Dichtomatik & IBT

If you ever repaired a leaky bathroom faucet, you've come in contact with an O-ring in its most common compound: Buna Nitrile, 70 Durometer*. Buna Nitrile is the synthetic rubber compound. 70 Durometer indicates the hardness of the ring. NBR 70, as it is often referred to, is by far the most popular O-ring material, primarily because of its low cost and good performance in most typical sealing applications.

But what happens if your application isn't typical? Heat, steam, oils or chemicals, and pressure can rapidly degrade an NBR 70 O-ring. That's why Dichtomatik offers eight standard compounds and several special compounds to deal with all the different combinations of these important environmental factors.

Below is a summary of some standard compound characteristics; always refer to the Dichtomatik O-Ring Handbook for specific details on compound properties, as well as a comprehensive chart showing performance ratings for each compound in almost every chemical imaginable.

NBR
70 Durometer and 90 Durometer
Good mechanical properties and it is resistant to many lubricants and grease. It can handle water to 80° C / 176° F. It is generally not resistant to aromatic and chlorinated hydrocarbons, fuels with high aromatic content, polar solvents, glycol based brake fluids and non-flammable hydraulic fluids.

EPDM
70 Durometer
Peroxide-cured ethylene propylene diene M-class rubber compounds are suitable for higher temperatures in water or steam, and are resistant to aging and many chemicals. However they are unsuitable for all mineral oil products, including  lubricants, oils, and fuels.

Silicone
70 Durometer
This compound is resistant to water to 100° C / 212° F and animal oils, plant oils, and fats which make it popular in food and drug processing applications. It is not resistant to steam, fuels, aromatic oils, acids, and alkalis.

FKM
75 Durometer; Available in black or brown
Typically referred to by the brand name Viton^®, this compound is noted for a high resistance to heat and many organic solvents and chemicals, including aliphatic, aromatic and chlorinated hydrocarbons, fuels, and non-flammable hydraulic fluids. FKM compounds are generally not resistant to hot water, steam, and low molecular weight organic acids.

Polyurethane
70 Durometer and 90 Durometer
These materials differ from the other elastomers in their resistance to abrasion, wear and extrusion under pressure. They are also resistant to aging and ozone, mineral oils and greases, silicone oils and greases, non-flammable hydraulic fluids, water up to 50° C / 122° F, and aliphatic hydrocarbons.

Special compounds for severe chemical and/or heat applications include FFKM (commonly known by brand names Kalrez®, Chemrez^®, or Simrez^®) and TFE/P (Aflas^®). Contact IBT with your special requirements.

An earlier PrimeMover talked about the O-ring and its important role in countless industrial applications. It explained how proper installation is crucial in getting good performance out of an O-ring application.

* Hardness of rubber, Durometer, is measured on a Shore scale. The rating is based on a test which places a stylus, under set load, into the substance being measured. The depth of penetration is then calculated, and a hardness or Durometer rating is then identified. The type of rubber used on Dichtomatik O-rings is rated on the Shore A scale, which uses a stylus that has a flat cone point. The relevant ASTM standard is D2240.