Géraldine Theiler

Polymer Composites for Tribological Applications in Hydrogen Environment

(Bundesanstalt für Materialforschung und -prüfung)Federal Institute for Materials Research and Testing

Berlin, Germany

2nd International Conference on Hydrogen Safety

11-13 September 2007, San Sebastián, Spain

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Cryo-, Hydrogen- & Vacuumtribology

Applications– Storage and distribution of hydrogen

Components– Bearings, seals, valves, pumps

Tribosystems in hydrogen

Introduction Materials and Experiments Results Conclusion

Tribological Behaviour

Materials

TemperatureEnvironment

Friction heatMaterial properties

Triboreaction

Deformation

Test parameters

Hydrogen Lowv

FN

(1)

(3)(2)

(4)

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Cryo-, Hydrogen- & Vacuumtribology

Materials

Polymer composites with good tribological performance

Introduction Materials and Experiments Results Conclusion

Polymer Matrix:

PTFE : polytetrafluoroethylenePEEK : polyetheretherketonePI : polyimidePA : PolyamidePEI : polyetherimideEP : epoxy

Fibers: CF : carbon fibers

Fillers:PEEK, PPSbronzeTiO2

Solid lubricants:PTFE, MoS2, graphite200µm

15% PTFE + 15% CF filled PEEK

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Cryo-, Hydrogen- & Vacuumtribology

Materials

Introduction Materials and Experiments Results Conclusion

Name Matrix Fibers Fillers Lubricants

A PEEK 10% CF 10% PTFE + 10% MoS2

B PI 15% MoS2

C PEEK 13% CF 10% PTFE

D PTFE 18,2% CF 13,5% PEEK

E PTFE 16,7% CF 9,2% bronze

F PTFE 20% PPS

G PA 30% PTFE

H PEEK 10% CF 10% PTFE + 10% graphite

I PEEK 15% CF 5% PTFE + 5% graphite

J EP 15% CF 5% TiO2 15% graphite

K PEI 5% CF 5% TiO2 15% graphite

L PA 15% CF 5% TiO2 5% graphite

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Cryo-, Hydrogen- & Vacuumtribology

Tribological Experiments

Pin-on-disc configuration Test parameters

Disc: Steel 52100 Ø 40 mm

Pin: Polymer composite4*4 mm² FN

Friction Pin

Normal load 50 NSliding speed 0.2 m/sSliding distance 2000 m

Wear

Normal load 16 NSliding speed 0.2 m/sSliding distance 2000 m

Experiments- at RT in air, hydrogen and helium gas- LH2 (-253°C)

Introduction Materials and Experiments Results Conclusion

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Cryo-, Hydrogen- & Vacuumtribology

Cryotribometer

CT2

LH2 ,(LN2 , LHe)

CT3

He, H2 Gas

Introduction Materials and Experiments Results Conclusion

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Cryo-, Hydrogen- & Vacuumtribology

Friction measurements at RT

Results Influence of the hydrogen environment

Lower friction in hydrogen

Influence of the composition

0

0,1

0,2

0,3

0,4

0,5

C D E H

fric

tion

coef

ficie

ntAir He H2

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Cryo-, Hydrogen- & Vacuumtribology

Wear measurements

Smaller wear in liquid hydrogen

0,0

0,5

1,0

1,5

2,0

2,5

3,0

C D H

wea

r ra

te [

mm

³/N

m]

10-6

RT, air LH2 RT, H2

Results Influence of the hydrogen environment

Influence of the composition

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Cryo-, Hydrogen- & Vacuumtribology

Surface analyses of the disc

Thinner transfer film in LH2 compared to RT in air or H2

LH2RT, H2RT, air

500µm 500µm 500µm

Results Influence of the hydrogen environment

Influence of the composition

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Cryo-, Hydrogen- & Vacuumtribology

Surface analyses of the polymer pin

RT, H2

RT, air

More iron on the surface of the polymer after test in air

EDX analyses of the polymer pins

Results Influence of the hydrogen environment

Influence of the composition

Fe

F

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Cryo-, Hydrogen- & Vacuumtribology

Friction measurements at RT in air

Results Influence of the hydrogen environment

Influence of the composition

at RT in air

0

0,1

0,2

0,3

0,4

0,5

0,6

A B C D E F G H I J K L

fric

tio

n c

oef

fici

ent

MoS2 graphite

Name Matrix

A PEEK

B PI

C PEEK

D PTFE

E PTFE

F PTFE

G PA

H PEEK

I PEEK

J EP

K PEI

L PA

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Cryo-, Hydrogen- & Vacuumtribology

in liquid hydrogen

0

0,1

0,2

0,3

0,4

0,5

A B C D E F G H I J K L

fric

tio

n c

oef

fici

ent

MoS2 graphite

Friction measurements at RT in air

at RT in air

0

0,1

0,2

0,3

0,4

0,5

0,6

A B C D E F G H I J K L

fric

tio

n c

oef

fici

ent

MoS2 graphite

Results Influence of the hydrogen environment

Influence of the composition

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Cryo-, Hydrogen- & Vacuumtribology

Conclusions and recommendations

• Hydrogen has a beneficial effect on the friction behaviour of polymer composites. H2 seems to prevent the iron from transferring onto the pin.

• Polymer transfer onto the counterpart (steel disc) is lower in hydrogen environment.

• In LH2, the wear rate is lower than at RT in hydrogen.

• The polymer matrix doesn‘t have a significant influence on the friction performance of the composite in hydrogen. However, the choice of the solid lubricant is more important.

Introduction Materials and Experiments Results Conclusion

From a tribological point of view, polymer composites are suitable and reliable in (liquid) hydrogen environment.

It is recommended to avoid MoS2 and to use graphite containing materials which give the best performance.

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Cryo-, Hydrogen- & Vacuumtribology

Thanks to

• BAM VI.2, BAM VI.4, Berlin

• IVW GmbH, Kaiserslautern

• German Research Association (DFG) (Hu 791/2-1)

Thank you for your attention

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Cryo-, Hydrogen- & Vacuumtribology

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Cryo-, Hydrogen- & Vacuumtribology

Experiments: Environments

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Cryo-, Hydrogen- & VacuumtribologyFriction power at low temperature

Low friction

Bubles at the friction contact

optimal cooling effect, small ΔT

Q Q

High friction

Gas film at the friction contact

max. Temperature over RT

v v

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Cryo-, Hydrogen- & Vacuumtribology

Critical heat flux

LN2 LHe