Viton® also named FKM & FPM, VITON and NBR are two of the most commonly used elastomers for sealing applications, and for good reason. ... While both Viton/ FKM and NBR seals act as very good sealing options at moderate temperatures, Viton®/ FKM is far superior for high temperature applications.
Rubber o-rings can be used in many applications as they are manufactured from many materials. O-rings are usually made from rubber, or more specifically, polymers / elastomers. And these polymers are usually cured by vulcanisation which results in strong, durable and more elastic rubber materials.
Because of many materials available, it can be difficult to determine which is the most suitable for a project. It’s important to remember that different materials have different properties; For example, some are more elastic and others are more tear resistant in addition to other key qualities.
Viton® / FKM and NBR can offer excellent compression set resistance, and both are designed to resist most oils and lubricants, especially petroleum-based lubricants. Additionally, moderate temperature applications between -15°C and 110°C are served by both compounds, making either material a very good choice for general industrial use.
However, for more specific applications, the decision on material becomes much more important. Viton®/ FKM and NBR compounds have several very crucial differences that make them well-suited to certain applications. While both seals act as very good sealing options at moderate temperatures, Viton®/ FKM is far superior for high temperature applications.
STANDARD VITON® / FKM VS STANDARD NITRILE
Standard Viton®/FKM compounds can provide continuous sealing at temperatures up to approximately +205°C.
Standard NBR on the other hand is only effective for continuous sealing at temperatures up to +110°C (with short term sealing at 130°C.)
At temperatures below -20°C, standard Viton/FKM seals are less effective as they become quite hard and inflexible. Special Viton® / FKM compounds can provide low temperature capabilities of -40°C.
Standard NBR will operate successfully at -35°C (However, some special NBR compounds can provide effective sealing down to temperatures of -55°C,)
In addition to temperature, other application conditions differentiate these two compounds. Viton® /FKM has a wide chemical resistance range, which makes it ideal for most applications involving oils, fuels, and mineral acids. Viton®/FKM also offers excellent resistance to oxidation, ozone, UV exposure, weather, fungus and mould. Although NBR also supports some of the same chemical resistances, it is much less universally resistant than its Viton®/FKM counterpart, suffering degradation from weather and ozone exposure. For most circumstances, however, this may not be an issue. NBR also offers the benefit of superior abrasion and tear resistance making them better suited for more heavy duty industrial applications.
Both of these elastomers are suited for an extensive list of diverse applications, and they serve as excellent general purpose seals. Nevertheless, to optimise your choice in seals it is essential to consider the advantages and disadvantages of both materials.