Material Selection – it is a major factor for the right performance of a seal is that it is made of the right materials. There are many different requirements to a seal. A seal must have many other qualities than just being tight. The requirements vary from application to application.
When a sealing material is chosen many factors must be taken into consideration:
The material must be compatible with the fluid and the mating surface.
The material must keep its strength at elevated temperatures. To Preserve the sealing efficiency the material must maintain its softness and elasticity at low temperatures.
For dynamic seals it is essential for the service life that the material has a good wear Resistance.
For dynamic seals it is essential that material is gentle to the mating surface. The seal material must not be abrasive to the mating surface.
At the combination of high temperatures and high pressure the material must be extrusion resistant. Dry running qualities:
For dynamic applications where the fluid is a gas or a liquid with poor lubricating properties, the seal material must have good dry running qualities.
For most seal materials ageing is a big problem. For applications where the seal is inactive for decades a decomposed seal material may be fatal when activated.
For most dynamic applications it is essential that the seal material has a low coefficient of friction. A seal with a high friction generates a lot of heat. If the system is not cooled the heat could reduce the service life of the seal dramatically. In all cases a seal with a high friction costs a lot of energy.
For a smooth and chatter free movement it is important that the material do not have stickslip. If an accurate positioning is important a stickslip free material is a must.