NBR Compounds


Acrylonitrile-Butadiene-Rubber is a polymer of butadiene and acrylonitrile. The acrylonitrile (ACN) component can be between 18 and 50% and affects the following properties of the NBR used to make seals:

  • Swelling resistance in mineral oils, greases and fuels
  • Elasticity
  • Cold flexibility
  • Gas permeability
  • Compression set

    Thus an NBR material with 18% ACN has very good cold flexibility down to ca. -38°C/-36°F and moderate resistance to oil and fuel, whilst a material with 50% ACN with optimum resistance to oil and fuels has in contrast a cold flexibility only down to -3°C/+26°F. With rising ACN content, the elasticity and the gas permeability decrease and the compression set becomes worse. Simrit materials based on these synthetic rubbers are suitable for many areas of application by virtue of their good physical properties. The proven Simmerring radial shaft seals in particular, most sealing elements for hydraulics and pneumatics, as well as O-Rings, are manufactured in large quantities from materials based on NBR. Simrit is the most experienced seal manufacturer with this elastomer base in the world.

    Good resistance to swelling in aliphatic hydrocarbons, eg, propane, butane, petroleum, mineral oils (lubricating oils, hydraulic oils of Groups H, H-L and H-LP) and greases, fire retardant hydraulic fluids of Groups HFA, HFB and HFC, vegetable and animal oils and greases, light heating oil and diesel fuel. A few materials are especially resistant to: hot water at temperatures up to +100°C/212°F (sanitary fittings), inorganic acids and bases at concentrations and temperatures which are not too high.

    Moderate resistance to swelling in fuels having a high content of aromatics (super grades of fuel).

    High swell in aromatic hydrocarbons, eg, benzene; chlorinated hydrocarbons, eg, trichloro-ethylene; flame retardant hydraulic fluids of the Group HFD; esters; polar solvents and brake fluids based on glycol, eg, ATE and Pentosin.

    Temperature range for use: Depending on the composition of the blend, this is between -30°C/-22°F and +100°C/+212°F and for short periods up to 130°C/265°F; the material hardens at higher temperatures. For special blends, the cold flexibility extends down to -55°C/-67°F.