Polymer Composites for Tribological Applications in Hydrogen Environment

1. Polymer Composites for Tribological Applications in Hydrogen Environment (Bundesanstalt für Materialforschung und -prüfung)Federal Institute for Materials Research and TestingBerlin, Germany 2nd International Conference on Hydrogen Safety 11-13 September 2007, San Sebastián, Spain

2. Tribosystems in hydrogen • Applications • Storage and distribution of hydrogen • Components • Bearings, seals, valves, pumps Deformation Materials Test parameters Tribological Behaviour FN (4) (1) Material properties Friction heat (3) Environment Temperature Low Hydrogen (2) v Triboreaction Introduction Materials and Experiments Results Conclusion

3. Materials • Polymer composites with good tribological performance • Polymer Matrix: • PTFE : polytetrafluoroethylene • PEEK : polyetheretherketone • PI : polyimide • PA : Polyamide • PEI : polyetherimide • EP : epoxy • Fibers: • CF : carbon fibers • Fillers: • PEEK, PPS • bronze • TiO2 • Solid lubricants: • PTFE, MoS2, graphite 200µm 15% PTFE + 15% CF filled PEEK Introduction Materials and Experiments Results Conclusion

4. Materials Introduction Materials and Experiments Results Conclusion

5. Tribological Experiments • Pin-on-disc configuration • Test parameters Friction Pin Normal load 50 N Sliding speed 0.2 m/s Sliding distance 2000 m Wear Normal load 16 N Sliding speed 0.2 m/s Sliding distance 2000 m Disc: Steel 52100 Ø 40 mm Pin: Polymer composite 4*4 mm² FN • Experiments • at RT in air, hydrogen and helium gas • LH2 (-253°C) Introduction Materials and Experiments Results Conclusion

6. Cryotribometer • CT2 • LH2,(LN2 , LHe) • CT3 • He, H2 Gas Introduction Materials and Experiments Results Conclusion

7. Friction measurements at RT • Lower friction in hydrogen Influence of the hydrogen environment Influence of the composition Results

8. Wear measurements • Smaller wear in liquid hydrogen Influence of the hydrogen environment Influence of the composition Results

9. Surface analyses of the disc RT, air RT, H2 LH2 500µm 500µm 500µm • Thinner transfer film in LH2 compared to RT in air or H2 Influence of the hydrogen environment Influence of the composition Results

10. Surface analyses of the polymer pin RT, H2 RT, air Fe F EDX analyses of the polymer pins • More iron on the surface of the polymer after test in air Influence of the hydrogen environment Influence of the composition Results

11. Friction measurements at RT in air Influence of the hydrogen environment Influence of the composition Results

12. Friction measurements at RT in air Influence of the hydrogen environment Influence of the composition Results

13. 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. • 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. Conclusion Introduction Materials and Experiments Results

14. 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

16. Experiments: Environments

17. Friction power at low temperature • Low friction • Bubles at the friction contact • optimal cooling effect, small ΔT • High friction • Gas film at the friction contact • max. Temperature over RT Q Q v v

18. Critical heat flux LN2 LHe