309 4 – Carboxylated Acrylonitrile Butadiene Rubber (XNBR)


Temperature Range:

-25°C to +125°C (-15°F to +260°F)

Intermittent High 140°C (Int 285°F)



Acrylonitrile or Nitrile as it’s more commonly referred to, is a copolymer of Acrylonitrile and Butadiene. The Nitrile content varies in commercial products from 18% to 50%, the higher the Nitrile content the better the resistance to petroleum oils and hydrocarbon fuels, but low temperature flexibility decreases.

As Nitrile has an excellent resistance to petroleum products, and an ability to be compounded for service over a wide temperature range, Nitrile is the most widely used elastomer in the seal industry today. Nitrile compounds are superior to most elastomers with regard to compression set, tear, and abrasion resistance but have limited resistance to ozone, sunlight, or weather. To obtain good resistance to lower temperatures, it is often necessary to sacrifice some high temperature resistance. Nitrile should not be kept near electric motors or other ozone generating equipment and should not be kept in direct sunlight.

By Introducing carboxylic acid groups to the polymer backbone of NBR (nitrile butadiene rubber) significantly alters the rubber's properties - extra crosslinks in the polymer - creating a polymer matrix with significantly increased strength, tear, modulus and abrasion resistance at the expense of reduced compression set, water resistance, resilience and some low-temperature properties.



Nitrile is the standard material for hydraulics and pneumatics; it has good resistance to oil-based hydraulic fluids, fats, animal and vegetable oils, flame retardant liquids (HFA, HFB, HFC), grease, water, and air. Special low-temperature compounds are available for mineral oil-based fluids. By hydrogenation, carboxylic acid addition, or PVC blending, the Nitrile polymer can meet a more specified range of physical or chemical requirements.

XNBR is recommended for applications requiring good heat, oils and abrasion resistance, such as automotive components.


EMI ReferenceSpecificationHardness IRHDSGTensile Strength (MPa)Elongation at Break %Colour
309 - XNBR501Commercial50°1.0222500Black
309 – XNBR601Commercial60°1.0219425Black
309 – XNBR701Commercial70°1.0218350Black
309 – XNBR801Commercial80°1.0217300Black
309 – XNBR901Commercial90°1.0216250Black

Full data sheets for all grades are available on request.

* The information above is supplied in good faith and believed to be correct. This information is supplied upon the condition that persons receiving this will make their own determination as to its suitability for their purposes prior to use. EMI makes no representations or warranties, either expressed or implied with respect to the information or the product to which this information refers.