The Different Types of O-rings: Choosing the Right Ring For Your Application

O-rings are used for sealing any application where there is a small orifice, such as a nozzle or an air valve. O-rings come in a variety of different sizes depending on the application and the size of the orifice that needs to be sealed. It is important to know the different types of o-rings so you can choose the right one for your application. There are four main categories of o-rings: synthetic o-rings, natural rubber o-rings, hybrid o-rings, and Viton® o-rings. Each type comes with its own set of advantages and disadvantages depending on the usage.

What is a Synthetic (Buna-N) O-Ring?

There are a quite few synthetic o-ring materials on the market. Nitrile, or Buna-N, for example is a synthetic rubber unique for its chemical resistance properties. Whereas other rubbers often react with fuel and oil, nitrile is resistant to these substances, as well as many diluted acids and alkalines. The main drawback of synthetic o-rings is their lower resistance to chemicals, extreme temperatures, and high pressures when compared to some other o-rings.  The material Nitrile, also known as Buna-N or acrylonitrile butadiene rubber, functions at a temperature range of between -65 F and 300 F. O-rings made from Nitrile are typically used for general sealing purposes, which includes sealing of hydraulic fluids, petroleum oils, water and so on.

What is a Natural Rubber O-Ring?

Natural rubber is the most common rubber used for sealing applications. It has excellent chemical and temperature resistance. You can find natural rubber o-rings in a variety of different rubber compounds and elastomer grades. Rubber compounds have different properties like durometer (hardness), resistance to oils, and resistance to acids and alkalis. The rubber grade tells you how fine the rubber granules are. The harder the rubber the more resistant it is to chemicals. Rubber compounds come in ashless, gray, and gray/black color varieties. Ashless rubber is the softest type and gray rubber is a medium-soft rubber. Natural rubber o-rings are available in a variety of different dimensions depending on your application. Most common sizes are 1/4", 5/16", 3/8", 1/2", 3/4", 1-1/8", and 1-1/4".

What is a Hybrid O-Ring?

Hybrid o-rings are a synthetic/natural rubber combination o-rings. This o-ring is a combination of the chemical resistance of a synthetic rubber o-ring and the natural rubber’s resistance to chemicals and extreme temperatures. Hybrid o-rings are great for sealing applications that require high levels of chemicals, acids, or alkalis. Hybrid o-rings are available in a variety of different sizes. Common sizes include 1/2", 5/8", 3/4", 1", and 1-1/4". Hybrid o-rings can also be custom-made and are available in custom sizes.

What is a Viton® O-Ring?

Viton® is a brand name for polypropylene/polyethylene/polypropylene (PPE/PE/PP) o-rings. This type of o-ring is resistant to extreme temperatures, chemicals, and high pressures. Unlike most synthetic and natural rubber o-rings, Viton® has a higher melting point. This allows it to seal applications that require extreme temperatures up to 1000°F/532°C. The most common sizes for Viton® o-rings are 1/4", 5/16", 3/8", 1/2", 3/4", 1", 1-1/8", 1-1/4", and 1-1/2". Viton® o-rings are available in different durometer (hardness) grades. The harder the durometer number the stronger the o-ring.

Which type of o-ring should you use?

It can be hard to tell which type of o-ring your sealing application requires. That's why we've rounded up all the types, so you don't have to guess. Each type of o-ring has its advantages and disadvantages depending on the application and usage. For example, you would use a synthetic o-ring for applications that require chemical resistance or extreme temperatures, whereas a natural rubber o-ring would be a better choice for applications that don't require chemical resistance or extreme temperatures. If your application requires a high level of chemical resistance, you will want to use a Viton® o-ring. If your application doesn't require extreme temperatures or high pressures, a natural rubber o-ring would be a better choice. Choosing the right type of o-ring for your application can make all the difference.

Conclusion

O-rings seal two surfaces together. The seal can be made between two surfaces (for example, a valve and a nozzle) or between a surface and a liquid (for example, between a surface and a container). Synthetic o-rings are typically low-temperature resistant and resistant to chemicals. Natural rubber o-rings are good for sealing at temperatures up to 500°F/260°C. Hybrid o-rings are a synthetic/natural rubber combination that is resistant to extreme temperatures, chemicals, and high pressures. Natural rubber is a common rubber used in sealing applications and it has excellent resistance to chemicals and high temperatures. Viton® o-rings are a high-temperature resistant type of polyethylene/polypropylene/polypropylene (PPE/PE/PP) o-ring. 

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