Friction is the resistance to motion of one object moving relative to another. The generation of microscopic friction is the result of several mechanisms including the surface energy of the material itself.
As such, polymers have very low surface energy values when compared with metals by less than one order of magnitude, and therefore characterized by a low friction coefficient.
This feature makes polymeric materials excellent candidates for tribological applications often coupled with metallic materials, in order to limit the sliding wear mechanisms.
Friction coefficient values metal-to-metal contact, nylon-nylon, nylon-steel
| Metal-Metal | Nylon-Nylon | Nylon-Steel | |
|---|---|---|---|
| Non lubricated | 0.80 | 0.50 | 0.24 |
| Slightly lubricated | 0.38 | 0.32 | 0.14 |
| Highly lubricated | 0.20 | 0.15 | 0.09 |
Source: " Friction and Wear, Methodologies of Design and Control" G.Straffelini , Springer
From these values, it is clear that lubricants are essential for metal-to-metal contact for reduced friction and consequential operating mechanisms of the components in use. Furthermore, due to the low friction coefficient, polymers such as nylon 6 and PEEK allow the realization of tribological components able to work in dry conditions or in environments with poor lubrication, as they possess self-lubricating properties that result in an increase in service life and reduced maintenance interventions.
Applications:
- Plain bearings
- Toothed wheels
- Gears
- Piston rings
- Seals
Advantages of metal replacement:
Wear reduction
Vibration reduction
Noise reduction