Coated or Encapsulated? - Apples or Oranges?
Encapsulated o-rings are covered with a PTFE (a generic compound of Teflon™, a trademark of The Chemours Company) tube. They are specifically designed to withstand the most hostile chemicals and extreme temperatures. The purpose of coated o-rings is to eliminate sticking. An ideal low-friction coating is Teflon®. This is where the confusion between the terms "coated" and "encapsulated" develops.Encapsulated o-rings are usually silicone or FKM. They consist of a solid or elastomeric core and are encapsulated in a clear sheath made of PTFE FEP (Fluorinated Ethylene Propylene) or PFA (Perfluoroalkoxy Alkane). The encapsulation itself actually enhances the seal and the elastomeric core ensures consistent compression on the seal. These o-rings behave like a highly viscous fluid; any pressure exerted on the seal is transmitted in all directions.
Solid core encapsulated o-rings are generally used in static applications. Hollow silicone core encapsulated o-rings are used where lower sealing force is required as in semi-dynamic applications.
Encapsulated O-ring dimensions comply with International standards. The encapsulation does not increase the cross section compared to a standard elastomer of the same size and doesn't change its color.Coated o-rings typically have a thin film of PTFE, aka "coating", adhered to the o-ring which is usually made of silicone or FKM. Coatings are available in many colors. The coating also offers additional benefits:
Positive assembly line identification
Ease of installation; reduces twisting
Lower initial running friction
Eliminates sticking during storage and auto-feeding