Nitrile Gaskets

What is Nitrile (NBR, Buna-N)?

Jul 07, 2026

Thanks to its versatility, nitrile ruber, a.k.a. NBR and Buna-N, is one of the most widely used gasket materials. In this blog we’ll take a look at the attributes that make it the first choice in many gasket applications. We’ll also discuss when not to use it, and we’ll identify some more costly alternatives.

Nitrile Chemistry

Nitrile is a synthetic rubber with properties similar to those of natural rubber. It’s produced by polymerizing clear liquid acrylonitrile, used in the manufacture of various acrylic products, with butadiene. The resulting polymer forms long chains of carbon and hydrogen atoms. These become entangled and provide the elastic properties sought in most gasket materials.

Important Properties of Nitrile for Gasket Material

Nitrile is fairly soft and strong, with good elongation and low compression set, and is known for being abrasion-resistant. Specific numbers depend on the exact formulation and grade but are around:

  • Durometer: 60
  • Tensile strength: 1,000psi
  • Elongation: 350%
  • Working temperature range: -30 to +200 °F (-34 to +93 °C)

Nitrile has good resistance to most oils and fuels but is attacked by solvents like acetone and MEK, by the esters used in many fragrances and flavorings, and by aromatic hydrocarbons like benzene.

Nitrile is produced in an FDA grade for food industry applications. This is usually referred to as “white nitrile”.

Nitrile Limitations

In addition to a narrow temperature range and limited chemical resistance, nitrile has some other restrictions on its use. In particular, being susceptible to attack by ozone and UV light, it’s not a good choice for outdoor applications.

Nitrile rubber swells when exposed to oils. The extent, as defined in ASTM D2000, is from 10% to 60%, depending on the proportion of acrylonitride in the formulation.

Alternatives to Nitrile

For a wider temperature range or increased chemical resistance, two other gasket materials to consider are EPDM and FKM or Viton®. EPDM provides a moderate improvement but is a little more expensive. FKM has significantly better performance but is also considerably more expensive.

Our experts can help you determine whether nitrile is the best material for your application. Contact us to ask.

Nitrile Gaskets
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Fuel-Resistant Gasket Materials

Aug 01, 2024

Gasoline, diesel and kerosene are difficult fluids to seal. Pick the wrong material and you risk a flammable liquid leaking. In this blog we’ll discuss fuel-resistant gasket materials and why it’s important to choose from the short list of those available.

The Fuel Sealing Challenge

Hydrocarbons, the basis of most liquid fuels, cause many materials to swell. This happens because either fuel causes a chemical reaction in the material, it acts as a solvent and partially dissolves the material, or the material absorbs some of the fuel. With some fuel/material combinations all three are possible.

These changes increase the load on the joint and may make the gasket extrude out sideways. They’ll also make the material less elastic and therefore more likely to fail. What’s more, the changes aren’t reversible.

The Best Fuel-Resistant Gasket Material

The first choice for almost every fuel application should be nitrile rubber, sometimes called NBR or Buna-N. Nitrile is a synthetic rubber with a working temperature range of -30 to 200⁰F. Hardness is typically 60 – 80 shore and it resists compression set and abrasion.

Nitrile resists attack by a long list of chemicals, especially hydrocarbons like oils, greases and of course fuels. Other chemicals it withstands include ozone plus solvents like acetone and MEK.

Alternatives to Nitrile

Most fuel applications don’t need the gasket material to have a high upper temperature limit. If this is necessary the best alternative is probably FKM/Viton®. Viton remains flexible at up to 400⁰F and has similar fuel-resistance to nitrile rubber. The main reason for choosing nitrile over Viton, assuming the upper temperature is below nitrile’s limit, is cost. Viton is not cheap.

Another fuel-resistant gasket material to consider is PTFE. This lacks the compressibility and elastic recovery of nitrile or Viton but conforms readily to uneven surfaces and has a very wide working temperature range.

Nitrile Rubber From Hennig Gasket & Seals

We carry nitrile gasket material in a range of sheet thicknesses and can waterjet, flash or die-cut it to the precise geometry you need. Contact us for more information.

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Where Not to Use Nitrile Rubber Gaskets

Dec 09, 2021

Nitrile rubber, also known as NBR and Buna-N is a useful gasket material that many buyers refer to as nitrile. Useful though it is, Nitrile Rubber Gaskets are not a solution to every sealing challenge. Here’s some advice on when and when not to use it.

Properties of Nitrile Rubber

Nitrile or NBR is a synthetic rubber with good flexibility and resilience over a temperature range of -30 to +200 °F (-34 to +93 °C). It has good strength and abrasion resistance and a low compression set, all of which make it an effective gasket material. It’s also available as FDA-approved white nitrile for food industry applications.

A particular strength of nitrile is its ability to withstand attack by oils and fuels. Many gasket materials swell and break down when exposed to lubricants, hydraulic fluids or gasoline, but not nitrile. As a result, it’s used extensively with engines, generators, and fuel and hydraulic systems.

It does however have some weaknesses. It’s not for high-temperature applications, it doesn’t have good weather resistance and it will be attacked by polar solvents.

Polar Solvents and Nitrile Rubber Gaskets

Polar solvents are those where the molecules are composed of atoms with significantly different electrical charges. One example is oxygen and hydrogen. Others are acetone, ethanol, and acetic acid. In chemistry terms, these are considered to have a high permittivity or dielectric constant. You might notice that compounds with a high dielectric constant, like pure water, are also good electrical insulators.

Nitrile is susceptible to attack by polar solvents like those listed above. Interestingly though, while water is also polar, it’s a solvent to which nitrile has some resistance. However, for sealing against water, better gasket material choices would be neoprene or EPDM.

Consider Conditions Before Asking for Nitrile

Nitrile Rubber gasket material is a good choice for sealing against fuels, oils, and lubricants. It should not be used with chemicals like acetone, ethanol, and acetic acid. Neither should it be used outdoors or where temperatures exceed 200 °F. If the application involves water, check with a materials specialist at Hennig Gasket before ordering.

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White Nitrile Rubber

Oct 14, 2019

Gaskets made from white nitrile rubber won’t impart any taste to food. That’s one reason they’re used in food and beverage production but it’s not the material’s only useful property. Here’s a look.

Understanding White Nitrile Rubber

White nitrile rubber – chemical name Acrylonitrile Butadiene – carries the ASTM designation NBR and is sometimes referred to as white Buna-N. A blend of neoprene and SBR, white nitrile rubber is an abrasion-resistant elastomer. Shore hardness is around 60, putting it somewhere between tire tread and a pencil eraser, making it firm yet flexible.

White nitrile is usable over temperatures from around -40°F to 220°F (-40 to 105°C.) It resists attack by oils, fats, greases and hydraulic fluids although it is vulnerable to ozone, ketones, esters and aldehydes. (These were explained in a previous blog post, “Ketones and Gasket Materials”.)

Nitrile rubber is produced in a range of colors, but white nitrile is, as the name suggests, white. This gives it some useful applications.

Applications for White Nitrile Rubber Gaskets

As it doesn’t mark surfaces or impart a taint, white nitrile is available in grades approved by the FDA for food use. It’s also non-allergenic. Consequently, white nitrile gaskets are common in food and beverage production as well as pharmaceuticals.

White nitrile rubber is also used in applications where appearance matters. The smooth white finish is often desirable, especially in medical applications, and has a secondary benefit: it shows up leaks that would be unseen against dark materials.

In addition to sealing and gasketing applications, white nitrile is used for cushioning and protection. You may see it as liner in food processing equipment and also as bumper protection strips. A less obvious, though still common application, is for food grade rubber scrapers.

Talk to Hennig Gaskets & Seals

Gaskets for food and pharma use must comply with FDA requirements. White nitrile is often a good choice for such applications, although it has other uses too. As an attractive, non-marking material it works well in situations where appearance matters. Learn more by talking to our specialists.

Food Grade Gaskets, Nitrile Gaskets
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Gasket Material for Natural Gas

Apr 16, 2018

Natural gas is widely used for heating and cooking and it’s the energy source for much of our electricity. Perhaps less well known, it’s also essential for fertilizers and plastics.

The systems that store and distribute natural gas need gaskets. Here we’ll discuss the materials most often used, but first, a short primer.

Hydrocarbon Origins and Uses

Like coal and oil, natural gas is formed from plant and animal remains. Decomposition produces methane, (CH4), and when trapped underground we call it natural gas. Natural gas is odorless, so a trace of mercaptan, (CH4S) is added to make it detectable.

Reacting natural gas with steam separates the hydrogen and a second reaction, this time with air, results in NH3, or ammonia. Chemists call this the Haber process and it’s the first step in producing fertilizers.

Like methane, plastics are also composed of carbon and hydrogen atoms. The difference is that the atoms are formed into long chains to create polyethylene, polypropylene and similar materials.

Storage and Distribution

When held above 200 bar (3,000 psi) natural gas is known as compressed natural gas (CNG). This makes it sufficiently dense for use as a vehicle fuel. When pipelines aren’t an option, for easier transportation cooling to below -184°F produces liquefied natural gas (LNG).

The Sealing Challenge

The biggest issues are permeability and flammability. Simply put, the very small methane molecules can find their way through some materials, and they burn readily. Fortunately, as it’s lighter than air, escaping natural gas tends to disperse quickly.

Sealing CNG and LNG presents additional challenges. Gasket materials must retain some flexibility at very low temperatures and should have the strength to resist extrusion through joint faces.

Materials for Natural Gas Gaskets

For most low pressure, ambient temperature applications nitrile and neoprene gasket materials are the first choice. In more challenging applications many engineers opt for more expensive Flexitallic spiral wound gaskets. PTFE and graphite are other options.

Every gasket application has some unique challenges. If you need material for natural gas gaskets, ask a product specialist at Hennig Gasket for advice.

Neoprene Gaskets, Nitrile Gaskets
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Best Gasket Material for Nitrogen

Feb 19, 2018

Many industries use nitrogen. Some users even generate their gas on-site. If your company is among them you ought to be familiar with the best gasket materials to use.

Industrial Uses of Nitrogen

Liquid nitrogen is used when very low temperatures are needed. This is often for preserving biological samples or other organic material although other uses include cooling for superconductors and to aid in machining.

Applications for gaseous nitrogen include fertilizer production, food preservation, and annealing stainless steel. It’s also used in the production of electronic components like transistors and diodes.

Nitrogen Production and Storage

Nitrogen is produced by separation from air. (The air around us is approximately 78% nitrogen.) There are two methods:

  • fractional distillation
  • pressure swing adsorption (PSA).

Distillation entails chilling air until it becomes liquid, then raising the temperature slowly to let the individual components boil. In contrast, PSA is done at ambient temperature and in simple terms consists of pushing air through a membrane that separates the various constituents.

Distillation produces higher purity gas but is energy-intensive. PSA scales more easily for local or on-site gas generation, and this is the process most often adopted by manufacturers who don’t want to depend on deliveries and storage.

Suitable Materials for Gaskets in Nitrogen Systems

Nitrile and natural rubber gasket materials are good choices for gaseous nitrogen, although EPDM is generally considered best. EPDM gasket material has good heat resistance and a working temperature range of around -60 to 320°F (-50 to 160C). Resistance to oxidation, UV, ozone, and abrasion are all good and it also withstands water, acids, and alkalies along with ketones and alcohols.

Handling liquid nitrogen demands a gasket material with excellent low-temperature performance. If an elastomer is needed Santoprene® may be a good choice. A trade name for a class of thermoplastic vulcanizate (TPV) materials, this behaves much like EDPM but some grades remain flexible at even lower temperatures.

Consult a Materials Expert

Every gasket application is different so it’s always prudent to learn more about the material before purchasing. Specialists at Hennig Gasket are ready to help.

EPDM Gaskets, Nitrile Gaskets
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Buna-N (Nitrile) Gaskets and Oil

Jun 06, 2016

When working with a gearbox, a pump, or part of a fuel system, it’s essential to select a gasket material with resistance to hydrocarbons. Mineral and vegetable oils, along with diesel, gasoline and similar fuels, attack many materials, causing them to swell or break down. The notable exception is nitrile rubber. Nitrile rubber gaskets, often referred to as Buna-N or NBR gaskets, offer excellent resistance to oil.

Nitrile Rubber Chemistry

Nitrile rubber is made from a blend of acrylonitrile (chemical formula C3H3N) and butadiene (C4H6.) Each component is mixed with water as an emulsion before being combined in a polymerization reaction. This makes the carbon (C) and hydrogen (H) atoms form into long chains that tangle round another to form a rubbery compound.

Increasing the proportion of acrylonitrile makes the rubber stronger and reduces its gas permeability. The trade-off is that it results in a rubber that’s stiffer at low temperatures.

Rubber and Swelling

Most rubber absorbs oil and swells up in size. This is a problem in gaskets used in gearboxes and engines because it can lead to leaks. However, acrylonitrile reduces this tendency. So the greater the proportion of acrylonitrile used in the nitrile rubber formulation the less it will swell.

Swelling is covered in the ASTM D2000 specification. Most nitrile gasket materials are classed as ‘BF,’ ‘BG’ or ‘BK.’ The ‘B’ indicates an upper temperature limit of 100°C and the second letter shows how much the rubber will swell. ‘F’ is swell of 60% by volume, (under specified conditions,) while ‘G’ is 40% and ‘K’ 10%.

When and When Not to use Nitrile Gaskets

Good applications are those where peak temperatures are moderate and there’s exposure to oils. However, nitrile rubber does not hold up well to ozone and oxygen, so should not be used in places where these are present. Water purification equipment is one such location.

The Application Dictates the Gasket Material

If there’s any question about the properties of various gasket materials, consult the specialists at Hennig Gasket. They can explain the material choices available for your application.

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Choosing Gasket Material

Jan 18, 2016

When changing a gasket most technicians choose a new one made from the same material. If a paper, fiber or cork gasket came out of the joint, then the replacement is usually the same.

That’s not necessarily bad, assuming the gasket hadn’t failed prematurely, but it could also be a missed opportunity. Other gasket materials might hold up better in the application. That would allow more time between inspection and replacement, reducing downtime frequency and saving on maintenance hours.

Gasket materials are specified by multiple criteria, and the importance of each depends on what the application needs. One way of looking at these properties is to divide them into mechanical – their gap-filling ability – and material – how well they handle the media.

Mechanical properties

Whether looking for boiler seals or food grade gaskets, the primary considerations are thickness and hardness. Thickness is easy to understand, (always choose the thinnest that will do the job,) but hardness is less obvious. Gasket material hardness is reported in terms of Durometer, usually on the Shore A scale. (See “Measuring Gasket Material Hardness.”) When comparing two materials of the same thickness, the softer one is usually the better choice.

Other properties to look at are compressibility and creep relaxation. Compressibility measurement is defined by the ASTM F36 standard and describes the load needed to provide a given level of deformation. In general, higher compressibility implies lower loads are needed to secure a joint. Creep relaxation, addressed in ASTM F38, indicates how the gasket thins over time, which reduces bolt loading.

Material properties

Gasket material must be appropriate for the media. For example, nitrile gaskets are preferred for applications involving petroleum, mineral or vegetable oils but don’t perform well with ozones, ketones, esters and aldehydes.

The ability to handle expected temperatures is also important. This is especially critical where the environment causes severe temperature gradients through the joint. (Imagine piping liquid nitrogen in the desert southwest.) Nitrile gaskets may be appropriate for the media but an alternative, like silicone, might handle the temperatures better, (although has poor hydrocarbon resistance.)

FAQs, Nitrile Gaskets
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The Difference Between Soft, Semi-Metallic and Metallic Gaskets

Jan 04, 2016

Gasket selection is driven by the needs of the application. Temperature, environment, media and pressure dictate the gasket required. While there are many different types, to aid selection they are usually separated into three classes:

  • Soft
  • Semi-metallic
  • Metallic

Soft gaskets

These are made from materials that compress easily, such as elastomers like nitrile, (NBR,) EPDM and silicone, as well as graphite, PTFE and fibrous materials. Their corrosion resistance is good but they are limited in the temperatures they can handle. Nitrile gaskets for example only work from -60 to 250°F (-51 to 121°C) and EPDM is only slightly better with a range of -70°F to 350°F (-57°C to 177°C). Silicone gaskets will however go up to 500°F (260°C) and PTFE is effective from cryogenic temperatures up to 450°F (232°C).

Soft gaskets are also limited in their ability to handle high pressures. The best applications are those involving sealing variable gaps as might be found around the doors of an electrical enclosure.

Semi-metallic gaskets

Bridging the gap between metallic gaskets and soft gaskets, the semi-metallics combine features of each. The two main types are spiral-wound and metal-jacketed, although other forms exist. Spiral wound gaskets are made from a ribbon of soft material like PTFE or graphite layered with metal, usually in a ‘V’ form to provide compressibility. Jacketed gaskets consist of a metal cover over a filler material.

Semi-metallic gaskets can handle a wide range of temperatures and pressures up to 6,000 psi, (based on ANSI pressure class 2,500,) so are used in applications ranging from refineries and chemical processing plants to aerospace.

Metallic gaskets

As the name implies, this type of gasket is made from metal. That allows it to resist pressures as high as 10,000 psi but also means it has virtually no compression. Very high bolt loads are needed to create enough deformation for joint sealing.

Metallic gaskets are vulnerable to galvanic corrosion. To minimize problems the gasket metal should be close to the flange material on the electrochemical scale. Alternatively, the material should be chosen to make the gasket the sacrificial element.

FAQs, Nitrile Gaskets, Spiral Wound Gaskets
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How Hot is too Hot? Choosing the Right Gasket Material for a Non-Metallic Gasket

Apr 17, 2015

For non-metallic gasket applications, the operating temperature of the finished product is a major consideration. You need to know the temperature range (and other strengths and weaknesses) of potential materials so you can get the most durable custom gaskets and seals. Otherwise, they could prematurely harden, crack, deform and lose strength, elasticity and resilience, etc.

The following is a list of common non-metallic gasket materials, their properties and their most stable operating temperature ranges (in Fahrenheit). Understand that while there may be wiggle room on either end, it’s best to aim for somewhere in the middle of each particular material’s temperature range so that the gasket or seal performs optimally for the longest period of time before replacement is needed.

Nitrile: -30 to 250F (very resistant to oils, aromatic hydrocarbons, fuels and solvents).

Neoprene: -35 to 225F (resistant to weather, water, combustion and a long list of chemicals).

Polyurethane: -35 to 225F (resistant to oxygen, ozone, cracking, abrasion, cuts, grease and heavy loads; frequently used in machine mounts, electrical equipment wear pads and applications needing shock absorption).

Ethylene Propylene: -70 to 250F (resists severe weather conditions, acids, oxygen, alkalis, hot and cold water and ketones; not suitable for use with oils or fuels).

Fluorocarbon: -15 to 400F (its low friction and resistance to wear and tear make this a good material for gaskets that endure movement, a wide temperature variation and frequent reassembly).

Silicone: -65 to 450F (very resistant to hot, cold and oxygen, but poor resistance to oils and fuels; frequently used in food processing and medical applications).

Polytetrafluoroethylene: -238 to 574F (extremely wide temperature range, also stands up to harsh conditions of all sorts; frequently used in food processing, pharmaceutical, laboratory, semi-conductor, petrochemical and chemical and electrical applications).

Temperature range is, of course, just one aspect of a non-metallic gasket material that you will need to consider before project implementation; nevertheless, temperature tolerance is crucial. If you need custom gaskets and seals for your project, please call us at 1-800-747-7661 to discuss your needs with us.

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