Seal & Design has updated it’s Teflon encapsulated o-ring page, and included a Adobe PDF link giving you the different options for core and jacket materials. Teflon Encapsulated O-rings combine the qualities of Teflon (PFA/FEP) with Viton® or Silicone rubber. They have an outer jacket of teflon protecting the resilient core from virtually all chemicals.
The rubber core is totally encapsulated by Teflon (PFA/FEP) and this unique combination enables encapsulated o-rings to give maximum protection against leaks in a wide range of sealing applications. Teflon (PFA/FEP) has always been recognized as an ideal, chemically resistant, sealing material but it lacks elasticity. The Viton® or Silicone rubber core provides this missing element of memory, together with exceptionally good resistance to compression set, even at high temperatures.