Nitrile butadiene rubber (NBR): properties and applications / Articles

Nitrile butadiene rubber (NBR) is a special-purpose synthetic elastomer, a copolymer of 1,3-butadiene and acrylonitrile (ACN). Thanks to the presence of polar nitrile groups in its macromolecules, this rubber possesses a unique combination of properties, the most important of which are exceptional resistance to oils, gasoline, fats and aliphatic hydrocarbons, as well as increased heat resistance and wear resistance. These qualities make NBR the most widely used special-purpose rubber in the world.

Chemical Structure and Synthesis

Nitrile butadiene rubber is produced by emulsion copolymerisation of 1,3-butadiene and acrylonitrile at a temperature of 32 °C (or at lower temperatures depending on the grade). The bound acrylonitrile content in commercial grades varies widely — from 17–20% to 36–40% and above, which determines the key performance properties of the material.

The molecular structure of NBR is characterised by the presence of polar nitrile groups (–C≡N), which impart specific properties to the polymer: resistance to non-polar solvents such as oils and gasoline, as well as increased heat resistance. The higher the acrylonitrile content, the higher the oil resistance and strength, but the lower the elasticity and low-temperature flexibility, and the higher the heat build-up under repeated deformation.

Classification and Grades

The NBR family is represented by several groups with different acrylonitrile contents, different Mooney viscosities, modifier types and delivery forms.

Main NBR grades:

BNKS-18AN — rubber with a bound acrylonitrile content of 17–20%. Mooney viscosity ML 1+4 (100 °C) is 90–110 units. Characterised by increased low-temperature flexibility and elasticity.

BNKS-28AN — grade with an acrylonitrile content of 27–30%. Mooney viscosity — 100–120 units. One of the most in-demand grades, providing a balanced combination of oil resistance and elasticity. Tensile strength — not less than 250 kgf/cm².

BNKS-33AN — rubber with an ACN content of 31–35%, a product of "low-temperature" polymerisation. Mooney viscosity — 100–120 units. Used for products requiring increased oil resistance.

BNKS-40AMN — grade with a high acrylonitrile content (36–40%), providing maximum oil and gasoline resistance. Elongation at break — not less than 450%.

Hydrogenated nitrile butadiene rubber (HNBR) — a special modification obtained by hydrogenating the double bonds of butadiene units. As a result, the elastomer acquires excellent heat and chemical resistance, as well as resistance to ozone and intense loads. HNBR density is 0.94–0.98 g/cm³, iodine value — 10–17 mg/100 mg, Mooney viscosity MML 1+4 (100 °C) — 73–87.

Physical, Mechanical and Chemical Properties

Oil and Gasoline Resistance. This is the key property of NBR. Polar nitrile groups provide high resistance to oils, gasoline, fats and aliphatic hydrocarbons. As the acrylonitrile content increases, oil resistance increases.

Heat Resistance. NBR possesses increased heat resistance compared to general-purpose rubbers. The long-term operating temperature for standard grades is up to 100–120 °C. HNBR withstands even higher temperatures.

Wear Resistance. The rubber is characterised by high wear resistance and resistance to compression set of rubber technical products based on it.

Strength Characteristics. Tensile strength of NBR vulcanisates is at least 250 kgf/cm² for most grades. Elongation at break — not less than 450%.

Low-temperature Flexibility. As the acrylonitrile content increases, low-temperature flexibility decreases. Rubbers with low ACN content (BNKS-18) offer better low-temperature flexibility.

Elasticity. NBR is inferior in elasticity to general-purpose rubbers (IR, BR, SBR). As the ACN content increases, elasticity decreases.

Dielectric Properties. The polar nature of NBR provides increased dielectric constant compared to other known polymers, allowing its use in special electrical applications.

Delivery Form. NBR is supplied in briquette and powder form.

Advantages and Disadvantages

Key Advantages:

Exceptional resistance to oils, gasoline and fats
Increased heat resistance
High wear resistance
Resistance to compression set
Good strength and tear resistance
Ability to adjust properties by varying ACN content

Main Disadvantages:

Limited low-temperature flexibility (especially for high-ACN grades)
Reduced elasticity compared to general-purpose rubbers
Low resistance to polar solvents (ketones, esters)
Limited ozone resistance for standard grades
Higher cost compared to general-purpose rubbers

Applications

Nitrile butadiene rubber finds wide application in various industries:

Automotive Industry. Production of oil and gasoline resistant hoses, fuel lines, oil seals, cuffs, gaskets, seals, as well as lining of metal rolls and rollers.

Oil and Gas Industry. Manufacture of reinforced hoses for pumping oil and gasoline, seals for oil production equipment.

Mechanical Engineering. Production of oil-resistant technical parts, conveyor belts, drive belts, sealing rings.

Cable Industry. Insulation of cables operating in contact with oils and fuel.

Chemical Industry. Manufacture of products resistant to aggressive media.

Medicine. Production of medical gloves, medical devices.

Construction. Floor coverings, foamed heat and sound insulation.

Production and Market

In Russia, the largest producer of nitrile butadiene rubbers is JSC Krasnoyarsk Synthetic Rubber Plant (KZSK) , part of the SIBUR Group. The enterprise produces a wide range of NBR grades, including SKN 1865/NBR 1865, SKN 2665/NBR 2665 NT, SKN 4045/NBR 4045 and others.

The global nitrile butadiene rubber market shows steady growth. In 2025, the market was valued at USD 2.56 billion. It is projected to reach USD 4.60 billion by 2033 at a CAGR of 7.58%. According to other estimates, the market was USD 2.83 billion in 2024 with a projected growth to USD 4.13 billion by 2031 (CAGR 4.60%).

Key players in the global market include Sinopec, TSRC Corporation, Kumho Petrochemical, JSR Corporation, Lanxess, Zeon Corporation, Sibur Holding, LG Chem and others.

The main market growth drivers are the expansion of the automotive industry, growing demand for oil-resistant products in the oil and gas sector, and the development of hydrogenated HNBR grades for high-temperature applications.

Conclusion

Nitrile butadiene rubber (NBR) is a critically important special-purpose elastomer combining unique oil and gasoline resistance with heat resistance and wear resistance. Thanks to the presence of polar nitrile groups in its macromolecules, NBR finds wide application in the automotive, oil and gas, mechanical engineering and cable industries. The development of hydrogenated HNBR grades and the expansion of production in Russia and worldwide ensure sustainable growth of this material's market in the long term.