Viton® is Specified for its Outstanding Performance

Outstanding resistance to heat, oxidation, weathering, ozone Outstanding resistance to a broad variety of fluids, including: aliphatic and aromatic hydrocarbons, halogenated fluids, strong acids Outstanding resistance to compression set, providing sealing performance and longevity unmatched by any non-fluorinated elastomer

These characteristics make Viton® fluoroelastomer the perfect choice for demanding sealing applications. Unfortunately, there are several low-cost "fluorelastomer imposters" on the market that may put your operations at risk of seal failure. A number of manufacturers of finished goods offer products which are being described as "commercial" or "industrial grades" of fluoroelastomer at reduced prices. These so-called "fluoroelastomers" can be offered at lower cost simply because they are not 100% virgin fluoroelastomer. Instead, some of these products are blends of FKM with hydrocarbon elastomers, such as ethylene-propylene, chloroprene or acrylic rubbers.

Many hydrocarbon rubbers can be (and typically are) blended to take advantage of specific features inherent in the individual rubbers. Fluoroelastomers in general cannot be blended with any hydrocarbon rubber without significantly degrading the resistance of the resulting vulcanizates to heat, fluids and compression set.

Since Viton® is so much better than hydrocarbon rubbers in fluid resistance in general, blends of cheaper rubbers with Viton® typically perform significantly poorer than 100% FKM. The chart below shows examples of blends of FKM with three different, cheaper hydrocarbon elastomers. A compound based on 100% Viton® A-401C is compared to blends of a Viton® (75% by weight) with various hydrocarbon elastomers (25%) ethylene-propylene and polyacrylic rubbers. These tests were run for 168 hours, per ASTM D-471, in the fluids indicated in the chart's legend.

Note that except for the FKM/PA blend tested in IRM 903 oil, all these blends exhibit significantly higher swell in oil, gasoline, sulfuric acid and in toluene.

As was mentioned, blends of hydrocarbon rubbers and Viton® typically exhibit significantly poorer resistance to compression set compared to compounds based on 100% Viton®. Compression set tests correlate very well with the retention of sealing force, a critical property in maintaining good sealing. The better the compression set resistance of a vulcanizate, the longer it will function as a seal (and with fewer "adjustments" required, such as re-torquing bolts on flange gaskets).

The figure below outlines the compression set resistance of a compound based on 100% Viton® A-401C, compared to vulcanizates based on blends of FKM with three different hydrocarbon rubbers. The compression set testing was performed in plied disks, and the tests were run per ASTM D-395, Method "B."

Blends of Viton® with hydrocarbon rubbers do not perform "almost like FKM" or anything close to it. Beware of the "good deal:" rather than being a "low-cost fluoroelastome,r" it instead performs like an over-priced hydrocarbon rubber. If your sealing application is one that is best handled by a fluoroelastomer, make sure you are getting 100% Viton® FKM, and not a "low cost" (low capability) blend of FKM and hydrocarbon rubber. Insist on parts made with Genuine Viton®. Our Genuine Viton® License Program guarantees the end-user that the elastomer portion of finished goods which bear the Genuine Viton® Label consist only of 100% virgin Viton® fluoroelastomer.