PTFE Gaskets

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PTFE (Polytetrafluoroethylene) has a unique set of properties making it one of the most valuable engineering materials available.  PTFE is a fluorocarbon polymer with both outstanding chemical and thermal resistance. It can be used to seal in virtually any chemical environment under a wide range of operating temperatures. It is a semi-crystalline plastic that doesn’t absorb UV light and has excellent resistance to sunlight.

PTFE gaskets are available in range of grades designed to meet diverse sealing applications. They have high dielectric strength, excellent resistance corrosion, hydrolysis and moisture absorption and an extremely low coefficient of friction, making them suited to applications with linear or rotary movements. PTFE gaskets are highly durable and are able to regularly compress and absorb impacts, meaning they can be in constant use without risk of warping or deterioration.

The most common grades of PTFE are pure (virgin) PTFE and expanded virgin PTFE. These grades are FDA compliant and are commonly used in the food, beverage and pharmaceutical industries. Expanded PTFE gaskets have increased compressibility and are commonly used on worn or damaged flanges. Many other specialised grades are available with fillers including bronze, carbon, glass, graphite and stainless steel. For more information on each grade, please see the table below.

Viking Extrusions supply PTFE gaskets, seals and washers cut to precise tolerances. We can supply single gaskets or large volume requirements. We can offer standard flange gaskets, picture frame gaskets and dovetail gaskets. We also have the capability to produce bespoke gaskets to dimensioned drawings or replicate samples.

PTFE Material Properties

  • Can operate in extremely low and high temperatures.
  • Good weathering, UV and ozone resistance.
  • Good electrical insulation properties
  • Excellent dielectric strength
  • Good gas impermeability
  • Very low coefficient of friction
  • Good for use with petrol and oils
  • Good for use with acids and alkalis
  • Exceptional chemical resistance
  • Suitable for use in food contact applications
  • Excellent resistance to corrosion and hydrolysis
  • Completely insoluble
  • Very low moisture absorption
  • Not suitable for use with highly abrasive materials
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PTFE Material Grades

PTFE is a waxy powder like substance that cannot be melted, it is pressed and formed into shapes. PTFE can be made into sheet material, washers, rings, tubes, spacers and more. PTFE is an incredibly versatile product; its properties can be enhanced by blending fillers with the base PTFE resin. These fillers can increase creep resistance, hardness, chemical resistance, corrosion resistance, wear resistance, thermal conductivity, reduce deformation under load  and meet compliance requirements for specific industries.

Pure (virgin)100% pure PTFE with no fillersBushings, slide bearings, insulators, washers, side plates, chemical linings
Expanded PTFEManufactured from virgin PTFE, expanded PTFE is extremely compressible and has excellent resistance to a wide range of chemicals, UV, ozone and corona. Expanded PTFE does not become brittle with ageFDA approved for use in the food and pharmaceutical industries. Used on delicate, worn or damaged flanges due to its low bold load requirement.
Carbon FilledAdding carbon filler to PTFE results in excellent mechanical and wear properties whilst maintaining a low coefficient of friction. Carbon fillers are electrically conductive, increase thermal conductivity and permeability. Carbon filled PTFE is often used where glass fibre filled PTFE fails. Carbon filled PTFE is a harder material with greater resistance to pressure under load.Dynamic seals, water contact applications , anti-static applications, high pressure applications, strong alkali and hydrochloric acid contact applications
Glass Fibre FilledGlass fibre is added to PTFE in different percentages (between 5% and 40%) and provides much improved compression and wear properties. Deformation under load is reduced resulting in a harder material with lower thermal expansion. However, the addition of glass fibre makes the material more abrasive and increases its coefficient of friction.Bearings, anti-extrusion rings, valve seats, seals and gaskets.
Stainless Steel FilledAdding stainless steel powder to PTFE greatly increases its strength and ability to withstand loads at extremely high temperatures whilst retaining a low coefficient of friction.Applications with steam and thermal fluid. A good seat material in ball valves due to its high wear resistance.
Bronze FilledAdding bronze powder to PTFE as an additive between 40% and 60% improves wear resistance, hardness and compressive strength. It also improves dimensional stability, reduces creep and cold flow and increases thermal and electrical conductivity. However, chemical inertness is reduced. Special bearings, valve seats, liners etc.
Graphite FilledAdding graphite filler to PTFE lowers its coefficient of friction and gives excellent self-lubricating properties. Graphite fillers enhance wear resistance and thermal conductivity. Graphite fillers can also be combined with carbon and/or glass fillers to further enhance the properties of the material.Graphite filled PTFE has exceptional performance in high speed contact applications where it has little wear, such as wearing against soft metals.
Molybdenum DisulphideAdding molybdenum disulfide (MoS2) to PTFE creates a harder, chemically unreactive and more slippery material resulting in improved compression and wear resistance. Molybdenum disulfide PTFE has a low static coefficient of friction and reasonable resistance to deformation. Molybdenum disulfide can also be combined with glass or bronze fullers.Dynamic sealing applications
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PTFE Gasket Applications

What is PTFE used for?

PTFE Gaskets are commonly used for pipework and flanges in environments where chemicals are present. PTFE Gaskets have good resistance to corrosion and moisture. They have an extremely low coefficient of friction making them the material of choice for applications where parts have linear or rotary movements.

PTFE Gaskets are commonly used for the following:

  • Food and pharmaceutical processes
  • Hydraulic cylinders
  • High speed applications
  • Aerospace
  • Oil and gas

Common solvents

PTFE Gasket FAQs

PTFE will not leave a carbon ‘track’ when subject to arcing. Its dielectric constant is largely independent of temperature. PTFE is unaffected by weathering or ageing; it is not wetted and does not absorb water. It can be used as an external electrical insulator.

  • Dielectric Constant: 2-13 over a wide range of frequencies
  • Dissipation Factor: 0.0004
  • Volume Resistivity: >10ᴵ⁶ ohm/cm
  • Dielectric Strength: >16kV/mm

Virgin PTFE (PTFE with no fillers) has an operating temperature range from 75⁰C to +260⁰C. It is best known for its non-stick properties and has a coefficient of friction comparable to wet ice on wet ice. PTFE is commonly encountered under the trademark Teflon, which is a PTFE coating for non-stick household items.

  • PTFE is chemical resistant. Pure PTFE can be used in the most corrosive environments without contaminating sensitive mediums. PTFE has very high intrinsic purity and is completely insoluble. It can be manufactured free of contamination for corrosive or ultra-pure applications.
  • PTFE is completely resistant to attack by all chemicals (apart from molten alkali metals, and some fluorine compounds at elevated temperatures and pressures). PTFE is unaffected by hydraulic fluids, aircraft/rocket fuel, lubricants and atmospheric conditions.