PTFE Gaskets

Is PTFE Safe?

Some PTFE material can be used for gaskets and seals in the food and medical equipment industries, and some cannot. Here’s why you might want to use PTFE, and the difference between material that is and is not FDA approved.

PTFE as a Sealing Material

Polytetrafluoroethylene, a.k.a. PTFE, also sold under the tradename Teflon®, has properties that make it an excellent choice for many sealing applications.

  • Extremely inert chemically – fluorine and nitric acid are its only vulnerabilities
  • Soft, so it conforms to uneven sealing surfaces
  • Remains plastic down to -400°F and is still usable at 500°F (-240 to 260°C)
  • Slippery surface assists fastener tightening

PTFE is sold in both sheet form and as expanded PTFE. Expanded, it’s softer and more compliant than the sheet version.

In high bolt load applications PTFE suffers from creep. This is reduced by adding fillers. Glass, carbon and graphite are the most commonly used. They increase strength without significantly impairing the other properties.

Safe and UnSafe PTFE

Pure or virgin PTFE is completely inert so can safely be used in applications where it will come into contact with food, pharmaceuticals or healthcare products. In fact it’s so safe the FDA classes it as “Generally Recognized As Safe” (GRAS). (The relevant regulation is 21CFR177.1550.) This means it’s suitable for gaskets, seals and washers on mixers, storage vessels, kettles and similar equipment.

Filled PTFE does not meet the GRAS criteria and is therefore not FDA approved for food and medical applications. Despite their higher strength, these grades of PTFE must not be used in places where they could be ingested or otherwise taken into the human body.

Expert Advice on Gasket Materials

When choosing a gasket material for food processing or medical equipment applications, a PTFE gasket can be a good choice. However, only the virgin grades are considered safe, and these are prone to creep under high bolt loads. Filled PTFE offers more strength but doesn’t come in FDA-approved grades.

Gasket material selection can be complicated. For expert advice on materials, chemical compatibility and FDA-approved materials, contact us and speak to a product specialist.

PTFE Gasket Sheet – Three Things to Know

PTFE is an extremely useful gasket material. So useful that it’s sometimes purchased in sheet form for cutting to shape as needed. Here we’ll talk about the strengths of PTFE gasket sheet and then we’ll discuss three things you should know.

Pros for PTFE Gasket Sheet

PTFE is chemically inert, which makes it a good material for sealing against almost everything except fluorines and nitric acid. It also has a very wide temperature range. Grades vary but it’s generally usable from -100 to 500 °F. Famously slippery, its low friction surface is advantageous in some applications.

Your gasket supplier can cut PTFE gaskets to shape (waterjet and die cutting both work well,) or you can buy sheet PTFE and cut gaskets yourself. Thin sheet is readily cut by knife and thicker sheet is easily milled.

Important Things to Know

Besides the strengths of this material, it’s important to be aware of:

  • Tendency to creep
  • Limitations for food applications
  • Sheet thickness tolerances


Creep is a progressive, non-reversible deformation that occurs under load. This reduces clamping force, which eventually causes leaks.

The solutions are to either use it only in low-load applications, which is often impractical, or use a filled grade. PTFE fillers include glass, carbon, graphite, bronze and other materials, sometimes in combination. These raise strength but at the expense of a less slippery surface and reduced chemical resistance.

Food Limitations of PTFE Sheet Material

Pure PTFE is so inert it can be used in applications where it comes into direct contact with food. This is not true for the filled grades. These are likely to discolor or taint foodstuffs so are not permitted in such applications.

Sheet Thickness Tolerances

Thickness is an important gasket characteristic. Thickness tolerance depends on how the PTFE sheet is produced. The options are molding or skiving. Skiving entails cutting a thin layer away from the surface of a cylinder of PTFE, and it produces a more consistent sheet. For precise PTFE sheet thickness, specify skived material.

PTFE Sheet From Hennig Gasket & Seals

We can supply molded and skived sheet 60” square. Thicknesses range from 1/32” to 4”. Contact us to learn more

PTFE Seals – When Elastomers Aren’t Up to the Task

Elastomers are often the first choice for sealing and gasketing, but they’re not always the best. Silicone, neoprene, EPDM and Buna-N all have limitations that disqualify them from some applications. When that’s the case it may be time to consider PTFE seals.

Limitations of Elastomers

Elastomers are challenged by temperature extremes, aggressive chemicals and UV light. Some swell when in contact with oils, others outgas or give up molecules to the fluid being sealed against.

Food processing is a difficult environment. While it’s important to avoid product taint the materials must also endure aggressive cleaning regimens. Medical and pharmaceutical equipment presents similar challenges.

Many elastomeric materials harden in UV light, making them unsuitable for outdoor environments. Others will outgas, making them a bad choice for vacuum applications.

How PTFE Seals Score

PTFE is composed of carbon atoms bonded to fluorine. That makes it almost totally inert and a good choice for food, pharma and medical applications.

Less flexible than an elastomer, PTFE can nevertheless seal down to around -460°F. It’s also functional at temperatures as high as 570°F.

PTFE is unaffected by UV light, making it useful for outdoor applications or those involving UV sterilization. It has excellent electrical insulating properties and won’t swell when exposed to steam or oils. Another benefit from using PTFE seals in dynamic applications is a very low coefficient of friction.

PTFE Seals Limitations

Under load, especially at elevated temperatures, PTFE will creep. Joints should be designed to minimize the clamping forces applied directly to the material.

A second limitation is low strength. Some elastomers offer higher tensile strength combined with less elongation at breakage.

To address these issues PTFE formulators incorporate a range of fillers. Ranging from glass and carbon fiber to bronze and molybdenum disulfide, these can increase strength and hardness and reduce friction.

Seek specialist advice

When your sealing application challenges elastomeric materials it may be time to consider PTFE. However, with a large number of PTFE formulations available it’s difficult to know which is ideal. In such cases consult a materials specialist like those at Hennig Gasket.

Why Use PTFE Seals in Food Industry Applications?

Commercial cooking kettles used for boiling and preparing foods usually have a food grade gasket around the lid. By creating a good seal this helps the vessel build and retain pressure. This raises the boiling point of water, shortening cooking time while also destroying pathogens. A defective gasket can result in food not reaching the required temperature, potentially creating a health hazard. Additionally, the gasket itself can provide places for bacteria to become established.

This gasket leads a hard life. Not only must it withstand the heat and pressure of cooking, but it’s also expected to go through multiple cleaning cycles. In addition, it’s essential that it not transfer anything or impart any taint to the food being cooked. Several materials are available for such gaskets, but in many situations the best sealing option is PTFE.

A Versatile Sealing Material

Polytetrafluoroethylene, or PTFE, better known by it’s DuPont tradename of Teflon, has a number of properties that make it an excellent choice for a food grade gasket. At the atomic level it consists of a long chain of carbon atoms, each one of which links to two fluorine atoms. This linkage is so strong that PTFE won’t bond to anything else, hence its non-stick properties.

PTFE doesn’t melt until 635°F and is usable at temperatures up to 260°F. At lower temperatures it remains flexible well below freezing, as low as -100°F or even lower, depending on formulation. It’s also a good electrical insulator. Of particular relevance for food industry gasket applications, it doesn’t absorb water and it’s biologically inert. It does however resist attack by almost all chemicals, including aggressive cleaning and disinfecting agents like chlorine dioxide.

PTFE Seal Alternatives

Other materials have properties that are close or superior to PTFE in some regards. Silicone for example is flexible at low temperature, has good compressibility and a higher upper temperature limit. However, silicone does not fare well with steam, which is found in many food preparation environments. It also lacks resistance to acids, alkalies and chlorinated solvents, so is limited in its potential as a food grade gasket.

FDA Approved Seal Material

Gaskets & Seals made entirely of PTFE are covered by 21 CFR 177.1550, meaning they have FDA approval for food industry use. (PTFE incorporating filler material may not meet FDA requirements.) At Hennig we can supply PTFE sealss in thicknesses ranging from 0.015″ to 0.50″. Call or email for further information.

PTFE Makes an Excellent Material for FDA Gaskets

Buying gaskets for dairy, brewery and food processing equipment is difficult. The choice is limited to FDA gaskets or FDA approved gasket material because it’s essential to avoid tainting or contaminating the product. Cleaning and sterilization routines are a way of life, so gasket material must stand up to high temperatures and caustic cleaning agents. And last, clamping forces are low in equipment like kettles, mixers and sanitary pipe fittings, so the material must be soft.

Polytetrafluoroethylene, (PTFE) sometimes referred to as Teflon®, meets all these requirements. That’s why it’s used for gasketing throughout the food industry. PTFE is listed by the FDA under 21 CFR 177.1550, although this approval really only covers virgin PTFE material. PTFE with markings, adhesive backing or filler can be used in food applications, providing the inks, adhesives and fillers also meet FDA standards. If purchasing gaskets like these for a food industry gasket application, have the material supplier confirm they qualify as FDA gaskets.

Some gasket materials will absorb traces of food preservatives, but PTFE is almost completely non-reactive. It doesn’t pick anything up and neither does it pass anything over so there’s no risk of food being contaminated with traces of elastomers or cleaning agents. The Shore D hardness of PTFE is around 50, so it’s soft and easily compressible. That’s important when pipes and vessels are secured with clamps rather than bolted flanges. PTFE also has the advantage of retaining its properties at temperatures as high as 400°F (204°C). That’s why it survives steam cleaning.

PTFE is not perfect though. It has a tendency to creep, which could lead to reduced clamping loads. This is because, unlike elastomeric gasket material, PTFE doesn’t cross-link, so bolted joints with PTFE gaskets may need occasional re-torquing.

In food processing it’s essential to use FDA gaskets. These will typically be PTFE, although some other materials are FDA approved too. If a gasket is going to contact food products it’s always best to discuss the application with the material supplier and make sure the correct material is chosen.

Properties of Neoprene Gasket Material

Neoprene, which is also known as “polychloroprene,” is a type of synthetic rubber produced by the polymerization of chloroprene. Neoprene gasket material has become very common due to the fact that it resists the likes of ozone, sunlight, oxidation and many petroleum derivatives. Additionally, neoprene is characterized as being weather-, combustion-, water- and chemical-resistant. As you can see, it’s popular because it is resistant to many types of damages. What’s more, it’s also resistant to damage from twisting and flexing.

Here’s a closer look at the properties of neoprene so you can judge whether or not it’s a good material for your application:

  • Stretch and cushioning properties: Neoprene is elastic and form-fitting, able to conform to various sizes and shapes. It’s also cushioning, able to absorb shock.
  • Various grades available: From cloth inserted neoprene, which is reinforced with nylon for additional stability, to flame retardant neoprene, which passes a variety of flammability specifications, there are several grades available to suit any application. Other popular grades include commercial, FDA approved, diaphragm and high tensile strength.
  • General gauge thicknesses vary in size from 3/32-inch up to 2 inches.
  • Hardness ratings vary from 40 to 80.
  • Plate finish.
  • Neoprene can withstand temperatures ranging from -20 degrees F to 180 degrees F.
  • Tensile strength ranges from 900 to 1,000 PSI.
  • Elongation ranges from 350% to 400%.
  • Finally, widths are 36 inches, 48 inches or 72 inches.
  • Pressure sensitive adhesive, or PSA, are available upon request.
  • We fabricate neoprene gaskets through proven manufacturing processes that include waterjet cutting, flash cutting and die cutting.

One other neat feature about neoprene is that it’s impermeable, meaning that it can work as a tight barrier to prevent the escaping of gases or liquids.

For more information on the neoprene material and neoprene gaskets, and to speak with someone about placing an order, contact us today.