Selecting an elastomeric material is important to the life of a radial shaft seal. The elastomer's resistance to temperature, abrasion, chemicals, weather, sunlight and ozone can affect a profile's success in an application. The base polymer must be selected to ensure that these parameters are satisfied without creating excessive costs. Table 3 and the material descriptions that follow will help in understanding the base polymers properties, limitations and strengths. |
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Radial Shaft seals are made from various elastomers, but the most widely used are Nitrile (NBR), Polyacrylate (ACM) and Fluorocarbon (FKM). There are a variety of compounds avaliable depending on the system parameters. Select the elastomer that best suits your application and consult the Fluid Compatiblity tables to confirm chemical resistance. For parameters or chemicals that are not listed, contact ESP Engineering for more information. |
| Nitirile elastomers are the most commonly used material in the radial shaft seal industry. Nitrile carries the ASTM designation of NBR and is covered by ASTM 02000/ SAE J200 - BF, BG, BK or CH classifications. Nitrile is a copolymer of acrylonitrile and butadiene. The higher the acrylonitrile content the greater the resistance to oil and fuel. This increase also has an adverse affect on elasticity and resistance to compression set. In general, NBR has good mechanical properties and wear resistance. Nitrile is recommended for general purpose sealing of the following media: dilute acids, salt solutions, alkali |
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solutions, HFA, HFB, HFC, aliphatic hydrocarbons (fuels and oils), vegetable and mineral oils, grease and water. It is not suited for use with strong oxidizing agents; chlorinated solvents such as carbon tetrachloride, nitrated hydrocarbons such as nitrobenzene or aniline; phosphate esters such as Skydrol, Fyrquel, or Pydraul; acetates; ketones such as methyl ethyl ketone and acetone; and aromatic hydrocarbons. Ozone will usually attack nitrile materials, but resistance can be greatly increased by the addition of antiozonant compounds |
Polytetrafluoroethylene (PTFE, Teflon) offers superior chemical resistance to oils, solvents, acids and salts. High temperature resistance and low friction are also advantages compared to other elastomers. |
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With the addition of appropriate fillers, PTFE has excellent mechanical properties, favorable for applications where low lubrication could be a problem. |
