1. Third International Conference
PolyAlphaOlefins
high-performance base fluids for lubricants
Third International Conference
Lubricants Russia 2007
Good afternoon Ladies & Gentlemen.
My name is Sandy Reid-Peters and I work for the Synthetic Fluids Group, part of the ExxonMobil Chemical organisation.
I’d like to thank the organisers for giving us the opportunity to talk to you today. I hope you will find something of interest.

2. PolyAlphaOlefins (PAO) synthetic fluid base oils
Objectives
PolyAlphaOlefins (PAO) synthetic fluid base oils
Chemical Description
Importance in Lubricants
Manufacturing Process
Features and Benefits
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Today, I am briefly going to talk about Polyalphaolefin synthetic base oils, commonly known as PAO’s.
As well as looking at their classification and how they are made, we will look at their principal features and the benefits they bring.

3. API* Basestock Categories
Manufacturing Process
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Before we look at synthetic fluids in more detail I just want to look at how they are classified by the American Petroleum Institute (API).
There are 5 groups with the first three groups being essentially mineral oil base stocks.
Group I oils are the most common with saturate levels below 90% and levels of sulphur above 0.03%.
Group II and III show improved levels of saturates and levels of sulphur below 0.03%. This achieved with increasing levels of processing to remove impurities and saturate the hydrocarbon chains.
With the increased processing, we can see that the viscosity index is rising, however due to the removal of aromatics and longer chains we also limit the viscosity range available.
All Polyalphaolefin base oils are classified as Group IV base stocks and we will look at those in more detail next.
Group V covers essentially all other products not previously classified, including other synthetics.
*API = American Petroleum Institute

4. GC Retention Time (minutes)
What are PolyAlphaOlefins (PAO)?
PAOs are high-performance, tailored fluids made by chemically reacting materials of specific chemical composition to produce compounds with planned and predictable properties.
Well-defined structure vs. multiple component composition of mineral oil
Hydrogenated (saturated) olefin polymers
Manufactured by the catalytic oligomerization of linear alphaolefins
Wax-free combination of molecules of predetermined chain length 30 5 10 20 25
GC Retention Time (minutes)
PAO 4 cSt
Mineral Oil 4 cSt 15
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So what is exactly is a PAO?
If we think about a mineral oil, we start with a large mixture of complex hydrocarbons, sulfurs, aromatics, and other foreign compounds. Through increasing levels of processing we try to remove all the impurities we don’t want and then rearrange the molecules into more desirable components.
In comparison, to make a PAO we take small discrete building blocks called alpha-olefins and build them up to create a fluid with well defined composition.
The chain length can be controlled to give desired viscosity characteristics whilst the lack of wax provides good low temperature performance.
PAOs are fully saturated molecules containing only carbon and hydrogen and are chemically stable.

5. Why Use PolyAlphaOlefins (PAO)?
PAO is used to formulate automotive and industrial lubricants with the following objectives:
To protect equipment in severe operating conditions
- Constant operation close to the design limits
- Demanding mechanical and thermal loads
- Adverse environmental conditions
To optimize use of the equipment
- Longer oil drain periods; less downtimes
- Lower maintenance costs
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Why do we use PAO to formulate high performance lubricants?
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Firstly we may want equipment to work under severe operating conditions. PAO’s allow equipment to work close to their design limits where the mechanical and thermal loads can be very high. This is particularly relevant in extreme environmental conditions such as the arctic or the desert.
Secondly PAO’s can optimise equipment use by extending oil drain periods, reducing equipment downtime and reducing maintenance costs.

6. PolyAlphaOlefins (PAO)
Manufacturing Process
◄ Low Viscosity
cSt at 100 °C
◄ High Viscosity
40 – 100 cSt at 100 °C
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As I said previously, to make a PAO, we start with small building blocks. These are known as alpha olefins and typically contain 10 carbon atoms – also known as a decene chain. Using a catalyst we build up the blocks into multiple decene chains called dimers, trimers, etc.
The chains are then hydogenated to saturate the chains and improve stability.
By carefully controlling the manufacturing process we can produce a wide range of viscosity grades.
This is the chain structure for the low and high viscosity PAO’s. Everywhere there is bend, this signifies a carbon atom.
By adjusting the manufacturing process, we can produce very high viscosity, high viscosity index PAO’s with a very stable structure.
◄ Very High Viscosity
150 – 1000 cSt at 100 °C

7. PolyAlphaOlefins (PAO)
Key Features
High Viscosity Index
Low-temperature fluidity
High-temperature viscosity retention
Low Pour Point
Low Volatility
Excellent Thermal, Oxidative and Hydrolytic Stability
Good Compatibility with Mineral Oils and Esters
High Shear Stability
Enhanced Film Thickness
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The key features of PAO are;
High viscosity index providing good low temperature and high temperature properties
Low pour points due to the lack of wax components
The lack of very short hydrocarbon chains gives low volatility leading to reduced oil consumption
PAO’s have good thermal, oxidative and hydrolytic stability
They have good compatibility with mineral oils
The lack of long chains means good shear stability giving stay in grade performance.
The high viscosity indices provides enhanced film thickness over equivalent mineral oil grades

8. PolyAlphaOlefin (PAO) Higher VI60 80
100
120
140
160
180 10
Viscosity
Temperature, oC
Mineral Oil
100
150
High Viscosity
Viscosity at low-temperature:
PAO < mineral oil
More rapid lubrication at startup.
Low Viscosity VI
PAO
Equivalent
viscosity
PAO
Higher
Viscosity Index
Mineral oil
Viscosity at high-temperature:
PAO > mineral oil
Should provide increased protection.
100 oC Viscosity, cSt
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Viscosity index provides an indication of how the viscosity changes with temperature. The higher the viscosity index, the less the fluid viscosity changes with temperature.
When we look at the viscosity index, PAO have a much higher viscosity index over a wider viscosity range then mineral oils.
What does this mean in practical terms?
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The illustration on the right shows how PAO viscosity changes compared to mineral oil.
If they have the equivalent viscosity at 100C, the synthetic oil response has a flatter slope.
This gives a higher viscosity at high temperatures and
at low temperatures it does not thicken as much. This means increased wear protection at high temperatures and increased fluidity at low temperatures.

9. PolyAlphaOlefins (PAO) Lower Pour Point20
Typical Mineral Oils
Pour Point, oC
PAO
PAO-based
-30
High Viscosity
PAO
Low Viscosity
-80 1
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The pour point is the lowest temperature at which an oil continues to flow.
This graph shows the pour point vs. viscosity. Due to the presence of wax in mineral oils, we can see that the typical range for finished mineral base oils lies in this region -6 to -20C. Pour point depressant additives are typically required for all commercial formulations.
PAO’s contain no wax and thus their pour point’s are much lower going down below -60C for the lower viscosity grades.
Here we can see an example of various engine oil samples showing the PAO based oils flowing much easier than the other grades after soaking at low temperature.
Speaker note – 48 hour soak at low temp. (thought to be -35C but not confirmed) 10
100
1000
Kinematic Viscosity at 100 oC, cSt

10. PolyAlphaOlefins (PAO) Lower Volatility5 10 15 20 25 30 2 4 6 8 12 14
100 °C, cSt
Noack Volatility, wt%
Typical Group I and II
Typical Group III
PAO
Mineral Oils
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Volatility is a measure of the evaporation rate of an oil, the higher the volatility, the greater the amount of oil will be lost as the oil heats up.
In the Noack volatility test, where oils are heated to 250C, compared to mineral oils at equivalent viscosity, PAOs have lower volatility.
PAOs’ low volatility translates into less oil loss under high temperature conditions. This results in lower oil consumption and reduced emissions.
This lower volatility for PAOs also translates into higher flash and fire points, reducing the risk of fire and increasing safety margins compared to mineral oils
Low volatility makes PAOs ideal for applications with high operating temperatures and low oil sump volumes.
PAOs have lower volatility than mineral oils
Low volatility may reduce oil consumption and emissions

11. PolyAlphaOlefins (PAO) Oxidative Stability
Oxidative stability of PAO exceeds mineral oil
Good oxidative stability for applications at elevated temperatures with air contact
PAOs show excellent oxidative stability when formulated with suitable antioxidants
PAOs are more responsive to antioxidants than mineral oil also to antiwear and other performance additives
Oxidation Stability Test
PAO Vs. Mineral Oil (2% Antioxidant)
Test Conditions: 163oC (325oF), 72 hours
Product
% Vis 100°C
TAN change, mg
Lead loss, mg
Sludge
Mineral Oil
Group II
215.7
14.5
160.7
moderate
6 cSt
PAO
3.5
0.1
0.9
nil
40 cSt
PAO
2.6
0.08
0.1
nil
100 cSt
PAO
1.8
1.1
0.2
trace
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Many applications require a lubricant to resist breakdown at high temperatures. With suitable antioxidant additives, the oxidation stability of PAO’s is much higher than mineral oils.
The chemical structure of PAO’s is such that additive response is more effective than mineral oils.
Here we see the results of an oxidation stability test where the base oil is held at 163C for 72 hours with oxygen being bubbled through the oil. A lead coupon is also used as a catalyst to promote oxidation
The group 2 mineral oil sample shows a significant increase in viscosity and acidity, loss of lead and the formation of sludge.
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By contrast, different PAO samples show negligible changes.
Speaker notes – additive responsiveness is reported to be due to fast adsorption of additives onto the surface due to weak cohesive forces between the additives and the PAO.
Research carried out by All Union Scientific Institute of Moscow and quoted in “Synthetic Lubricants and High Performance Fluids”

12. HVI-PAO such as SpectraSyn Ultra™ exhibit superior VI and Pour Points
HVI-PAO Superior VI and Pour Point
240
better
Pour
Point, oC
-70
-60
-50
-40
-30
-20
-10 10
100
1000
100oC Viscosity, cSt
Mineral oil
better
HVI-PAO
PAO
High Viscosity
Low Viscosity
HVI-PAO
220
200
180
High Viscosity
PAO
Low Viscosity VI
160
Gr III
140
120
100
Mineral Oil
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As I said before, by adjusting the manufacturing process, ExxonMobil can manufacture a unique range of very high viscosity PAO’s called SpectraSyn Ultra. The se new base stocks have outstanding viscosity Index, VI.
Recall that VI is a number that measures the change of viscosity as a function of temperature. Higher VI is better.
Here we see the typical range for Gp1 mineral oils. Group 3 oil have better VI’s but limited viscosity range.
Conventional PAO’s have good VI’s along with a wide viscosity range.
The new HVI-PAO has more than 40 VI units better than current PAO over a wide viscosity range.
This is the same level of improvement as we saw between mineral oil and normal PAO base stocks many years ago.
The graph on the right shows the pour point for the new HVI oils vs mineral and conventional PAO’s.
As I said previously, Pour point is the lowest temperature the oil still flows. The lower the pour point, the better. That means the oil can continue to flow to the critical engine parts and provide protection at low temperature.
HVI-PAO has pour points 10 to 20 °C better than current PAO.
This difference in basic lube property is due to the molecular structure difference 80 4 10
100
100oC Viscosity, cSt
HVI-PAO such as SpectraSyn Ultra™ exhibit superior VI and Pour Points

13. HVI-PAO Improves EHL Film Thickness
Ball-on-disk, point contact test
Sequence VE Wear Test 50
100
150
200
Ave. Cam Wear, um
Oil A
Oil A + HVI-PAO
Oil B
Oil B + HVI-PAO
Limit 1 10
100
0.01
0.10
1.00
10.00
Speed (m/sec)
Film Thickness (nm)
With
HVI-PAO
Without
Theoretical
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The unique properties of HVI PAO’s helps to improve the oil film thickness in elastohydrodynamic (EHL) lubrication.
Using a ball on disk traction machine, we measured the actual film thickness of an oil sample with and without some HVI PAO and compared it to the theoretical film thickness.
As you can see, the sample containing HVI PAO shows a higher film thickness especially at lower speeds where boundary conditions may be encountered.
You can see practical effect of adding some HVI PAO to an engine oil in terms of cam wear in the Sequence VE wear test.
The additional protection delays the onset of boundary lubrication conditions and may improve efficiency.
Speaker notes – Ball on disk traction machine – ball and disk are driven separately to adjust degree of rolling and sliding. Film thickness is measured optically through glass disk.
Delayed onset of boundary lubrication ⇒ Increased protection against wear
Reduced boundary friction ⇒ Improved efficiency

14. PolyAlphaOlefins (PAO) Product Applications
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This table shows the range of PAO’s available from ExxonMobil Chemicals and the typical applications they can be used in.
They are available under the SpectraSyn brand with the number after the name indicating the nominal viscosity in cSt at 100C.
As you can see there is a wide viscosity range available.
The large dots in the table indicate most common applications. Smaller dots are less common.
 Most common application uses

15. PolyAlphaOlefins (PAO) Summary
Advantages:
High Viscosity Index
Wide range of viscosities (2 – 1000 cSt)
Low Pour Point
Low Volatility
Thermal, Oxidative and Hydrolytic Stability
Enhanced film thickness
PAOs are engineered
high-performance molecules
Formulated Lubricant Drivers:
Solve a technical problem
Wide range temperature application
Environmental benefits
Energy savings
Extended service life capability
Lower maintenance costs
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In summary, PAO’s are engineered molecules giving excellent performance in comparison to mineral oils. The advantages are
High viscosity indices
Wide viscosity range
Low pour point
Low volatility
Good chemical stability
Enhanced oil film thickness
This allows PAO’s to be used to formulate oils which can
- solve technical problems
- Cover a wide temperature range
- Provide environmental benefits
Energy savings
- Extended service life
- Lower equipment maintenance costs.
PAOs have excellent
service behavior

16. Thank you
Questions ?
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That concludes my presentation for today and I hope that you found something of interest, Thank you for listening.

17. ©2007 Exxon Mobil Corporation
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All charts included in the presentation based on ExxonMobil data.