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

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

When it comes to selecting an O-ring, understanding the differences between available materials is crucial. Two of the most common and effective materials are Viton® and Nitrile. Each has its unique properties, making them suitable for different applications. Both materials offer excellent characteristics, good compression sets, and varied chemical resistances. So how do you decide which material is right for your specific application?

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Nitrile O-rings

Nitrile O-rings, also known as NBR or Buna-N, are the most prevalent O-rings in the market due to their affordability. However, they come with certain chemical and environmental limitations. Nitrile is a synthetic copolymer of acrylonitrile and butadiene. The percentage of acrylonitrile can be altered to change the properties of the O-ring.

Adjustments in acrylonitrile percentage can increase the temperature range but reduce resistance to oil and fuel, and vice versa. Depending on these changes, the cost of Nitrile O-rings can increase. Furthermore, Nitrile O-rings can be hydrogenated (HNBR) to enhance the temperature range and resist oils, fuels, ozone, and some harsh chemicals, though this also elevates the material cost.

Viton® O-rings

Viton® is a brand name for the FKM or FPM material and is synonymous with high durability and a broad temperature range. Viton® O-rings are often relied upon for applications requiring resistance to extreme conditions and chemicals.

The fluorine content in Viton® materials varies: Viton® A contains 66%, Viton® B has 68%, and Viton® F includes 70%. For this comparison, we’ll focus on Viton® A, the most commonly used version.

Viton® vs Nitrile – What is the Difference?

Deciding between Nitrile and Viton® depends on a full understanding of their differences and application needs.

Temperature

Nitrile O-rings operate within a temperature range of -35°C (-30°F) to 120°C (250°F). Viton® O-rings have a wider range of -20°C (-5°F) to 210°C (410°F).

Benefits

Viton® O-rings offer better resistance to chemicals, extreme conditions, and mold compared to Nitrile. While both have good abrasion and tear resistance, Nitrile provides higher resistance.

Limitations

Nitrile O-rings do not perform well with harsh chemicals or outdoor applications. Their liquid resistance can be reduced with special formulations for varying temperature ranges. On the other hand, Viton® O-rings should be avoided in brake fluids, ketones, hot water, or low-temperature settings.

Common Applications & Uses

Nitrile O-rings are popular in hydraulic, pneumatic, and fuel systems, especially in automotive, off-road, military, marine, and aircraft fuel systems. Viton® O-rings are often used in automobiles, aircraft, and mechanical devices requiring harsher chemicals.

Cost

Nitrile O-rings are generally cheaper, though special formulations increase their costs.

Which Material Is Right for Your Application?

The best material depends on the application requirements. Both Nitrile and Viton® have their pros and cons. For instance, if the operating temperature ranges from 0°C (32°F) to 100°C (212°F), the application is internal, a standard hydraulic oil is used for lubrication, and no harsh chemicals are present, Nitrile would be more cost-effective.

If the application involves higher temperatures, exposure to elements or UV rays, or harsher chemicals, Viton® would be the better choice. A comprehensive review of your application will guide you to the most suitable O-ring material.

For support in choosing the right seal for your project, consult with seal experts who have extensive experience and connections with seal manufacturers globally. Whether you need seals, gaskets, O-rings, or other specialty items, expert advice can help you make the best choice for any application.

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Factors to Consider When Picking O-rings

Choosing the right O-ring involves several factors: operating conditions, chemical compatibility, sealing pressure, temperature, durometer, size, and cost. You may also need to consider abrasion, tear, and ozone resistance, as well as electrical resistance properties. Appropriate field tests can ensure compatibility with your O-ring choice.

O-ring Material Selection Guide

Manufacturers use various elastomers to accommodate different applications. Below are some common materials:

Nitrile Butadiene Rubber (NBR)

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

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

Temperature Range: -40°F to +250°F

Ethylene-Propylene (EPDM)

EPDM is highly resistant to heat, water, steam, alkali, mild acids, oxygenated solvents, ozone, and sunlight (UV).

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°F to +450°F

Fluorocarbon (Viton)

Fluorocarbon (FKM) compounds, like Viton, offer high-temperature resistance and excellent chemical resistance. Commonly used in 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: -15°F to +400°F (can extend to -65°F to +450°F for some compounds)

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