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Silicone Copolymer Based Lubricants Chad Chichester, Dow Corning Molykote Lubricants

1(AV23345, AV23347)All claims in this presentation are in TIS report 2013-I0000-69191 Chad Chichester and 29 Feb. 2016

IntroductionBrief Siloxane PrimerFluoro/Phenyl Siloxane CopolymerNeat Fluid & Additized Fluid PerformanceFluoro/Phenyl Copolymer-based GreaseMolecular Structure Design Based Development2

No claims

Script

This paper begins with a brief primer on siloxane based lubricants as an introduction to newly developed fluorosiloxane/phenylmethylsiloxane copolymers. Fluoro/phenyl siloxanes are built on the thermal and oxidative stability of siloxane backbone molecules, functionalized with phenylmethyl pendant groups for great thermal stability, and fluorinated pendant groups for improved wear and friction performance. Neat fluids as well as additized fluids are described and performance levels will be shared. Greases formulated with Siloxane copolymers are explained and performance described. And a method using molecular structure modeling to design copolymer fluids is explained.2

What is Silicone?3TerminologyDefinitionSiliconThe silicon atom or silicon metalSiloxaneTypically a polymer with Si-O-Si repeating backbone (PDMS)SiliconeGeneric term for Si-based materials

28.085514SiSiliconA=end blockB=functional branch groupm=Methyl Siloxane repeating unitn=functional group repeating unitABA

How Silicone is made : TIS 2012-I0000-66351

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Silicon is the 14th element of the periodic table, and is considered semi metallic, or metalloid. Widely popularized in the semiconductor and solar industries for its dielectric and photovoltaic properties, silicon can also be combined with oxygen to form polymeric materials known as siloxanes. These siloxane polymers can be functionalized with hydrocarbon-based pendent groups to make a category of materials known as silicones. Different types of silicones having different functional groups exist for many types of materials, including silicone-based lubricants. 3

Silicones Functionalized organo chemistry with Si-O-Si backboneStrong bonds: Si-O (460 kJ/mol) vs. C-C (348 kJ/mol)Long bonds: Si-O (0.164 nm) vs. C-C (0.153 nm)High bond angle: Si-O-Si (143) vs. C-C-C (110) = FlexibilityLow steric hindrance: Unencumbered OxygenLow glass transition temperature (148 K) Low Temperature FlowabilityHigh oxidative stability PDMS (573 K) to PPMS (649 K)Thermal-viscous stability: PDMS (15 kJ/mol) vs. PAO (30 kJ/mol)Viscosity indices over 300Permanent shear stability: Very low monomeric frictionLow volatility (even low viscosities)Plastic and rubber compatibility Chemical resistanceWater Insolubility

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= Si= O= C= H

TIS #20013-I0000-69191

Script

Siloxanes are characterized as having very strong bonds. The Si-O bond requires 460 kJ/mol to break as compared to the Carbon-Carbon bond, which requires 348 kJ/mol to break. This gives the backbone structure very high thermal stability. In addition, the long bond lengths (0.164 nm) and high bond angles allow siloxanes to be extremely flexible and have low steric hindrance. Leading to low monomeric friction. Strong, flexible bonds lead to good permanent shear stability. The fact that siloxane backbones are already fully oxidized gives them great oxidative stability and low volatility. Because the chemistry of siloxanes is rooted in silicon instead of carbon they have good compatibility with many plastics, elastomers, and chemicals. Generally, siloxanes are hydrophobic, making them water insoluble.

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Three Primary Types of Silicones5Standard siliconesDimethyl fluids are usually silica-thickenedPoor metal-to-metal lubricationExcellent rubber and plastic lubricationL: Low loadsE: Resists moisture, some chemicalsT: -50 to 200oC temperature rangeS: Low speedsUsually Lithium thickenedWidest temperature range siloxanesImproved metal-to-metal vs. PDMSL: Low to moderate loads (poor E.P.)E: Resists moisture, oxidation and corrosionT: -70 to 250oC temperature rangeS: Moderate speedsUsually fluorocarbon-thickenedExcellent chemical resistanceBetter load capacity & wear resistanceL: Moderate to high loadsE: Harsh chemical and solvent environmentsT: -40 to 230 oC temperature rangeS: Slow to moderate speedsDimethyl Silicone Phenyl-Methyl Silicone

H3C Si O Si O Si O CH3

CH3

CH3

nCH3CH3CH3CH3

H3C Si O Si O Si O CH3

CH3

CH3

nCH3CH3C6H5CH3

Fluoro Silicone

H3C Si O Si O Si O CH3

CH3

CH3

nCH3CH3CH2CH3

CH2

CF3

5TIS #2013-I0000-69191

Script

Today, most silicones used as lubricants fall into 3 primary categories. Dimethyl silicones are the most common. Made of siloxanes with methyl functional groups these silicones are filled with silica to be used as static lubricants on elastomers and plastics, however, dimethyl silicones are poor metal-to-metal lubricants. Phenylmethyl silicones feature phenyl functional groups and have wider temperature ranges and improved metal-to-metal lubricity compared to dimethyl silicones. Fluoro silicones employ fluoro functional groups for even better metal-to-metal lubricity and have excellent chemical resistance, but these features come at the expense of a slightly reduced temperature range compared to phenyl silicones.

What if?6LubricityHigh temperature stabilityOutput is a Silicone Phenyl/Fluoro Copolymer Base FluidSo far, Viscosity ranges from 400cSt 5000cSt (@ 50/50 Ratio)Additive acceptance near traditional lubricant base fluids

Module LModule TPhenyl FunctionalityFluoro FunctionalityVariableRatio

Variable Viscosity

No Claims

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So, imagine combining the lubricity of fluoro silicones with the thermal stability of a phenyl silicones all within the same molecular structure? This is the essence of fluoro/phenyl silicone lubricants. These polymers can be made to have varying ratios of fluoro to phenyl content to design base fluids for either higher lubricity or higher thermal stability. Like existing siloxanes many viscosities can be produced. So far, viscosities ranging from 400 to 5000 cSt have been synthesized using a 50:50 ratio of fluoro to phenyl. Additives generally are not soluble in many silicone fluid, however, the fluoro/phenyl copolymers show great additive acceptance. This will be discussed in more detail, later in this paper. 6

7Module LLubricity of Fluid

Additives now enable respectable lubrication performance as compared to other technologies

GREASES | PASTES | OILS | COMPOUNDS | DISPERSIONS | ANTI-FRICTION COATINGS

Claims substantiation

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Examining lubricity aspects of silicone copolymers, the graph shows a comparison between neat fluids and additized fluids. Silicone copolymers alone, while better than dimethyl silicones still do not perform as well in 4-ball wear testing as compared to other lubricant technologies. However, with additives silicone copolymers rival even additized PAOs showing excellent promise for the use of additives in silicone fluids intended for lubricant materials.

Wear Resistance of Neat Copolymer Fluids8DIN 51350As Fluoro content wear resistance as expected

Phenyl/Fluoro synergy against wear at lighter load conditionFluid Ph:F 400 N load800 N loadAverage Wear Scar DiameterPhenylmethyl Silicone100:0Not measurableNot measurablePhenyl Fluoro Copolymer Fluid75:251.53 mmNot measurable50:501.48 mm2.82 mm25:751.81 mmFluorosilicone0:1001.18 mm1.17 mm

0.55 mm

TIS 2014-I0000-71109

Script

When examining phenyl and fluoro silicones used as lubricants, base fluids of 100% phenylmethyl silicone show immeasurable wear scars, which is certainly the reason phenylmethyl silicones are rarely used in metal-to-metal contacts, except at extremely low temperatures. On the other hand, fluorosilicones have better lubricity properties than phenylmethyl silicones. So, when considering a copolymer made of phenyl and fluoro functional groups, copolymers with higher fluoro functional group percentages exhibit lower 4-ball wear scars than copolymers with lesser fluoro functional groups. Interestingly, a neat copolymer fluid with 25% phenyl content has lower 4-Ball wear scar than even 100% fluorosilicone fluid. This contradicts the hypothesis that there wear resistance is always proportionate to the percentage of fluoro content. This is being explored; however, it will not be further discussed in this paper.8

Wear Resistance through Additization of 50:50 Si-Copolymer9

TIS 2014-I0000-71109

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Another exciting property of new phenyl/fluoro siloxane copolymer fluids is additive acceptance. Various wear improvement additives at treat rates of 1.0% and 2.5 % were added to 50:50 Copolymer base fluid. Wear scars of neat fluid were compared to additized phenyl/fluoro silicone copolymer at 400N and 800 N loads. Significant wear scar reduction was observed by additizing phenyl/fluoro silicone copolymer. At 400 N loads the highest response was obtained by using zinc diamyldithiocarbamate (2.5%), resulting in a 71% reduction in wear scar. Conversely, amin alkylisooctylphosphate additive (1.0%) showed no wear scar improvement. At 400 N loads the average wear scar improvement through additization (withholding 0% response of amin alkylisooctylphosphate ) was 53%. Looking at 800 N load conditions, three additives; antimony o,o-dialkylphoshorodithionate, dithiocarbamate, and zinc dialkyldithiophosphate yielded a 59% reduction in wear scar. Interestingly, amin alkylisooctylphosphate, which had no impact at 400 N loads, yielded 33% reduction in wear scar. The average response of additives at 800 N was 46%. This data indicates that phenyl/fluoro silicone copolymers exhibit good additive response.

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SRV Measurement Results10DIN 51834-4

T = 50C, Freq. = 50 Hz, Load = 300 N, Stroke = 2 mmIn case of 100:0 (Phenylsilicone) not measurablePh/F Ratio:

TIS 2014-I0000-71109

Script

SRV testing was also conducted on the three ratios of phenyl/fluoro silicone copolymer as well as 100% fluorosilicone. In this case, the coefficient of friction values reduce as the percentage of fluoro content increases.

T = 50C, Freq = 50 Hz, Load = 300N, Stroke = 2 mm10

4-Ball Wear Comparison with Existing Technologies11

ChemistryViscosity -35CViscosity40CViscosity100CViscosityIndex4-ball Wear Scar (DIN 51350) (400 N)4-ball Wear Scar (DIN 51350) (800 N)

75/25 Phenyl/Fluoro304 k408632291.53Too high50/50 Phenyl/FluoroSolid328562391.623.0525/75 Phenyl/FluoroSolid314552420.551.81Poly--olefineSolid345371550.77Too highPolyol-esterSolid171211451.032.30Poly-glycolSolid471862680.530.65Phenyl-methyl-polysiloxane17,40010029322Too highToo highSolid24440220Too highToo highFluoro-silicone 44,410188362411.181.71PFPE (branched)?80101081.011.58PFPE (linear)?159453381.572.07

TIS Report #2014-I0000-71109

Script

Broadening comparison, the table shows phenyl/fluoro silicone neat fluid wear scar performance relative to other exiting base fluid technologies. The 25% phenyl/75% fluoro was nearly the best performing with a wear scar of 0.55 mm, second only to poly-glycol at 0.53mm.

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Higher Fluoro content => higher wear resistanceOne interesting anomaly with 25% phenylHigher Fluoro content => lower CoFAdditives soluble in copolymer improve wear scar an average ~50%Comparable wear resistance to other synthetic formulations

Summary of Copolymer Lubricity12

Script

Lubricity of newly synthesized phenylmethyl/fluoro siloxane copolymers with higher fluoro content generally offer improved wear resistance and low frictional coefficient to other silicones. However, an interesting anamoly occurs when 25% phenyl functional group are added. Additives soluble in these copolymers improve wear scar values, on average 50%. This enables phenyl/fluoro copolymers to be considered for lubricant formulations.12

High Temperature Stability of Fluid13Module T

Viscosity Index: Maintained at traditional silicone fluid levels.TGA: 99% of material remains at 250CDSC: Grease Onset Oxidation temperature between phenyl and fluoro Evaporation: Lower evaporation rates at 200C

Claims Substantiation

Script

Now considering the high temperature aspects of phenyl/fluoro silicone copolymers.

Silicones are known to have high viscosity indices. Dimethyl silicones may have VIs that reach as high as 400; however they may not always be applicable as a lubricant in many applications. Phenyl and Fluoro silicones will have VIs around 220 and 240, respectively. Phenyl/Fluoro copolymers, as expected have VIs that range between 220 and 240, depending on the ratio of phenyl to fluoro functional groups. Higher phenyl content yields VIs closer to 220, while higher fluoro content produces VIs closer to 240.

Thermographic Analysis (TGA) was performed from 30C to 500C. The exposure temperature begins at 30C and increases at a rate of 10C per minute. At 250C shows that approximately 99% of the copolymer material remained. This is nearly the same as phenyl silicone and linear PFPE, and surpasses the performance of PAO, POE, Fluorosilicone, and branched PFPE.

Differential Scanning Calorimetry (DSC) was used to identify Onset Oxidation Temperature (OOT) of phenyl/fluoro silicone copolymers, as well as other common synthetic fluids. Phenyl silicones have the highest OOT over 360C, and Fluorosilicone has an OOT of about 250C. Copolymers examined varied in OOT between 250C and 360C depending on the amount of phenyl content. Copolymers with higher phenyl content had higher OOT than copolymers with higher fluoro content. This consistent with what was expected given the high thermal stability of phenyl silicone.

Also observed was lower evaporation rates for all three ratios of phenyl/fluoro copolymers as compared to PAO, POE, and even pure phenyl and fluoro silicones.

Thermal & Oxidative Comparison with Existing Technologies14

ViscosityViscosityIndexTGADSCEvaporation200C, no cover% Chemistry-35C40C100CVI150C200C 250COx. OnsetTemp6 h24 h7 d75/25 Phenyl/Fluoro304 k4086322999.198.898.6282C0.020.040.1350/50 Phenyl/FluoroSolid3285623999.499.299.0283C0.040.130.4725/75 Phenyl/FluoroSolid3145524299.699.499.0277C0.130.270.65Poly--olefineSolid3453715599.399.097.4205C0.541.947.85Polyol-esterSolid1712114599.699.596.5203C0.623.7713.38Poly-glycolSolid4718626898.188.1-154C26.6966.4187.18Phenyl-methyl-polysiloxane17.4 k1002932299.799.599.1307C0.080.190.48Solid2444022099.799.499.1366C0.110.281.46Fluoro-silicone 44.4 k1883624199.799.397.2246C1.744.9918.50PFPE (branched)?801010899.598.993.4348C?5.0?PFPE (linear)?1594533899.799.699.3330C?8.0?

TIS Report #2014-I0000-71109

Script

The table is a more complete listing of thermal and oxidative stability data generated, comparing phenyl/fluoro silicone copolymers to other common synthetic lubricants.14

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8000700060005000400030002000100000 10 20 30 40 50 60Thermal Stability Open Cup (250C)Viscosity at 40C (mPas)

4504003503002502001501005000 20 40 60 80 100 120DaysThermal Stability Closed Cup (250C)Viscosity at 40C (mPas)

75:2550:5025:75Ph/F Ratio:

TIS 2014-I0000-71109

Script

In addition to TGA and DSC, temperature-viscosity stability was evaluated. Samples of the 3 ratios of copolymers, 25:75, 50:50, and 75:25 were exposed to a 250C environment. Samples were cooled to 40C and the viscosity was measured. Then heated back to 250C, held for 24 hours and viscosity re-measured. This process was repeated for several consecutive days. In open cup conditions the viscosity began increasing after about 21 days, 28 days, and 42 days for the 25:75, 50:50, 75:25 phenyl/fluoro ratios, respectively. The rate of change of the 75:25 was much lower than the 25:75 and 50:50. This indicates better temperature-viscosity stability of the higher phenyl containing copolymer, as compared to other ratios. In closed cup conditions, viscosity decreases over time in a more linear fashion, with less change, again in the 75:25 copolymer. Both of these data sets illustrate better thermal stability in higher phenylated copolymer.15

Summary of Copolymer High Temperature Properties16Higher Phenyl Content => Higher Thermal StabilityHigher Viscosity IndexLess Weight LossHigher Onset Oxidation TemperatureVery good thermal performance among other synthetics

Claims Substantiation from slides 7 & 13

Script

Phenyl functional groups contribute greatly to the thermal performance of phenyl/fluoro copolymers. Copolymers with higher phenyl content have higher viscosity indices and onset oxidation temperatures, and show less evaporative weight loss. Phenyl/fluoro copolymers thermal performance is very good, even among commonly used synthetics available today.16

Grease Made with Phenyl/Fluoro CopolymerPTFE thickened, no additivesTwo viscosities: 460 mPa-s (390 cSt) and 750 mPa-s (640 cSt)FAG FE9 high speed, high temperature testingSKF EMCOR corrosion testingOther typical grease properties testingPenetrationDropping PointBleed & EvaporationetcLithium Complex Thickened Copolymer

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No claims

Script

Two greases, each PTFE-thickened were formulated using phenyl/fluoro copolymer fluids of 460 mPa-s (390 cSt) and 750 mPa-s (640 cSt) viscosities. These greases were evaluated using many standard grease tests. Specifically FAG FE9 testing was selected to examine the high speed, high temperature performance. And, SKFs EMCOR test was used to determine corrosion resistance. Many other typical grease properties like penetration, dropping point, bleed & evaporation, etc.. were also conducted. Additionally, a prototype grease thickened with lithium complex was also completed.17

18Test Method Norm, SpecificationSilicone greasePFPE grease 1PFPE grease 2PFPE grease 3Ester grease 450/50 Copolymer (460 mPas) 50/50 Copolymer(750 mPas) Base Oil TechnologyPh-SiPFPEPFPEPFPEPolyol-esterSi-CopolymerSi-CopolymerHigh temperature performance: FAG FE9, (6000 rpm & 1.5kN); F50DIN 51821 @ 220Cnot tested max service temp is 200C15 h 44 h42 h87 h (@ 180C) 62 h66 h

High Temperature (220C) FAG FE9 TestDIN 51821(mod)

Claims SubstantiationTIS 2014-I0000-71109

PFPE grease 1= Klber Barrieta L55/2-PFPE grease 2=Krytox Corrugator 226FG-PFPE grease 3=IKV Triboflon MYA 242FG-Branched one Ester grease 4= Molykote BG 20 (FE9 value at 180C is average of 3 different measurements)Comment DH/CK: - Add test data of ester grease (BG-20) will be done by CK

Script

FAG FE9 is a lubricant test using spindle, rolling element bearings, packed with grease. The spindle rotates at 6,000 rpm with an axial load of 1500 Newtons. The test concludes when the bearing torque increases due to lubricant failure. This test was modified to run at 220C to push the temperature limits of the phenyl/fluoro copolymer grease. The copolymer-based greases, 3 varieties of PFPE-based greases, and a POE-based grease were tested, because those types of greases are often used in high temperature applications. The results show the copolymer greases performed well. Logging over 60 hours until failure.18

19Test Method Silicone greasePFPE grease 1PFPE grease 2PFPE grease 3Ester grease 450:50 Copolymer(460 mPas) 50:50 Copolymer (750 mPas) Base Oil TechnologyPh-SiPFPEPFPEPFPEPolyol-esterSi-CopolymerSi-CopolymerCorrosion resistance: SKF EMCOR 1 week, dest. water10-101-2000

SKF EMCOR Testing (DIN 51802)

Claims SubstantiationTIS 2014-I0000-71109

Script

SKF EMCOR Corrosion testing was also completed on the copolymer, PFPE, and POE greases, as well as phenyl silicone grease. There was little evidence of corrosion in the EMCOR test, scoring a 0 on the EMCOR scale, which is indicate.ve of little or no corrosion.19

20Si-Co polymer1.4g/ccPFPE2g/ccTest Method Norm, SpecificationSilicone greasePFPE grease 1PFPE grease 2PFPE grease 3Ester grease 450:50 Copolymer(460 mPas) 50:50 copolymer (750 mPas) Base Oil TechnologyPh-SiPFPEPFPEPFPEPolyol-esterSi-CopolymerSi-CopolymerDensity @ at 20CISO 28111,05 g/cm1,95 g/cm31,95 g/cm31,95 g/cm31,01 g/cm31,42 g/cm31,42 g/cm3

Density comparison to other High Temperature Lubricants

Claims SubstantiationTIS 2014-I0000-71109

Script

Another feature of phenyl/fluoro copolymer-based greases that may have utility is lower density compared to other high temperature greases, like PFPE. The density of copolymer greases is around 1.4 grams per cubic centimeter. This is about 30% lower in density.20

50:50 Copolymer Grease Performance Summary

21Test Method Norm, SpecificationSilicone greasePFPE grease 1PFPE grease 2PFPE grease 3Ester grease 450:50 Copolymer(460 mPas) 50:50 copolymer(750 mPas) Base Oil TechnologyPh-SiPFPEPFPEPFPEPolyol-esterSi-CopolymerSi-CopolymerDensity @ at 20CISO 28111.05 g/cm1,95 g/cm31,95 g/cm31,95 g/cm31,01 g/cm31,42 g/cm31,42 g/cm3ConsistencyDIN 5118 NLGI #NLGI 2-3NLGI 2NLGI 2NLGI 2NLGI 2-3NLGI 2NLGI 2Dropping Point DIN220C198C169C161C> 295C285C302CFlow Pressure at -40CKesternich test1150 mbar1175 mbar700 mbar575 mbar775 mbar950 mbar1525 mbar (800 mbar @ -35C)Bleed after 24H 200CFed Stan 791-321.29.59%8.74%12.28%10.00%4,50%3,67%3,19%Evaporation after 24H 200CFed Stan 791-321.21.75%0.08%0.08%0.14%2,44%0,33%0,36%High temperature performance: FAG FE9, (6000 rpm & 1.5kN); F50DIN 51821 @ 220Cmax temp is 200C15 h 43 h42 h87 h @ 180C 62 h66 h Four Ball Wear ScarDIN 513502,61 mm1,45 mm1,18 mm0,72 mm1,03 mm1,18 mm1,18 mmFour Ball Weld LoadDIN 513501400 N7500 N> 8500 N> 7500 N2600 N2300 N2300 NCorrosion resistance: SKF EMCOR 1week, =