the report they are used in modern lubricants either in formulations containing vegetable oils or after chemical processing to be used as synthetic additives. The first method has a lower energy process requirement but the range of products produced is very limited: unfortunately they have poor stability properties and low temperature properties.

According to a recent survey [23] the approximate annual lubricant demand in the EU is 5.1 Mtes of which 2.65 Mtes (52%) is consumed in use. This leaves 2.45 Mtes (48%) generated as waste oils, from this 0.6 Mtes (25%) is not accounted for and presumed to be dumped into the environment or be illegally burned. The other 75% is collected, from this 75% 36% is re-refined into lubricating oils and the remaining 64% is burned as fuel. As shown in the figure below.

[24]

Dependant on the severity of the application, and the degree of control that can be applied to recovering the lubricant and its collection process, re-refining lubricants can be difficult.[24] One way of re refining the lubricants is to periodically launder them by filtration, ion exchange and additive replenishment thereby restoring them to their standard specifications. This process is not recorded as used oil, therefore this type of re-refining is not captured in the EU figures given earlier. [24]
Lubricant additives cannot be recycled because of the degradation, so they are removed from the lubricants as sludge. This occurs during the lubricant re-refining and this adds to waste generation. But, most lubricant additives can be combusted because they contain long chain hydrocarbon substituents which are used to render them oil soluble. Under suitable conditions the additives do not need to be removed from the lubricants.[24]

The range of materials that can be used as fluids is limited to the ones which maintain a liquid state at the required temperature. [22]

A large proportion of lubricant production is released into the environment on its first use, commonly as spills or leaks of oils, or from emission of partially combusted oil derivatives. Lubricating oils are insoluble and less dense than water. This means that they have a tendency to spread over the surface of water as oil slicks. [24] These have a damaging effect on sea life well documented by news reports and are visually polluting. [25] As a result of this there has been a focus on making lubricants biodegradable and non harmful to the environment.

For most lubricants biodegradation is a complex process, but scientists are continuing to create new ways of doing so. There are different measurements that can be used to describe the rate or extent of biodegradation. The biodegradability of lubricants is assessed by two different test protocols, they are primary biodegradability and ultimate biodegradability. When the base oils in the lubricants begin to biodegrade, they first become carboxylated or hydroxylated intermediates which have higher water solubility, this removes the oil slick. The rate of these first steps of this biodegradation is known as primary biodegradability. [24]

These results show that the biodegradability of mineral oils is much lower than the biodegradability of vegetable oils. This is due to there being branched alkyl groups in vegetable oils which are more resistant to biodegradation.[26] These properties can be used to select create synthetic base fluids which will be more biodegradable.

From all of this information we can see that engineers and scientists try to make lubricants more environmentally friendly by placing a strong emphasis on recycling, re-refining or using them as a form of fuel. Also we can see that scientists put a lot of effort into making lubricants as biodegradable as possible in order to help preserve the environment.

8. Coolants in the manufacturing process. The coolants most commonly used in manufacturing processes are used as cutting fluids to regulate heat control. [10] Coolants which are used in the manufacturing process can roughly be divided into three categories, a) gases, b) liquids and c) solids. [27] The most important technical characteristics of a coolant are freezing protection, thermal and microbiological stability, physical properties which ensure good heat transfer properties, and low induced corrosion. The environmental legislation and public attitude means that improved environmental performance and non-toxicity are a focus for coolants. The main environmental characteristics of a coolant are that it has a low environmental impact, it is not toxic, safe to use, and easy to dispose of or recycle, and that the total costs over the product's life cycle financially viable.[28]

Lubricant type
Primary biodegradability over 21 days

9. Environmental impact of coolants.

One environmental problem with coolants in cutting fluids is that they become contaminated over time with foreign substances such as tramp oil, moulds and fungi. [10] There are several health risks with the use of coolants which inherently cause environmental risks. Dermatitis is one of the risks associated with coolants. Straight oil coolants can cause dermatitis, however with water-based coolants, there is less fungi present and therefore less outbreaks of dermatitis. [29]

Due to the growing concern for the environment, disposing old fluid is now costly and contrary the general public welfare. To get around this modern manufacturing tries to recycle as much as possible. This is accomplished by using filtrations systems to prevent contamination so that the coolants can be used again. The advantages of this filtration system are 1) an extended life of the coolant, instead of replacing the coolant once or twice a month the coolant can be used up to one year. 2) Since the coolant is disposed of less frequently there is less cost to remove it. 3) It provides a reduced health hazard and a cleaner cutting fluid for a better working environment. 4) Less maintenance for machining tools. 5) A longer tool life. [10]

For scientist and engineers to make coolants more environmentally friendly there is a focus on biodegradability and recycling coolants. There are many specialised machines provided by companies that filter used coolant and make it reusable. [30]

Originally, the coolants first used were mineral oil. This type of coolant remains in use today but mainly in small operations. Water-based coolants are now more commonly used. Water-based coolants can be grouped as synthetic, semisynthetic, and soluble. Synthetic coolants contain no oil and are made from detergents, synthetic lubricants, and water. Semisynthetic coolants have small amounts of oil combined with detergents, synthetic lubricants, and water. Soluble coolants are oil and water emulsions.[29]

Since cooling fluids used in the manufacturing industry are most commony used as cutting fluids, there are various ways in which they are applied. The first and most common method is called flooding or flood cooling. In this method, a steady stream of fluid is directed at the tool-work interface of the machining operation. [10]
The second method of delivery is known as mist application, it is most commonly associated with water based coolants. This method is performed by directing a high-speed mist carried by a pressurized air stream towards the operation. Generally mist application is not as effective as flooding, because it cools the tool down at a slower rate. However because the coolant is subjected to high speed air streams mist application is more useful in reaching areas in which flooding cannot be used. [10]

One other method is known as Manual application. This is done by using a squirt can or brushes to apply the fluid to operations where the cutting speed is low and friction becomes a problem. The method is not preferred by production machine shops due to the variability of its application. [10]

* Greater awareness of recycling.

The use of filtration machines in industry shows a greater interest in the environment, more and more coolants and lubricants are being filtered to be reused. This increases the tool life and reduces cost of production by eliminating the need to purchase new coolants and lubricants and the cost of disposing the used products.

* Use of lubricants as fuel.

Petroleum based lubricants and coolants or those containing long hydrocarbon chains can be combusted and used as fuel, therefore are not released into the environment in a form that is non biodegradable.

* Making products more biodegradable.

There is now a great deal of research done by companies to make their products more biodegradable and thus friendlier to the environment. Scientists and engineers are more commonly making synthetic lubricants and coolants from a natural base rather than a mineral base. This method improves biodegradability and is more beneficial to the environment.

However most machines available do so by separating the coolant into permeate and an oil, from this the permeate can then be disposed of. [30] Petroleum products are normally not readily biodegradable because of the size and complexity of their molecules, and the presence of impurities that slow or kill the bacteria which break down the coolant. Low viscosity and extreme purity allow its molecules to be easily used by bacteria as a food source. The most applicable solution would be to use coolants made from food grade synthetic oils, with food grade additives. [31]

10. Conclusions.

In this report it is shown that engineers and scientists have worked to improve lubricants and coolants by making them environmentally friendly. From this several conclusions can be drawn, these show the improved awareness of making lubricants and coolants environmentally friendly and the environmental impact of lubricants and cutting fluids.

* Health and environment risks

In this report it is shown that there are numerous health risks to humans associated with lubricants and coolants, specifically mineral oils. These dangers not only apply to workers but to creatures in the environment too.

* Non water soluble products.

Since most lubricants and coolants are derived from some form of oil they are not soluble. This is one of the risks to the environment because they will remain for a long time and continue to do damage.

This process involves the small amounts of lubricant being applied to the tool. The important point of this process is atomizing the lubricant using air as a carrier in an aerosol. The main advantage of this method is that the lubricant can be used on machining operations such as drilling and sawing. The limitations of near dry machining occur with high-volume machining. The cost of near-dry machining is greater than conventional machining because the lubricant is used in one pass instead of recirculated.[34]
12. References

[1] FUCHS Lubricants (UK) plc company brochure
[2] Ullmann's Encyclopaedia of Industrial Chemistry. 7th edition. Wiley 2007.
[3] R. M. Mortier, S. T. Orszulik. Chemistry and technology of lubricants. 2ndedition. Springer 1996.
[4] Petrov. Nikolay P. Lubrication engineering. 2000.
[5] Lubricant. http://dictionary.cambridge.org/ Accessed 23rd November 2010.
[6] J. Song. Foundations of engineering course notes. Chapter 11 simple machines. 2010.
[7] M. P. Groover. Fundamentals of modern Manufacturing. Prentice-Hall 1996.
[8] Boundary lubrication. Engineers edge. http://www.engineersedge.com/ Accessed 25th November 2010
[9] Solid lubrication. Engineers edge. http://www.engineersedge.com/ Accessed 25th November 2010
[10] M. P. Groover. Principles of Modern Manufacturing. 4th edition. Wiley 2010.
[11] Industrial lubrication. Lube.com. http://www.lube.com/ Accessed 26th November 2010.
[12] Roy E. Beal. Engine Coolant Testing. 3rd volume. ASTM 1993

11. Future trends

One modern trend that is becoming more common is something known as dry machining. This involves no cutting fluid, the advantages of dry machining are that since no cutting fluid is used there is no risk of contamination and no need to dispose and filter the fluid. However there are disadvantages with this method. The first being that due to the increased friction the tool overheats faster and must be operated at a lower cutting temperature. The second being that since there is no liquid there will be an absence of chip removal benefits in grinding and milling. [10] Looking into the future the trend is to create lubricants and coolants with a greater purity, lower volatility and a longer life. [32] An emerging trend is the use of group III base lubricants. Group III base lubricants are formed from hydrocracked polymers, whereby hydrocracking is the process of breaking down long polymers into smaller chain polymers. [33] The main advantages of group III lubricants are: 1) lower pour point than conventional lubricants, this enables them to be used at lower temperatures.
However in the additives in most group II synthetic lubricants lowers the pour point of the lubricant close to group III stocks. This means that Group III base oils can be made into lubricants suitable for all but the very coldest applications. 2) Group III lubricants undergo a hydrofinishing process after the hydrocracking process. This means that they become very pure resulting in high thermal and oxidative stability. [32]

One final use of lubricants and coolants in the future is a process known as near dry machining.

[25] BP oil leak aftermath: Slow-motion tragedy unfolds for marine life. http://www.guardian.co.uk/ Accessed 17th December 2010.
[26] D. T. Gibson, Marcel Dekker. Microbial Degradation of Organic Compounds New York. 1984.
[27] Information provided on request by The Dow Chemical Company http://www.dow.com/heattrans/contact/ Accessed 27th November 2010.
[28] Janne Jokine. Betaine based heat transfer fluid as a solution for toxicity and corrosion problems in heating and cooling systems. 1. 2003.
[29] Harriet Burge. Machining Coolants. The environmental reporter. EMLab. October 2006.
[30] CARDEV C700-MK2. Users Manual.
[31] Ortech International Laboratories. The Biodegradability of Three Dielectric Fluids. Ontario, Canada. 1990.
[32] Performance of Base Oils and Future Trends - The Evolution of Base Oil Technology - Part 3. http://www.machinerylubrication.com/ Accessed 4th January 2011.
[33] Conventional Oil, Synthetic Oil, Synthetic Blend. http://www.articlesbase.com/ Accessed 4th January 2011.
[34] Neil Canter. The Possibilities and Limitations of Dry Machining. http://www.stle.org/. March 2009.

[13] CFR - Code of Federal Regulations Title 21. http://www.accessdata.fda.gov Accessed 2nd December 2010.
[14] Cosmetics Directive. http://ec.europa.eu Accessed 2nd December 2010.
[15] E. Vavsour, J. Chen. Who food additives series 50 mineral oils (medium- and low-viscosity) and paraffin waxes http://www.inchem.org/ Accessed 2nd December 2010.
[16] S. Boyde. Green lubricants. Environmental benefits and impacts of Lubrication. Uniqema Lubricants, Wilton, UK. 1. 2002.
[17] John A. Schey. Metal Deformation Processes friction and lubrication. Marcel Dekker Inc. 1970.
[18] S. Boyde. Green lubricants. Environmental benefits and impacts of Lubrication. Uniqema Lubricants, Wilton, UK. 3. 2002.
[19] L.B. Bourne. Skin Disease from Oils, Causes and prevention. Mason House. London. 1967.
[20] H. C. Bramer. Industrial wastewater Control. Academic Press. New York. 1965.
[21] Disposal of waste wire drawing lubricants. http://www.condat-lubricants.com Accessed 12th December 2010.
[22] S. Boyde. Green lubricants. Environmental benefits and impacts of Lubrication. Uniqema Lubricants, Wilton, UK. 5. 2002.
[23] A. S. Patil, V. A. Pattanshetti and M. C. Diwedi, ‘Functional Fluids and Additives based on Vegetable Oils and Natural Products’, Synth. Lubr. 15. 1998.
[24] S. Boyde. Green lubricants. Environmental benefits and impacts of Lubrication. Uniqema Lubricants, Wilton, UK. 6. 2002.