Which materials of the sealing rings are resistant to moisture?

Here are several sealing ring materials with excellent moisture resistance and their characteristic analyses:

1. Perfluoroethylene-based rubber (FFKM)

Temperature range: -15°C to 327°C (long-term use), intermittent resistance to 316°C high-temperature steam.

Core advantages:

Extremely chemically inert: exhibits excellent tolerance to strong acids, strong bases, organic solvents, ethers, ketones, esters, etc., for almost all chemicals.

Outstanding hydrolysis resistance: The perfluoro groups form a chemical barrier, effectively resisting the attack of active water molecules in high-temperature steam, preventing material swelling or chemical bond breakage.

Application scenarios: Extreme environments such as petrochemicals, aerospace, nuclear power plant steam pipelines, etc., is the preferred material for 300°C steam environments.

Limitations: High production cost, expensive (thousands of yuan per kilogram), usually used in high-end fields.

2. Triethylene terephthalate rubber (EPDM)

Temperature range: -55°C to 150°C (long-term use), can be stable in 230°C superheated steam for a short period.

Core advantages:

Excellent water vapor resistance: The saturated main chain structure gives it outstanding water resistance, superior to thermal resistance indicators.

Widespread chemical resistance: Resistant to alcohols, ketones, dilute acids and various chemicals, suitable for high-temperature steam environments.

High cost-effectiveness: Relatively low price, is a cost-effective choice for 100°C to 200°C steam environments.

Application scenarios: Bathroom equipment, automotive radiators, high-pressure steam pipelines, etc.

Limitations: Not resistant to mineral oil, avoid food use.

3. Silicone rubber (SIL)

Temperature range: -55°C to 250°C (long-term use), short-term temperature resistance up to 260°C.

Core advantages:

Resistant to wet heat aging: Saturated steam can withstand 121°C × 30 minutes high-pressure sterilization cycle for 500 times, with a volume change rate < 3%.

Food-grade safety: Passes ISO 10993-5 cell toxicity test, odorless and no leaching, complies with FDA standards.

Application scenarios: Food processing equipment (such as high-temperature sterilization kettles), medical devices (such as steam sterilizers), household appliances (such as pressure valves of electric rice cookers).

Limitations: Low tensile strength, not resistant to oil-based media.

4. Fluorine rubber (FKM/VITON)

Temperature range: -20°C to 250°C (long-term use), some models can withstand 270°C.

Core advantages:

Resistant to high-temperature hydrolysis: In a 200°C steam environment, the shielding effect of fluorine atoms reduces the rate of hydrolysis reaction.

Excellent oil resistance: Resistant to most oils and solvents, suitable for diesel engines, fuel systems.

Application scenarios: Precision equipment requiring low friction coefficient (such as nuclear power plant steam pipelines).

Limitations: Low tensile strength, not resistant to ketones, low molecular weight esters, and nitro compounds.

5. Polytetrafluoroethylene (PTFE) composite materials

Temperature range: Long-term resistance to steam above 260°C, some special models can work at 300°C.

Core advantages:

Extremely strong chemical stability: Resistant to strong acids, strong bases, organic solvents and high-temperature steam.

Low friction coefficient: When combined with rubber, it has both sealing and wear resistance.

Application scenarios: Precision equipment requiring low friction coefficient (such as nuclear power plant steam pipelines).

Limitations: High price (hundreds to thousands of yuan per kilogram), poor elasticity recovery compared to rubber.

Material selection suggestions

Short-term temporary sealing (such as equipment maintenance):

Triethylene terephthalate rubber (EPDM): Low cost, resistant to 100°C to 200°C steam, suitable for most industrial scenarios.

Long-term high-temperature high-pressure sealing (such as nuclear power plant steam pipelines):

Perfluoroethylene-based rubber (FFKM): Although expensive, its resistance to 300°C steam and chemical inertness is the only reliable choice.

Food and medical fields:

Food-grade silicone rubber: Certified by FDA, resistant to wet heat aging, ensuring safety.

Extreme chemical environment:

Polytetrafluoroethylene (PTFE) composite materials: Resistant to strong acids and strong bases, suitable for chemical equipment sealing.

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