In this blog post, we discuss the tribological properties of high performance polymers and what to consider when selecting materials for sliding applications.
In
tribology, the friction coefficient µ plays an important role. It is the
resistance of two different surfaces to each other. Also, wearing of the
surfaces is of interest. It is measured in µm/km. Tribological properties of
plastics are described with the friction coefficient (µ) and wear (µm/km).
Friction
properties of high performance polymers
In Figure 1,
the friction properties of selected high performance polymers are shown. PTFE
has a very low dynamic coefficient of friction compared to other high
performance polymers. If you consider the wear too (Figure 2), it can be seen
that PTFE has a high wear factor due to its low mechanical strength.
 |
| Figure 1: Coefficient of friction of different high performance polymers |
 |
| Figure 2: Wear of different high performance polymers |
Polyimides
(PI, PAI, PBI) have low wear properties, combined with a low coefficient of
friction of 0.4. It is beneficial to select materials in sliding applications
which have a low wear rate together with a low coefficient of friction.
Optimization
of tribological properties is done by using additives such as graphite, carbon
fibers, molybdenum sulfide, and carbon nanotubes. However, certain additives
can reduce the mechanical strength of the base resin (up to 50% reduction).
Conclusion
Friction and
wear properties should be evaluated as good as possible on the life part. Among
the high performance polymers, polyimides (PI, PAI, PBI) have overall good
tribological properties due to their high resistance molecular structure. Using
additives can help to reduce the wear of the material and improvement of
friction coefficient is limited.
Thank you for reading and #findoutaboutplastics
Best regards,
Herwig Juster
Literature
[1] Saechtling Kunststoff Taschenbuch
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