There’s no denying that choosing an O-Ring is a daunting decision for newcomers. Just take a look at this website designed to simplify the O-Ring selection. While this website does a great job of compiling O-Ring-related information into a single, easily digestible place, there are simply simply a large number of factors that relate to your O-Ring selection. Understanding the benefits of each material Real Seal provides for your application will make your decision much easier. This blog has already covered silicone more in-depth, so please take a look if you can’t find a material that suits your application here.
EPDM
Ethylene propylene diene monomer rubber, or EPDM, is a versatile material used in a wide variety of applications. It provides excellent resistance to a wide variety of application factors, including: steam, water, heat, ozone, sunlight, mild acidics, alkali, and oxygenated solvents.
EPDM may also be cured with sulphur or peroxide if your application requires it. Real Seal focuses on peroxide-cured EPDM, since peroxide provides better chemical and thermal resistance compared with sulphur. Peroxide-cured EPDM resists up to 150 C (300 F), while sulphur can only resist up to 120 C (250 F). For this reason, peroxide is recommended for applications seeing heavy use.
Peroxide-cured EPDM will improve the heat stability, modulus (elastic stiffness), aging, and compression of the O-Ring. It will be resistant to the following common substances:
- Alcohols
- Engine coolant
- Hot water
- Ketones
- Organic and inorganic acid
However, it cannot be used with fuels, greases, or mineral oils. If your application involves drinking water, food, or beverages, peroxide-cured EPDM will likely be the best material.
Poyurethane
Polyurethane is a thermoplastic resin which also has elastometric properties. You may recognize polyurethane in various materials around your home. But its unique properties – such as the highest tensile strength and resistance (i.e. to abrasion and tear) of any elastomer – has allowed it to carved out a special niche as an O-Ring or seal as well. Most polyurethanes will work in temperatures ranging from -40 C to 82 C.
Real Seal also offers variant of polyurethane called polyester-polyurethane (AU) and polyether-polyurethane (EU). Within a temperature range of -40 C to 82 C, AU can resist hydrocarbon fuels, oxygen, ozone, and weathering well. AU also features improved abrasion, heat, and oil resistance; however, it deteriorates quickly when exposed to acids, ketones, and chlorinated hydrocarbons.
EU is more resistant to water and humidity than other polyurethanes. Its toughness and abrasion resistance also make it very suitable for hydraulic systems where high pressures, shock loads, wide metal tolerances, and abrasive contamination are involved.
NBR/Nitrile
Acrylonitrile butadiene rubber is also called simply Nitrile or NBR. This elastomer is a great choice for a seal in most hydraulic and pneumatic applications, since it can handle compression set, tear, and abrasion better than most other elastomers. The only downside is that it must be protected from sunlight, though it may resist sunlight better if it is compounded with hydrogenation, carboxylic acid addition, or another substance.
It is used with a wide variety of substances:
- Fluids
- Fats
- Animal and vegetable oils
- Flame retardant liquids (HFA, HFB, HFC)
- Grease
- Water
- Air
HNBR
Hydrogenated nitrile rubber, or HNBR, is similar to NBR, but with better resistance to oil and chemicals, and temperatures up to 150 C. NBR, by contrast, may be used between -35 C and 120 C. HNBR is typically used in rubber moulded parts, O-rings, and dynamic seals, as well as high-tensile strength and abrasion applications such as:
- Mud motors
- Rotary steerable tools
- Measurement While Drilling (MWD)
- Logging While Drilling (LWD)
FKM
Fluorocarbon rubber is a rubber compound with high chemical resistance, as well as low compression set at elevated temperatures. Though FKM cannot be used with bases, it is compatible with applications involving:
- Mineral oils and greases
- Aliphatic
- Aromatic and chlorinated hydrocarbons
- Fuels
- Oils
- Silicone oils and greases
FFKM
FFKM is essentially FKM with a fully fluorinated polymer backbone that offers superior thermo-chemical resistance. This allows it to be used in most harsh environments, including hot amines, steam, solvents, and hydrocarbons. The downside is that its resistance to lower temperatures is poor.
Aflas/FEPM
Aflas has a chemical structure with excellent heat resistance, chemical resistance, and electrical resistivity. It can also resist chemicals like acids, alkalis, steam, as well as other strong bases (unlike FKM). It does, however, have a weakness to low temperatures in aromatic oils, and poor resistance to mineral oils. It can be used in temperatures from -5 C to 200 C.
No matter what material you need, Real Seal will have the material perfect for your application. Keep checking back here for more information on O-Rings and seals, or contact Real Seal if you have any particular questions.
