fluoroelastomer

fluoroelastomer, any of a number of synthetic rubbers made by copolymerizing various combinations of vinylidene fluoride (CH₂=CF₂), hexafluoropropylene (CF₂=CFCF₃), chlorotrifluoroethylene (CF₂=CFCl), and tetrafluoroethylene (C₂=F₄). These fluorinated elastomers have outstanding resistance to oxygen, ozone, and heat and to swelling by oils, chlorinated solvent, and fuels.

Fluoroelastomers were developed in the 1940s and 1950s after the discovery at E.I. du Pont de Nemours & Company (now DuPont Company) of the heat-resistant resin polytetrafluoroethylene, subsequently sold under the trademark Teflon. Exhibiting service temperatures up to about 250 °C (480 °F), fluorocarbon elastomers such as DuPont’s trademarked Viton (a copolymer of vinylidene fluoride and hexafluoropropylene) have become materials of choice for use in aerospace and industrial equipment subjected to severe conditions. However, they have a high density, are swollen by ketones and ethers, are attacked by steam, and become glassy at temperatures not far below room temperature. Also, their low chemical reactivity makes the interlinking of the polymer chains (necessary for the production of a rubbery material) a long and complex process. Principal applications are as temperature-resistant O-rings, seals, and gaskets.