O-rings, essential for sealing applications in various sectors (discover the main characteristics here), are available in a wide range of hardnesses. This parameter, measured in Shore A, for rubbery materials, and Shore D, for rigid materials, depends on the material they are made of and affects fundamental properties such as elasticity, mechanical resistance and chemical compatibility. Therefore, identifying the correct material, with the right degree of hardness, has a significant impact on the reliability and duration of the application, avoiding failures or breakages.
Let's find out the typical O-ring hardness of the most common materials and their uses:
- NBR (Nitrile Butadiene Rubber)
O-ring hardness: Shore A 40-90
Use: NBR is ideal for applications that require resistance to oils and fuels, such as the automotive and hydraulic sectors.
- FKM (Fluorocarbon, also known as Viton®)
O-ring hardness: Shore A 55-90
Use: FKM is perfect for aggressive environments due to its resistance to high temperatures, solvents and chemicals.
- EPDM (Ethylene Propylene Diene Monomer)
O-ring hardness: Shore A 40-90
Use: EPDM is resistant to ozone, atmospheric agents and water, but is not compatible with oils and hydrocarbons.
O-ring hardness: Shore A 20-80
Use: Silicone works well in extreme temperatures, but has lower chemical and mechanical resistance than other elastomers.
- HNBR (Hydrogenated Nitrile)
O-ring Hardness: Shore A 50-90
Use: HNBR has improved resistance to high temperatures, oxidation and chemicals compared to NBR.
- Neoprene (CR - Chloroprene)
O-ring Hardness: Shore A 40-80
Use: Neoprene is often chosen for marine and weathering applications.
O-ring Hardness: Shore A 70-95
Use: Polyurethane, prized for its abrasion resistance, polyurethane is ideal for high-pressure applications.
- PTFE (Polytetrafluoroethylene), like Teflon®, has a Shore D hardness scale, suitable for hard materials.
O-ring Hardness: Shore D 50-65.
Use: PTFE requires mechanical compression to ensure a seal. It has exceptional resistance to almost all chemicals, oils, solvents and acids and resistance to extreme temperatures. Low permanent deformation: retains its shape even under constant loads. PTFE is used primarily in static (not dynamic) applications where chemical resistance, stiffness and thermal stability are critical.
The choice of material and itshardness should always be guided by the specific needs of the application, including factors such as temperature, pressure and the media with which the O-ring will come into contact.
