HNBR Rubber Solutions

Hydrogenated nitrile butadiene rubber (HNBR) is a unique elastomer that is known for its physical strength and retention of properties after exposure to heat, oil and chemicals.

HNBR was developed in the early 1980s as companies were looking for an alternative to nitrile rubber for applications requiring high tensile strength at higher operating temperatures along with excellent resistance to chemicals, heat, and ozone.  HNBR delivered these desired properties, proving itself superior to nitrile butadiene rubber (NBR) and other polymer alternatives.

NBR is a copolymer of acrylonitrile and butadiene, and contains carbon-carbon double bonds along the polymer backbone. During the production of HNBR, the nitrile groups of NBR are unaffected but the carbon-carbon double bonds are converted into more stable, single bonds, which provide the elastomer’s improved resistance to chemical attack, thermal degradation, and oxidation. The basic structure of HNBR is shown below.

hnbr formulahnbr formula

HNBR production starts with dissolving NBR in a solvent then introducing hydrogen gas, in the presence of a catalyst, to initiate the hydrogenation of the double bonds in the butadiene along the polymer chain. The degree of hydrogenation can vary from partially hydrogenated, where some double bonds remain, to fully hydrogenated where virtually no double bonds remain.  After hydrogenation, HNBR elastomers are typically cured with either peroxide or sulfur.

There are 3 main factors that influence the properties of the final product and these factors can be used to ensure the best grade of HNBR is selected: acrylonitrile (ACN) content, level of hydrogenation, and Mooney viscosity of the polymer.

  • ACN content of the polymer impacts the fluid resistance and low-temperature performance. If the ACN content is decreased, the material will have improved low-temperature flexibility but less fluid and chemical resistance.
  • Hydrogenation level of the polymer influences heat, chemical, and ozone resistance. As the hydrogenation level is increased, the degree of heat and ozone resistance improves. The other characteristic that depends on the hydrogenation level is the selection of the appropriate cure system; specifically, partially hydrogenated materials can be crosslinked using either sulfur and peroxide cure systems but fully hydrogenated HNBR can only be cross-linked with peroxides.
  • Mooney viscosity of the polymer impacts the physical properties and material manufacturing options; for example, an HNBR grade with the desired viscosity can be selected to best suit the method of manufacturing, such as compression or injection molding or extrusion.

Lastly, additives such as plasticizers, process aids, or mineral fillers can be added during the formulation of HNBR for material handling benefits or to fine-tune the desired physical properties.  HNBR rubber can be manufactured in several forms including sheets, slab, strip and preform.

HNBR Advantages and Uses

HNBR rubbers are high-temperature and oil-resistant elastomers that are created to meet demanding applications and environments with a range of operating temperatures. Below are some of the key benefits of HNBR, noting that the specific formulation or grade of HNBR will determine the exact attributes and properties of the compound.

  • High tensile strength and elongation
  • Wide temperature range
  • Great abrasion resistance
  • Excellent heat and oxidation stability
  • Strong resistance to weather, ozone, fuels, oils, sour gas, steam, animal and vegetable fats, automotive fluids, and many other chemicals

HNBR is replacing standard NBR in many applications due to its high tensile strength, high and low temperature ratings, and strong chemical and abrasion resistance. HNBR usage spans a wide range of industries such as automotive, industrial, medical and other performance-demanding applications. Additionally, HNBR parts often last longer than NBR parts during use as well as in storage, making HNBR a cost-effective solution. Some specific HNBR rubber applications include:

  • Within the automotive sector, HNBR is used in dynamic and static seals, hoses, o-rings and belts
  • Within the oil field exploration and processing, HNBR is used in measurement while drilling, and measurement while logging components
  • With the medical field, HNBR is an ideal option for sanitary gaskets due to its steam and chemical resistance, and long shelf life

Echo Engineering's HNBR Rubber Solutions

Since 1966, Echo has been partnering with customers to create and supply meaningful solutions for Connecting, Fastening, NVH, and Sealing challenges. The company has designed, engineered, and manufactured thousands of value-added rubber components and assemblies within many industries. Echo’s success with designing and manufacturing complex rubber components stems from its team of in-house design and materials engineers, 3D rapid prototyping, quality management, internal and third-party testing, and supply chain management.

Echo Engineering takes the time to understand what role a part plays in a customer’s manufacturing process or product development in order to confidently recommend a solution. Whether a customer needs a standard stock component or one that requires customization, the Echo team is equipped to provide what is needed - fast.

Echo Engineering’s rubber component manufacturing capabilities are broad. Echo utilizes various materials, including HNBR rubber, and its manufacturing abilities extend across a range of methods such as compression molding, injection molding, extrusion, over molding, and transfer molding.

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