O-Rings are an integral component in most industrial and mechanical systems. Because o-ring material selection is driven by an industrial or mechanical system, that system will define which material is best suited to fulfill the application requirements of the O-Ring. Therefore, the best O-Ring material is the material best-suited for the application. Today, the familiar donut-shaped gasket is used in a variety of static or dynamic applications and is one of the most common seals used in machinery throughout the world.

The O-Ring is very much an indispensable component. Any mechanical system whose parts requires fluids, oils, or like lubrication to function also requires gaskets such as O-Rings. Gaskets act as seals when compressed between surfaces. The seals do just that—they join mechanisms together within a mechanical device and prevent leakage or spills from seeping out of the device. They are the most widely used sealing product. With the further development of elastic polymer materials, O-Rings are utilized in nearly any mechanical application under any environmental condition or temperature, with exceptional chemical compatibility.

When O-Ring failure does happen, it may be a result of such factors as improper installation, lubrication, or incorrect size. Above all, selecting the wrong material for the application can greatly contribute to product failure. O-Rings are made through a number of manufacturing techniques such as injection or compression molding, or extrusion, with a number of elastomeric materials.

What is the Best O-Ring Material For the Application?

The diversity of O-Ring applications in large part is due to the wide variety of material used in its fabrication. O-Rings are manufactured with elastic polymers known as elastomers. When you think of elastomers, think elastic—the prime mechanical property that sets it apart from other polymers. These polymers are cured most often through vulcanization. The process produces long rubber molecules to resulting in improved elasticity, tensile strength, durability, viscosity, hardness and weather resistance. Different elastomeric materials have different properties for different applications. Some may be more elastic and others may be more weather resistant.

The key in O-Ring material selection is in ensuring the components mechanical properties are compatible with the sealing requirements for the device. Because your engineer or contractor may not always be on hand to consult, knowing which type of elastomer is compatible can be the difference between downtime and productive time. To assist with your decisions, here are six of the more common O-Ring materials and the mechanical properties they are best suited for:

• Nitrile (Buna-N) is a general purpose material suited for petroleum oils, water, and some hydraulic fluids. It is an inexpensive popular seal that is also resistant to tears and abrasive treatment and will function in temperatures between -35 degrees Fahrenheit and 250 degrees Fahrenheit. It has good wear resistance and good compression set resistance, too. The material is not well-suited for automotive brake fluid, ketones, phosphate ester hydraulic fluids, or nitro and halogenated hydrocarbons. Its ozone and weather resistant can be improved through compounding.
• Ethylene Propylene Rubber (EPR) operates in a temperature range between -60 degrees Fahrenheit to 250 degrees Fahrenheit. EPR offers good heat resistance, as well as sunlight and weathering. EPR O-Rings work well with Skydrol and other hydraulic fluids, as well as applications utilizing steam, water, silicone oils, brake fluids, and alcohols. It has poor resistance to petroleum oils and fuels.
• Fluorocarbon (Viton) is an all-around, versatile material with excellent high-temperature capability. Its temperature range is -15 to 400 degrees Fahrenheit. It can handle a number of applications and is suited for use with petroleum oils, silicone fluids and gases, acids and some halogenated hydrocarbons, and like carbon tetrachloride. It is not for use with Skydrol, amines, esters, and ethers with low molecular weight, hot hydrofluoric acids, and hot water or steam.
• Neoprene is commonly used to seal refrigerants in refrigeration and air conditioning units. It has very good resistance to tears, flexing, sunlight, and weathering. It is well-suited for use with alcohol, engine coolant, vegetable oils or animal fats, and ammonia refrigerants. It has a temperature range of -40 to 450 degrees Fahrenheit. It should not be used with petroleum oils and fuels, and because finished neoprene products are often compounded with lead-based agents, it can be hazardous to human health.
• Polyurethane has a temperature range of -60 degrees Fahrenheit to 200 degrees Fahrenheit. It’s known for its general toughness and features abrasion and extrusion resistance. You’ll find the material used with petroleum oils, oxygen/ozone chlorinated solvents. Polyurethane O-rings can be found in hydraulic fittings, cylinders and valves, pneumatic tools, and firearms. It is not good with ketones, acid, and water-based applications.
• Silicone has been shown to withstand -175 degrees Fahrenheit for short periods of exposure and can operate in a range between -120 degrees Fahrenheit and 450 degrees Fahrenheit. Because silicone has a poor tear and abrasion resistance, and low tensile strength, it is better suited for static applications than dynamic ones. It performs well with vegetable oils, alcohol, oxygen, ozone, in dry heat, sunlight, and weathering. It’s also odorless and non-toxic.