HNBR (hydrogenated nitrile butadiene rubber) is a high-performance elastomer designed for applications that combine heat, oil, chemical exposure, and mechanical stress. To make HNBR, NBR is chemically hydrogenated to improve sour gas (H₂S), excessive heat, ozone and weathering resistance as well as durability in dynamic service, while retaining nitrile’s inherent properties of resistance to oils and fuels.
These enhanced characteristics make HNBR an ideal material for many automotive, oil and gas, aerospace, and industrial sealing applications where sour gas is present and/or oil resistance, high temperatures and robust physical properties are critical.
Key Strengths of HNBR
- Sour Gas (H₂S) resistance, especially relevant in downhole applications
- High tensile and tear strength, elevating its ability to hold up well in dynamic seals
- Good abrasion resistance in dynamic applications
- Oil and fuel resistance is better than NBR under higher temperatures and harsh operating conditions
- Ozone, weathering, and oxidation resistance well above NBR
- Hot water and steam resistance to 300°F, when peroxide cured
Potential Limitations of HNBR
- Flame, HNBR burns and has poor flame resistance unless specially formulated
- Heavy swell is caused by aromatic and chlorinated solvents, Toluene, benzene, and chlorinated hydrocarbons
- HNBR is attacked by Ketones, esters, and ethers, much the same way they attack NBR
- Acid degradation, Strong and concentrated acids can degrade the material
- Electrical insulation, HNBR has poor electrical insulating properties unless specially formulated
Please Note: This overview of HNBR’s strengths and limitations is for general reference. Performance and material properties depend on the specific compound and application.
HNBR Rubber Characteristics
*These are typical ranges across a number of HNBR compounds. Actual performance depends on the manufacturer’s ability to formulate and the specific compound selected for the application.
Table 1 – Physical Properties of HNBR*
| Property | Typical Range | Test Method |
|---|---|---|
| Hardness (Shore A) | 40 to 90 | ASTM D2240 |
| Tensile Strength (psi) | 1,500 psi to 3,500+ psi | ASTM D412 |
| Elongation at Break (%) | 100% to 500% | ASTM D412 |
| Compression Set, 22 hrs @ 302°F | 25% to 30% | ASTM D395, Method B |
| Service Temperature Range | -40°F to +300°F | N / A |
| IRM 901 Volume Change, 70 hrs @ 302°F | −5% to +5% | ASTM D471 |
| IRM 903 Volume Change, 70 hrs @ 302°F | 0% to +25% | ASTM D471 |
| Heat Aging, 70 hrs @ 302°F: Tensile Change | As low as -30% | ASTM D573 |
| Heat Aging, 70 hrs @ 302°F: Elongation Change | As low as -30% | ASTM D573 |
| Heat Aging, 70 hrs @ 302°F: Hardness Change | +5 to +15 points | ASTM D573 |
Table 2 – HNBR Chemical Resistance Guide
| Chemical | Resistance Capability |
|---|---|
| Mineral Oils & Greases | Excellent |
| Fuels | Excellent |
| Hydraulic Fluids | Excellent (petroleum-based), Poor to Fair (phosphate ester) |
| Aliphatic Hydrocarbons | Excellent |
| Aromatic Hydrocarbons | Poor to Fair |
| Alcohols | Good |
| Acids | Poor to Fair |
| Bases | Good |
Table 3 – HNBR Characteristics
| Category | Property | Performance |
|---|---|---|
| Mechanical | Abrasion Resistance | Excellent |
| Impact Resistance | Excellent | |
| Rebound Rating | Good | |
| Tear Resistance | Excellent | |
| Flex Cracking Resistance | Good | |
| Environmental | Chemical Resistance | Good |
| Oil Resistance | Excellent | |
| Weather Resistance | Excellent | |
| Ozone Resistance | Excellent | |
| Oxidation Resistance | Excellent | |
| Sunlight Resistance | Good | |
| Application Specific | Flame Resistance | Poor |
| Minimum Service Temperatures | Good | |
| Maximum Service Temperatures | Very Good | |
| Gas Permeability | Good | |
| Radiation Resistance | Good |
Common HNBR Applications
HNBR is often used where parts see heat, oil, and mechanical stress simultaneously:
- Automotive systems and seals, including timing belts, fluid transfer and power steering applications
- Downhole Oil and Gas seals and gaskets exposed to sour gas, crude oil, drilling fluids, and heat
- Hydraulic and pneumatic seals, including wipers and rod seals
- Industrial gaskets and dynamic seals in rotating and reciprocating equipment
WARCO’s HNBR Rubber Products
WARCO’s ability to formulate and compound HNBR Rubber includes producing:
- Calendered rolls and sheets
- Molded sheets & custom parts
- Extrusions, including cord, tubing, rectangles, wipers, P-seals, and custom profiles
- Spliced seals and large O-rings
Unlike many other rubber manufacturers that depend upon external laboratories, mixing and testing facilities, WARCO can develop compounds, in-house mix, and thoroughly test and process your rubber products in a single facility.
Our wealth of experience in material design and engineering, unique manufacturing processes, and tight control over each step of production, are among the key contributors to how WARCO remains America’s Choice.
Have a specification or drawing that calls for HNBR? Send your requirements to sales@warco.com, or (714) 532-3355 and we’ll identify one of our catalogued compounds or develop one and manufacture the part that you need.
