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Should I use EPDM or silicone rubber?
Use EPDM for outdoor seals, weatherstrip, and water or steam service up to about 300 °F (150 °C): it is tougher, more tear resistant, and costs less than half as much. Use silicone above that, to about 400 °F (200 °C), or when parts need food or medical grades, translucent colors, or precise liquid silicone molding. Neither belongs in petroleum oil.
EPDM rubber
Silicone rubber (VMQ)
By the numbers
Priced on the same representative part: extruded seal, rubber, 5,000 pcs.
Tensile strengthMPa
EPDM
12
Silicone
8
Densityg/cm³
EPDM
1.15
Silicone
1.15
Max service temp°C
EPDM
150
Silicone
200
Elongation%
EPDM
300
Silicone
400
Raw material cost$/kg
EPDM
5
Silicone
12
Which should you pick?
Pick EPDM when
- The part is outdoor weatherstrip, a gasket or a seal
- It sees hot water, steam, glycol coolant or brake fluid
- Parts see rubbing, tearing or abrasion
- Lowest-cost solid or sponge extrusions are the goal
Pick Silicone when
- Continuous heat runs above 300 °F (150 °C), as on oven doors and lighting
- Food contact under FDA 21 CFR 177.2600 or medical tubing is required
- Precise, nearly flash-free LSR parts are needed at high volume
- Keypads and membranes need translucent or custom colors
Key differences
| EPDM | Silicone | |
|---|---|---|
| Tear and abrasion | Good | Low; poor for rubbing dynamic seals |
| Heat by cure system | Peroxide cure to about 300 °F (150 °C); sulfur cure near 250 °F (120 °C) | About 400 °F (200 °C); heat-stabilized grades to 450 °F (230 °C) |
| Food and medical grades | Available, less common | Standard; post-cured for food contact |
| Molding options | Extrusion, compression, transfer and injection | HCR by compression, transfer or extrusion; LSR by injection |
| Gas permeability | Moderate | High |
| Compound cost | Baseline | More than twice |
Questions
Is silicone better than EPDM?
Only where its temperature range or purity is needed. Silicone covers about −75 to 400 °F (−60 to 200 °C) and is cleaner for food and medical use. EPDM is tougher, more tear resistant and cheaper, and is the better outdoor and water seal up to about 300 °F (150 °C).
Which is better outdoors, EPDM or silicone?
Both have excellent ozone, UV and weather resistance. EPDM is the usual choice for weatherstrip and outdoor gaskets because it costs less and resists tearing. Silicone is used outdoors when the seal also sees high heat, as on light fixtures.
Can EPDM or silicone be used with oil?
No. Both swell in petroleum oils and fuels. Use nitrile (NBR) for oils and fuels, FKM for hot oils and aggressive fuels, or fluorosilicone where silicone's temperature range is also needed.
Try both on your part.
The builder prices the same geometry in every suitable process and material, with DFM for each.