As manufacturers of PTFE tape, we are frequently sent enquiries for the same. It usually baffles the client to know what the term “PTFE Tape” is not specific enough for us to know exactly what they need. As a versatile polymer, PTFE is also unique in that different processing methods can result in different tapes – each with its own unique properties and end applications.

Here we take a look at the four most common variants – Thread Seal Tapes, Expanded PTFE (ePTFE) Gasket Tapes, Skived Sintered PTFE Tapes, and Tensilized PTFE Tapes.

PTFE Thread Seal Tape

PTFE Thread Seal Tape is usually referred to simply as “Teflon tape”. It is a common product and is used primarily for sealing pipe threads. This tape – also called Plumber’s Tape - is made from extruding and calendaring PTFE resin. The process is rather simple and as a result the tape has become fairly commoditized and is relatively cheap. However, the tape does exhibit excellent resistance to chemicals, heat, and has non-stick properties.

Properties:

• Chemical Resistance: PTFE Thread Seal Tape is resistant to most chemicals, making it suitable for a wide range of applications involving corrosive substances.

• Temperature Resistance: It can withstand temperatures ranging from -450°F to 500°F (-268°C to 260°C), making it ideal for both high and low-temperature environments.

• Lubricity: The tape’s low friction surface allows for easy assembly and disassembly of threaded connections.

• Non-reactive: It does not react with most substances, ensuring long-term stability and reliability.

Applications:

• Plumbing: Widely used in residential and commercial plumbing to seal pipe threads, preventing leaks.

• Gas Lines: Suitable for sealing connections in gas pipelines due to its chemical resistance.

• Automotive: Used in various automotive applications to ensure leak-proof seals in fluid systems.

• Industrial Machinery: Employed in machinery where chemical resistance and high-temperature tolerance are critical.

ePTFE (Expanded PTFE) Gasket Tape

ePTFE Gasket Tape is also called Joint Sealant Tape. Like thread seal tape, it is made by extrusion. However, it is then subjected to an expansion process under heat, giving it a soft, marshmallow-like feel. The texture is unique in that it is porous to gasses and vapour, but not to liquids (a property that allows these tapes to be further processed into membranes). However, with a compressibility of up to 60%, thick ePTFE tapes are specifically designed for use as a gasket material. The soft, conformable property allows the tape to fill irregularities in flange surfaces, providing a reliable seal.

Properties:

• Flexibility: ePTFE Gasket Tape is highly flexible and can conform to uneven surfaces, ensuring a tight seal.

• Chemical Inertness: Like PTFE Thread Seal Tape, it is chemically inert and resistant to a broad range of chemicals.

• Compressibility: Its compressible nature allows it to create an effective seal under various pressure conditions.

• Temperature Resistance: It can operate in temperatures ranging from -450°F to 600°F (-268°C to 315°C), making it suitable for extreme environments.

Applications:

• Flange Sealing: Used in industries like chemical processing, food and beverage, and pharmaceuticals for sealing flanges.

• Heat Exchangers: Provides reliable seals in heat exchanger applications where temperature variations are common.

• Pipe Systems: Suitable for sealing pipe joints and systems carrying aggressive chemicals.

• Pump and Valve Packing: Employed in pumps and valves to prevent leakage and maintain system integrity.

PTFE Skived Tape

Unlike the above tapes – which are extruded - PTFE Skived Tape is manufactured by skiving thin layers from a solid PTFE block. It is a unique, “peeling” process that is peculiar to PTFE and can result in films as thin as 25 microns. This tape is known for its excellent dielectric properties, low friction, and high-temperature resistance. 

Properties:

• High Dielectric Strength: PTFE Skived Tape is an excellent electrical insulator, making it suitable for electrical applications.

• Low Friction: Its low coefficient of friction makes it ideal for applications where a smooth, non-stick surface is needed.

• Temperature Stability: It maintains its properties over a wide temperature range, from -328°F to 500°F (-200°C to 260°C).

• Chemical Resistance: Resistant to most chemicals, similar to other PTFE tapes.

Applications:

• Electrical Insulation: Used in wiring and cable applications for insulation due to its high dielectric strength.

• Release Surfaces: Ideal for lining chutes, hoppers, and other surfaces where a non-stick property is required.

• Bearings and Bushings: Used in mechanical applications to reduce friction and wear.

• Packaging Machinery: Employed in packaging machines to prevent sticking and ensure smooth operation.

Tensilized PTFE Tape

Tensilized PTFE Tape is a variant of tape that few have been able to successfully manufacture. The tape takes the base properties of skived PTFE tape and amplifies this manifold to give a film with higher tensile and dielectric properties. The 

Properties:

• High Tensile Strength: At least 3-4X the strength of regular PTFE Tapes

• Tear Resistance: Enhanced tear resistance compared to non-tensilized PTFE tapes.

• Chemical and Temperature Resistance: Maintains the excellent chemical resistance and temperature stability of PTFE.

• Dimensional Stability: Improved stability under mechanical stress.

Applications:

• Industrial Wrapping: Used for wrapping rollers, guides, and other components in industrial applications where high strength and chemical resistance are required.

• Sealing and Gasketing: Suitable for sealing and gasketing applications in harsh environments.

• Electrical Insulation: Employed in high-strength electrical insulation applications.

• Aerospace: Used in aerospace applications where both high strength and resistance to extreme conditions are essential.

Property/Application	PTFE Thread Seal Tape	ePTFE Gasket Tape	PTFE Skived Tape	Tensilized PTFE Tape
Chemical Resistance	Excellent	Excellent	Excellent	Excellent
Temperature Range (°C)	-268°C to 260°C	-268°C to 315°C	-200°C to 260°C	-200°C to 260°C
Tensile Strength (MPa)	5-10	5-15	20-40	90-120
Flexibility	High	Very High	Moderate	High
Compressibility	Low	High	Low	Moderate
Electrical Insulation	Low	High	High	Highest
Primary Applications	Sealing pipe threads	Gasketing	Electrical insulation, non-stick surfaces	Industrial wrapping, high-strength sealing

Conclusion

PTFE tapes offer a range of properties that make them suitable for various applications across different industries. PTFE Thread Seal Tape is ideal for sealing threaded connections in plumbing and gas systems. ePTFE Gasket Tape provides flexible, reliable sealing for flanges and irregular surfaces. PTFE Skived Tape offers excellent dielectric properties for electrical insulation and non-stick surfaces for mechanical applications. Tensilized PTFE Tape combines high tensile strength and chemical resistance, making it suitable for demanding industrial and aerospace applications.

Understanding the differences between these types of PTFE tapes allows engineers and technicians to select the right material for their specific needs, ensuring optimal performance and reliability in their applications.

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Among the varied high-performance attributes of PTFE, its electrical properties are probably the least understood. PTFE’s insulative properties make it useful in various applications, particularly in the electronics and electrical industries. However, the electrical properties of PTFE can vary based on the grade and type of resin used, the filler content, and the final part being produced.  

PTFE comes in many grades, each suited to a specific end shape. For example, granular moulding resins are used for basic compression moulding, whereas fine powder resins are used in the extrusion of PTFE tubes, profiles, and in making expanded PTFE tapes and sheets. Presintered resins are also used to make rods and high wall thickness tubes and pipes.

Further to the type of resin, the material itself can either be used in its virgin form or with fillers that may enhance or reduce the properties.

Virgin PTFE

Virgin PTFE, also known as unfilled PTFE, is the purest form of the polymer. It exhibits the highest electrical properties among PTFE grades due to the absence of fillers. This grade is often used in applications where high dielectric strength and low dissipation factor are crucial, such as in high-frequency cables, capacitors, and insulators.

Filled PTFE

Filled PTFE is modified with various fillers such as glass, carbon, graphite, and bronze to enhance its mechanical properties. While the addition of fillers can improve attributes like wear resistance and thermal conductivity, it generally impacts the electrical properties. For instance, glass-filled PTFE maintains good dielectric strength but may have a higher dissipation factor compared to virgin PTFE. Carbon-filled PTFE, on the other hand, exhibits lower dielectric strength due to the conductive nature of carbon and are used to make anti-static PTFE. Special fillers such as mica can help enhance dielectric properties but need to be used in the right concentrations.

Several PTFE products are commonly used in insulation applications and their properties need to be better understood.

Thickness (Microns)	Dielectric Strength (kV/mm)
15	115-230
25	89-180
50	63-130
75	52-100
100	45-90
150	37-70
200	32-60
300	26-50
500	20-40

1. Skived PTFE tapes – skived PTFE tapes, or films are usually made in thicknesses between 25 and 75 microns. Skiving is a process specific to PTFE and involves “peeling” a layer of PTFE in a controlled manner to produce a continuous length of tape with a specific thickness. For the best quality tapes, high-purity granular resins need to be used with a low particle size. The purity of the resin ensures a higher breakdown voltage, while the particle size allows for a very consistent film that will not have any pinholes.

   Sintered PTFE tapes – as they are often called – can be used in a range of applications including cable wrapping, as battery separators, and can be wrapped around high-intensity electrical points for insulation.

   At these low thicknesses, the breakdown voltage can be as high as 250kV/mm for films less than 15 microns. However, one cannot assume this would sustain as the material gets thicker. As the thickness increases to 100+ microns, there would be a reduction in the breakdown voltage, going to as low as 20kV/mm for lower grades and thicknesses in excess of 3mm.

   PTFE Tubes – both thin and thick-walled tubes are used in insulation. Thin-walled tubes would typically have wall thicknesses within 2mm, with thick-walled tubes having between 2 and 5mm.

   Both thin and thick-walled tubes can be made via paste extrusion, which employs the use of “fine powders”. These powders need to be mixed with a volatile extrusion aid in order to allow for extrusion. Thick-walled tubes can also be made via ram extrusion, wherein a ram repeatedly compresses charges of “presintered resin” to create a continuous tube or pipe.

2. Expanded PTFE – made using special “fine powders”, ePTFE is also extruded, but then undergoes a process wherein it is rapidly stretched at high temperatures. The resulting material has microporosity but is also an excellent insulator. Like skived films, it can be used to wrap cables and to act as an insulating medium in electrical systems.

Electrical Properties of PTFE

The key electrical properties of PTFE that are critical for its applications in the electrical and electronics industries include dielectric strength, dielectric constant, dissipation factor, and volume resistivity.

Because of the varied methods to make different end-products, standards exist to define the dielectric strengths accordingly. While ASTM D4894 covers the basic properties for granular resins, the following standards are a few that cover the more specific values expected:

ASTM Standard	Item Covered	Breakdown Voltage (kV/mm)	Remarks
D3293	PTFE Sheet	4-24	Value increases with grade purity
D3294	Basic PTFE Shapes	12-24	Value increases with grade purity
D3295	Thin-walled PTFE Tubes	35-55	Value reduces as wall-thickness increases
D3308	PTFE Skived Tape and Film	20-250	Value reduces as thickness increases
D1710	Thick-walled PTFE Tubes	10-30	Applies to tubes made using granular resins

Dielectric Strength

Dielectric strength is the maximum electric field that a material can withstand without breaking down. Virgin PTFE typically exhibits a high dielectric strength, often exceeding 30 kV/mm. However, as the table above shows, for skived PTFE films of extremely high purity, very thin films can easily exceed 200 kV/mm, if properly processed. The dielectric strength of filled PTFE varies depending on the type and concentration of fillers. For example, glass-filled PTFE may have slightly lower dielectric strength compared to virgin PTFE but still maintains good insulating properties. However, for the most part, ASTM standards do not have specific values for various fillers.

Dielectric Constant

The dielectric constant (relative permittivity) of PTFE is low, typically around 2.1. This property remains relatively stable across a wide range of frequencies and temperatures, making PTFE an excellent material for high-frequency and microwave applications. Filled PTFE grades may exhibit slightly higher dielectric constants, but the values generally remain low enough to be suitable for most electrical applications.

Dissipation Factor

The dissipation factor (loss tangent) of PTFE indicates the energy loss as heat in an insulating material when subjected to an alternating electric field. Virgin PTFE has an exceptionally low dissipation factor, typically in the range of 0.0002 to 0.0004, making it ideal for high-frequency applications where minimal signal loss is critical. Filled PTFE grades usually have higher dissipation factors due to the presence of fillers that can introduce additional energy losses.

Volume Resistivity

Volume resistivity is a measure of a material's resistance to electrical conduction through its volume. PTFE exhibits extremely high volume resistivity, often exceeding 10^18 ohm-cm. This property ensures excellent insulation and minimal leakage currents. Even filled PTFE grades retain relatively high volume resistivity, making them suitable for various electrical insulation applications.

Applications of PTFE Based on Electrical Properties

The unique combination of electrical properties in PTFE makes it an indispensable material in numerous applications:

• High-Frequency Cables and Connectors: Virgin PTFE's low dielectric constant and dissipation factor are crucial for maintaining signal integrity in high-frequency and microwave cables and connectors.

• Insulators and Capacitors: The high dielectric strength of PTFE ensures reliable performance in insulators and capacitors used in high-voltage and high-frequency applications.

• Printed Circuit Boards (PCBs): PTFE laminates are used in PCBs for high-frequency and microwave circuits due to their stable dielectric properties and low signal loss.

• Seals and Gaskets: ePTFE's combination of electrical insulation and mechanical flexibility makes it ideal for seals and gaskets in electrical and electronic equipment.

• Antennae and Radomes: PTFE's low dielectric constant and excellent weather resistance make it suitable for antennae and radomes, ensuring minimal signal distortion and protection against environmental factors.

Conclusion

PTFE's remarkable electrical properties, including high dielectric strength, low dielectric constant, low dissipation factor, and high-volume resistivity, make it a preferred material for a wide range of electrical and electronic applications. While the electrical properties can vary depending on the grade and type of resin used, PTFE remains an exceptional choice for applications demanding reliable insulation, minimal signal loss, and high-frequency performance. Understanding the nuances of different PTFE grades and resin types allows engineers and designers to select the optimal material for their specific needs, ensuring enhanced performance and longevity of electrical components and systems.

Finally, most applications that have electrical requirements would consequently need the PTFE being used to be tested. It is important to note that fillers can play an important role here, as they can improve the properties in some cases. However, the choice of filler and the concentration can only be arrived at by trial and error. Further, it is vital that the right material is tested. Testing a moulded sheet can produce a very different result when compared with testing an extruded tube. It would be wise to ensure that the grade, filler, and process are all being checked so that the end-product conforms to the requirements of the application.

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Among the various properties of PTFE, that of its chemical resistance is one that industries are increasingly leaning on for newer applications. PTFE is resistant to almost all known chemicals, with the exception of some alkali metals (molten or in solution) and rare fluorinated compounds at high temperatures and/or pressures. This uniqueness means that PTFE is one of the few materials that can be left inside the human body indefinitely with no adverse effects.

Polytetrafluoroethylene (PTFE) impellers have become an essential component in various industrial applications, especially in fluid dynamics, due to their unique properties and versatile applications. Known for their exceptional chemical resistance, non-stick surface, and durability, PTFE impellers offer significant advantages over traditional materials.

Why PTFE Impellers?

Impellers are rotating components designed to move fluids by mechanical means in pumps and other fluid-handling equipment. The choice of material for impellers is crucial, as they are often exposed to harsh conditions. PTFE impellers stand out due to several key characteristics:

• Chemical Resistance: PTFE is virtually inert to almost all chemicals, making PTFE impellers suitable for handling aggressive substances, including acids, bases, and solvents. This resistance ensures long-lasting performance and reduces the risk of corrosion.

• Non-Stick Properties: The non-stick nature of PTFE prevents the build-up of materials on the impeller surface. This is particularly beneficial in processes involving sticky or viscous fluids, as it minimizes maintenance and cleaning requirements.

• Thermal Stability: PTFE can withstand a wide temperature range, from -200°C to 260°C. This makes PTFE impellers ideal for applications that involve extreme temperatures, ensuring consistent performance without degradation.

• Low Friction: PTFE has one of the lowest coefficients of friction of any solid material. This property reduces energy consumption and wear, leading to improved efficiency and longer service life of the impeller.

Applications of PTFE Impellers

PTFE impellers are used across various industries due to their robust characteristics. Some notable applications include:

• Chemical Processing: In chemical plants, PTFE impellers are used in pumps that handle corrosive chemicals. Their resistance to chemical attack ensures the integrity and reliability of the pumping system.

• Pharmaceutical Manufacturing: The non-reactive and non-stick properties of PTFE impellers are ideal for pharmaceutical processes, where contamination must be avoided. They help maintain the purity of products and prevent cross-contamination.

• Food and Beverage Industry: PTFE impellers are used in food processing equipment to handle ingredients and products that may be sticky or prone to contamination. Their easy-to-clean nature ensures hygiene and compliance with food safety standards.

• Water Treatment: In water treatment plants, PTFE impellers are employed in pumps that handle various chemicals used in water purification. Their durability and resistance to chemical wear enhance the reliability of the water treatment process.

Advantages Over Traditional Materials

Traditional impeller materials such as metals or ceramics may suffer from corrosion, wear, or chemical attack, leading to frequent replacements and maintenance. PTFE impellers, on the other hand, offer a longer lifespan and reduced downtime. This translates into cost savings and increased operational efficiency.

Furthermore, PTFE impellers contribute to energy savings due to their low friction properties. In high-speed applications, this can result in significant reductions in power consumption and operational costs.

Challenges in Development

One of the notable drawbacks of PTFE is that it cannot be moulded using traditional methods. As a result, the blades of a PTFE impeller need to be made by moulding a block of PTFE and machining the impeller from this. This poses two problems. The first is that it is very time consuming. A single impeller might take anywhere from 3-4 hours to machine, making it expensive. However, this is not a huge problem since these are fairly specialised items and the need for using PTFE negates any commercial hurdles that might present. More problematic, however, is the shape itself. The impeller blade has specific angles, and these can often not be machined using simple equipment. Usually, a 5-axis machine is needed to adequately make the final shape, with special CAM programming to allow the tool to finish the part to the desired dimensions. Even if the equipment is available, PTFE is extremely difficult to machine and it requires both a machining knowledge and an in-depth understanding of the polymer to get the right result.

Conclusion

PTFE impellers represent a significant advancement in the field of fluid dynamics, offering unmatched chemical resistance, non-stick properties, thermal stability, and low friction. Their application across various industries underscores their versatility and effectiveness. As technology advances, the use of PTFE impellers is likely to expand, driving improvements in efficiency and reliability in fluid-handling systems. Embracing PTFE impellers can lead to enhanced performance, reduced maintenance, and long-term cost savings, making them a valuable investment for any industry dealing with challenging fluid environments.

As 5-axis capabilities develop – as it the case at Poly Fluoro – these vital components can be handled with ease and with the precision needed.

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