Buna-N O-Rings

Buna O-rings are the most common o-rings on the market. Ideal for water or hydrocarbons (Oil & Gas), they are a staple in the industry.

Buna-N (Nitrile) O-Rings

Nitrile butadiene rubber (NBR) is a family of unsaturated copolymers of 2-propenenitrile and various butadiene monomers (1,2-butadiene and 1,3-butadiene).The additives used to accomplish this are NOT always compatible with Buna-N and has resulted in the auto industry upgrading o-rings to Viton® elastomers.

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Nitrile® (Buna-N) O-Ring


Nitrile® (NBR or Buna N) (Acrylonitrile-Butadiene Copolymers)

Trade Names:
   Hycar................................Zeon Chemical
   Ny Syn....................................Copolymer

Nitrile® o-ring sizes:

-001 to -024 -025 to -049 -050 to -125 -126 to -150
-151 to -175 -176 to -222 -223 to -247 -248 to -272
-273 to -321 -322 to -346 -347 to -371 -372 to -395
-400 to -424 -425 to -449 -450 to -474 -475 to -932



Media Compatibility 

Petroleum Fluids
Water (to 212oF)
Silicone Fluids
Ethylene Glycol
General purpose

If the size you need is not listed or is metric, please call us at (714) 593-9780.   

To determine the o-ring size you require go to the following link: http://www.usseal.com/Oringdim.htm

While most people assume all Buna-n , (also called NBR or Nitrile orings) are the same, the simple truth is they are not. Regardless of what rubber compound you are referring to, it is a compound. Compounds by definition are made up of multiple types of rubber and fillers, to maximize performance of specific characteristics . Those characteristics may be tensile, recovery, durometer, color, finish, grip (if they are used as belts) ozone resistance or any specific chemical or heat compatibility.

Ever wonder why one manufactures product holds up better than anothers? Specific compound characteristics are added by blending another material with the base material. In this case Buna N or Nitrile. Other compounds may include Neoprene, carboxylated nitrile (XNBR), Hydrogenated Nitrile (HNBR), EPDM, EP, EPR, SBR, Chloroprene, Polyacrylate, Ethelene Acrylic, acrylonitrile-butadiene (this is not a complete list). All or a couple of these natural or synthetic rubbers can be mixed to various ratios, combined with fillers to form a specific compound. No two compounds are alike, just like grandma’s cookies.

If a manufacture knows the equipment the o-rings are used in spend most of their time exposed to ozone (sunlight), they may blend EPDM into the base Nitrile to increase the life span of the o-ring (more likely they would just buy EPDM, but in this example they are hoping for a cost savings). A Nitrile o-ring can be NSF or FDA if compounded properly. Ever wonder why the repair you did lasted less time than the products original life? It just may be due to the compound of the Nitrile rubber in your o-ring or gasket.

A great example of rubber compounding to maximize performance is the “Super Ball” the question of why it bounced so high can be answered with one word “compounding”. Two balls can look the same, feel equally dense and yet one will bounce high and the other can bounce very little or not at all.

In today’s market we do see o-rings and rubber gaskets considered as a commodity. The ironic thing is often repairs are done at industrial plants using the lowest bidders product. In reality the 25% savings purchasing was excited about finding, can often result in a 1000%+ increase in repair costs. In contrast to total costs, the o-rings, gaskets and other seal expenses pail in comparison to labor and other components costs. Supplying cheap seals is the biggest gamble with your budget you can make.

American Seal & Packing provides quality o-rings from high quality sources. Parko, a USA company provides much of our product and allows us to meet the most stringent specifications. We have very carefully selected our factories, and have done business with each of them for many years. All are ISO 9001 certified and have earned our respect.

So, whether your looking for a quality Buna o-ring, Buna-N o-ring or Nitrile o-ring (trick statement because they are all Nitrile Butadiene rubber) , make sure you buy a quality compound designed for your service.

If the size you need is not listed, please call us at (714) 593-9780.   

Compounds of these polymers are the backbone of the O-Ring line. Polymers vary from 18% to 50% acrylonitrile content. Resistance to petroleum products increases as acrylonitrile increases; conversely, low temperature flexibility decreases.  Government specifications on o-rings require low acrylonitrile. Nitrile® o-ring Compounds can exhibit excellent compression set, tear and abrasion resistance. Unless especially compounded, they do not have good resistance to ozone, sunlight, or weather. They should not be stored near motors or other ozone generating electrical equipment.  They should be kept from direct sunlight.

Compounds from nitrile rubber can exhibit a temperature range of -65 F to +300 F,on o-rings, although no one formulation may exhibit the total range.

Buna-N O-Rings Properties

Good Wear Resistance, Good Compression Set Resistance, Good Short-Term Resilience, Good Permeation Resistance.

*Can be ordered in higher durometers for high pressure applications to prevent extrusion or ordered in lower durometers for fast sealing in lower pressure applications.

Temperature Range

-35º F to 250EF

Buna-N O-Rings : Recomended For

Silicone Greases / Oils, Water, Petroleum Oils / Fuels, Ethylene Glycol Fluids


Phosphate esters
Brake fluids
Strong acids
Ozone or weathering 

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