Tip: Comparison of Nitrile, Carboxilated Nitrile and Highly Saturated Nitrile

Nitrile O-ring

(Buna-N)
-40 C to +135 C
(Low-Temp)
-65 C to +120 C

Presently this is the most widely used elastomer for an o-ring. It has excellent resistance to petroleum based oils and fuels, silicone greases, hydraulic fluids, water and alcohols. It has a good balance of working properties such as low compression set, high tensile strength, high abrasion resistance, combined with a low cost.

Use this elastomer with petroleum oils, water and hydraulic oils but do not use it with brake fluid, ketones, phosphate esters, and H2S.

Carboxilated Nitrile O-ring
-54 C to +135 C

A carboxilated nitrile o-ring will work at low temperatures and has excellent abrasion resistance. It is commonly used in Downhole applications.

Use a carboxilated nitrile o-ring with petroleum oils and water but do not use with brake fluid and phosphate esters.

Highly Saturated Nitrile O-ring (HSN, HNBR)
-26 C to +160 C

Hydrogenated Nitrile Butadiene Rubber (HNBR), also known as Highly Saturated Nitrile (HSN), is special class of nitrile that has been hydrogenated to increase saturation of the butadiene part of the carbon polymer. New improvements in the material properties include greater chemical resistance, more thermal stability and greater tensile strength.

HNBR is classified by ASTM as a DH-type polymer. This classification indicates 150ºC service temperature as well as less than 30% swell in IRM 903 oil. HNBR can meet application temperatures that are between -50°C and 165ºC.

An HSN or HNBR nitrile o-ring has excellent resistance to petroleum oils and sour gas. With the extended temperature range, HSN and HNBR o-rings are becoming a preferred compound in the oil patch.

Use a highly saturated nitrile o-ring with petroleum oils, H2S and CO2 and avoid using it with brake fluid.

It is interesting to note that the resistance to petroleum based oils and hydrocarbons increases when the nitrile content is increased in the elastomer (the elastomer may have a low, medium or a high content). At the same time, the low temperature flexibility decreases when you increase the content.