Product Information
Vulcan Chem-Ring Seals combine the resilience and sealing force of an elastomer with the chemical resistance of Teflon. They consist of an elastomeric core of Silicone or Viton® with a relatively thin, moulded encapsulation of Teflon FEP or PFA polymer. This produces an elastomeric PTFE seal with maximum sealing capability.

Elastomeric, rubber "O" Rings suffer from high friction and limited resistance to aggressive chemicals and gas permeation. Solid Teflon "O" Rings are rigid with no effective memory and high compression set.

FEP Encapsulated "O" Rings are solvent resistant and chemically inert (except for attack by alkaline metals, fluorine and some halogenated compounds at high temperatures) yet have an elastomeric memory near that of rubber "O" Rings. FEP polymer, also, has an extremely low coefficient of friction (0.1 to 0.2) and very low permeability to gases, making Chem-Rings a virtually universal seal for use in hostile environments.

Function
The seamless, uniform Teflon polymer encapsulation provides the CHEM-RINGS near universal sealing capability, whilst the continuous reset, and the constant pressure of the encapsulation onto the sealing point, is performed by the elastomeric core.

The result is an overall sealing compression that increases with media pressure. The CHEM-RING behaves like a highly viscous fluid, any pressure exerted on the seal is transmitted practically undiminished in all directions.

Compression Set
Vulcan CHEM-RINGS resist hardening and embrittlement due to the TEFLON FEP encapsulation. The "O" Seals retained elasticity and recovery properties at temperatures up to 205 deg. C., is due to the Silicone or Viton® core material. The results of compression set tests, which compare the retained sealing force of perfluoroelastomer (Kalrez®), fluoroelastomer (Viton®) and the FEP encapsulated "O" Ring can be observed in the following diagram.

The results of these tests demonstrate that, by combining the mechanical properties of Viton® or Silicone elastomers and the chemical resistance of TEFLON FEP/PFA resins, the CHEM-RING possesses the ability to resist compression set and retain its mechanical properties.

Kalrez and Viton are registered trademarks of Dupont Dow Elastomers.

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"Teflon" Resins