by Jackie Johnson Jackie Johnson No Comments

The Benefits of Modified PTFE

Spring Energized PTFE Seal

Polytetrafluoroethylene (PTFE) is a chemically resilient fluoroplastic. An incredibly versatile material, PTFE is used (at least in some capacity) in nearly every industry imaginable. PTFE has its limitations, however.

Modified PTFE (or MPTFE) pushes the limits of regular PTFE, offering exciting new possibilities for a wide variety of applications. The reason behind such improvements? MPTFE, also known as TFM (trade name of Daikin) is a copolymer of tetrafluoroethylene and a small quantity of a perfluorinated modifier (perfluoropropyl vinyl ether, PPVE).

In other words, MTFM has added chemicals that make it stronger and more versatile than regular PTFE. And because of its strength and versatility, modified PTFE is used in a wide variety of industries. These include, but are not limited to, automotive, aerospace, medical device, LNG and more.

A Strong and Versatile Material

Modified PTFE has several advantages over regular PTFE. It has a substantially reduced deformation under load- 4% for Modified PTFE vs 10% for PTFE. This, as well as improved flexibility, makes modified PTFE great for devices that need a little give but won’t break under pressure.

MPTFE also has a lower porosity and permeability which helps reduce the amount of liquid absorption, making it perfect for products such as seals for wet environments. On top of that, modified PTFE has smoother surfaces, nonstick and dielectric properties, and a reduced cold flow. It has good metering properties, good electrical and mechanical properties. And with excellent fuel and additive resistance, MPTFE can replace conventional materials such as PTFE and make it easier to use more aggressive lubricants and seal designs.

In Conclusion

As you can see, MPTFE is an incredibly versatile and strong material to use. It can withstand more abuse than the average PTFE, giving it a clear advantage for a variety of applications. Use modified PTFE for your next project and let Advanced EMC Technologies help you create products that take full advantage of this wonderful material.

Contact us today to learn more!

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Why PTFE Rotary Shaft Seals Are a Great Choice for Food Processing Applications

 

Food processing plant processing corn

While there are several options when it comes to approved polymeric or elastomeric seals for food processing applications, PTFE is one of the more popular choices–and that includes rotary shaft seals, as well.

Rotary shaft seals for food processing equipment have to do more than an ordinary seal:  they also need to withstand aggressive cleaning and sanitation regimens that may involve corrosive chemicals, be approved for contact with food, and offer effective, reliable performance. 

Where Shaft Seals are Used in Food Processing

Food processing machines that make use of shaft seals include mixers, food portioning equipment, dry product filling systems, ice cream dispensers, milk dispensers, high pressure homogenizers, water purification equipment, and distilled water pumps. They may be used with adhesives, flavorings, water, powders, preservatives, sauces, condiments, steam, and various fluids.

Operating Conditions

Rotary shaft seals for use in the food processing industry must  be able handle the standard operating conditions involved such as speed, temperature, and pressure. However, their operating environment can involve more than that: consideration has to be given to the type of media they will be exposed to (e.g., powders, extremely viscous fluids). 

PTFE is one of the polymers that has a proven track record with rotary shaft seals that have to function over a wide range of temperatures, pressures, and speeds, with various grades available that can offer more customized performance.

CIP/SIP

Rotary shaft seals must withstand the sterilization or cleaning procedures involved. CIP (Clean in Place), SIP (Sterilize in Place) and COP (Clean Out of Place) methods often require aggressive cleaning agents and/or superheated steam, powerful disinfectants, and potentially corrosive acids. 

PTFE is highly resistant to a wide range of aggressive chemicals, can handle repeated exposure to hot water and superheated steam, and will not react chemically to the powerful disinfectants and sanitizers that food processing equipment is exposed to.

Safe for Contact with Food

Any part of a rotary shaft seal that comes into contact with food must conform to the appropriate regulations, such as  FDA 21 CFR 177.1680, (EC) No. 1935/2004, and/or USP Class VI. Such approval is not easy to achieve: it takes into account whether the material releases any chemicals, tends to absorb moisture, goes through physical changes when exposed to high temperatures, reacts chemically to ingredients that are acidic, exhibits off gassing, and more. 

PTFE comes in grades that are fully compliant with regulations regarding contact with food and FDA approved, making it a safe choice for rotary shaft seals for food processing equipment. In addition, it is the most chemically unreactive polymer on the market today.

Conclusion

Finally, PTFE rotary shaft seals have proven themselves to be highly reliable, which is why you will see them used in dangerous, mission critical applications where safety and ruggedness is vital, such as those found in the oil and gas or aerospace industries. If you are looking for a FDA-approved rotary shaft seal for use in food processing applications, PTFE seals should be at the top of your list.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

PTFE Rotary Shaft Seals versus PTFE Spring-Energized Seals

PTFE is an excellent material for seals: it has extremely low friction, can operate in extreme temperatures, is dimensionally stable, available in FDA approved grades, and is compatible with a wide range of chemicals. When it comes to seals for rotating shafts, PTFE is often used with both standard rotary shaft seals as well as spring-energized seals — but aren’t they the same? The short answer is no, they are not.

Dynamic Seals

Dynamic seals, including those used in connection with rotating shafts, face far more challenges that static seals. If the shaft is misaligned, it is possible for the seal lip to lose contact with the shaft surface during rotating, compromising the integrity of the seal. Shaft surfaces must be extremely smooth when rotation is taking place to minimize the wear on the seal lip and to make the seal more effective — and this is especially true when high speeds are involved. 

PTFE Rotary Shaft Seals

Rotary shaft seals are designed to provide a seal (and in some cases a wiping functionality) for circular shafts that are rotating or swiveling. Their job is to keep lubricants (either for the bearing or for the shaft itself) from leaking out while preventing the ingression of contaminants, which is why they are often called oil seals or grease seals. There are many different designs that are well adapted for specific sealing applications, such as mechanical pump seals, cryogenic temperatures, and harsh environments.

When designed and specified correctly, PTFE rotary shaft seals can provide excellent performance at relatively high speeds as long as the pressures are low (there are high speed shaft seals that can handle higher speed levels, but again the pressure must remain low). In addition, the shaft must meet strict tolerances for surface finish and must be straight and correctly aligned. They are a cost effective sealing solution for many designs

Spring Energized Teflon Seals

PTFE Spring-Energized Seals

PTFE spring-energized seals serve the same purpose as rotary shaft seals and can achieve all that rotary shaft seals can, with a few additions made possible by the spring energizer. For example, the presence of a spring-energizer enables the sealing lip to remain in contact with the surface of the shaft even when there is a significant pressure difference or the shaft is eccentric. The springer energizer also maintains seal integrity when there are significant changes in temperature that can affect the dimensions of the shaft size or the PTFE seal lip. The drawback for this enhanced performance, however, lies in the price: PTFE spring-energized seals are going to be more expensive than PTFE rotary shaft seals.

Polymer Spring Energized Teflon Seals

Conclusion

PTFE is an excellent material choice for many dynamic sealing applications, including those that involve high speeds, dry running capabilities, FDA approved materials, extremely high temperatures, or cryogenic temperatures. There are some dynamic applications where a PTFE rotary shaft seal simply cannot provide the necessary performance, and in those instances then a PTFE spring-energized seal should be considered.

by admin admin No Comments

Factors Influencing Rotary Shaft Seal Performance: Pressure, Velocity, and Temperature


There are various factors that have a significant impact on the performance and behavior of a rotary shaft seal, including operating conditions (speed, pressure, temperature, environment), the mating shaft (hardness, surface finish, lead), and the choice of material for the seal itself.

In this blog post, we are going to review the operating conditions that must be considered for a successful rotary shaft seal.

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