Hydrogenated Nitrile
Rubber - HNBR
Properties
Hydrogenated acrylonitrile butadiene rubber (HNBR) is a unique elastomer. It can be produced from conventional nitrile rubber by hydrogenation of the unsaturated bonds in the butadiene units of the polymer:
The properties of hydrogenated nitrile rubber (HNBR) depend upon the acrylonitrile content and the degree of hydrogenation of the butadiene copolymer. HNBRs have better oil and chemical resistance than nitrile rubbers and can also withstand much higher temperatures. Like NBR, this type of elastomer has excellent resistance to oils and fuels but it also has excellent resistance to many chemicals, heat (steam / hot water) and ozone. The mechanical properties like tensile and tear strength, elongation, and abrasion resistance are also excellent. Furthermore, HNBRs have good dynamic behavior at elevated temperatures.
Disadvantages include higher cost and limited resistance to aromatic oils and polar organic solvents, poor electrical properties, and poor flame resistance. The typical working temperature range is -25°C to +160°C (-40°F to +320°F). Special grades that are sulfur or peroxide cured have improved dynamic applications but also have a lower maximum application temperature. As with nitrile, many properties can be influenced by varying the acrylonitrile content in the rubber. High-nitrile HNBR elastomers have better resistance to mineral oils, whereas peroxide/sulfur cured HNBRs have the best compression set and heat resistance.
COMMERCIAL HNBR Elastomers
Major manufacturers of HNBR elastomers are LG Chem, Lanxess and Zeon.
Applications
HNBR elastomers offer an excellent range of performance at a cost between nitrile rubber (NBRs) and (per)fluoroelastomers (FMKs). They fill the gap between these two elastomers in many areas of application where resistance to heat and aggressive media are required simultaneously. They are an excellent choice for applications where resistance to ozone and weathering, industrial lubricants, amine based corrosion inhibitors, sour gases (H2S), and hot water / steam up to 150°C is required.
Typical applications include gaskets and seals, especially for the oil and gas industry, and accumulator bladders, and diaphragms.
The typical working temperature range is -25°C to +160°C