Updated: August 5, 2026 · Topic: EPDM foam vs PU foam weatherstrip
Quick Answer
EPDM sponge weatherstrip is generally preferred for robust outdoor weather resistance and a broad range of extruded profile shapes. PU foam weatherstrip with a protective coating is often selected when very low closing force, soft compression and smooth surface contact are priorities. The right choice depends on exposure, compression load, mounting design and required service life—not material name alone.
Key Selection Factors
| Factor | What to check | Why it matters |
|---|---|---|
| Construction | Extruded closed-cell EPDM sponge | Soft PU foam core with protective outer film |
| Typical strength | Weather resistance and profile versatility | Low closing force and smooth compression |
| Mounting | Adhesive, channel, clips or co-extruded carrier | Usually inserted, bonded or integrated into a frame system |
| Specify | Density, hardness, profile, adhesive and tolerance | Core density, coating, geometry, recovery and attachment |
Recommended Buying Process
- Measure the application at several points and record minimum and maximum values.
- Share a section drawing, clear photos and details of the mating surface.
- Confirm material, color, mounting method, operating environment and order quantity.
- Test a sample on the real assembly before approving mass production.
Common Specification Mistakes
- Comparing materials without matching compression and geometry
- Assuming every PU coating has the same weather resistance
- Ignoring adhesive compatibility and surface preparation
- Ordering by width and height without a cross-section drawing
What to Include in Your RFQ
Send the application, cross-section dimensions, mating-part dimensions, preferred material, color, length, quantity and packaging request. If the profile replaces an existing part, include an uncompressed sample and photos showing where it is installed. Onaseal can review drawings or samples for OEM/ODM production.
Related Onaseal Solution
See PU Foam Coated Weatherstrip, or send your drawing and target quantity for a free sample and engineering review.
Frequently Asked Questions
Is PU foam always softer than EPDM foam?
PU foam weatherstrips are often designed for low closing force, but actual softness depends on density, geometry and coating. Compare tested samples at the intended compression.
Which is better outdoors?
EPDM sponge is widely used outdoors. A coated PU design may also work when its coating and construction are qualified for the exposure.
Can both be supplied with adhesive?
Many EPDM foam profiles and some PU foam constructions can use adhesive or carrier mounting. Confirm substrate, temperature and assembly method.