Viton® vs. Nitrile O-rings – Which to Choose?

May. 06, 2024

Viton® vs. Nitrile O-rings – Which to Choose?

When looking for an O-ring, there are many different materials out there. Viton® and nitrile are two of the most common materials used to create O-rings, and for a good reason. Both have excellent properties, a good compression set, and varied chemical resistances. So which material is suitable for your application?

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Nitrile O-rings

Nitrile O-rings, commonly called NBR or Buna-N, are the most frequently used O-ring in the market. These O-rings are also usually the cheapest option out there. However, there are many chemical and environmental limitations to nitrile O-rings.

Nitrile is a synthetic copolymer of acrylonitrile and butadiene, but the percentage of acrylonitrile can change the properties. With a change in the acrylonitrile percentage, the temperature range can be increased but will cause a lower resistance to oil and fuel, and vice versa. Whether increased or decreased, this change in acrylonitrile percentage will increase the cost of the nitrile O-ring.

Additionally, nitrile O-rings can be hydrogenated, also known as HNBR, to increase the temperature range and resist oils, fuels, ozone, and some harsh chemicals. However, this will also increase the cost of the material. For this comparison, let’s assume a standard acrylonitrile content is used, and the material is not hydrogenated.

Viton® O-rings

Simply put, Viton® is the name-brand for FKM or FPM material. However, the material is equivalent, whether called Viton®, FKM, or FPM. Viton® O-rings are another extremely common O-ring used due to their high-temperature range and durability.

There are many types of Viton® material used to make O-rings: Viton® A, Viton® B, and Viton® F, as well as many others. The main difference between Viton® A, Viton® B, and Viton® F is the fluorine content, with Viton® A having 66%, Viton® B having 68%, and Viton® F having 70%. Viton® A is the most commonly used version, but Viton® B and Viton® F are also used frequently when the application requires. For this comparison, let’s assume Viton® A is used.

Viton® vs Nitrile – What is the Difference?

When comparing nitrile and Viton®, the next step is to decide which one is right for your application. But, we still need to better understand the differences between nitrile and Viton® O-rings. So, what is the difference between Viton® vs. nitrile O-rings?

Temperature

Nitrile O-rings have a temperature range of -35°C (-30°F) to 120°C (250°F).

Viton® O-rings have a temperature range of -20°C (-5°F) to 210°C (-410°F).

Benefits

Viton® O-rings are resistant to more chemicals than nitrile, extreme conditions, and mold. Both Viton® and nitrile O-rings have good abrasion and tear resistance, but nitrile will have higher resistance.

Limitations

Nitrile O-rings perform poorly in harsh chemicals or outdoor applications. Additionally, the resistance to different liquids is reduced when a particular formulation is required for higher or lower temperature ranges. Furthermore, Viton® O-rings should not be used in brake fluid, ketones, hot water, or with low temperatures.

Common Applications & Uses

Viton® and nitrile O-rings are used in various applications. Nitrile O-rings are commonly found in hydraulics, pneumatics, and fuel applications. This is especially true in automotive equipment, off-road equipment, some military applications, marine devices, and aircraft fuel systems. Viton® O-rings can usually be found in automobiles, aircraft, and other mechanical devices, especially those requiring harsher chemicals.

Cost

Nitrile is generally significantly cheaper than Viton®. However, special formulations of nitrile will increase the price.

Which Material Is Right for Your Application?

The suitable material depends heavily on the application. While there are positives and negatives for both nitrile and Viton®, either material may be ideal for your needs. For example, suppose the standard operating temperature is between 0°C (32°F) and 100°C (212°F). In this case, the application is internal, a standard hydraulic oil is used for lubrication, and no harsh chemicals are present; nitrile would be the better option based on the cost.

But, if the temperature were to increase, the applications were to be outside in the elements or in UV, or a harsher chemical would be used, Viton® would be the better option. But, again, a full review of all aspects of your application will help you decide which O-ring is most suitable.

If you need help navigating this process to find the right seal for your project, talk to a seal expert at Wyatt Seal. We’ve spent 50 years building relationships with seal manufacturers worldwide to offer you access to thousands of seals, gaskets, O-rings, and other specialty items for any application.

Which O-ring material is right for my application?

O-rings and seals are used in a wide range of industries to help you tightly seal the connections in pipes, tubes, and other elements of complex hydraulic and pneumatic systems. Due to many applications, there is also a wide variety of O-ring material choices available. Nitrile (Buna), Neoprene, Ethylene Propylene (EPDM Rubber), Silicone, Fluorocarbon (Viton), and PTFE (Teflon) are among the most commonly used compounds for O-rings and seals.

To answer many of your questions about O-rings, The Hope Group has created an advanced O-ring material selection guide, where we will look at the properties and compatibility as well as the temperature range and hardness of each O-ring material.

Factors to Consider When Picking O-rings

When picking the right O-ring for your specific application, there are many factors to consider. They include but are not limited to operating conditions, chemical compatibility, sealing pressure, temperature, durometer, size, and cost. Depending on the specific situation, you may also look at abrasion, tear, ozone, electrical resistance properties. Additionally, you can perform appropriate field tests to ensure the fluid, temperature, pressure, and environmental conditions are compatible with the O-ring of your choice.

O-ring Material Selection Guide

In order to accommodate a large variety of applications, manufacturers make O-rings and seals using various elastomers with different physical and chemical properties. Let’s look at some of them below:

Nitrile Butadiene Rubber (NBR)

Resistant to: Water, Petroleum Oils & Fluids, and Hydraulic Fluids

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Not recommended for: Phosphate ester base hydraulic fluids, automotive brake fluids, ketones, strong acids, ozone, freons, halogenated hydrocarbons, and methanol

Temperature Range: -40° to +250°F, although that’s an average for the lower and upper tolerances for the various nitrile butadiene rubber (NBR) compounds manufactured by Parker. Parker’s Buna-N compound, which ranges from 70 to 90 durometer hardness nitrile, withstands temperatures from -30°F up to 250°F which includes compounds N0674

Hardness: 40 to 90 durometers Shore A

Buna Nitrile

Most popular elastomer O-ring material. Parker Hannifin uses 70 durometer hard nitrile (Buna-N) for most of its standard O-rings supplied, with 90 durometer available for tube fittings and adapters. Seal professionals value Buna-Nitrile elastomer for competitive price and excellent resistance properties to petroleum-based oils and fuels, silicone greases, hydraulic fluids, water, and alcohols.

Ethylene-Propylene (EPDM)

EPDM has a spotless reputation in the sealing world because of its excellent resistance to heat, water and steam, alkali, mild acidic and oxygenated solvents, ozone, and sunlight (UV). Nevertheless, experts do not recommend EPDM compounds for gasoline, petroleum oil and grease, and hydrocarbon environments.

Resistant to: Extreme cold, steam, hot water, sunlight and UV, dilute acids, ketones, alkalis

Not recommended for: Petroleum base oils and di-ester base lubricants

Temperature Range: -65° to +450°F

Hardness Range: 40 to 90 durometers Shore A

Neoprene (CR)

Neoprene is a general-purpose elastomer with moderate resistance properties to petroleum oils and weather (ozone, sunlight, UV, and oxygen). Neoprene O-rings have a relatively low compression set, good resilience, abrasion, and are flex cracking resistant.

Resistant to: Refrigerants (freons, ammonia), high aniline point petroleum oils, mild acids, and silicate ester lubricants

Not recommended for: Phosphate ester fluids and ketones

Temperature Range: -45° to +250°F

Hardness: 50 to 80 durometers Shore A

Fluorocarbon (Viton)

When we talk about fluorocarbon O-rings, Viton is a popular trade name that may come into your mind. Fluorocarbon (FKM) compounds combine high-temperature resistance with excellent chemical resistance. These properties make them a popular choice for many applications, including aircraft and automotive industries.

Resistant to: Petroleum base oils and fluids, some phosphate ester base fluids, silicone and silicate ester base lubricants, acids and halogenated hydrocarbons

Temperature Range: Standards -15°F to +400°F, but some Parker FKM Viton compounds can tolerate temperatures down to –65F and up to +450F.

Hardness: 50-95 Durometers Shore A

Perfluoroelastomers (FFKM) (Parfluor)

Perfluoroelastomers (FFKM) are an extension of the Fluorocarbon FKM elastomers extending the compatibilities of the FKM while at the same time extending the upper temperature limits of the materials while compromising the lower temp limits. FFKMs are the cleanest/purest compounds available on the market. They are the first choice for clean applications and are particularly popular in the semiconductor industry.

Silicone

Silicone O-rings have many outstanding properties, including excellent flexibility and fatigue life, strong ozone, and UV radiation resistance. Despite the abovementioned characteristics, experts do not recommend silicone O-rings for dynamic applications. The low strength and poor abrasion resistance as well as high gas permeability, make them not compatible with the most petroleum fluids, ketones, water, and steam.

Resistant to: Dry heat (air to 400°F) and high aniline point oils

Not recommended for: Most petroleum fluids, ketones, water and steam

Temperature Range: -175F to +450°F

Hardness: 40-80 Durometers Shore A

Polytetrafluoroethylene (PTFE)

Polytetrafluoroethylene (PTFE) O-rings are designed to be used in harsh environments with temperatures ranging from -450°F to 600°F. PTFE O-rings are compatible with the widest range of chemicals, such as acetone, isopropyl, methyl, etc. Furthermore, they have low gas permeability and low absorption. Unfortunately, due to polytetrafluoroethylene material properties, pure PTFE O-rings are very rigid and hard to apply. Therefore, manufacturers, including Parker, solve this problem by mixing PTFE material with various fillers to provide users with more flexibility. PTFE seals are often used in food, pharmaceutical, and medical industries.

Resistant to: Most chemicals, excluding alkali metals, fluorine, a few fluoro-chemicals such as chlorine tri-fluoride and oxygen difluoride

Not recommended for: Applications requiring O-Ring stretch and compression

Temperature Range: -260°F to 300°F

Hardness: 55 to 60 durometer Shore D

All Elastomer Families:

All of the above elastomer families as well as those specials not listed are available in many specialty formulations. There are FDA, USP Class VI, Nuclear Grades and compounds that meet AMS, Mil standards as well as other specifications. There are colored and translucent materials as well as internally lubricated materials to meet special needs. There should be a material fit for your application.

Standard vs. Custom O-ring Materials

As an authorized Parker distributor in addition to standard O-ring materials mentioned above, The Hope Group also offers custom seals that are designed exclusively for your specific application. We take care of any functional requirements, gland limitations, installation improvements, etc. Contact us to learn more or speak to our seal specialists.

Viton® vs. Nitrile O-rings – Which to Choose?