Full definition
Hydrogenated Nitrile Butadiene Rubber (HNBR) is a specialized elastomer that stems from the hydrogenation of standard Nitrile Butadiene Rubber (NBR). This process saturates the unsaturated C=C double bonds in the polymer backbone, resulting in a material that boasts significantly enhanced thermal stability, ozone resistance, and aging properties, while still maintaining the exceptional oil and fuel resistance that NBR is known for. The continuous service temperature range for HNBR spans from -30°C to +150°C, which is an improvement over NBR's range of -30°C to +100°C. This enhanced temperature capability allows HNBR to be effective in more demanding environments, making it suitable for various industrial applications.
The mechanical properties of HNBR are impressive, with tensile strengths ranging from 20 to 30 MPa, placing it among the top elastomers in terms of strength. This high tensile strength, coupled with outstanding abrasion resistance, makes HNBR an ideal choice for applications where durability and resilience are critical. The Acrylonitrile (ACN) content in HNBR typically ranges from 17% to 50%. Higher ACN levels correlate with better oil resistance but may compromise flexibility, creating a trade-off that engineers must consider when selecting HNBR for specific applications.
HNBR is classified under ASTM D2000 as a DH material, which denotes its suitability for high-performance applications. Its primary use is in automotive applications, particularly in timing belt tooth compounds, where it provides the necessary durability and longevity. Additionally, HNBR is utilized in serpentine belt backing, high-performance shaft seals, hydraulic seals for applications requiring high-temperature service, and downhole seals in oilfields, where the combination of oil resistance and thermal stability is paramount. Although HNBR is priced 3-5 times higher than standard NBR, the investment is justified by its 2-3 times longer service life and superior performance characteristics.