NBR – Nitrile rubber

NBR, or nitrile-butadiene rubber (often shortened as “Nitrile Rubber”) is a general term for a number of unsaturated rubber types based on polymer compounds of acrylonitrile and butadiene. As with SBR, they are produced through hot or cold polymerization of an emulsion.
Nitrile rubber is currently made by a number of companies in different countries; available as a solid or as latex, it is one the most widely used kinds of rubber all over the world.

Depending upon their ACN (acrylonitrile) content, we may distinguish five major types of NBR:

1) Very high ACN content (45 to 50%)
2) High ACN content (38 to 40%)
3) Intermediate ACN content (31 to 34%)
4) Low ACN content (25 to 28%)
5) Very low ACN content (20 to 25%)

A high ACN content has the following effects on the properties of the product:
Greater resistance to gasoline and mineral oils.
Greater elasticity.
Lower flexibility at low temperatures.
Lower gas permeability.
Lower resilience (Higher deformation by compressive stress)

Properties

  • The properties of vulcanized nitrile rubber types are chiefly due to their acrylonitrile content and to the kind and quantity of plasticizer. Generally speaking, however, one might say that cured NBR products can withstand quite well the effects of gasoline and mineral oils and fats, but perform less satisfactorily with regard to aging; however, they can be made as strong as natural rubber by adding some reinforcing extender.
  • Impact strength: 10 to 50%
  • Extensibility: 100 to 700% and beyond
  • Resistance to low temperatures: -10°C to -50°C.
  • Electrical properties: nitrile rubber can be regarded as a semiconductor, so vulcanized products made thereof are not suitable for electrical insulation.
  • Gas permeability: much lower than that of NR, IR, BR, SBR, EPM, EPDM vuclanized rubber types.
  • Resistence to ozone, aging and weathering: poor, yet better than that of hevea rubber.
  • Resistence to chemicals:
    • Very good, because of the presence of a saturated polymeric chain.
    • Good resistance to:
      Aliphatic hydrocarbons like propane, butane, gasoline (petrol) and mineral oils and fats.
      Hydraulic fluids not easily flammable belonging to the HCF group.
      Silicone-based oils and fats.
      Water (some types can withstand up to 100°C.)
      Many diluted acids, bases and saline solutions at room temperature
    • Intermediat resistance to:
      Fuel with a high percentage of aromatic hydrocarbons such as four-star (premium) gasoline
      Hydraulic fluids belonging to the HFA group
    • Does not withstand:
      Aromatic hydrocarbons (benzol), chlorinated hydrocarbons (trichloroethylene), polar solvents (acetone)


Applications

Vulcanized nitrile rubber is used whenever great resistance to gasoline and mineral oils is necessary. Articles involving such requirements are for instance gaskets and seals, membranes, hose, cylinder linings, conveyor belts for fat food, soles, gloves, cable sheaths, foam rubber, hard rubber coatings, jar lids.



   

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