Viton® is a brand of synthetic rubber and fluoropolymer elastomer commonly used in O-rings and other moulded or extruded goods. The name is a registered trademark of DuPont Performance Elastomers L.L.C..
Viton fluoroelastomers are categorized under the ASTM D1418 & ISO 1629 designation of FKM. This class of elastomers is a family comprising copolymers of hexafluoropropylene (HFP) and vinylidene fluoride (VDF or VF2), terpolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP) as well as perfluoromethylvinylether (PMVE) containing specialties. The fluorine content of the most common Viton grades varies between 66 and 70%.
Viton's Four Families of Polymers
- A(Dipolymers of VF2/HFP): General purpose sealing. Automotive, Aerospace fuels & lubricants
- B(Terpolymers of VF2/HFP/TFE): Chemical Process plant, Power Utility Seals & Gaskets
- F(Terpolymers of VF2/HFP/TFE): Oxygenated Automotive fuels. Concentrated aqueous inorganic acids, water, steam
- Viton Extreme™(Copolymers of TFE/Propylene and Ethylene/TFE/PMVE): Automotive, Oil Exploration, Special Sealing, Ultra Harsh Environments
The performance of fluoroelastomers in aggressive chemicals depends on the nature of the base polymer and the compounding ingredients used for moulding the final products (e.g. O-rings). This performance can vary significantly when end-users purchase Viton polymer containing rubber goods from different sources. Viton is generally compatible with hydrocarbons (an advantage over Buna-N, which is the most common O-ring material), but incompatible with ketones such as acetone. O-rings made of Viton are typically color coded as black.
Viton O-rings have been used safely for some time in the SCUBA diving world for divers who dive with gas blends referred to as Nitrox. Viton is used because it has a lower probability of catching fire, even with the increased percentages of oxygen found in Nitrox. It is also less susceptible to decay under increased oxygen conditions.