What factors should be considered when choosing the appropriate sealing ring material?

The suitable sealing ring material needs to comprehensively evaluate the following core factors, which are interrelated and jointly determine the performance and lifespan of the sealing ring:

1. Temperature range

Low-temperature adaptability: The material needs to maintain elasticity at low temperatures to avoid cracking or shrinking that leads to leakage.

Example: Silicone rubber (-55℃~250℃) is suitable for refrigerators and cold storage; Fluorosilicone rubber (-50℃~200℃) is suitable for low-temperature oil environments.

High-temperature tolerance: The material needs to not decompose or harden at high temperatures while maintaining sealing performance.

Example: Fluorine rubber (-20℃~250℃) is used in diesel engines; Perfluoroether rubber (up to 327℃) is used in semiconductor manufacturing.

Temperature fluctuation: Frequent alternating between cold and hot may accelerate material aging; materials with good thermal shock resistance (such as fluorine rubber) should be selected.

2. Medium compatibility

Oil resistance: The material needs to resist swelling or corrosion by oil (such as mineral oil, synthetic oil, fuel).

Example: Nitrile rubber (NBR) is resistant to common mineral oil; Fluorine rubber (FKM) is resistant to aviation fuel and diesel.

Chemical resistance: The material needs to resist erosion by acids, alkalis, solvents, oxidants, etc.

Example: Polytetrafluoroethylene (PTFE) is resistant to strong acids and alkalis; Perfluoroether rubber (FFKM) is resistant to plasma and organic solvents.

Water resistance/vapor resistance: The material needs to not hydrolyze or expand in humid or high-temperature steam environments.

Example: Ethylene propylene diene monomer rubber (EPDM) is resistant to hot water vapor; Silicone rubber (SIL) is resistant to boiling water.

3. Pressure conditions

Static sealing: The material needs to withstand medium pressure without plastic deformation or extrusion.

Example: Rubber materials (such as NBR, EPDM) are suitable for low-pressure static sealing; Metal rubber is used for ultra-high-pressure pipelines.

Dynamic sealing: The material needs to maintain low friction and wear resistance in reciprocating or rotating motion.

Example: Polyurethane (PU) has good wear resistance and is suitable for hydraulic cylinders; Fluorine rubber has good flexibility and is suitable for high-speed rotating shafts.

Pressure fluctuation: Frequent pressure changes may cause material fatigue; materials with good fatigue resistance (such as hydrogenated nitrile rubber HNBR) should be selected.

4. Motion state

Rotary motion: The material needs to have low friction and wear resistance to avoid high temperatures.

Example: Fluorine rubber (FKM) or polytetrafluoroethylene (PTFE) coated rubber is used for high-speed rotating shafts.

Pulsating motion: The material needs to resist compression and tearing to prevent wear on the sealing surface.

Example: Nitrile rubber (NBR) or polyurethane (PU) is used for piston seals in hydraulic cylinders.

Static state: The material needs to maintain elasticity for a long time to avoid creep or cold flow.

Example: Silicone rubber (SIL) or ethylene propylene diene monomer rubber (EPDM) is used for static sealing of valves.

5. Cost and lifespan

Initial cost: There is a significant difference in material prices, and a balance needs to be struck between performance and budget.

Example: Nitrile rubber (NBR) costs only 1/5 to 1/10 of fluorine rubber and is suitable for mass production.

Maintenance cost: Long-lifespan materials can reduce the frequency of replacement and lower the total cost.

Example: Fluorine rubber has a lifespan of up to 10 years, although the initial cost is high, the maintenance cost is low.

Application scenarios: High-end equipment (such as semiconductors, aerospace) should prioritize high-performance materials (such as FFKM), while general scenarios can use more cost-effective materials (such as EPDM).

6. Special working condition requirements

Food/medical industry: The material needs to meet hygiene standards (such as FDA, USP Class VI), be non-toxic and odorless.

Example: Silicone rubber (SIL) or ethylene propylene diene monomer rubber (EPDM) is used for medical devices.

Environmental protection requirements: The material needs to be recyclable or low-polluting and comply with regulations such as RoHS, REACH.

Example: Avoid using rubber formulations containing harmful substances such as lead and mercury.

Lightweighting requirements: The material needs to have a low density to reduce the weight of the equipment (such as in the aerospace field).

Example: Fluorosilicone rubber (FLS) has a density lower than metal rubber, suitable for lightweight design.

7. Installation and operation convenience Dimensional stability: The material should maintain its shape after compression, avoiding excessive rebound or permanent deformation.

Example: Metal rubber or filled PTFE material has excellent dimensional stability.

Malleability: The material should be easy to shape, cut or bond, and suitable for complex sealing structures.

Example: Silicone rubber can be processed by various methods such as injection molding, extrusion, etc.

Resistance to permanent deformation under compression: The material should not fail under long-term compression and maintain sealing force.

Example: Fluororubber (FKM) has better resistance to permanent deformation under compression than nitrile rubber (NBR).

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