Full definition
Hydrogenated Nitrile Butadiene Rubber (HNBR) is a premium-grade elastomer developed through the process of catalytic hydrogenation, which targets the carbon-carbon double bonds within the Nitrile Butadiene Rubber (NBR) backbone. This modification significantly enhances HNBR's resistance to heat, ozone, and aging effects while preserving its superior oil and fuel resistance characteristics. The hydrogenation level typically ranges from 90% to 99%, with a higher percentage resulting in improved resistance but complicating the curing process, especially with sulfur. The typical operating temperature range for HNBR is between -30°C to +150°C, substantially outperforming standard NBR, which has a maximum continuous temperature of around +100°C. This makes HNBR suitable for demanding applications that require excellent thermal stability.
The physical properties of HNBR are noteworthy, with hardness ranging from 50 to 90 Shore A and tensile strength between 20 to 30 MPa, positioning it among the strongest elastomers available. Additionally, HNBR showcases exceptional abrasion resistance and a low compression set at elevated temperatures, making it particularly effective in dynamic sealing applications. The acrylonitrile (ACN) content in HNBR can vary from 17% to 50%, similar to NBR; this variation impacts oil resistance and flexibility, necessitating careful selection based on specific application requirements. HNBR is commonly utilized in automotive applications, particularly in timing belt tooth compounds and serpentine belt backings, where durability and heat resistance are paramount. Furthermore, it is essential in downhole oilfield seals and industrial shaft seals designed for high-temperature environments, as well as high-performance hydraulic seals.
Despite its higher cost—typically 3 to 5 times that of standard NBR—HNBR is justified by its extended service life, often lasting 2 to 3 times longer than its conventional counterparts. Cure systems employed for HNBR include peroxide curing, which is standard for high-performance applications, and sulfur curing for partially hydrogenated grades. Leading brands producing HNBR include Zetpol from Zeon and Therban from Lanxess, both recognized for their high-quality elastomer products.