NBR O-Rings: Everything You Need to Know

NBR, also known as Nitrile or Buna-N, is one of the most widely used and economical elastomers. This material offers excellent sealing capabilities at a very low cost. NBR is a copolymer of butadiene and acrylonitrile, and depending on the application, the proportions of acrylonitrile can vary from 14% to 50%. The higher acrylonitrile content, the greater resistance to oil and fuel. 

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NBR Formulation

When formulating NBR compounds, filler, plasticizer, antioxidant or antiozonant, zinc oxide, accelerator, and vulcanizing agents may be used to increase specific sealing properties of the material. When it comes to filler, carbon black is typically used in standard NBR compounds. Altering the amount of carbon black will change the hardness of the final compound. 

Plasticizers increase the processability and modify physical properties of the final compound. Some of the modifications include lower hardness, improved flexibility, and low temperature performance. Sulfur is commonly used as a curing agent for NBR compounds. For sulfur cure systems, vulcanizing agents and accelerators are used to speed up the reaction rate between NBR and sulfur. 

Properties and Advantages

NBR is an ASTM D1418 designation. These standard compounds have a working temperature range of -40°F to 257°F and hardness range of 40 to 90 Shore A. NBR compounds can be formulated to offer additional temperature ranges from -85°F to 275°F.

NBR features excellent resistance and mechanical properties, including: 

• Resistance to petroleum-based oils and fuels, silicone greases, hydraulic fluids, water and alcohols

• Low compression set

• High tensile strength

• High abrasion resistance

• Low gas permeability

While NBR offers great resistance to many chemicals and solutions, there are some limitations to be aware of. NBR should have limited contact with:

• Ozone, sun exposure, rain, wind

• Highly aromatic fuels

• Non-polar solvents

• Glycol-based brake fluids

Contact us to discuss your requirements of oil seal manufacturing. Our experienced sales team can help you identify the options that best suit your needs.

Typical Applications

Because of NBR’s compatibility with oils and fuels, NBR seals are commonly used in the automotive industry. However, NBR is a go-to material for oil applications of any kind. NBR is also commonly used in applications such as:

• Low temperature military applications

• Off-roading equipment

• Marine devices

• Aircraft fuel systems

NBR can also be formulated to meet FDA standards, which increases the number of ways to apply NBR o-rings.

Want to learn more about NBR o-rings?

Contact an engineer today. 

NBR O-Rings: Everything You Need to Know

Category: Rubber moulding, Technical Features

Nitrile, Buna-N or NBR rubber is a widely used elastomer, thanks in large part to its highly oil & fuel resistant properties and tensile strength. In this article, Martin’s Rubber Company explains more about the properties, applications, pros and cons of this versatile rubber material.   Nitrile rubber is a synthetic rubber copolymer of acrylonitrile (ACN) and butadiene that you may know better under trade names like Nipol, Krynac and Europrene N. Why might you consider specifying nitrile for your application? Let’s find out, with a closer inspection of this rubber material.

What is Buna-N?

Nitrile (also known as NBR rubber and Buna-N) is the seal industry’s most widely used and economical elastomer. This is partly because it displays excellent resistance to petroleum-based oils, fuels, water, alcohols, silicone greases, hydraulic fluids. However, it also has a good balance of desirable working properties like low compression set, high abrasion resistance and high tensile strength.

NBR rubber properties

Nitrile is a family of unsaturated copolymers of 2-propenenitrile and butadiene monomers (1,2-butadiene and 1,3-butadiene). Its physical and chemical properties vary depending on the polymer’s composition of nitrile. The more nitrile there is within the polymer, the higher its resistance to oils but the lower its flexibility. Nitrile rubber is more resistant than natural rubber to oils and acids, and has superior strength, but suffers from inferior flexibility.

Where is nitrile used?

Nitrile rubber is used in a wide variety of applications, such as O-rings, gaskets, oil seals, automotive transmission belts, hoses, V belts, synthetic leather, disposable non-latex gloves, printer’s form rollers and cable jacketing. NBR latex can also be used in the preparation of adhesives or as a pigment binder.

Pros and cons of Buna-N

Nitrile offers the following advantages:

• Excellent abrasion resistance.
• Good rebound.
• Good tear resistance.
• Good non-polar solvent resistance.
• Good water resistance.
• Good oil resistance.
• Cheaper than fluoroelastomers

Nitrile suffers from the following disadvantages:

• Poor ozone, sunlight, and weather resistance.
• Limited high temperature resistance.
• Poor flame resistance.

Nitrile rubber products from Martin’s Rubber

Speak to one of our advisers today to find out more about our nitrile rubber manufacturing capabilities. We can talk you through your options and give you honest and informed guidance to help you to specify the ideal product for your application. Speak to us today on 023 8022 6330 or email [email protected]. For more information on why nitrile rubber is so popular for heat resistance, see our post: Why Buna N is so popular for use with hydrocarbons.

The post The pros and cons of nitrile rubber, NBR or Buna-N appeared first on Martin’s Rubber Company.

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