New Silicone Copolymer Lubricants - the alternative to PFPE lubrication

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

New Silicone Copolymer Lubricants

Dr. Christian Kranenberg

20th International Colloquium

12.-14. January 2016 Ostfildern, Germany


Outline of presentation

• Polysiloxanes: Structure and Properties

• Phenyl / Fluoro Siloxane Copolymer Lubricants

– Structure

– Properties

– Additive acceptance

– Greases

• Applications

• Summary

2


Polysiloxanes: Structure and Properties

Silicone or Polysiloxanes (IUPAC) are chain polymers with a

Si-O-Si backbone:

3

They have some unique properties like:

High thermal stability High oxidative stability

Chemically inert Low vapor pressure

Low surface tension


Polysiloxanes: Structure and Properties

4

Dimethyl

Silicone “Standard” silicones H3C –Si – O – Si – O — Si – O – CH3

CH3 CH3

n

CH3

CH3CH3CH3

Phenyl

Methyl

Silicone

Additional thermal

and oxidation stabilityH3C –Si – O – Si – O — Si – O – CH3

CH3 CH3

n

CH3

CH3C6H5CH3

Fluorosilicone

Better load-carrying capacity

and wear resistance

Excellent chemical

resistance H3C –Si – O – Si – O — Si – O – CH3

CH3 CH3

n

CH3

CH3

CH2CH3

CH2

CF3





– Structure

– Properties


– Greases

• Applications

• Summary

5


Structure of Phenyl / Fluoro Siloxane

Copolymer Lubricants

6

FluoroPhenyl

Thermal stability Wear resistance

Phenyl / Fluoro Copolymer

Different Ph/F ratio allowes to

ballance between thermal stability

and wear resistance


Properties – Thermal Stability

7

• Samples stored in

an oven at 250°C

• Viscosity measured

weekly / biweekly

until gelling

Sample with high phenyl

content (75:25) has best

thermal / oxidation

stability

Open cup allows evaporation of fluid


Properties – Thermal Stability

8

• Samples stored in

an oven at 250°C

• Viscosity measured

weekly / biweekly

• All ratios behave

similarly

• Slight viscosity

decrease

Closed cup prevents evaporation of fluid


Properties – Viscosity

9

Temperature

(°C)

Viscosity

(mPas)

-30 607300

-20 88000

-10 20500

0 6300

10 2650

20 1380

30 780

40 480

50 330

60 230

70 170

80 130

90 95

100 80

110 65

120 55

Ph/F ratio

50:50Fluid density: 1.15 – 1.20 g/cm3


Properties – Comparison

10

Fluid Ph/F

75:25

Ph/F

50:50

Ph/F

25:75

PAO

40

Polyol-

ester

Silicone

fluids

(PMPS)

Fluoro-

silicone

PFPE(branched)

PFPE (linear)

Viscosity (40°C),

mPas408 328 314 345 171 244 188 80 cSt 159 cSt

Viscosity Index 229 239 242 155 145 220 241 108 338

TGA (250°C) 98,6% 99,0% 99,0% 97,4% 96,5% 99,1% 97,2% 93,4% 99,3%

DSC (onset

temperature)282°C 283°C 277°C 205°C 203°C 366°C 246°C 348°C 330°C

Evaporation

(200°C, 7d)0,13% 0,47% 0,65% 7,85% 13,38% 1,46% 18,50%

Not

tested

Not

tested

TGA and DSC: 30-500°C, 10°C/min, air 60ml/min

Evaporation: internal test method (open cups in oven)

• Viscosity indices 230 – 250

• DSC onset temperatures > 270°C

• Low evaporation


Properties – Wear Resistance of Neat Fluids

11

Fluid Ph/F ratio 400 N load 800 N load

Average wear scar diameter

Phenyl / Fluoro Siloxane

Copolymer

75:25 1,53 mmNot

measureable

50:50 1,48 mm 2,82 mm

25:75 0,55 mm 1,81 mm

Polyphenylmethylsiloxane Not measurable

Fluorosilicone 1,18 mm 1,17 mm

4-ball wear scar test (DIN 51350-3)

• 400 N load typically too high for Phenyl-Si-fluids

• Copolymer fluids are able to generate results

• The higher the fluoro content the smaler the wear scars


Properties – Wear Resistance of Neat Fluids

12

T = 50°C

Freq.= 50 Hz

Load = 300 N

Stroke = 2 mm

Cylinder / Plate

Phenylmethyl-

polysiloxane

fluids are not

measureable

(300 N)


Additive Acceptance

13

Polysiloxane fluids have

limited miscibility with

additives

Fluorosiloxane fluids are

immiscible with additives

Phenyl / Fluoro copolymer fluids show good

acceptance with many commercial available additives

New lubricants using commercial available additives


Wear Resistance Improvements by Additives

14

Additivation Chemistry % 400 N load 800 N load

average wear scar diameter

(change compared to particular neat fluids)

antimony

o,o-dialkylphoshorodithionate2,5% 0,55 mm (-69%) 1,03 mm (-59%)

zinc diamyldithiocrbamate 2,5% 0,51 mm (-71%) 1,07 mm (-57%)

dithiocarbamate, ashless1,0% 0,66 mm (-55%) 1,29 mm (-54%)

2,5% 0,62 mm (-58%) 1,16 mm (-59%)

dialkylpentasulfide1,0% 0,65 mm (-56%) 1,98 mm (-30%)

2,5% 0,82 mm (-45%) 2,07 mm (-27%)

zinc dialkyldithiophosphate1,0% 0,76 mm (-49%) 1,21 mm (-57%)

2,5% 0,66 mm (-55%) 1,16 mm (-59%)

amine alkylisooctylphosphate 1,0% 1,48 mm (± 0%) 1,89 mm (-33%)

Wear resistance improvements of about 50% compared to pure fluids


Copolymer Greases

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• Greases can be prepared by using single and complex thickener

systems. For example Li- and Li-complex soaps

• Non soap thickerners like polyurea or PTFE are also suitable to

prepare copolymer greases

Grease preparation process is similar to

current polysiloxane greases


Li-complex Grease (50:50 Ph/F ratio)

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Characteristic Test

method

Value

Penetration

(unworked / 60 / 10k / 100k

strokes)

DIN ISO

2137

258 / 261 / 282 /

303

Base oil viscosity (40°C) 246 mPas

Bleed / Evaporation

(24h / 200°C)

ASTM

D 61840,46% / 1,17%

Dropping point IP 396-2 340°C

Flow pressure (-35°C) DIN 51805 925 mbar

Emcor corrosion

(7d, dist. water)DIN 51802 0

Water resistance (3h, 90°C) DIN 51807 1

DIN 4 ball test (ok-load) DIN 51350 1700 N*

DIN 4 ball test

(wear scar, 400 N, 1h)DIN 51350 1,05 mm

* Outside DIN measurement range


PTFE grease (50:50 Ph/F ratio)

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Characteristic Test

method

PTFE

grease A

PTFE

grease B

Additivation No additives Additives

Penetration

(unworked / 60 / 100k strokes)

DIN ISO

2137324 / - / -

290 / 290 /

296

Base oil viscosity (40°C) 790 mPas 460 mPas

Bleed / Evaporation

(24h / 200°C)

ASTM

D 61844,58% / 0,44% 3,67% / 0,33%

Dropping point IP 396-2 332°C 285°C

Flow pressure (-40°C) DIN 51805 1125 mbar 950 mbar

Emcor corrosion

(7d, dist. water)DIN 51802 4 0

Water resistance (3h, 90°C) DIN 51807 0 0

DIN 4 ball test (ok-load) DIN 51350 1900 N* 2300 N

DIN 4 ball test

(wear scar, 400 N, 1h)DIN 51350 1,02 mm 1,18 mm

FE9 (B, 6000rpm, 1500N, 220°C)

F50 value

DIN

51821-269h 63h

* Outside DIN measurement range





– Structure

– Properties


– Greases

• Applications

• Summary

18


Applications of Siloxanes as Lubricants

19

Dimethyl

Silicone • O-ring and valve lubricants

• Damping grease

• Plastic gears

• Brake caliper

Phenyl Methyl

Silicone

• Overrunning clutch

• Clutch release bearing

• Bearings operating at low temperatures

Fluorosilicone• Chemical mixers and pumps

• O-rings or gaskets exposed to aggressive chemicals

• Brake compressor

• Plug valves

• Circuit breakers

Phenyl-

Fluoro-

silicone

• High-temperature applications (corrugators bearings, oven chains, automotive powertrain components...)

• Wide service temperature applications (-35°C to +220°C)





– Structure

– Properties


– Greases

• Applications

• Summary

20


Summary

21

• Phenyl- Fluoro- copolymer siloxane fluids are a totally new

class of lubricating polysiloxane fluids that opens new

opportunities and possibilities

• Their flexible structure allows to design fluids with high

thermal stability and improved wear resistance properties

• Ph/F copolymer fluids have an improved additive acceptance

which allows to create lubricants for a broad range of

applications.

• Copolymer greases are available with different kind of

thickener systems

• PTFE copolymer greases show excellent thermal resistance at

applications running at high temperatures (>200°C)


Acknowledgement

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• Vesna Weber

• Aleksandra Nevskaya

• Dr. Manfred Jungk

• Dr. Detlev Hesse

• Dr. Michael Schütz

• Molykote® laboratory and testfield team


THANK YOU!

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Engineering

New Silicone Copolymer Lubricants - the alternative to PFPE lubrication