PTFE (Teflon) O-Rings

Better known by the brand name Teflon, polytetrafluoroethylene (PTFE) provides a nonstick surface to cookware, nail polish, hairstyling tools, fabric/carpet treatment, and windshield wiper blades. However, manufacturers are seeing increased benefits from using PTFE as a way to manufacture quality O-rings. O-rings built using PTFE provide superior thermal and chemical insulation, and they can resist friction and water as well.

PTFE versus Teflon

Although they differ in branding, PTFE and Teflon share a common origin and properties.

PTFE

PTFE is a synthetic polymer derived from chemical bonding between carbon and fluorine, taking advantage of free radicals’ tendency to polymerize with tetrafluoroethylene. This material was accidentally discovered in 1938, when DuPont chemist Roy J. Plunkett attempted to create a new type of refrigerant, and mixed these materials together without knowing the reaction that it would cause.

Teflon

Kinetic Chemicals, a partnership company between DuPont and General Motors, trademarked PTFE under the brand name Teflon in 1945. In essence, Teflon is PTFE. However, PTFE is also available under a variety of other brand names, such as:

  • Daikin-Polyflon
  • Fluon
  • Dyneon

Properties

Several properties distinguish PTFE from other substances, including:

  • Low friction coefficient: PTFE has the third lowest friction coefficient of any substance known to man, meaning that it’s really
  • Functions at temperature extremes: Rated at 600 K, PTFE melts at 327ºC or 620ºF, and it also functions well at temperatures as low as −268ºC or −450ºF.
  • Resists water: Water beads up on the surface of PTFE, meaning that surfaces treated with this material resist oxidation.
  • Nonreactive: PTFE doesn’t react with the vast majority of corrosive substances, making it ideal for use in pipes, valves, seals, and O-rings.

PTFE’s High Temperature Range

The temperature range (-1,000F to +4,000F), nonreactivity, water resistance, and low friction properties of PTFE make it an ideal material to build O-rings for use in a wide variety of applications. These properties make PTFE O-rings an ideal choice for weather-resistant applications as well as applications involving electricity and thermal insulation. 

Due to their density, PTFE O-rings are not “melt-formed”—instead, they are compressed and sintered to provide the necessary shape.

 

Teflon/PTFE Seals

O-rings made of PTFE are present in a wide variety of industrial applications that require seals that can stand adversity. PTFE O-rings appear in many applications that are exposed to the following risk factors:



Top ApplicationsMechanical Weaknesses
  • Outdoors
  • Lubricants
  • Hydrocarbons
  • Acids
  • Alkalis
  • Detergents
  • Alcohol
  • Ketones
  • Steam
  • Refrigerants
  • High Vacuum Seals
  • Low-Compression Vacuum Sealing Flanges
  • Super-Heated Steam

Therefore, PTFE O-rings benefit applications such as:

  • Mills, crushers, and grinders
  • Pumps
  • Stirring and agitator systems
  • Transmissions and gear boxes
  • Rotary or screw-type air compressors
  • Machining tools
  • Centrifuges
  • Blower systems

Enhanced Mechanical Properties with Filled Grades

As shown in the table above, PTFE O-Rings have some mechanical vulnerabilities compared to other plastics. If needed, these properties can be enhanced by adding fillers, such as:

  • Glass Fibers
  • Carbon
  • Graphite
  • Molybdenum disulphide
  • Bronze

“Filled” O-Rings maintain their excellent chemical and temperature resistance while fillers improve mechanical strength, stability, and wear resistance.

Filler

Physical Form

Amount (% Weight)

Effect of Filler

Glass FibersMilled FibersUp to 40% (also in combination with graphite, MoS2, and carbon)
  • Increased Wear Resistance
  • Increased Compressive Strength
  • Reduced Cold Flow
  • Resistant to Organic Solvents
  • Increased Rigidity
CarbonPowderUp to 35% (also in combination with graphite, bronze, and glass)
  • Increased Compressive Strength
Carbon FibersMilled FibersUp to 30%
  • Increased Hardness
  • Increased Wear Resistance
  • Improved Thermal Conductivity
  • Good Dry-Running Properties
  • Electrically Conductive at Higher Filler Contents
  • Resistant to Hydrofluoric Acid
GraphitePowderUp to 25% (also in combination with glass, bronze, and carbon)
  • Improved Sliding Properties
  • Reduced Coefficient of Friction
  • Improved Thermal Conductivity
BronzePowderUp to 60% (also in combination with carbon, graphite, and MoS2)
  • Increased Compressive Strength
  • Increased Hardness
  • Increased Wear Resistance
  • Improved Thermal Conductivity
  • Reduced Cold Flow
Molybdenum Disulfide (MoS2)PowderUp to 5% (also in combination with glass and bronze)
  • Improved Sliding Properties
  • Increased Wear Resistance
Stainless SteelPowderUp to 60%
  • Improved Thermal Conductivity
  • Reduced Cold Flow
  • Resistance to Most Chemicals
PolymersPowderUp to 20% (also in combination with inorganic fillers)
  • Increased Wear Resistance
  • Not Abrasive to Mating Surface
  • For Soft Mating Surfaces
PigmentsPowderUp to 2%
  • For Coloring (Identification)

Quality PTFE O-Rings from Allied Metrics

With so many applications across so many industries, it’s easy to see why manufacturers turn to PTFE O-rings when they seek a quality sealing solution. You can find PTFE O-rings in such industries as:

  • General manufacturing
  • Medical device assembly
  • Packaging
  • Aerospace and automotive manufacturing
  • Applications that meet FDA, USDA, and 3-A dairy requirements

If you would like to learn more about how to incorporate our PTFE O-rings in your next project, be sure to request a quote or contact us for more information.