Silicone and EPDM are two widely used elastomers for custom seals, gaskets, profiles, and extruded rubber components. Both offer excellent resistance to weathering and environmental exposure, but they have important differences that can make one better suited than the other for a particular application.
EPDM is commonly selected for outdoor weather sealing, water resistance, and applications requiring excellent resistance to ozone and UV exposure. Silicone is frequently considered when temperature extremes, long-term flexibility, or specialized application requirements are major concerns.
So, how do you choose between silicone and EPDM?
The answer depends on temperature, environmental exposure, chemical compatibility, physical requirements, regulatory considerations, and the expected service conditions of the finished component.
Northwest Rubber Extruders (NWRE) manufactures both custom rubber extrusions and custom silicone extrusions for industrial and OEM applications.
This guide compares silicone vs. EPDM and explains some of the most important factors to consider when selecting between these two materials.
Silicone vs. EPDM: Quick Comparison
Silicone and EPDM share several desirable characteristics, particularly when it comes to environmental resistance. However, they aren’t interchangeable.
Here’s a general comparison:
| Characteristic | Silicone | EPDM |
|---|---|---|
| Weather Resistance | Excellent | Excellent |
| Ozone Resistance | Excellent | Excellent |
| UV Resistance | Excellent | Excellent |
| Water Resistance | Good | Excellent |
| High-Temperature Performance | Excellent | Good |
| Low-Temperature Flexibility | Excellent | Good |
| Outdoor Applications | Excellent | Excellent |
| Petroleum Oil Resistance | Limited | Poor |
| Compression Set Performance | Compound dependent | Compound dependent |
| Color Options | Excellent | Available |
| Specialized Applications | Excellent | Excellent |
| General Weather Sealing | Very Good | Excellent |
These are general characteristics only. Actual performance depends on the specific formulation, durometer, operating temperature, exposure conditions, and application.
What Is Silicone Rubber?
Silicone is a synthetic elastomer known for maintaining useful physical properties across a broad range of environmental conditions.
One of silicone’s most recognizable characteristics is its ability to perform in demanding temperature environments.
Depending on the specific compound, silicone can remain flexible at temperatures where some conventional rubber materials become less suitable.
Silicone also provides excellent resistance to:
- Ozone
- UV exposure
- Environmental aging
- Weather
- Temperature extremes
These characteristics make silicone extrusions useful across industries including aerospace, transportation, medical equipment, food processing, electronics, industrial manufacturing, and other specialized applications.
What Is EPDM Rubber?
EPDM stands for ethylene propylene diene monomer.
It is a synthetic rubber particularly well known for its resistance to weather, ozone, water, and UV exposure.
EPDM is widely used in outdoor applications because it can withstand environmental conditions that may cause some other rubber materials to deteriorate.
Common EPDM applications include:
- Weatherstripping
- Door seals
- Window seals
- Construction products
- HVAC equipment
- Automotive weather seals
- Outdoor machinery
- Industrial enclosures
- Water-resistant seals
EPDM’s combination of environmental resistance, flexibility, and cost effectiveness makes it a popular material for custom rubber extrusions.
The Biggest Difference: Temperature Performance
One of the most important differences between silicone and EPDM is their performance at temperature extremes.
Silicone at High Temperatures
Silicone is particularly well known for high-temperature performance.
This makes it valuable for applications near:
- Engines
- Industrial equipment
- Heating systems
- Lighting equipment
- Electronics
- High-temperature processing equipment
When elevated temperatures exceed the capabilities of conventional elastomers, silicone is often one of the first materials evaluated.
Silicone at Low Temperatures
Silicone can also maintain flexibility at very low temperatures.
This makes it useful for applications exposed to extreme cold or wide temperature fluctuations.
EPDM Temperature Performance
EPDM also performs across a useful temperature range and is suitable for many outdoor and industrial applications.
However, when extreme high- or low-temperature performance becomes a primary design requirement, silicone may offer advantages.
The exact operating limits depend on the specific compound and should always be confirmed for the application.
Which Is Better for Outdoor Use?
Both EPDM and silicone provide excellent resistance to outdoor environmental conditions.
Both materials offer strong resistance to:
- UV exposure
- Ozone
- Weather
- Environmental aging
For conventional outdoor weather seals, EPDM is frequently an excellent choice.
Examples include:
- Building seals
- Equipment enclosures
- Automotive weatherstripping
- HVAC seals
- Exterior access panels
- Construction products
Silicone may become more attractive when the same outdoor application also involves extreme temperatures or specialized performance requirements.
If an application primarily requires reliable outdoor weather resistance without demanding temperature extremes, EPDM can often provide a practical solution.
Which Is Better Around Water?
EPDM is widely used in applications involving water and moisture.
Its water resistance makes it a common choice for:
- Outdoor seals
- Weatherstripping
- HVAC equipment
- Construction applications
- Enclosures
- Water-related industrial components
Silicone also performs well in many environments involving moisture, but the specific application and exposure conditions should be evaluated.
Material compatibility should never be determined from a single characteristic alone.
Silicone vs. EPDM for Compression Seals
Both silicone and EPDM can be used to manufacture compression seals.
The performance of the seal depends on several factors beyond the base material, including:
- Durometer
- Profile geometry
- Wall thickness
- Compression percentage
- Temperature
- Duration of compression
- Compound formulation
For example, a hollow bulb profile can compress significantly more easily than a solid profile manufactured from the same general material.
Sponge versions of silicone and EPDM may provide even greater compressibility depending on the application.
When designing a seal, material and profile geometry should therefore be evaluated together.
What Is Compression Set?
Compression set is an important consideration for rubber seals that remain compressed for long periods.
Imagine a gasket around an equipment door.
When the door is closed, the gasket compresses.
When the door opens, the gasket should recover toward its original shape so it can continue creating an effective seal the next time the door closes.
If the rubber remains permanently deformed, sealing performance may decrease.
Compression-set performance can be affected by:
- Material
- Compound formulation
- Temperature
- Compression level
- Duration
- Profile design
Silicone is often considered for applications where compression performance at elevated temperatures is particularly important.
However, the actual compound should always be evaluated rather than assuming all silicone or EPDM materials perform identically.
Silicone vs. EPDM for UV and Ozone Resistance
Both materials perform very well in this category.
UV radiation and ozone can contribute to cracking and deterioration in certain rubber compounds.
EPDM is known for excellent resistance to both.
Silicone also provides excellent environmental aging and UV resistance.
For an application based exclusively on UV and ozone exposure, either material may potentially work.
Other requirements—especially temperature, cost, physical properties, and chemical exposure—may ultimately determine which material is more appropriate.
What About Oil and Fuel?
Neither standard EPDM nor silicone should automatically be selected for applications involving petroleum-based oils or fuels.
EPDM generally has poor resistance to petroleum oils and hydrocarbons.
Standard silicone may also have limitations depending on the substance and exposure conditions.
If oil or fuel resistance is a major requirement, another elastomer such as nitrile or a specialized compound may be more appropriate.
This is an important example of why the operating environment must be evaluated before selecting a rubber material.
Never assume that because a material performs exceptionally well in one environment, it will perform equally well in another.
Silicone for Specialized Applications
One area where silicone can offer significant advantages is specialized industrial use.
Depending on formulation and application requirements, silicone materials may be considered for industries such as:
Aerospace
Aerospace components can encounter demanding temperature changes and environmental conditions.
Medical Equipment
Certain silicone formulations are used in medical and healthcare applications where specialized material requirements may apply.
Food Processing
Specific silicone compounds may be available for applications involving food-processing environments and related regulatory requirements.
Electronics
Silicone’s temperature and environmental characteristics can make it useful for seals and components around electronic equipment.
Transportation
Transportation applications may use silicone where temperature performance or long-term environmental stability is important.
The exact compound and applicable specifications should always be verified for regulated or specialized applications.
NWRE serves customers across a broad range of industries and applications.
EPDM for General Industrial and Construction Applications
EPDM’s performance characteristics make it especially useful in general industrial and construction environments.
Common applications include:
- Building seals
- Weather barriers
- Equipment enclosures
- HVAC components
- Outdoor machinery
- Automotive weather seals
- Door and window seals
- Protective profiles
When the primary requirements involve weather, water, ozone, and UV resistance, EPDM is often a strong candidate.
This makes it one of the most commonly considered materials for outdoor custom rubber extrusions.
Solid vs. Sponge Silicone and EPDM
Both materials may be available in solid or cellular configurations depending on the manufacturing requirements.
Solid Rubber
Solid material is denser and generally requires greater force to compress.
It may be appropriate for:
- Gaskets
- Protective profiles
- Channels
- Tubing
- Bumpers
- Industrial seals
Sponge Rubber
Sponge material contains a cellular structure that allows it to compress more easily.
It may be useful for:
- Door seals
- Weather seals
- Enclosures
- Access panels
- Cushioning
- Gap filling
The choice between solid and sponge construction can be just as important as the choice between silicone and EPDM.
Durometer Matters
Another important consideration is durometer, which measures rubber hardness.
A lower-durometer material is generally softer and easier to compress.
A higher-durometer material is generally harder and more resistant to deformation.
The correct hardness depends on:
- Required compression
- Profile geometry
- Sealing force
- Installation
- Mechanical load
- Flexibility
- Wear requirements
Simply specifying “silicone” or “EPDM” doesn’t fully define the material requirements for a custom extrusion.
The compound, hardness, and profile all need to work together.
Silicone vs. EPDM: What About Cost?
Cost can be a consideration when choosing between materials.
For many conventional weather-sealing applications, EPDM may provide an economical solution while delivering excellent environmental performance.
Silicone can be more appropriate when the application requires characteristics that justify the material, such as demanding temperature performance or specialized requirements.
However, material price shouldn’t be evaluated independently from service life and performance.
A lower-cost material isn’t economical if it fails prematurely or cannot meet the application’s requirements.
The goal should be to select the most appropriate material for the operating environment rather than simply choosing the lowest material cost.
Questions to Ask Before Choosing Silicone or EPDM
Before selecting either material, answer the following:
What temperatures will the component experience?
Consider both minimum and maximum temperatures.
Will the component be outdoors?
Evaluate UV, ozone, weather, and water exposure.
Will it encounter oil or fuel?
Neither standard EPDM nor silicone may be ideal depending on the substance.
How much compression is required?
Profile geometry and durometer may influence the answer.
Will the component remain continuously compressed?
Compression-set characteristics may become important.
Are there industry-specific requirements?
Medical, food, aerospace, and other specialized applications may require specific compounds or documentation.
How long is the expected service life?
Long-term environmental exposure should be considered.
What is the profile geometry?
Material selection and extrusion design should be evaluated together.
Additional material information is available through NWRE’s Material & Engineering resources.
Silicone vs. EPDM: Which Should You Choose?
Neither silicone nor EPDM is universally better.
Each material has characteristics that make it valuable for different applications.
Consider EPDM when:
- Outdoor weather resistance is important
- UV and ozone exposure are major concerns
- Water resistance is required
- The application involves conventional weather sealing
- Extreme temperature performance isn’t the primary requirement
Consider silicone when:
- High-temperature performance is important
- Low-temperature flexibility is required
- The application experiences a wide temperature range
- Specialized material requirements are involved
- Long-term environmental stability is important
If petroleum oils or fuels are present, another elastomer may need to be considered.
The best material should always be selected based on the complete operating environment.
Custom Silicone and EPDM Extrusions from Northwest Rubber Extruders
Northwest Rubber Extruders manufactures custom rubber, silicone, and flexible plastic extrusions for customers across a variety of industries.
Custom profiles can be manufactured based on customer drawings and specifications, with material, durometer, dimensions, and geometry selected around the requirements of the application.
Learn more about our Silicone Extrusions, Rubber Extrusions, Material & Engineering, and Industries Served capabilities.
Not sure whether silicone, EPDM, or another elastomer is appropriate for your project? Request a Quote and provide your drawing, specifications, and application requirements to Northwest Rubber Extruders.