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What’s the Difference Between Molded and Skived PTFE Sheets?

Polytetrafluoroethylene (PTFE) is a versatile material that has gained popularity in various industries due to its unique properties. PTFE sheets are widely used in gaskets, seals, and electrical insulation applications. The manufacturing process of PTFE sheets can be either molded or skived, each with its advantages and disadvantages.

skived ptfe sheets

Molded PTFE Sheets

Molded PTFE sheets are produced by compressing fine powder of PTFE resin at high pressures and temperatures. This process creates a solid sheet with uniform thickness and density. The molded sheets have a smooth surface finish and excellent mechanical properties. They exhibit low friction characteristics, high chemical resistance, and excellent electrical insulation properties.

One of the significant advantages of molded PTFE sheets is their superior strength. Due to the compression process, the molecules in the resin align themselves in a uniform pattern, resulting in increased tensile strength and improved dimensional stability. This makes them suitable for applications where high mechanical stress is expected.

Another advantage of molded PTFE sheets is their high purity level. During molding, any impurities present in the raw material are eliminated through filtration techniques. This ensures that the final product is free from contaminants affecting its performance.

However, there are certain limitations associated with molded PTFE sheets as well. One limitation is their limited size availability compared to skived sheets. Due to manufacturing constraints, it can be challenging to produce large-sized molded sheets without compromising quality.

Skived PTFE Sheets

Skived PTFE sheets are produced by slicing or cutting thin layers from larger blocks of compressed resin using specialized skiving machines. This results in thinner but wider sheets compared to molded ones.

One significant advantage of skived PTFE sheets is their flexibility and conformability properties.

Skiving allows precise control over sheet thickness variations across different sections or areas. This flexibility in thickness enables engineers and designers to tailor the sheet according to specific requirements, making it ideal for intricate applications where a customized fit is necessary.

Moreover, skived PTFE sheets have excellent surface smoothness and uniformity, which can be attributed to the slicing process. The smooth surface minimizes friction, making them useful in applications requiring a low coefficient of friction, such as bearings or sliding surfaces.

However, skived sheets do have some limitations as well. One limitation is their reduced tensile strength compared to molded sheets. The cutting process disrupts the molecular alignment of the resin, resulting in weaker mechanical properties overall. Thus, they may not be suitable for applications with high mechanical stress or load-bearing requirements.

Another limitation of skived PTFE sheets is their potential for surface imperfections due to the slicing process. Although efforts are made to ensure a smooth finish during manufacturing, certain defects like micro-tears or uneven edges may occur. These imperfections can affect the performance and integrity of the sheet in specific applications.

Choosing between Molded and Skived PTFE Sheets

Several factors need consideration depending on the application requirements when selecting between molded and skived PTFE sheets. Molded sheets are preferred due to their superior strength properties for applications demanding high tensile strength and dimensional stability under mechanical stress or load-bearing situations.

On the other hand, applications that require precise thickness control or customized fitting benefit from skived sheets due to their flexibility and conformability properties.

The choice may also depend on size availability, as larger molded sheets may not always be feasible for specific applications.

In conclusion, molded and skived PTFE sheets offer unique advantages depending on specific application needs. Molded sheets provide superior strength while maintaining excellent chemical resistance, electrical insulation capabilities, and a smooth finish.

Skived sheets offer flexibility, precise thickness control, and conformability for intricate applications. It is crucial to carefully evaluate the requirements of the intended application to decide which type of PTFE sheet is most suitable.

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Unveiling the Versatile Power of PTFE Expansion Bellows in Technology

In the vast realm of technology, numerous components are crucial in ensuring seamless functionality and efficiency. The PTFE expansion bellows is one such component that often goes unnoticed but is integral to various applications. These versatile devices serve many purposes, primarily to separate fluids from nearby branches. From pulse dampers to HVAC systems, pharmaceutical processing to pollution control, piping systems, and much more – PTFE expansion bellows have become an indispensable part of modern technological advancements.

Understanding PTFE Expansion Bellows

Polytetrafluoroethylene (PTFE), commonly known as Teflon, has become the go-to material for expansion bellows applications. This remarkable material possesses unique properties that make it highly suitable for various technological needs.

The Functionality of PTFE Expansion Bellows

At its core, an expansion bellow is a flexible connector between two pipes or vessels, accommodating movement caused by thermal expansion or contraction. The primary function of a typical PTFE expansion bellow is effectively isolating fluid flow from adjacent components. These bellows ensure smooth operations and prevent potential damage by providing flexibility and absorbing movements caused by temperature variations or vibrations in machinery.

Versatility across Industries

The adaptability and versatility offered by PTFE expansion bellows have made them indispensable across various industries. Let’s delve into some key sectors where their usage has revolutionized technological processes:

  1. Pulse Dampeners: In industries where pulsating flows occur regularly, such as chemical processing plants or oil refineries, pulse dampeners are crucial in reducing pressure fluctuations within pipelines. The high chemical resistance PTFE offers makes it an ideal choice for constructing these dampeners.
  2. HVAC Systems: Heating Ventilation Air Conditioning (HVAC) systems rely on PTFE expansion bellow’s to accommodate thermal expansions and contractions without causing structural damage. These bellows ensure the seamless flow of air and prevent leaks or blockages.
  3. Pharmaceutical Processing: The pharmaceutical industry demands strict adherence to hygienic standards, making PTFE bellows an ideal choice for processing applications. These bellows maintain the desired level of cleanliness while accommodating movements caused by temperature changes during various stages of pharmaceutical production.
  4. Pollution Control: Environmental regulations necessitate efficient pollution control systems in industries emitting harmful gases or substances. PTFE expansion bellows play a vital role in these systems by isolating gases, preventing leaks, and absorbing vibrations that can compromise efficiency.
  5. Piping Systems: In intricate piping networks with multiple connections, using PTFE expansion bellows becomes crucial to absorb movements resulting from thermal fluctuations or vibrations caused by machinery operations. This ensures longevity and reliability while minimizing maintenance requirements.

Advantages of Using PTFE Expansion Bellows

The utilization of PTFE bellows offers numerous advantages over traditional alternatives:

  1. 1. Chemical Resistance: The chemical inertness possessed by PTFE makes it highly resistant to various corrosive substances found in industrial environments, ensuring longevity and durability even when exposed to harsh conditions.
  2. Temperature Resistance: With an exceptional operating temperature range (-200°C to +260°C), PTFE can withstand extreme heat or cold without compromising its structural integrity or functionality.
  3. Flexibility and Absorption Capabilities: The unique composition and design allow these bellows to accommodate axial (lengthwise) and lateral (sideways) movements caused by thermal expansions/contractions or external vibrations, thereby preventing stress build-up within the system.
  4. Low Friction Coefficient: Due to its low friction coefficient, Teflon minimizes pipeline resistance, reducing energy consumption while promoting efficient fluid flow.
  5. Hygienic Properties: PTFE is inherently non-toxic, non-reactive, and resistant to microbial growth, making it an ideal choice for applications in the pharmaceutical and food processing industries where hygiene is paramount.

In conclusion, the versatility and functionality offered by the PTFE expansion bellows have revolutionized various sectors within the technology realm. From pulse dampeners to HVAC systems, pharmaceutical processing to pollution control systems, and complex piping networks – these bellows have become indispensable component ensuring seamless operations while preventing potential damage or leaks. With their exceptional chemical resistance, temperature tolerance, flexibility, low friction coefficient, and hygienic properties – PTFE expansion bellows continue to pave the way for technological advancements across multiple industries. As technology progresses further into uncharted territories, it is sure that these remarkable devices will continue to play a vital role in shaping our future.

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Understanding the Different Types of Composite Bushings in Technology

In the world of technology, composite bushings play a crucial role in various applications. These bushings reduce friction and lubricate mechanical systems, ensuring smooth and efficient operation. However, “composite bushing” can be ambiguous as different manufacturers may use different product materials and designs. This article will explore the composite bushings commonly found in technology applications.

composite bushings

Composite Bushing Design 1: Steel Backed with Sintered Bronze Layer and Polymer Lining

One popular design for composite bushings involves combining a steel backing with a sintered bronze layer covered by a polymer lining such as polytetrafluoroethylene (PTFE). This design offers excellent load-bearing capabilities due to the steel backing while benefiting from the self-lubricating properties of PTFE.

The steel backing provides strength and structural support to withstand high loads and shock forces experienced during operation. It also acts as a solid foundation for the sintered bronze layer, which increases wear resistance and enhances load distribution across the surface area.

The sintered bronze layer compresses powdered bronze particles under high pressure and temperature. This process creates tiny interconnected pores that retain lubricants such as oil or grease, allowing continuous lubrication even under extreme conditions.

A polymer lining like PTFE is applied over the sintered bronze layer to optimize performance further. PTFE offers exceptional low-friction properties resulting in reduced wear on both mating surfaces. It also provides excellent chemical resistance against corrosive fluids or gases commonly encountered in technology applications.

Composite Bushing Design 2: Polymer Resin with Glass Fibers Filament Wound and PTFE Lining

 Another common type of composite bushing utilizes a combination of polymer resin reinforced with glass fibers that are filament wound followed by applying a PTFE lining. This design offers excellent mechanical strength, high wear resistance, and low friction characteristics.

The polymer resin acts as the primary load-bearing material in this design. It is chosen for its ability to withstand high loads while providing flexibility to absorb vibrations and shocks during operation. The resin is typically reinforced with glass fibers to enhance its mechanical properties further.

Glass fibers are known for their exceptional tensile strength and stiffness, making them ideal reinforcements for composite materials. These fibers are arranged in a specific pattern using filament winding techniques, creating a robust and durable structure that can withstand heavy loads without deformation.

A PTFE lining is applied over the filament wound composite structure to reduce friction and provide lubrication. PTFE’s self-lubricating properties ensure smooth operation by minimizing wear between moving parts. Additionally, it offers excellent thermal stability and chemical resistance, making it suitable for various technology applications subjected to harsh environments.

Applications of Composite Bushings

Composite bushings find wide-ranging applications in technology due to their unique properties. Some common examples include:

  1. Automotive Industry: Composite bushings are used in suspension systems, steering columns, engine components like connecting rods or camshafts, and gearbox assemblies.
  2. Aerospace Industry: Composite bushings are utilized in landing gear systems, control surfaces like flaps or rudders, engine mounts, actuator mechanisms, etc., where lightweight yet robust components are required.
  3. Industrial Machinery: Composite bushings find application in heavy machinery such as conveyor systems or hydraulic cylinders where high load capacity and reduced maintenance requirements are desired.
  4. Medical Equipment: Medical devices like surgical instruments or prosthetic limbs require smooth movement with minimal wear on joints or pivot points.

Benefits of Using Composite Bushings

The utilization of composite bushings offers several advantages over traditional bearing materials:

  1. Self-Lubricating Properties: Composite bushings eliminate the need for additional lubrication systems, reducing maintenance requirements and associated costs.
  2. Low Friction: The low-friction characteristics of composite bushings reduce wear on mating surfaces, resulting in extended service life and improved efficiency.
  3. Resistance to Corrosion: Composite bushings can withstand exposure to harsh chemicals or corrosive environments without degradation, making them suitable for various applications.
  4. High Load Capacity: Combining different materials in composite bushing designs provides excellent load-bearing capabilities, ensuring reliable operation even under heavy loads.

Composite bushings are essential in technology applications by providing friction reduction and lubrication properties. Manufacturers offer various designs based on the materials used, such as steel-backed with a sintered bronze layer and polymer lining or polymer resin reinforced with glass fibers filament wound and PTFE lining. Understanding the different types of composite bushings allows engineers to select the most suitable option for their specific application requirements. Whether it’s automotive suspension systems, aerospace components, industrial machinery, or medical equipment, the benefits offered by composite bushings make them an integral part of modern technological advancements.

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Selecting the Right Seals for Cold Temperature and Cryogenic Valves

Cold temperatures can cause materials to become brittle and lose elasticity, leading to seal failure. Additionally, thermal expansion and contraction can cause seals to break down over time. For these reasons, selecting the proper seals for cold temperature and cryogenic valves is crucial.

cryogenic valves

When selecting seals for cold temperature applications, it’s essential to consider the following factors:

  • Temperature range: The seal must withstand the extreme temperatures of cryogenic fluids.
  • Pressure range: The seal must withstand the pressure of the processed fluid.
  • Chemical compatibility: The seal material must be compatible with the processed fluid.
  • Wear resistance: The seal must withstand repeated valve cycling without breaking down.

 Factors to Consider When Selecting Cold Temperature Seals

When selecting the proper seal for your cold temperature application, there are several factors you need to consider:

Temperature Range

The first factor to consider is the temperature range your application will require. Cryogenic seals operate in temperatures ranging from -460°F (-273°C); you’ll want to choose a material specifically designed for these conditions. 

Pressure Range

You’ll also need to consider the pressure range your application will be operating under, as this will affect which type of seal you’ll need to use.

Chemical Compatibility

Another essential factor to consider is chemical compatibility with the fluid or gas your cryogenic valves system processes. Not all materials perform well with every substance they encounter over time.

Wear Resistance

Finally, wear resistance is an important consideration when selecting seal materials since repeated valve cycling and exposure to pressure can cause wear over time, eventually leading to breakdowns if not properly addressed beforehand.

Types of Cryogenic Valves Seals for Cold Temperature Applications

PTFE (Polytetrafluoroethylene), FEP (Fluorinated Ethylene Propylene), and UHMW (Ultra High Molecular Weight PE) are popular choices due to its exceptional chemical resistance and low coefficient of friction. It also has excellent thermal stability and can withstand temperatures as low as -460°F (-273°C). 

Another critical aspect of designing polymer seals for cryogenic applications is the seal geometry. The seal design must provide sufficient compression force to ensure proper sealing while compensating for any dimensional changes caused by temperature fluctuations or external forces. A common approach in these applications involves creating a labyrinth seal design where multiple grooves in the seal face interlock with corresponding ridges on the mating surface, creating various barriers between gasses while allowing relative movement between two mating surfaces.

Cryogenic valves’ sealing surfaces should be smooth and free of surface defects, as imperfections can compromise sealing integrity. Surface roughness is measured in Ra (arithmetic average deviation) or Rz (average peak to valley height). A typical Ra/Rz value for cryogenic seals should be less than 20/100 micro inch respectively.

Cryogenic applications often involve extreme pressure differentials, making it essential to select a polymer seal material that can handle high-pressure environments without extruding or deforming under load. In some cases, this requires designing the seal with an additional support element, such as a metal spring or an energizing lip that helps maintain proper compression force over time.

Proper installation procedures must be followed to ensure optimal performance and longevity of cryogenic seals, which includes ensuring that all mating surfaces are clean and free from debris or other contaminants that could compromise sealing integrity. The assembly process must also account for thermal expansion, which can cause dimensional changes in both components leading to reduced compression forces if not accounted for during installation.

Selecting the correct seals for cold temperature and cryogenic valves requires careful consideration based on multiple factors, including temperature range, pressure range, chemical compatibility, and wear resistance, among others discussed above. Choosing the proper seal can ensure that your valve system will function optimally and prevent leakages, which could be catastrophic in many processing applications. Be sure to work with a trusted supplier who can help you choose the proper seal for your needs and provide expert advice on installation and maintenance.

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Advanced Properties and Applications of PTFE in Sealing Technology

PTFE has a unique combination of properties that make it ideal for use in sealing technology. One of its most notable characteristics is its ability to withstand extremely high and low temperatures. PTFE can operate in temperatures ranging from as low as -200°C to as high as 260°C, making it an excellent choice for applications where sealing performance needs to be maintained at extreme temperatures.

PTFE

Another significant advantage of PTFE is its chemical resistance. It is highly resistant to various chemicals, including acids, alkalis, and organic solvents. This makes it an excellent choice for use in chemical processing plants or other facilities where exposure to harsh chemicals is common.

PTFE also has excellent non-stick properties, which make it ideal for use in applications where adhesion could compromise the effectiveness of the seal. Its low coefficient of friction means that even under heavy loads or with repeated cycles of movement, PTFE will not experience significant wear or degradation.

In addition to these properties, it has outstanding electrical insulation characteristics and acts as a barrier against moisture and dust.

Manufacturing PFE Gaskets

Pure PTFE gaskets are produced by molding directly from suspended material or cutting (turning) from PTFE sheets (rods). Molding plates have uneven density and poor flexibility while turning plates have a relatively uniform density. Still, their material is curved due to the influence of the processing technology, which is not conducive to installation and use.

Modified PTFE gaskets add a certain proportion of functional materials, such as glass fiber or graphite powder, during production. The resulting gasket provides improved strength and durability compared with pure PTFE gaskets while maintaining this advanced material’s desirable properties.

Despite its many advantages, however, some limitations are associated with using PTFE in sealing applications. For example:

  • It can be difficult to achieve consistent compression when using pure PTFE gaskets due to their poor flexibility
  • PTFE can be prone to creep under sustained pressure, which can result in a loss of sealing performance over time
  • PTFE is unsuitable for high-pressure applications as it has low tensile strength and may deform or fail under high loads.

Applications for PTFE 

Despite these limitations, PTFE remains one of the most advanced materials available in sealing technology. Its unique combination of properties makes it ideal for use in various applications where reliable sealing is essential.

One potential application area where PTFE could increase use is the automotive industry. As electric vehicles become more prevalent, there will be an increased demand for seals that withstand harsh operating conditions. Its excellent temperature resistance, chemical resistance, and non-stick properties make it an ideal choice for use in battery enclosures and other critical components.

Another potential application area is within the food processing industry. Many food products are highly acidic or alkaline, which can cause traditional seals to degrade over time. PTFE’s chemical resistance makes it an excellent choice for acidic or alkaline foods. At the same time, its non-stick properties mean that any residue left on the seal after cleaning can easily be removed.

In conclusion, Polytetrafluoroethylene (PTFE) has many advanced properties that make it ideal for use in sealing technology. Its ability to withstand extreme temperatures while maintaining effective sealing performance sets it apart from other materials commonly used in this field. While some limitations are associated with using the material in certain applications, such as those involving high-pressure loads, its unique combination of properties means it remains one of the most important materials currently available. Over time, we may see even greater advances made with this remarkable material with continued research and development into new formulations and manufacturing techniques.

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Exploring the Benefits of Fluorolon PTFE in Industrial and Engineering Applications


Fluorolon PTFE (Polytetrafluoroethylene) is a unique synthetic polymer with many benefits for industrial and engineering applications. This versatile material can be used for a wide range of purposes, from chemical processing to cookware. In this article, we will explore some of the key benefits and uses of Fluorolon PTFE.

FEP encapsulated helical spring seals are approved for cryogenic and FDA use. Fluorolon PTFE

Chemical Resistance


One major benefit of using Fluorolon PTFE is its excellent chemical resistance properties. This material is highly resistant to acids, bases, solvents, and other corrosive substances. This makes it an ideal choice for use in applications such as chemical processing plants or food processing industries where harsh chemicals are often used. It can also be used as a protective coating on metal surfaces to protect them from corrosion or damage from exposure to corrosive materials.

High-Temperature Resistance


Another benefit associated with Fluorolon PTFE is its high-temperature resistance properties. This material can withstand temperatures up to 260°C (500°F) without losing its strength or shape – making it an excellent choice for use in insulation, gaskets, seals, and other high-temperature applications such as aerospace parts or engine components that require superior heat resistance capabilities. The thermal stability offered by this polymer also ensures that parts maintain their original dimensions even under extreme conditions making them ideal for precise manufacturing processes where dimensional accuracy is critical.

Low Friction Properties


Fluorolon PTFE also offers exceptionally low friction properties, making it suitable for use in various mechanical components such as bearings and slides where minimal friction between moving surfaces is desired. Its low coefficient of friction helps reduce wear on machinery parts resulting in increased operational life spans while simultaneously providing smoother operation with less vibration compared with traditional materials like steel or bronze alloys. Furthermore, since no lubricants are required, energy consumption costs due to frequent maintenance procedures associated with lubrication are significantly reduced compared to traditional metals.

Non-Stick Properties


In addition, Fluorolon PTFE has impressive non-stick properties, making it ideal for use in cookware, baking sheets, conveyor belts, and other industrial equipment. Its non-stick characteristics enable food products like cakes, cookies, etc., to slide easily off surfaces resulting in efficient production processes while maintaining product quality standards at the same time. Furthermore, these non-stick characteristics help reduce clean-up times after the production process, thereby saving both time & money.

Electrical Insulation Properties

Last but not least, one important benefit this polymer provides includes its electrical insulation capabilities making it perfect for use within high-voltage industrial equipment & electronic components alike. Its ability to prevent electricity from leaking out allows companies within the electronics industry to create safer products without having to worry about hazardous shocks occurring during usage, thus ensuring customer safety at all times, leading to higher customer satisfaction & loyalty levels over time.

At Advanced EMC Technologies we use Flourolon Virging PTFE primarily for seals, seats, bearings, and insulaotrs. All our Flourolon PTFE is FDA and dairy approved. We offfer both Virgin PTFE ASTM-D4894 and filled PTFE ASTM D4745-06.

PropertySpecifiedUnitsMethod
Specified Gravity (FEP) Only2.14 –2.19gr/ccASTM D792
Maximum Recommended  Stretch2 %N/AASTM D638
ES Seals Are For Type ServiceStatic N/A–
Coefficient of Friction (FEP)0.19StaticASTM D3702
Dielectric Constant (FEP)N/AN/AASTM D150
Dielectric Strength (FEP)N/AN/AASTM D257
Thermal Expansion No Spring8.3 x 10^5thin/in/°FASTM D696
Compressive StrengthN/AN/AASTM D695-57
FEP Seal Temperature Range-420 to 428°F–
PFA Seal Temperature Range-420 to 500°F–

To summarize, the many benefits associated with using Fluorolan PTE should not be overlooked, especially when considering various industrial & engineering-related applications that call out these specific attributes offered by this synthetic polymer beyond any other commonly available alternatives currently present in the market today. Its ability to resist chemicals and withstand higher temperatures than most polymers without losing shape/strength, alongside offering superior low friction/non-stick qualities coupled with excellent electrical insulation capabilities, clearly demonstrates why so many industries opt to choose Fluorolon PTFE over any other material available.

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The Effect Surface Finish Has on PTFE Seals

Surface finish plays an essential role in the effectiveness of PTFE seals. The different finishes provide different degrees of contact between the two components, which affects the seal’s strength and reliability. In this paper, we will discuss the effect of surface finish on PTFE seal performance and suggest ways to improve seal quality.

Surface finish on PTFE

The Influences of Surface Finish on Friction

The surface finish is critical for polymer-based seals. Despite being considered a soft plastic, PTFE is significantly harder than traditional o-ring materials. Because of this, if the mating surface is designed for other materials, it can cause the PTFE seals to leak.

As you can see in the graph below, the improvement in the surface finish has a favorable effect on the frictional force required.

The following specifications were used in the force test that resulted in the above data.

  • Stroke Speed: 4 in/min (102 mm/min)
  • Shaft Diameter: 0.1875in. (4.762mm)
  • Ambient Temperature: 73°F (23°C)
  • Mating Surface Material: 17 -4 PH S.S.
  • Mating Surface Hardness: -40 Rc

Surface Finish Influences on Wear

The finish of the mating surface is one of the main factors in the PTFE seal wear. Wear on the seal is generally proportional to frictional force. In other words, less friction reduces the wear on the seal. 

The following graph shows how a smoother surface finish reduces the PTFE seal wear rate.

To calculate the wear rate in microinches RMS, we used the formula IN3 -MIN/LB-FT-HR -10-9. For microinches Ra, we used the formula CM3 -MIN/KG-M-HR -10-9.

We used the following test parameters during our testing to ensure accuracy for each test.

  • Surface Speed: 55 fpm (17 m/min)
  • Loading Stress: 55 lb./in2 (4 bar)
  • Wear Rate in Air: @ PV 3025 lb./in2 x ft/min (7.5 N/mm x m/min)
  • Mating Surface Hardness: Rc 42
  • Matin Surface Maerial 17 -4 PH Stainless steal
  • Mating Surface Finish: 1.6 to 111.1 microinches RMS (1.4 to 100 microinches RA)
  • Ambient Temperature: 70°F (21°C)
  • Ambient Relative Humidity 75% RH
  • Duration 5 Hours
  • Seal material FP

Influences on Sealing Ability

Finally, we looked at how the surface finish affected PTFE’s sealing ability. In general, the sealing ability of PTFE is proportional to the fluid’s viscosity. If a media, like gas, has a reduced viscosity, it is more difficult to seal. In these situations, having a smoother finish on the mating surface can help ensure fewer leaks.

We’ve found that different mediums require not only different finish ranges between them but also different finish ranges when considering if the surface is dynamic or static. You can see our suggested finish in the table below.

MediaDynamic Surface Static Surface 
Gases and Liquids at Cryogenic Temperatures2 to 4 microinches RMS
(1.8 to 3.6 Microinches Ra)		4 to 8 Microinches RMS
(3.6 to 7.2 Microinches Ra)
Gas at Non-Cryogenic Temperatures6 to 12 Microinches RMS
(5.4 to 10.8 Microinches Ra)		12 to 32 Microinches RMS
(10.8 to 28.8 Microinches Ra)
Liquids8 to 16 Microinches RMS
(7.2 to 14.4 Microinches Ra)		16 to 32 Microinches RMS
(14.4 to 28.8 Microinches Ra)

As you can see, the mating surface finishes can profoundly affect PTFE seals. Because of this, if the mating surface is designed for other materials, it can cause the PTFE seals to leak. Finally, we examined how this affected PTFE’s sealing ability. In general, the sealing ability of PTFE is proportional to the fluid’s viscosity. 

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Introduction to PTFE Lip Seals

PFTE Lip seals

Radial shaft seals are often found in aggressive environments with high temperatures and pressures. Unfortunately, these environments are also frequently dry-running and unsuitable for traditional radial shaft seals. So, what are the options if traditional radial shaft seals won’t work? Using PTFE lip seals as rotary shaft seals can offer better protection and longer life than conventional radial shaft seals. Understanding these lip seals are essential to helping you make the right choice for your sealing needs.

What Are PTFE Lip Seals

PTFE (polytetrafluoroethylene) lip seals have a lip on the interior diameter (ID) that allows it to fasten to an outer diameter (OD) of a metal casing or shaft. The seal is completed with a gasket sandwiched between the sealing lips.

Not all lip seals are spring-energized. Therefore, the force from radial contact is lower. The lower pressure allows the seal to function at higher surface speeds of up to 10,000 sfpm. This type of seal is for high rates, making it the go-to choice for sealing rotating shafts.

PTFE Lip Seal Fillers

PTFE Lip seals can be enhanced by using fillers instead of virgin PTFE. Fillers can help the seal withstand sintering temperatures. Some of the filled compounds include:

  • Carbon-Graphite
  • Carbon Fiber
  • Aromatic Polyester
  • Molybdenum Disulfide and Fiberglass
  • Fiberglass
  • Graphite
  • Mineral
  • Stainless Steel

Each filler offers higher temperature resistance and lower creep rates than virgin PTFE. In addition, some offer lower abrasion or better corrosive protection depending on the filler type. Which type of filler you want will rely on the application where you use the lip seals. 

Applications That Use PTFE Lip Seals

PTFE lip seals are found in most applications where speed is concerned. However, they also are ideal for conditions where highly corrosive compounds or in dry, abrasive environments. 

Aerospace

The aerospace industry needs seals that can cope with extreme temperatures, surface velocities, and high pressures. External gearbox seals are just one place where PTFE lip seals are used in the aerospace industry.

Lip seals can handle the extremes and offer advanced fuel consumption efficiency. Better efficiency of burning about half-gallon of fuel per mile can save airlines an operating cost of $1.7 million per year. 

Other instances in which the aerospace industry uses lip seals include military applications such as:

  • Lift fans for vertical lift
  • Wing flap and slats actuator seals
  • Rotorhead
  • Equipment in arresting system to catch aircraft as it lands on aircraft carrier decks

Automotive

In the automotive industry, PTFE lip seals are employed in the drive shafts of the top-fuel blowers in NASCAR engines. Traditional crankshaft seals were burning out in these engines due to the high speeds and rapid pressure increases within five minutes at racing speeds.

They are also in e-drive and cooling systems in electric vehicles. Lip seals in electric cars can handle the shaft speeds seen in these automobiles. Electric vehicles can run at over 18,000 RPM, a higher rate than gas-powered cars. 

Conclusion

PTFE lip seals are ideal for rotary shafts operating at high speeds and temperatures, such as in the automotive or aerospace industries. Choosing suitable fillers can also help extend the seal’s life. Contact us today, and we can help you determine which PTFE lip seal options you want.

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5 Common reasons of Valve Seat Failure

valve seat failure

 

Valve seat failure can lead to costly and time-consuming issues. Under certain circumstances, a ball valve seat failure can cause explosions and lead to life-threatening situations. In this article, we will cover the top five causes of failure.

Material Choice

The material choice of the valve seat can contribute to valve seat problems if you pick the wrong option. Different materials work in different operating conditions, so you want to ensure that you research the material carefully before choosing.

The most common material options are 

  • PEEK
  • PTFE
  • TFM
  • PCTFE
  • Acetal
  • Vespel

The wrong material can cause unexpected issues that may damage the hardware of mating components or even physical injury.

Cold Flow

While PTFE, or Teflon, is a common material in valve seats, there could be some cold flow resistance issues. Cold flow is the process when solid material slowly deforms under the influence of long-term mechanical stress.

The cold flow of material during us and cycling causes a slow deterioration in valve performance. Despite cold flow issues, PTFE is still the best choice in many industries. Choose a filled PTFE instead of virgin PTFE to mitigate complications from cold flow. Filled is less susceptible to stress and has better resistance to cold flow.

Excessive Friction

Excessive friction can also cause valve seat issues. Excessive circumferential seal force accelerates wear on the valve, which leads to an increase in torque requirements. The friction between the ball and the valve seat affects how much torque is necessary to turn the ball valve. 

 When the temperature in the valve increases, the pressure between the valve seat and the ball increases. Increased temperature creates greater friction between the valve ball and the seat. 

Eventually, the valve can become locked either open or closed. As the required torque increases, the valve seat is torn apart, and mechanical failure occurs.

Valve Seat Failure: Seat and Seat Carrier Design

The valve seat is one of the most critical components. However, poor seat design can lead to a shortened lifespan, leakage, or catastrophic failure. The catastrophic failure could lead to explosions or life-threatening damage in particular environments.

Soft seat valves typically use metallic seat carriers with the valve seats pressed into them. As with the seat design, the seat carrier design can have similar problems. If the seat carrier design is slightly off, it could make it difficult to determine where the problem lies.

Permanent Deformation

In high-pressure applications, the valve setting of soft seats is necessary. To correctly set soft seals, the valve is repeatedly actuated during part of the build process. This repeated actuation can cause permanent deformation during normal use.

A failure to understand the initial deformation will cause the valve to fail. It won’t fail on initial use, but it will eventually stop working, and the valve will either need to be rebuilt or replaced as a result.

Valve Seat Failure Conclusion

Whether your valve requires PTFE, PEEK, or any other material, you want to ensure you get the appropriate material for your valve seat. Incorrect materials and excessive friction, seat design malfunctions, and permanent deformations can cause failures. 

Contact us today to learn more about the valve seats we offer and assist you in finding the appropriate material for your applications.

 

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Molded PTFE Billets: An Overview

Molded PTFE Billet

Teflon (PTFE) billets are compression molded tubes and rods made of Polytetrafluorethylene used in numerous industrial applications covering almost every industry, including chemical processing, automotive, food, aerospace,  medical device, semiconductor, and fluid handling. These functional parts are popular due to Teflon’s chemical resistance, extreme temperatures, low friction properties, and ability to mold them into the precise shape and size needed.

Types of Molded  PTFE Billets

The molded processing techniques we employ are compression, isostatic, and automatic. The determination of which method to use will depend on the type and size of billets being produced, the industry they are being used in, and the manufacturer’s preference.  

Compression

Compression molding for PTFE  billets is one of the three main processes, with isostatic and automatic as the other options (we will discuss these in a later article). To make a billet using this process, one must design and create the source mold for the rod or tube. The compression mold is a two-part mold that includes a preform component.

The performance has the same shape as the tube or rod being processed.  The material is loaded into the mold, pressed under specific pressure and time depending on the grade of PTFE being processed, and then ejected for the mold. 

The pressure causes the material inside the preform to conform to the mold’s shape. As a result, any excess material leaks out of the mold. Once the molding process is complete, the billet is ejected from the mold.

Once the billet is extracted from the mold, it is now in what is called the “Green State,” compact into the desired shape, but no molecular change has occurred; this only happens after sintering in our ovens for a designated time between 650 to 715 degrees F. 

The billet is left to cool at room temperature. Once cooled, excess material can be machined off to make a smooth, perfectly formed Teflon billet. 

Advantages of using compression molding include:

  • Strong parts
  • Lower tooling costs
  • Broad design options
  • Lower waste generation
  • Large part manufacturing

Sintering Molded Tubes, Rods, or Semi-Finished Parts.

Sintering results in a change in the PTFE powder that reorganizes the molecules into a compound. To sinter Teflon billets:

PTFE Powder

 

  • Temperatures must be between 675°F and 700 °F (357°C and 371°C).
  • The oven must have good airflow.

  • Billets must be supported to ensure that they do not sag

Adding an annealing cycle during the sintering processes will help to stop cracks from forming while the compound bakes. Once the billets are out of the oven and cooled to room temperature, they can be machined.

Molding Process

While all molds have physical property variations, the overall process is similar. Therefore, the variations between compression, isostatic, and automatic molded billets are inconsequential to the prevalent use. 

The molding process is two-step. It begins with packing the mold and pressing the powder,  called the “green state.” Next, the mold is placed under specified pressures depending on whether the material is unfilled (Virgin) or filled with various fillers, glass, carbon, graphite, etc. pressure of up to i.

After pressing, the item is removed from the mold. Workers must be careful during the ejecting of the tube or rod. Mishandling of the green material could result in cracks. Once the mold is removed, the billet is sintered.

conclusion

Molded PTFE billets are ideal for many industries. The properties of PTFE make them chemical resistant, have a low coefficient of friction, and can be manufactured compliant with FDA, Class VI Medical, NACE, Aerospace, and Semiconductor  Standards approved for use in medical and food industries. In addition, clean Room Molding for Ultra Pure applications is available.