While technology is continually advancing and evolving, there are some things that have stood the test of time. One of those longstanding things is the humble O-ring. First patented in 1896, the O-ring is a doughnut-shaped seal that is designed to prevent the passage of gases or liquids. O-rings are used in many different industries for many different sealing applications. They are one of the most widely-used sealing products, as well as one of the simplest.
O-rings can be made of various elastomeric (rubber) materials to prevent liquids or gases from leaking or escaping through any gaps in mating pieces of hardware. Because O-rings are malleable, they can be mechanically squeezed to cover those gaps and prevent leaking.
Different Materials for O-Rings Have Different Properties
One of the things that makes O-rings so versatile and widely used is that they are manufactured using a variety of different elastomers. This provides users with a product that is durable and functional for the specific need. When working with strainers, there are a few different options for O-rings to choose from depending on what the exact need is.
Whenever there are choices of products to use, as it is with O-rings, it’s important to know the qualities of each type – strengths and weaknesses – so you can make the best decision for your project. To help you with your decision, we have put together a list of the most common materials used for O-rings, what each is typically used for, and the strengths and weaknesses of each.
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Nitrile
- Nitrile, also known as Buna-N, O-rings are a general-purpose seal that is widely used, cost-efficient, and have strong mechanical properties and wear-resistance. Nitrile O-rings can withstand temperatures from -70 to 275 degrees Fahrenheit. This type of O-ring is typically used for petroleum-based oil and fuel applications.
Strengths: Nitrile O-rings are known to have good wear resistance, short-term resilience, compression set resistance, and permeation resistance. Nitrile performs well in applications with limited temperature and resistance requirements.
Weaknesses: Nitrile O-rings are not recommended for use with ketones, brake fluids, nitro and halogenated hydrocarbons, and phosphate ester hydraulic fluids. -
Viton
Viton®, or flurocarbon (FKM), is a versatile material that can handle a wide range of applications and is ideal for sealing jobs in which movement is involved. Viton® O-rings can withstand temperatures from -54 to 437 degrees Fahrenheit. O-rings made from this material frequently are used in various applications including automotive, chemical processing, and appliances.
Strengths: Viton® O-rings have good wear resistance, moderate short-term resilience, excellent compression set resistance, and excellent permeation resistance.
Weaknesses: Viton® O-rings shouldn’t be used with Skydrol, ethers with low molecular weight, brake fluids, hot water and steam, amines, esters, ketones, or hot hydrofluoric acids. -
Neoprene
Neoprene, or chloroprene, is a general-purpose elastomer that is unique in that it’s moderately resistant to weather (ozone, oxygen, UV) and petroleum oils. That makes it ideal for certain applications where other materials will not work. Neoprene O-rings work well in temperatures ranging from -67 to 250 degrees Fahrenheit. They are commonly used to seal refrigerants in air conditioner and refrigeration units.
Strengths: Neoprene O-rings have good wear resistance, moderate short-term resilience, moderate compression set resistance, and good permeation resistance.
Weaknesses: Neoprene O-rings should not be used with esters, ketones, or aromatic and chlorinated hydrocarbons. -
Silicone
Silicone O-rings work well in applications that use water, steam, and petroleum fluids. They are known for having high temperature and insulating qualities. They operate well in temperatures from -100 to 500 degrees Fahrenheit. Silicone O-rings are often used for specialized medical device and FDA applications.
Strengths: Silicone O-rings have excellent compression set resistance and permeation resistance.
Weaknesses: Silicone O-rings should not be used in abrasive applications because they have poor tear resistance and tensile strength. They are much better suited for static, rather than dynamic, applications. -
Propylene
Polyurethane O-rings are known for their general durability and their remarkable extrusion and abrasion resistance. That said, they are not ideal for applications that require good compression and heat resistance. That is due to an operational temperature range of only -65 to 250 degrees Fahrenheit. Polyurethane O-rings are most frequently used for firearms, hydraulic fittings, cylinders and valves, and pneumatic tools.
Strengths: Polyurethane O-rings have excellent wear resistance and short-term resilience.
Weaknesses: Polyurethane O-rings should not be used with ketones, acids, brake fluids, water, or chlorinated hydrocarbons. -
Ethylene Propylene
Ethylene propylene O-rings work well with corrosive Skydrol hydraulic fluid, as well as water, steam, brake fluids, silicone oils, and alcohols. However, ethylene propylene isn’t suitable for a variety of applications because it has some issues with wear and tear. Ethylene propylene O-rings can withstand temperatures from -65 to 300 degrees Fahrenheit and are commonly used in the aerospace industry in hydraulic pumps.
Strengths: Ethylene propylene O-rings have good wear resistance, moderate short-term resilience, good compression set resistance, and good permeation resistance.
Weaknesses: Ethylene propylene should not be used with mineral oil products or hydrocarbon fluids. -
FFKM
Perfluoroelastomer, also known as FFKM, is the highest performing temperature and chemical properties of any elastomeric material on the market. It is also the most expensive. It has excellent chemical resistance to most chemicals, and it can withstand temperatures from -50 to 650 degrees Fahrenheit. O-rings made of FFKM are used in applications related to chemical processing, vacuum, and semiconductors.
Strengths: FFKM O-rings have good wear resistance, moderate short-term resilience, good compression set resistance, and good permeation resistance.
Weaknesses: FFKM O-rings should not be used with molten alkali metals, halogenated freons, uranium hexafluoride, or in dynamic applications.
Final Thoughts
O-rings have been around for a long time, making quick work of sealing jobs. There are many more different, less common materials not mentioned in this list that are used to make O-rings. While the above list informs you of the more common options, it’s important that you do your research and find which type is right for your job. Be sure to pair the proper O-ring with your liquid strainer based on the product you are working with.