Ask for a rubber gasket and you will usually be offered one of three materials: EPDM, neoprene or nitrile. On the bench they look almost identical, black, flexible and easy to cut. In service they could hardly be more different. One shrugs off sunlight for decades but swells in oil. Another sits happily in gearbox oil but cracks outdoors. The third is a good all-rounder that is not the best at anything in particular.
Choosing the wrong one is one of the most common reasons a gasket fails early. This guide compares the three side by side, explains what each one is good and bad at, and gives a quick way to choose. For the wider range of gasket rubbers, including FKM and silicone, see our guide to rubber gaskets.
The three rubbers in one sentence each
- Nitrile (NBR) is the oil rubber: the standard choice wherever a gasket meets mineral oil, fuel or hydraulic fluid.
- EPDM is the weather and water rubber: outstanding outdoors and in hot water and steam, but no use near oil.
- Neoprene (CR) is the all-rounder: good weather resistance, some oil resistance and flame resistance, without being the best at any one of them.
EPDM, neoprene and nitrile compared
The table gives typical values for solid sheet. Compounds vary, so the data sheet for the grade supplied always applies to your part.
| Property | Nitrile (NBR) | EPDM | Neoprene (CR) |
|---|---|---|---|
| Typical service temperature | -30°C to +100°C | -50°C to +150°C (peroxide-cured) | -40°C to +100°C |
| Hardness range | 50 to 90 Shore A | 40 to 90 Shore A | 40 to 80 Shore A |
| Mineral oils, greases and fuels | Very good | Poor: swells and softens | Moderate: occasional contact only |
| Sunlight, ozone and weather | Poor: cracks outdoors | Excellent | Good |
| Hot water and steam | Good in water; not for steam | Very good in peroxide-cured grades | Not the first choice |
| Flame resistance | Not flame resistant | Burns more readily | Good, resists burning |
| Cold | Stiffens below about -30°C | Flexible to about -50°C | Stiffens below about -40°C |
| Typical uses | Engines, gearboxes, pumps, hydraulics, fuel systems | Outdoor seals, water pipework, heating, cooling systems | Marine, vehicles, enclosures, general covers |
Nitrile: the rubber for oil and fuel
Nitrile, also called NBR or Buna-N, is made from acrylonitrile and butadiene. The acrylonitrile makes the rubber polar, and oils and fuels, which are not, find little to dissolve into. So a nitrile gasket keeps its size and strength in engine oil, gear oil, grease and hydraulic fluid, where other rubbers swell and soften.
Nitrile's weakness is the open air. Sunlight and ozone attack its structure, and an unprotected nitrile seal outdoors can crack within a few seasons. It is also not flame resistant. Use it inside the machine, in contact with the oil, and choose something else for the weather seal on the outside. Our guide to nitrile gaskets explains the grades in detail, including how the acrylonitrile content trades oil resistance against flexibility in the cold.
EPDM: the rubber for weather, water and steam
EPDM, ethylene propylene diene monomer rubber, has a chemical backbone with nothing for ozone and ultraviolet light to attack. That is why EPDM door seals, roof membranes and pipe gaskets last for many years outdoors. It also handles hot water, low-pressure steam, glycol coolants and many dilute acids and alkalis, and stays flexible in severe cold.
The way EPDM is cured matters. Peroxide-cured grades take heat and steam best, to about +150°C, while sulphur-cured grades are economical for general weather and water seals to about +120°C.
EPDM has one big weakness, and it is absolute: oil. EPDM and mineral oils are both hydrocarbons, so oil soaks into the rubber, which swells, softens and loses its strength. Never use EPDM in an engine, gearbox, hydraulic system or fuel line, or anywhere it will be splashed with oil. See our guide to EPDM gaskets.
Neoprene: the all-rounder
Neoprene is the best-known name for polychloroprene, or CR. The chlorine in its structure protects it from ozone and weather and makes it resist burning, and it gives neoprene a moderate resistance to some oils and greases. It is also tough, with good resistance to tearing and abrasion.
That balance makes neoprene a sensible choice when a seal faces a bit of everything: an equipment cover outdoors that may be splashed with light oil, a marine cabinet seal in salt spray, or a vehicle part that meets road spray. Its oil resistance has limits, though. Immersed in oil, especially when hot, it softens and swells, and a sump or fuel system is better served by nitrile. Read more in our guide to neoprene gaskets.
Head to head
Neoprene vs nitrile
Choose nitrile when the gasket sits in or is regularly wetted by oil, fuel or hydraulic fluid. Choose neoprene when the seal lives outdoors or near flame and only meets oil occasionally.
Neoprene vs EPDM
Both weather well, but EPDM generally lasts longer in sunlight and ozone, copes with hot water and steam, and stays flexible at lower temperatures. Choose neoprene where the seal may also meet some oil or grease, or where flame resistance matters.
Nitrile vs EPDM
These two are opposites. Nitrile is excellent in oil and poor outdoors; EPDM is excellent outdoors and poor in oil. If a single gasket has to face both, neither is a good answer: look at neoprene for light duty, or FKM for demanding service.
When none of the three is right
- Fuels, solvents and heat together: Viton™ (FKM) fluoroelastomer resists fuels, oils, aromatics and many acids to about +200°C, at a higher price.
- Extreme heat or cold, or food contact: silicone works from about -60°C to +200°C and is available in food-grade sheet, though it tears more easily.
- Covers that need more give: nitrile-bonded and neoprene-bonded cork compress further than solid rubber, which suits pressed-steel covers and uneven faces.
Our gasket material chart compares all the common materials on temperature, hardness and resistance.
Three common mistakes
- EPDM near oil. A gasket on a compressor, pump or gearbox may never be immersed, but drips and oil mist are enough to swell EPDM over time.
- Nitrile in the sun. A nitrile seal that is perfect inside a machine can crack on an outdoor cover or hatch.
- Getting the hardness and thickness wrong. The right rubber still leaks if it is too hard for a lightly bolted cover or too thin for uneven faces. For most flat gaskets, 60 to 70 Shore A is a good starting point, and our rubber gaskets guide explains how to choose hardness and thickness.
A quick way to choose
- Oil, fuel or hydraulic fluid? Nitrile, or FKM if it is hot or the fuel is aggressive.
- Outdoors, water or steam, and no oil? EPDM.
- A mix of weather and occasional oil, or flame resistance needed? Neoprene.
- Very hot, very cold or in contact with food? Silicone.
Gaskets cut to your drawing
We cut custom gaskets, washers and pads to your drawing in solid neoprene and nitrile rubber from 1 to 25 mm, and in food-grade silicone, bonded cork and foams. Ask us about EPDM and FKM for your part. Thin parts in volume are usually die cut, and thicker rubber is water jet cut, so the edges stay clean and square. To learn more about where custom gaskets are used, read our guide to custom gasket applications.
Not sure which rubber you need? Send us your drawing and the service conditions: the fluid or exposure, the highest and lowest temperatures, the pressure and the quantity. We will recommend the right rubber and come back to you with a quote.
Viton™ is a trademark of The Chemours Company.
