A basic yet essential thing to know regarding elastomers is that each different type of rubber offers a unique set of properties that set it apart from the rest. For example, silicone rubber is one of the few rubber sheets that can withstand temperatures as high as 500 degrees Fahrenheit. There is, however, one elastomer that stands out from the rest. Nitrile Buna-N rubber, also known as NBR or Buna-N, is a unique synthetic elastomer that has an excellent degree of resistance when fuels, oils and greases are present whereas other rubbers would degrade and deform. Unlike other rubber varieties like SBR or EPDM, this oil resistant rubber sheet exhibits an excellent lifespan.
Although each type of rubber specializes in handling certain conditions and applications, it should not be assumed that elastomers like Buna rubbers are single-faceted. Interestingly enough, NBR products can be tailored to excel in specific traits and this can be done with a simple tweak in the recipe, or chemical composition, of the Buna-N rubber. It is because of these qualities that Buna-N nitrile has remained popular for decades. Even today, many companies in the automotive and food service industries use NBR products extensively in their day-to-day operations.
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Buna-N Rubber: Ideal Rubber Sheet for Oil, Fuel, and Grease
Nitrile Buna-N rubber is made up of two polymers: acrylonitrile and butadiene. Butadiene is essential in the production of synthetic elastomers. Acrylonitrile is actually the polymer that is responsible for many of the properties in Buna-N nitrile. The amount of acrylonitrile included in nitrile Buna-N rubber determines several characteristics.
The Buna-N nitrile was first introduced in 1930 by the German chemists Eduard Tschunkur and Erich Konrad. Given the new mechanical and automotive nature of warfare in the 20th century, industrialized nations around the world saw the need for acquiring synthetic rubber. Natural rubber simply could not last against the oil and grease inside the new jeeps and tanks that were becoming commonplace in militaries. When the oil resistant rubber sheet finally hit the market, it made waves around the world. Soon enough, people began to learn that the rubber in these NBR products could be altered in their chemical makeup to suit a specific need. It did not take long for chemists and manufacturers around the world to begin experimenting with the oil resistant rubber sheet, trying to find new variations of the revolutionary material for their own specific applications.
When the Buna rubbers have a higher content of acrylonitrile, the resulting NBR products possess the following traits:
- Increased resistance to oils, fuels, and greases
- Increased air and gas impermeability
- Greater tensile strength
- Higher abrasion resistance
- Increased resistance to heat-aging
- Increased hardness
When there is a lower content of acrylonitrile, the nitrile Buna-N rubber possesses another set of augmented traits:
- Lower compression set
- Increased physical resilience
- Lower temperature flexibility
- Increased elasticity
Obviously, the ability of Buna rubbers to resist oil, fuel, and grease are their biggest strength. It is, after all, what made it such a popular product in the first place. However, sometimes it is beneficial to increase that strength even more, especially for large-scale industrial applications. Manufacturers always appreciate a greater degree of abrasion resistance and tensile strength because it means that the rubber will not break in strenuous operations.
As listed above, increasing the amount of acrylonitrile usually leads to a strengthening of various properties that the Buna-N nitrile possesses. That is great because many manufacturers want those qualities for their needs. However, some people may have applications that require NBR products at a lower cost point. Lowering the acrylonitrile quantities in the nitrile material will increase resilience and elasticity, but at the same time will lower the rubber’s compression set (the ability to return to it’s original form) and temperature flexibility. Everyone has different requirements for their products and Buna rubbers are great for adapting to those various applications.
The ability to change the characteristics of nitrile Buna-N rubber by simply altering the amount of acrylonitrile allows manufacturers to easily produce custom NBR products. Thus, the ability to fine tune NBR proves that nitrile is anything but single-faceted. It’s practical flexibility has made this elastomer so much more than simply an oil-resistant rubber. It can be heat resistant, abrasion resistant, harder to break, more elastic, etc. The possibilities are so great and variable that Buna-N rubber has been an industry standard for decades and will continue to remain a standard for many more.