Nitrile butadiene rubber (NBR), in short nitrile rubber, also known under the trade names Nitrile® / Perbuna® / BUNA-N® is an elastomer, a synthetic polymer obtained by the copolymerization of acrylonitrile and 1,3-butadiene.
It is a “random” copolymer, that is, the order of the acrylonitrile and butadiene groups in the polymer chain is unordered. More generally, nitrile rubber is a copolymer of an unsaturated nitrile (e.g., acrylonitrile or methacrylonitrile) with diene having a double bond (e.g. 1,3-butadiene or isoprene – in the latter case nitrile isoprene rubber or NIR).
The polymer still contains double bonds and can therefore be vulcanized with sulfur into synthetic rubber.
Buna-N is the contraction of butadiene and sodium; where the N stands for Nitrile.
It has excellent resistance to petroleum products and the ability to be used for a temperature range of -35 ° C to + 120 ° C (-30 ° F to + 250 ° F),
Nitrile / NBR is the most commonly used elastomer in the seal industry.
NBR rubber specifications for fuel and oil-resistant O-rings also require nitrile-based compounds. NDS-Seals also has a high-quality BIO-NBR quality for biofuel applications.
NBR has reasonable to good mechanical properties and is resistant to oils, fats, hydrocarbons and diluted acids. The UV, weather & ozone resistance can only be obtained with additives and is therefore always a special material. It is not resistant to aromatic compounds, halogenated hydrocarbons, ketones, car brake fluid or strong acids. NBR materials are also available for special low temperature applications.
By saturation with hydrogen, carboxylic acid addition or PVC blending, the nitrile polymer can meet a more specified package of physical or chemical requirements. NBR is resistant to oil-based hydraulic fluids, greases, animal and vegetable oils, flame retardant liquids (HFA, HFB, HFC), water and air.
The operating temperature is limited in the range of (-40 º – 120 º) with good compression set values.
The properties of nitrile rubber are also determined by the content of acrylonitrile, standard NBR contains about 31% acrylonitrile. More acrylonitrile improves the mechanical properties and resistance to oil and fuel, but increases the temperature at which the rubber becomes brittle / glazing point is reached.
NBR is the most commonly used elastomer for standard seals such as O-rings, but is also frequently used for other types of seals. Nitrile compounds generally have good technical values with respect to the compression set, tear resistance and abrasion resistance.