Nitrile Rubber History

Acrylonitrile butadienerubber

other names: Nitrile butadiene rubber; Nitrile rubber; NBR rubber; Acrylonitrile butadiene rubber; Nitrile butadiene rubber; Nitrile rubber

Short designation: NBR

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Historical

In November 1925, well-German chemical companies, including Farbenfabriken former. Friedr. Bayer & Co. (Leverkusen), the Farbwerke former.

 

Meister Lucius und Brüning AG (Höchst) and Badische Anilin- und Sodafabrik AG (Ludwigshafen) with the intention of abandoning competing business activities in the future and jointly exploiting the scientific and economic potential. Within this association, which operated as Interessengemeinschaft Farbenindustrie Aktiengesellschaft with the official abbreviated name I.G. Farbenindustrie AG, the focal points for product development and production were now located where the most favourable conditions for their realization offered themselves. For example, elastomer research was established at the Bayer plants in Leverkusen, where the chemists Walter Bock (1895-1948) and Eduard Tschunkur (1874-1946) had already developed styrene-butadiene rubber (SBR) in the late 1920s. Around 1930, Erich Konrad (1894-1975), who had taken over as head of the central rubber laboratory of I.G.Farbenindustrie in Leverkusen in 1927, and Eduard Tschunkur, together with Helmut Kleiner (1902-1987), synthesized acrylonitrile-butadiene rubber (NBR) here. Production of the synthetic rubber, which very soon became essential for armaments, began in 1934.

Acrylonitrile-butadiene rubber has remained an economically important synthetic rubber to this day, although, like all other synthetic rubber products, it does not have the important physical-technical properties of the natural product, namely shear-induced crystallization under spontaneous stress. For this reason, natural rubber has not lost its importance, for example in the production of aircraft tires (for more details, see Natural rubber).

General description

Acrylonitrile-butadiene rubber is usually only referred to as nitrile rubber. Synthetic rubber is the co-polymer of acrylonitrile, the nitrile of acrylic acid (2-propenenitrile) and the doubly unsaturated hydrocarbon 1,3-butadiene, as shown in the following diagram, which does not take the steric conditions into account:

Chemical formula NBR

The technical abbreviation NBR for this synthetic rubber is derived from the English name Nitrile Butadiene Rubber and should not be confused with the technical abbreviation NR, which stands for Natural Rubber.

 

The proportions of both monomeric components in the macromolecule, which are marked in the above diagram with the indices k for acrylonitrile and m for 1,3-butadiene, largely determine the technical properties of the synthetic rubber. The acrylonitrile content is usually between 18 and 51 mass %. By varying the proportions of the two starting monomers and by selecting the other synthesis parameters, mainly the polymerization temperature, the desired properties of the end product can be preset very precisely.

By mixing different types of NBR, blending NBR with other elastomers to form blends, such as polyvinyl chloride (PVC) or styrene-butadiene rubber (SBR), and incorporating fillers, its properties can be further modified and optimally adapted to the intended application.

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Processing and application

Nitrile rubber comes very close to natural rubber in terms of its technical properties and is, therefore, one of the essential surrogates for this natural product, which has long been unable to meet world demand.
 

The majority of the nitrile rubber produced worldwide is consumed by the automotive supply industry, primarily for pneumatic tires, oil and fuel lines and compressed air hoses, but also for dirt traps and sound-absorbing mats, sealing elements and corrosion-reducing coatings for metal surfaces. Another major customer for synthetic rubber is the shoe industry, where it is used as a basic material for laboratory and surgical gloves and for chemical-resistant textile finishes. Finally, nitrile rubber hoses are universally applicable in laboratories and technical plants as flexible media lines for liquids and gases. They are offered in many dimensions and technical designs.

Numerous nitrile rubber types comply with the regulations of the German Technical and Scientific Association for Gas and Water (DVGB) and are expressly approved for use in gas and water supply systems. Due to its low ohmic resistance values, however, NBR is not suitable as an electrical insulation material.

 
 
Chemical properties
Acrylonitrile-butadiene rubber or nitrile rubber is a broad term for rubber-like elastomers obtained by emulsion polymerization of acrylonitrile and 1,3-butadiene in varying proportions.

The reaction is temperature-controlled in aqueous suspension, whereby cold polymerization and hot polymerization yield differently cross-linked products. However, crosslinking can also be achieved by classical vulcanization with sulfur.

As a general rule, the elasticity of nitrile rubber decreases as the acrylonitrile content increases, and the associated reduction in its tendency to swell increases its stability against chemicals and solvents.

Nitrile rubber with equal proportions of acrylonitrile and butadiene has the highest resistance to oils and fuels. The gas permeability of nitrile rubber decreases with increasing acrylonitrile content. For all acrylonitrile-butadiene rubber types, it is still lower than the gas permeability of natural rubber (NR) and also of styrene-butadiene rubber (SBR).

Technical data

Due to the different compositions and structures of acrylic butadiene rubber (nitrile rubber), general technical data cannot be given. The values given here are based on parameters of different nitrile rubber qualities from Reichelt Chemietechnik. However, they are only rough guide values for orientation purposes; the actual values of a product may differ considerably from these values.
 

The proportions of both monomeric components in the macromolecule, which are marked in the above diagram with the indices k for acrylonitrile and m for 1,3-butadiene, largely determine the technical properties of the synthetic rubber. The acrylonitrile content is usually between 18 and 51 mass %. By varying the proportions of the two starting monomers and by selecting the other synthesis parameters, mainly the polymerization temperature, the desired properties of the end product can be preset very precisely.

By mixing different types of NBR, blending NBR with other elastomers to form blends, such as polyvinyl chloride (PVC) or styrene-butadiene rubber (SBR), and incorporating fillers, its properties can be further modified and optimally adapted to the intended application.

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Technical data

General properties

Color black

Density         

1.35 g to 1.50 g / cm3

Thermal properties 

Operating temperature range – 30 °C to +120 °C

Fire class UL 94 V-0   

Oxygen index (LOI) < 25

Electrical properties   

Contact resistance 1.2 x 104 Ω – cm

Mechanical properties 

Shore hardness A up to 80

Elongation at break   

250 % to 350 %

Tear strength             

7 MPa to 13 MPa

Compression set           

 

Chemical resistance

Alcohols
resistant
Aldehydes, esters, ketones
volatile
Aliphatic hydrocarbons
resistant
Gasoline and diesel fuel
resistant
aromatic hydrocarbons
volatile
Halogenated hydrocarbons
volatile
Hydraulic oils, mineral oils and greases
resistant
Diluted acids
resistant
Diluted alkaline solutions
resistant
Hot water
resistant
UV radiation and ozone
volatile