Summary:
Nitrile butadiene rubber (NBR) is a synthetic elastomer engineered for high resistance to oils, fuels, and industrial greases, making it a preferred sealing material in hydrocarbon-rich environments. It operates within a temperature range of -40°C to 120°C, offering strong abrasion resistance and stable mechanical performance under compression.
However, the material fails under prolonged UV exposure, ozone attack, and glycol-based brake fluids, limiting its use in exposed outdoor systems. In such conditions, EPDM or silicone-based elastomers are typically selected instead.
Typical applications include fuel hoses, hydraulic O-rings, static seals, gaskets, and oil-exposed conveyor systems, where fluid resistance and sealing reliability are critical design requirements.
How Rebonded Foam Is Manufactured
Nitrile butadiene rubber, or NBR, is a synthetic elastomer designed for industrial environments where oil, fuel, and chemical exposure are constant design constraints. It is selected primarily for sealing integrity, fluid resistance, and predictable mechanical stability under load.
This guide explains the material composition, performance characteristics, and engineering selection criteria, supporting decision-making for industrial designers, procurement teams, and system engineers.
Understanding Nitrile Butadiene Rubber (NBR)
NBR is a copolymer elastomer engineered to balance oil resistance, mechanical strength, and formulation flexibility. It is preferred in sealing systems where hydrocarbon exposure would degrade standard rubber materials.
Chemical Composition and Key Characteristics
The elastomer is formed from acrylonitrile (ACN) and butadiene, with performance determined by ACN concentration, typically 18%–50%.
High ACN Content: Increased oil and fuel resistance, reduced flexibility at low temperatures.
Low ACN Content: Improved elasticity and cold flexibility, reduced chemical resistance.
This structural tuning allows application-specific formulation selection, where material grade is matched directly to operating conditions rather than general use.
Key engineered properties:
Strong Resistance to Petroleum Oils, Fuels, and Lubricants: Prevents swelling and seal degradation.
Abrasion Resistance: Supports dynamic contact applications such as rotating shafts.
Thermal Stability Up to ~120°C: Maintains sealing integrity under moderate heat load.
Low Gas Permeability: Reduces leakage in pressurised systems.
Material Compatibility with Metals and Polymers: Supports multi-material assemblies.
Overview of the Manufacturing Process
NBR is produced through emulsion polymerisation under controlled conditions, forming a stable polymer latex.
Process stages:
- Polymerisation of ACN and butadiene in aqueous emulsion
- Coagulation and purification to form raw elastomer
- Compounding with fillers, plasticisers, and curing agents
- Vulcanisation to improve elasticity, strength, and compression recovery
- Carbon black reinforcement that increases tensile strength and wear resistance
- Plasticiser optimisation adjusts low-temperature flexibility.
Material performance variation is therefore formulation-dependent rather than uniform, requiring grade-specific selection.
Properties and Advantages of NBR
NBR’s fluid resistance and mechanical performance make it reliable across sealing, gasketing, and protective applications.
Resistance to Oils, Fuels, and Chemicals
The elastomer is preferred for hydrocarbon exposure systems, where petroleum-based oils would degrade conventional rubber.
It is commonly selected for applications involving engine oil, diesel, hydraulic fluid, and lubricants, where it:
- Prevents swelling and dimensional instability
- Maintains sealing pressure under continuous exposure
- Reduces maintenance cycles in fluid systems.
It also offers moderate resistance to dilute acids and alkaline solutions, extending use into controlled chemical environments.
Weather Resistance and Long-Term Durability
The material degrades under UV exposure, ozone attack, and prolonged outdoor weathering.
- Fails Under Direct Sunlight Exposure: Surface cracking and embrittlement.
- Limited Ozone Resistance: Unsuitable for long-term outdoor sealing.
- Not recommended for glycol-based brake fluid systems.
For exposed environments, EPDM is typically selected due to superior weather resistance, while HNBR is preferred where improved chemical and heat stability is required.
Weather Resistance and Long-Term Durability
The elastomer delivers stable tensile strength and abrasion resistance, making it suitable for both static and dynamic sealing systems.
Operational performance:
- -20°C and 120°C typical range
- Maintains compression set resistance under sustained load
- Supports repeated mechanical cycling without rapid fatigue.
Lower ACN grades are selected when flexibility at sub-zero temperatures is required, while higher ACN grades are preferred for fuel-heavy environments.
Industrial Applications of NBR
NBR is widely used in applications where oils, fuels, abrasion, and sealing reliability matter. This makes it a practical material for automotive, HVAC, and general industrial systems.
Automotive Components and Sealing Solutions
The material is widely specified in automotive systems where oil and fuel compatibility is essential.
Typical uses:
- Fuel hoses and filler neck seals
- O-rings and hydraulic gaskets
- Engine and transmission fluid seals.
It is preferred in internal combustion systems due to consistent resistance to hydrocarbons, even as system designs evolve.
Air Conditioning and Industrial Sealing Systems
In HVAC and refrigeration, the elastomer is used for oil-resistant seals with low gas permeability, reducing refrigerant leakage risk.
However:
- Standard grades are not suitable for modern synthetic refrigerants
- HNBR is selected when exposure to R134a or R1234yf systems occurs.
In hydraulic systems, it is preferred for seals, valves, and piston assemblies where pressure stability and oil resistance are critical performance factors.
Industrial Hoses, Belting, and Protective Sheathing
The material is commonly used in:
- Fuel and Oil Transfer Hoses: Prevents fluid degradation.
- Conveyor Belt Coverings: Resists grease and abrasive contact.
- Cable Sheathing: Protects against lubricants and mechanical wear.
It is selected in environments where standard elastomers fail under continuous oil exposure and abrasion loading.
Not sure which material selection suits sealing systems?
Contact us for practical material guidance based on your fluid, temperature, and mechanical requirements.
Comparing NBR with Other Elastomers
Choosing the right elastomer depends on the application. The table below compares NBR against common alternatives.
Elastomer | Strength Profile | Limitation Profile | Selection Guidance |
NBR | Strong oil/fuel resistance, high abrasion durability | Fails under UV and ozone exposure | Preferred for hydrocarbon sealing systems |
EPDM | Excellent weather and steam resistance | Poor oil compatibility | Selected for outdoor sealing systems |
Neoprene (CR) | Balanced ageing and moderate chemical resistance | Limited fuel resistance | Used in general-purpose industrial sealing |
Silicone (VMQ) | Wide thermal stability and weather resistance | Low tear and abrasion strength | Selected for high-temperature, low-load systems |
Comparing NBR with Other Elastomers
Choosing NBR means matching the specification to fluid exposure, temperature, and mechanical demands.
Material Specifications and Quality Standards
Material performance is defined by precise specification matching rather than general-grade selection.
- Acrylonitrile Content: Determines the balance between oil resistance and low-temperature flexibility. Medium ACN grades (25% to 40%) are typically preferred for balanced industrial use cases.
- Hardness (Shore A): Ranges from 40–90 Shore A, where softer grades are selected for sealing performance, and harder grades are preferred for abrasion-heavy environments.
- Tensile Strength and Elongation: indicate structural integrity under load and are critical in dynamic or pressurised systems.
- Compression Set: Lower values are preferred for long-term sealing retention under sustained compression.
- Temperature Range: Must be matched to system limits to prevent thermal deformation or premature seal failure.
Comparing NBR with Other Elastomers
Nitrile butadiene rubber (NBR) is preferred in industrial sealing systems where oil resistance, compression stability, and predictable mechanical performance are required.
It is commonly selected for fuel systems, hydraulic assemblies, and oil-exposed industrial components, where material failure would lead to system leakage or downtime.
If your application requires material selection support, grade matching, or custom sealing solutions, contact our team at WTEC Group for technical guidance and supply support tailored to industrial requirements.
