I. Core Characteristics of Common Sealing Ring Materials

Nitrile Butadiene Rubber (NBR)

1. Core properties: Excellent oil resistance (high tolerance to non-polar media such as mineral oil, hydraulic oil and fuel oil), good elasticity, outstanding cost-effectiveness and moderate mechanical strength.

2. Key parameters: Operating temperature range -40℃~120℃; applicable pressure ≤35MPa (static sealing), ≤15MPa (dynamic sealing).

3. Typical applications: Hydraulic system seals, automotive engine oil seals, gearbox seals, general machinery seals for oil environments; often used with engineering plastic components such as nylon and POM.

4. Notes: Poor ozone and weather resistance; not suitable for polar media (e.g., ketones, esters) or high-temperature conditions.

Fluororubber (FKM/Viton)

1. Core properties: Excellent high-temperature and chemical resistance, capable of withstanding harsh media such as strong acids, strong alkalis, fuel oil and organic solvents; low compression set and high sealing stability.

2. Key parameters: Operating temperature range -20℃~200℃, short-term tolerance up to 250℃; applicable pressure ≤40MPa (static sealing), ≤20MPa (dynamic sealing).

1. Typical applications: Chemical equipment seals, aerospace seals, high-temperature automotive engine seals, oil drilling equipment seals; suitable for extreme working conditions with engineering plastic substrates.

2. Notes: Poor low-temperature elasticity and higher cost than conventional rubber; avoid contact with low-molecular ketones and amines.

Silicone Rubber (Si)

1. Core properties: Wide temperature adaptability, excellent elasticity, good weather and ozone resistance, non-toxic and odorless, compliant with FDA food-grade and medical-grade standards.

2. Key parameters: Operating temperature range -60℃~230℃; applicable pressure ≤10MPa (static sealing), ≤5MPa (dynamic sealing).

3. Typical applications: Food machinery seals, medical device seals, electronic equipment waterproof seals, low-temperature environment seals; e.g., seals for plastic tableware production equipment and medical silicone sealing rings.

4. Notes: Low mechanical strength and wear resistance; not suitable for high-pressure friction or oil-based environments.

Polyurethane (PU)

1. Core properties: Exceptional wear and tear resistance, high mechanical strength, strong compression set resistance and excellent dynamic sealing performance.

2. Key parameters: Operating temperature range -20℃~80℃; applicable pressure ≤50MPa (static sealing), ≤30MPa (dynamic sealing).

3. Typical applications: High-pressure hydraulic system seals, pneumatic component seals, construction machinery reciprocating seals, cylinder sealing rings; often used with metal and engineering plastic parts.

4. Notes: Limited temperature resistance; not suitable for high-temperature conditions; poor tolerance to strong polar solvents (e.g., DMF, acetone).

Ethylene Propylene Diene Monomer (EPDM)

1. Core properties: Excellent weather, ozone and water resistance; capable of long-term exposure to steam, hot water and harsh outdoor environments; good electrical insulation performance.

2. Key parameters: Operating temperature range -50℃~150℃; applicable pressure ≤20MPa (static sealing), ≤10MPa (dynamic sealing).

3. Typical applications: Sanitary equipment seals, automotive cooling system seals, outdoor plastic housing seals, air conditioning condenser tube seals, steam pipeline seals; e.g., washing machine sealing rings and photovoltaic equipment outdoor seals.

4. Notes: Extremely poor oil resistance; strictly prohibited for oil-based environments; verify compatibility with polar plastic substrates.

Special Sealing Materials

1. Perfluoroelastomer (FFKM): High-end special sealing material with nearly universal chemical resistance (including strong oxidants, organic solvents and high-temperature molten salts) and excellent high-temperature performance. Key parameters: Operating temperature range -20℃~300℃, short-term tolerance up to 320℃; applicable pressure ≤45MPa (static sealing). Typical applications: Semiconductor manufacturing equipment, high-end chemical reactors, aerospace extreme condition seals. Notes: Cost 10–20 times higher than conventional rubber; only for core sealing parts of critical equipment.

2. Hydrogenated Nitrile Butadiene Rubber (HNBR): Modified NBR with superior temperature resistance, aging resistance and oil resistance compared to standard NBR. Key parameters: Operating temperature range -40℃~150℃; applicable pressure ≤40MPa (static sealing), ≤25MPa (dynamic sealing). Typical applications: Automotive transmission seals, high-temperature hydraulic system seals, oil drilling equipment seals. Notes: Slightly inferior low-temperature elasticity compared to NBR; adjust formula based on low-temperature working conditions.

3. Chloroprene Rubber (CR): Good weather and flame resistance; moderate tolerance to weak acids and alkalis. Key parameters: Operating temperature range -30℃~120℃; applicable pressure ≤15MPa (static sealing). Typical applications: Outdoor low-pressure sealing, ship deck seals, fire-fighting equipment seals. Notes: Average oil resistance; not suitable for aromatic solvent environments.

II. Core Principles of Sealing Ring Material Selection

1. Match working media: Prioritize material selection based on the type of contact medium to prevent material swelling, degradation and accelerated aging (e.g., choose NBR/FKM for oil-based media, EPDM for water/steam media).

2. Adapt to temperature range: Ensure the material’s operating temperature fully covers the actual equipment temperature range with a 10–20℃ safety margin (e.g., choose FKM/FFKM for high-temperature conditions, Si/NBR for low-temperature conditions).

3. Meet pressure requirements: Select materials with appropriate mechanical strength based on sealing type (static/dynamic) and working pressure; prioritize PU/HNBR for high-pressure dynamic sealing.

4. Ensure substrate compatibility: Verify compatibility between sealing materials and matching plastic/metal substrates to avoid sealing failure or substrate damage caused by material interactions.

5. Balance cost and reliability: Choose cost-effective materials (e.g., NBR, EPDM) for normal working conditions; prioritize sealing reliability and select special materials (e.g., FFKM) for extreme conditions.

III. Conclusion