Viton® is a trade name for a fluoropolymer elastomer produced by Dupont Performance  Elastomers. It is important to note that Viton® has become a generic reference within the Seals Industry,  in much the same way  as a vacuum cleaner is often called a hoover

Is there such a thing as a standard Viton grade?

There is. Viton A grade (66% fluorine content) is the most standard material from a stock-holding and general availability prospective. The material out of which the seals are produced generally, as a minimum, has to conform to certain industry standard criteria set out for that material classification. The criteria used is normally to requirements set out in ASTM D2000. One particular key attribute is its excellent compression set.

The upper limit is around 200 deg C, and can go higher in certain situations, but it depends  on the actual application. Fairway Seals has its own in house technical team who will be happy to answer any queries you may have.

This is where it gets a little tricky. Many people associate temperature as the be all and end all no matter what other application criteria is involved. Water turns to steam at 100 deg C. Having already said that the upper temperature limit of Viton is 200 deg C so surely it should be OK? Not so I am afraid. Due to the crosslinking make up of standard vitons the additives used do not react too well with steam and create an effect known as hydrolysis which effectively over time breaks down the Polymer chain. Now for the good news, Fairway Seals technical team are on hand to give the required information after taking into account all the relavent detail.

You have to remember that, in general terms Viton is mainly selected for its excellent chemical resistance, often at high temperatures and in the first case was not designed with low temperature in mind. Having said that it is a matter of – “How low do you want to go? With a Viton A grade-15/ -20 deg C is generally achievable. There are numerous  laboratory tests. Within ASTM D2000 a 3 minute none brittle test is the norm(ASTM D2137) whereas the more clearly defined industry test is the temperature retraction test (known generally as TR-10, i.e the temperature at which an elastomer is able to retract 10%. See ASTM D1329) The material will probably be able to go approx.. 10 deg lower than this, but this is only a guide as the end result can be greatly affected by other application criteria, such as chemical contact media..

Firstly, please stipulate DUPONT VITON. As mentioned earlier, there is much confusion brought about due to the fact that so many people refer to Viton, even when it is not. Made with original Viton stickers can be affixed to the packaging, but the simple way is to state DUPONT VITON.

It is important to note that the information detailed above is only a guide. The responsibility is with the client to be sure that the product meets its required purpose via their own tests. Results from data sheets are usually based on tests of solid test buttons of a fixed size, shape and mass and tested in laboratories with controls maybe far different from those conducted elsewhere. The results on the component pieces will generally be considerably different to test piece results due to differing size, shape & mass.

There are many factors which result in reduction in seal life or failure, such as selecting wrong material, incorrect installation and so on. Elastomeric Science is an imprecise art, and all application criteria has to be considered in order to ensure the selected material has the best possible chance of success in the application.

Please note:, Sealing performance in service must also include considerations of other factors such as resistance to compression set, mechanical strength at service temperatures, seal design, and seal cost.