Choosing the right sealing material depends on more than cost or availability. Engineers must evaluate operating conditions, environmental exposure, compliance requirements, and expected performance over time.
Rubber, plastic, and metal sealing materials each offer distinct advantages depending on the application. Understanding how those materials perform under different conditions can help OEMs make more informed sourcing and design decisions.
Quick Comparison: Rubber vs. Plastic vs. Metal Seals
| Decision Factor | Rubber | Plastic | Metal | Flexibility | High | Moderate | Low | Dynamic Motion | Excellent | Good | Limited | Chemical Resistance | Compound-dependent | Excellent | Alloy-dependent | High Temperature Resistance | Moderate to High | High | Extreme | Pressure Resistance | Moderate | High | Extreme | Common Applications | O-rings, gaskets, dynamic seals | Wear components, chemical processing | Aerospace, high-pressure systems | Compliance Availability | NSF, FDA, UL options available | FDA, NSF options available | Application-specific certifications |
Key Factors Engineers Consider When Selecting Seal Materials
Temperature Resistance
Operating temperature plays a major role in sealing performance and material lifespan.
Rubber Materials
Rubber materials are commonly used because they provide flexibility and reliable compression sealing across a wide range of temperatures.
Common elastomer options include:
- Silicone for high- and low-temperature flexibility
- EPDM for steam and weather exposure
- Nitrile (Buna-N) for petroleum-based applications
- FKM and Viton® for elevated temperatures and chemical resistance
Rubber materials are often selected for applications requiring elasticity and dynamic movement.
Related Resource: Rubber Solutions
Plastic Materials
Engineered plastics are often chosen for dimensional stability and thermal resistance.
Materials such as:
- PTFE
- UHMW
- Nylon
- PEEK
can maintain performance in demanding thermal environments while resisting wear and friction.
Related Resource: Plastic Solutions
Metal Materials
Metal seals are typically reserved for extreme operating environments involving:
- Very high temperatures
- Vacuum systems
- Combustion environments
- Cryogenic applications
Common materials include stainless steel and specialty alloys such as Inconel®.
Related Resource: Metal Solutions
Pressure Requirements
Pressure conditions often determine whether a flexible or rigid sealing material is more appropriate.
Rubber for Moderate Pressure Systems
Rubber seals are widely used in hydraulic and pneumatic systems because they conform well to mating surfaces and maintain sealing force under moderate pressure.
Applications commonly include:
- O-rings
- Gaskets
- Molded sealing components
Plastics for Stability and Extrusion Resistance
Engineered plastics can offer greater rigidity and extrusion resistance than elastomers.
PTFE components, for example, are often used in backup rings and sealing systems exposed to higher pressures or aggressive media.
Metals for Extreme Pressure Environments
Metal seals are frequently used in:
- Aerospace systems
- Oil and gas processing
- Vacuum chambers
- High-pressure industrial equipment
where sealing integrity must be maintained under severe mechanical stress.
Chemical Exposure
Chemical compatibility is critical for long-term seal performance.
Rubber Material Compatibility
Different elastomers resist different chemicals.
For example:
- EPDM performs well with water and steam
- Nitrile resists many petroleum-based fluids
- FKM materials are commonly selected for aggressive chemicals and fuels
Improper material selection can lead to swelling, cracking, or premature seal failure.
Plastics for Aggressive Chemical Environments
Plastics such as PTFE are widely used in corrosive environments because they resist a broad range of chemicals.
These materials are commonly found in:
- Chemical processing
- Semiconductor manufacturing
- Food processing
- Pharmaceutical equipment
Metal Material Considerations
Metal sealing solutions may require specialty alloys or coatings to address corrosion risks and environmental exposure.
- Engineers often evaluate:
- Corrosion resistance
- Surface treatments
- Environmental compatibility
- Galvanic interaction
before selecting a metal sealing material.
Static vs. Dynamic Motion
Seal performance requirements change depending on whether components move during operation.
Rubber in Dynamic Applications
Rubber materials are commonly used in dynamic sealing because they provide flexibility and recoverability during repeated movement.
Typical applications include:
- Rotary shafts
- Hydraulic cylinders
- Pneumatic systems
- Vibration-prone equipment
Plastics for Wear Resistance
Some engineered plastics offer low friction and excellent wear resistance in sliding or high-cycle applications.
PTFE and UHMW are frequently incorporated into sealing systems where friction reduction is important.
Metal Seals in Static Environments
Metal seals are most commonly used in static applications where environmental extremes outweigh the need for flexibility.
Regulatory and Compliance Requirements
Many industries require sealing materials that meet specific compliance standards.
Depending on the application, engineers may need materials aligned with:
- NSF 51 & 61
- FDA
- UL
- ASTM
- FST
- Aerospace specifications
Industries such as food processing, medical manufacturing, transportation, and energy often require documentation, traceability, and certified materials during the sourcing process.
Selecting the Right Sealing Material
No single material is ideal for every application. The best sealing solution depends on the operating environment, motion requirements, pressure conditions, chemical exposure, and compliance standards involved.
That’s why many OEMs work with suppliers capable of supporting multiple material categories and application requirements.
North Coast Seal supports manufacturers with:
- Rubber sealing solutions
- Engineered plastic components
- Metal sealing products
- Material selection support
- Custom fabrication and sourcing assistance
Related Resources
Frequently Asked Questions
What is the difference between rubber, plastic, and metal seals?
Rubber seals provide flexibility and compression sealing, plastics often offer chemical resistance and dimensional stability, and metal seals are typically used in extreme temperature or pressure environments.
How do engineers select sealing materials?
Engineers typically evaluate operating temperature, pressure, chemical exposure, motion requirements, compliance standards, and expected product lifespan when selecting sealing materials.
When are metal seals used instead of rubber seals?
Metal seals are commonly used in applications involving extreme heat, vacuum conditions, high pressure, or aerospace and energy systems where elastomers may not perform reliably.
What sealing materials resist chemicals best?
Chemical resistance depends on the specific media involved, but PTFE and certain FKM compounds are commonly selected for aggressive chemical environments.
Are rubber seals better for dynamic applications?
In many cases, yes. Rubber materials are often preferred for dynamic sealing because they provide flexibility and recoverability during repeated movement.
