Buna-N, also known as Nitrile, is the sealing industry’s most economical and widely used elastomer. This synthetic rubber material is ideally used for o-rings, gaskets, seals and custom molded components for a variety of industries and applications.
Material selection plays a critical role in successful seal design. Before using Buna-N for your application, here’s everything you need to know about it.
Key Advantages
Buna o-rings feature a wide variety of benefits that make them highly desirable for many applications. Buna-N offers excellent chemical resistance to petroleum-based oils and fuels, silicone greases, hydraulic fluids, water and alcohol. Some of the other key advantages this material offers includes:
- High tensile strength
- Low compression set
- High abrasion resistance
- Cold and heat resistance
- Temperature range from -40° to +257°F
- Standard hardness range of 40 to 90 Shore A
Buna-N polymers come in various acrylonitrile (ACN) content, ranging from 18% to 50%. The higher the ACN, the less swell it experiences in oil–the lower the ACN, the more swell it experiences in oil and the better it performs in low-temperatures. With all of these unique benefits, it’s no wonder why Buna-N is often the go-to sealing material for tough applications.
Limitations
While there are a number of benefits that make Buna-N a highly desired material, there are a few drawbacks. With low ozone resistance, Buna-N compounds are often attacked by small amounts of ozone in outdoor applications. It also offers poor flame resistance, so it should not be employed in applications involving open flames. Buna o-rings should not be used to seal against brake fluids or acetones, as its resistance to these chemical compounds is not strong to handle long-term exposure.
Typical Applications
With excellent resistance to many commonly used fluids, Buna o-rings are typically found in fuel tanks and other components for automotive, marine and aerospace applications. Other rubber polymers often lack the same resistance capabilities and negatively react with fuel, oil and other liquids, making Buna-N the necessary choice for these applications.
Buna-N can be compounded to meet FDA food contact regulations. This makes Buna-N a trusted choice for applications that involve contact with fats and oils. It can also be compounded to specially meet milk and dairy applications.
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