Nitrile Butadiene Rubber

What Nitrile Butadiene Rubber Is and Why It Remains a Critical Elastomer

Nitrile butadiene rubber, designated BNKS and SKN in Russia and NBR internationally, is a copolymer of 1,3-butadiene and acrylonitrile produced by emulsion polymerization. The polar nitrile groups in the macromolecule give the rubber resistance to non-polar oils, gasoline, diesel fuel and other hydrocarbons, making it an indispensable material for seals, hoses and other articles contacting petroleum products.

For procurement and process teams, BNKS matters primarily as an elastomer with a tunable property balance: by varying the acrylonitrile content from 17 to 40 percent, producers obtain grades differing in oil resistance, low-temperature flexibility and elasticity. The rubber is processed by all standard rubber techniques and blends with polyvinyl chloride, phenolic resins and other ingredients, enabling compositions tailored to specific service conditions. A separate niche is occupied by hydrogenated grades, in which the majority of double bonds are saturated with hydrogen, radically improving heat and ozone resistance.

Chemical Identification and Procurement Data

• Chemical name: copolymer of 1,3-butadiene and acrylonitrile.
• Synonyms: BNKS, SKN, NBR (nitrile butadiene rubber), nitrile rubber.
• CAS number: 9003-18-3 for nitrile butadiene rubber of general designation.
• HS code: 4002590000 for nitrile butadiene rubber.
• Commercial form: briquettes from light yellow to brown, 30 kg, packed in corrugated or plywood containers.

In the Russian regulatory system, the primary document for nitrile butadiene rubbers is TU 38.30313-2006, covering BNKS grades with various acrylonitrile contents. The supplier confirms batch conformity to the applicable technical specification and provides a certificate of quality with actual values for each indicator. For hydrogenated grades (HNBR), the regulatory basis is formed by manufacturer standards, in particular ASTM D1418, and confirmed by a safety data sheet.

Quality Parameters Relevant to Processing

The properties of nitrile butadiene rubber are determined by two key parameters: bound acrylonitrile content and Mooney viscosity. The first sets the ratio of oil resistance to low-temperature flexibility; the second governs processability during mixing and processing.

• Bound acrylonitrile content: 17-20 percent for BNKS-18; 27-30 percent for BNKS-28; 31-35 percent for BNKS-33; at least 36 percent for BNKS-40.
• Mooney viscosity ML 1+4 at 100 degrees Celsius: 40-50 or 51-60 units for BNKS-18 depending on group; 50-60 or 61-70 units for BNKS-28; 100-120 units for BNKS-40AN.
• Volatile matter content: not more than 0.8 percent.
• Ash content: not more than 0.5 percent for standard grades.
• Tensile strength: at least 16.7 MPa for BNKS-18, at least 22.5 MPa for BNKS-28.
• Elongation at break: at least 400 percent for BNKS-18, at least 450 percent for BNKS-28.

As acrylonitrile content increases, resistance to swelling in oils and aromatic hydrocarbons grows, but low-temperature flexibility and elasticity decrease. For applications requiring both oil resistance and low-temperature performance, blends of BNKS with butadiene rubber or plasticized grades are used.

Technical Grades and Supply Forms

The Russian grade range of nitrile butadiene rubbers, produced by the Krasnoyarsk Synthetic Rubber Plant (KZSK, SIBUR group), covers a wide range of acrylonitrile content and viscosity.

BNKS-18

Acrylonitrile content 17-20 percent. The most low-temperature-resistant grade in the line, with high elasticity at low temperatures. Used in articles contacting petroleum products at moderate and low temperatures, and as a blend component to improve low-temperature flexibility.

BNKS-28

Acrylonitrile content 27-30 percent. The base grade with an optimal balance of oil resistance and processability. Widely used in oil and fuel hoses, gaskets, seals, reinforced sleeves for oil and gasoline transfer, and conveyor belts.

BNKS-33

Acrylonitrile content 31-35 percent. Increased oil and gasoline resistance compared to BNKS-28, used in more severe hydrocarbon contact conditions.

BNKS-40

Acrylonitrile content at least 36 percent. Maximum oil resistance in the line, used in sealing articles for the oil and gas and chemical industries where resistance to aromatic oils and solvents is required.

Hydrogenated Grades (HNBR)

Hydrogenated nitrile butadiene rubber (HNBR) is produced by saturating the double bonds of the backbone with hydrogen. Residual unsaturation is less than 0.5-1.0 percent, providing exceptional heat resistance (up to 150-160 degrees Celsius in continuous service), ozone resistance and resistance to aggressive lubricants. On the global market, hydrogenated grades are available under the trade names Zetpol (Zeon), Therban (ARLANXEO), Tornac and others. In Russia, hydrogenated NBR is also known as GBNK. They are used in automotive belts, oilfield equipment seals, shaft seals and articles operating at elevated temperatures in contact with oils.

Standard grades are supplied as 30 kg briquettes in 540 kg corrugated containers or 1.08 tonne plywood containers. Hydrogenated grades are typically supplied in bags or big bags depending on the manufacturer.

Regulatory Framework for Incoming Inspection

• TU 38.30313-2006 - synthetic nitrile butadiene rubbers BNKS. Specifications.
• ASTM D1646, GOST R 54552 - determination of Mooney viscosity.
• ASTM D5668, GOST R 54546 - determination of volatile matter.
• ASTM D5667, GOST R 54545 - determination of ash content.
• ASTM D3187 - standard practice for rubber from NBR, preparation of test pieces.
• ASTM D412 - determination of tensile properties.
• ASTM D1418 - classification of rubbers and latexes, including HNBR.

For imported batches, the specification is based on manufacturer standards and harmonized ASTM and ISO methods. The batch specification is confirmed by the manufacturer certificate of quality and the results of incoming laboratory control by the recipient.

Mechanism of Action and Functional Role

The polar nitrile groups create dipole-dipole interactions between macromolecules, increasing chain packing density and reducing the penetration of non-polar oil and solvent molecules. The higher the acrylonitrile content, the stronger this effect and the higher the oil resistance. At the same time, increasing polarity reduces chain flexibility, leading to a higher glass transition temperature and loss of low-temperature flexibility.

In hydrogenated grades, saturation of the double bonds eliminates sites sensitive to oxidation and ozone attack, multiplying heat resistance and service life. The ability of BNKS to blend with polyvinyl chloride enables compositions with increased ozone resistance, flame resistance and wear resistance, expanding the application range beyond classical rubbers.

Applications by Industry

Automotive Industry

This is the dominant consumption direction. BNKS is used in fuel and oil hoses, crankshaft seals, gaskets, hydraulic system seals, belts and vibration isolators. Hydrogenated grades are demanded in timing belts and seals operating at elevated temperatures.

Oil and Gas and Chemical Industry

BNKS is used in hoses for oil and petroleum product transfer, pump and valve seals, diaphragms, flange gaskets, and as covering for metal rolls. Hydrogenated grades are used in drilling and production seals requiring resistance to aggressive media and high temperatures.

Mechanical Engineering and Machine Tool Building

Oil-resistant seals, rings, shaft seals and gaskets for hydraulic and pneumatic systems, guides and seals of moving joints.

Cable Industry and Specialty Articles

BNKS and its blends with PVC are used for cable sheaths operating in contact with petroleum products, as well as for floor coverings, foamed heat and sound insulation. Powdered NBR (PBNK) is used as a modifier for cable PVC compounds.

Medical and Other Industries

Nitrile butadiene latex is used for medical diagnostic and protective gloves. In printing, BNKS is used for rolls and coverings.

Comparison with Alternative Elastomers

Compared with chloroprene rubber, BNKS is superior in resistance to aromatic oils and fuels but inferior in ozone resistance, weathering resistance and non-flammability. Compared with acrylate rubbers (ACM), BNKS is inferior in heat resistance but superior in low-temperature flexibility and processability. Compared with fluoroelastomers (FKM), BNKS is significantly inferior in heat and chemical resistance but has an advantage in cost and processability. Hydrogenated HNBR grades occupy an intermediate position between standard NBR and fluoroelastomers in heat resistance while retaining the advantage in oil resistance and mechanical strength.

Supplier Selection Criteria and Specification Development

The specification for BNKS must include the grade, bound acrylonitrile content, Mooney viscosity, stabilizer type (staining or non-staining), and for hydrogenated grades, residual unsaturation and acrylonitrile content. The supplier confirms batch-to-batch consistency and readiness to support import procedures. When choosing between grades with different acrylonitrile contents, service conditions are taken into account: the higher the contact with aromatic hydrocarbons, the higher the nitrile content required, but the lower the low-temperature flexibility.

Typical Handling and Processing Errors

• Ignoring acrylonitrile content when substituting grades. Switching from BNKS-28 to BNKS-18 or BNKS-40 without reformulation changes the balance of oil resistance and low-temperature flexibility of the final article.
• Violation of storage conditions. BNKS briquettes should be stored at a temperature not above 30 degrees Celsius, protected from direct sunlight and precipitation. The shelf life is 18 months from the date of manufacture.
• Use of damaged packaging. Moisture ingress and contamination negatively affect compound properties and vulcanization reproducibility.
• Incorrect stabilizer selection for light-colored articles. Grades with a non-staining antioxidant must be used for uncolored and light-colored rubbers.
• Neglecting Mooney viscosity control. Viscosity spread within a batch affects mixing stability and product quality.

Quality Control and Laboratory Methods

Incoming inspection of BNKS includes determination of Mooney viscosity, bound acrylonitrile content, volatile matter and ash, as well as vulcanization characteristics and tensile properties of vulcanizates. For hydrogenated grades, residual unsaturation (iodine value) and glass transition temperature are additionally controlled. Sampling is performed by standardized methods, and the combined sample is analyzed in the plant laboratory.

Storage and Transportation Conditions

Nitrile butadiene rubber is not classified as a hazardous good. Storage is carried out in closed dry warehouses at a temperature not above 30 degrees Celsius, without access to direct sunlight and atmospheric precipitation. The shelf life of standard grades is 18 months from the date of manufacture; for hydrogenated grades, the term may differ and is established by the manufacturer. Transportation is by rail, road and sea in covered cars, containers or vans.

Finding Analogues and Interchangeability

When replacing BNKS, a grade with similar acrylonitrile content and Mooney viscosity is selected. Switching between grades with different nitrile contents is possible but requires formulation adjustment and confirmation of vulcanizate properties. To replace standard BNKS with a hydrogenated analogue, the difference in glass transition temperature and vulcanization systems must be taken into account (HNBR is vulcanized with peroxides or special systems). The decision is based on laboratory testing.

Supply Routes: Russia, China and Other Regions

The sole producer of nitrile butadiene rubber in Russia is the Krasnoyarsk Synthetic Rubber Plant (KZSK, SIBUR group), which covers 100 percent of the Russian BNKS market and exports to 46 countries, including China, Europe and Southeast Asia. The capacities allow production of a wide grade range, including hydrogenated grades.

Chinese producers such as Sinopec and PetroChina have large NBR capacities. The SIBUR and Sinopec joint venture (Sibur-Sinopec Rubber Holding) is also focused on nitrile butadiene rubber production. Supplies are delivered by sea with subsequent transfer to rail or road transport. Other global producers of hydrogenated grades (Zeon, ARLANXEO) and standard NBR (India, Japan, Europe) are engaged when required, taking into account logistical and regulatory factors.

Logistics and Customs Clearance

Transportation is carried out in covered rail cars, containers and road vans. Customs clearance includes classification under HS code 4002590000, preparation of a safety data sheet (if required) and conformity declaration. The portal provides customs broker services and supports all clearance stages.

Risk Factors and Safety Measures

The main risks are associated with moisture ingress, contamination and violation of storage temperature, which lead to quality degradation and processing instability. Maintaining packaging integrity and warehouse conditions minimizes these risks.

FAQ: Common Questions from Procurement and Process Specialists

How does BNKS-28 differ from BNKS-18 and BNKS-40

The differences are determined by acrylonitrile content: 27-30 percent in BNKS-28, 17-20 percent in BNKS-18, at least 36 percent in BNKS-40. Higher nitrile content means higher oil resistance and lower low-temperature flexibility. BNKS-28 is the base grade with a property balance, BNKS-18 is preferred for low temperatures, and BNKS-40 for aggressive hydrocarbon environments.

Why are hydrogenated BNKS grades needed

Hydrogenated grades (HNBR) provide heat resistance up to 150-160 degrees Celsius, high ozone resistance and resistance to aggressive lubricants, which is unattainable for standard BNKS. They are used in automotive belts, oilfield equipment seals and other demanding articles.

Which BNKS grade is suitable for fuel hoses

Typically BNKS-28 or BNKS-33 is used depending on requirements for resistance to the specific fuel and service conditions. For hoses contacting aromatic gasoline components, grades with higher acrylonitrile content are preferred.

What is the shelf life of BNKS

The shelf life of standard BNKS grades is 18 months from the date of manufacture under proper storage conditions (temperature not above 30 degrees Celsius, protection from moisture and direct sunlight).

What documents are required for BNKS import

Import requires a contract, invoice, packing list, manufacturer certificate of quality, transport documents and a declaration of conformity (if required). The portal organizes the preparation of the document set and interaction with the customs broker.

Conclusion

Nitrile butadiene rubber remains an indispensable elastomer for oil- and gasoline-resistant articles in the automotive, oil and gas, chemical and cable industries. Acrylonitrile content determines the balance between hydrocarbon resistance and low-temperature flexibility, while hydrogenated grades extend the service temperature range to 150-160 degrees Celsius. For procurement teams, the practical task reduces to correct grade selection by nitrile content and viscosity, confirmation of batch conformity to TU 38.30313-2006 and organization of supplies with observance of storage conditions.

Contact Us

For procurement inquiries and supply chain organization, contact the portal team at info@apptrade.ru.