PTFE FEP Encapsulated Silicone FKM Viton O Ring/O-Ring

Welcome to contact us for encapsulated O-rings

Encapsulated O-rings can have two different types of core, which enables them to be suitable for different applications. The two types are:

Solid core: These are standard encapsulated O-rings which have either a silicone energiser ore or a core made from FKM, also known as Viton. FKM cores have excellent elasticity and a good compression set. Silicone has very much the same benefits, but because it is softer it has a higher standard of heat resistance. For very cold temperatures, a silicone core would be recommended as they remain flexible to a lower temperature too.

Hollow core: For applications where extreme elasticity is required, no core at all outperforms both FKM and silicone cores. This may come with a compromise in terms of compression set and recovery, but for fragile applications a hollow core encapsulated O-ring will perform well.

As well as having various options for the elastomeric core, the outer jacket of the encapsulated O-ring can be made in a choice of materials too. Most commonly, we make them with either PFA or FEP outer jackets.

PFA: To give it its full title, perfluoroalkoxycopolymer is excellent at resisting a range of corrosive chemicals. These include alcohol, naphtha, acid, petroleum and aromatic solvents. Compression set is low, and their operating temperatures range from -60°C to +260° Compared to FEP, they have higher mechanical strength and improved resistance to cracking and stress.

FEP: Fluorinated ethylene propylene jackets for encapsulated O-rings have very similar qualities to those of PFA. They resist chemicals, have low coefficient of friction and a low compression set. However, they are slightly weaker mechanically and have a narrower operating temperature range, of -60°C up to +205° Their service life is slightly shorter, but they are FDA approved and are generally lower cost too.

Viton Core encapsulated O-rings

PTFE FPA Coated O-rings / silicone core

Description

FEP is a thermoplastic material with properties similar to PTFE. O-rings which are seamlessly coated with FEP have an elastic core made from FPM or VMQ and are used if very high thermal or chemical loads are present. The high chemical resistance of the coating protects the core against damage by the potentially aggressive medium.

FEP coated O-rings are used – similar to PTFE-rings – where the chemical resistance of the normal elastomer O-ring is no longer sufficient, but where a certain elasticity is needed. The elasticity is ensured by the inner ring and the chemical resistance is achieved by the seamless FEP coating.

Applications

FEP coated O-rings are perfectly suited for the chemical and petrochemical sector, medical technology, food sector, water and waste water technology and similar industrial applications. A typical application for FEP coated O-rings is the sealing of valve stems and as a secondary sealing element for slow switching and rotary movements.

Properties

·         Very good chemical resistance against most liquids and chemicals

·         Temperature range from approx. –60 °C to 200 °C [depending on inner ring material]

·         No contamination of food, pharmaceutical or medical products

·         Physiologically harmless, can be sterilised

·         Sufficient elastic behaviour

·         FEP O-rings can be replaced with standard O-ring seals without limitation

·         No changes to the groove dimensions are necessary

·         The O-rings are less flexible than elastomer O-rings due to the FEP coating. They can only be stretched minimally and have a lower elasticity or a higher permanent deformation