When you order a seal, O-ring, membrane or any technical rubber part, the first question we'll ask isn't about dimensions — it's where the part operates. The answer determines the material, and the two compounds that cover most industrial applications are EPDM and NBR.
The choice between them is actually simple, because their weaknesses are opposites: NBR handles oil excellently but can't handle weathering. EPDM handles weathering, water and steam excellently — but can't handle oil. Everything else is nuance. Let's walk through it.
What Is NBR?
NBR (nitrile rubber, acrylonitrile-butadiene) is the standard material anywhere a part comes into contact with oil, grease or fuel:
- Hydraulic and pneumatic systems (seals, O-rings, cup seals)
- Engine compartments: oil and fuel sealing
- Pumps, compressors, gearboxes
Operating temperature: roughly −40 °C to +110 °C.
Key weakness: NBR handles ozone, UV radiation and atmospheric exposure poorly. An NBR part permanently exposed to sun and open air will surface-crack over time, even without mechanical load. That's why NBR is not the choice for outdoor installation — unless the part is shielded from the atmosphere.
What Is EPDM?
EPDM (ethylene propylene diene) is the material for water, steam and outdoor conditions:
- Seals in plumbing, heating and HVAC systems
- Parts exposed to the atmosphere: profiles, door and window seals, outdoor buffers
- Steam installations and water treatment equipment
- Contact with glycols and milder acids and alkalis
Operating temperature: roughly −50 °C to +150 °C.
Key weakness: EPDM must never contact mineral oils, greases or fuels. In contact with oil it swells, softens and loses its mechanical properties — often within just a few days.
Side-by-Side Comparison
| Property | NBR | EPDM |
|---|---|---|
| Mineral oils and fuels | Excellent | Poor (swells) |
| Water and steam | Good (water), limited (steam) | Excellent |
| Ozone, UV, weathering | Poor | Excellent |
| Operating temperature | −40 to +110 °C | −50 to +150 °C |
| Glycols, brake fluid | Poor | Good |
| Mechanical durability (abrasion) | Very good | Good |
| Typical use | Hydraulics, engines, pumps | Water, steam, outdoor |
Three Questions That Settle the Choice
1. Does the part contact oil, grease or fuel?
If yes — NBR. If oil is combined with high temperature (above ~110 °C) or aggressive chemicals — consider FKM (Viton®).
2. Is the part exposed to sun, open air and weather?
If yes — EPDM. Outdoor installation practically rules out NBR.
3. Is the medium water, steam or glycol?
If yes — EPDM. For pressurized steam, EPDM is the standard choice.
If the answers contradict each other (e.g. oil plus outdoor exposure), that's a sign to talk to the manufacturer — the solution may be FKM, a special compound, or a design change that shields the part. You can also run a quick check yourself with our interactive material selector, which suggests a compound based on your service conditions.
Common Mistakes We See in Practice
- An EPDM seal in a hydraulic system. The most frequent mistake: the parts look identical, but EPDM in contact with hydraulic oil fails within days. If you're not sure what the original is, send us a sample — the material can be identified.
- An NBR profile on a facade or the exterior of a vehicle. It cracks within one or two seasons. For outdoor profiles and door seals, EPDM is the standard.
- Choosing on price alone. NBR and EPDM are similarly priced; the cost difference on a finished part is negligible compared to the cost of downtime caused by the wrong material.
What If Neither Fits?
For more demanding conditions, special compounds exist:
- FKM (Viton®): high temperatures (up to +250 °C) and aggressive chemicals; also oil-resistant.
- Silicone (VMQ): wide temperature range (−60 to +200 °C), food industry; lower mechanical durability.
- SBR: an economical choice for general mechanical applications without oil or weather exposure.