What is Polytetrafluoroethylene (PTFE) Fabric: Properties, How its Made and Where

White PTFE Fiberglass Fabric

What Is PTFE Fabric?

PTFE stands for polytetrafluoroethylene, which is a type of synthetic polymer called a fluoropolymer. A fluoropolymer is a type of polymer that consists of carbon and fluorine molecules, and the main constituent of polytetrafluoroethylene is tetrafluoroethylene (TFE), which is a member of the fluorocarbon family.

The most notable attribute of PTFE is that, due to its low dielectric constant, it is entirely hydrophobic, which means that water cannot pass through this synthetic material. This attribute has made PTFE highly popular in any application where the blockage of water is desired on a large or small scale.

In addition, PTFE has an incredibly high melting point. According to Chemours, PTFE can resist temperatures of up to 600 degrees Kelvin, which is the equivalent of 327 degrees Celsius or 620 degrees Fahrenheit. Polytetrafluoroethylene also has one of the lowest friction coefficients of any polymer, which means that it is slippery to the touch and easy to clean. Furthermore, PTFE has high abrasion resistance, and it has high tensile strength.

PTFE was not purposefully created; rather, it was discovered by accident by a DuPont Corporation scientist named Dr. Roy Plunkett in 1938. At the time, DuPont was the world leader in the development of synthetic textiles along with a number of other synthetic materials, and Plunkett made polytetrafluoroethylene in the process of trying to develop a new form of chlorofluorocarbon refrigerant.

PTFE Lifetime Thread

An unexpected reaction in the refrigerant development process resulted in the appearance of a white, slippery substance on the inside of the bottle Plunkett was using in his experiment. Upon analysis, the impressive attributes of this accidental creation were discovered, and a joint venture of General Motors and DuPont called Kinetic Chemicals patented PTFE in 1941.

In 1945, Kinetic Chemicals registered polytetrafluoroethylene under the trademark Teflon, and one of the first uses of this polymer was as a valve and seal coating material in uranium enrichment applications as part of the Manhattan Project. In the mid-1950s, the benefits of PTFE as a non-stick coating on cookware were discovered. Due to its high heat resistance and hydrophobic qualities, many companies immediately leaped on the prospect of using Teflon as a cookware coating.

ePTFE

Since the early days of its production, PTFE has been used as an insulator in electrical wiring. For instance, most types of coaxial cable use PTFE, and in the late 1950s, a DuPont employee named Bill Gore became interested in the potential applications of polytetrafluoroethylene in the computing industry.

With the help of his son, Bob, Bill Gore developed a type of computer wiring called Multi-Tet. Within just a few years, Multi-Tet became widely used around the country; this cable was even used in the modules of the Apollo 11 spacecraft.

Bob Gore, however, realized that PTFE had even greater potential. As he started to experiment with expanding PTFE, he noticed that this material became much more flexible and lightweight the more air it admitted. Bob’s experiments resulted in the discovery of expanded polytetrafluoroethylene ePTFE, which is now used in dozens of industrial and consumer applications.

Like normal polytetrafluoroethylene, ePTFE is highly heat-resistant and hydrophobic, but it is also easy to shape into a thin, fabric-like material that can be deployed in many more applications than traditional PTFE, which is more rigid.

GORE-TEX

As its name suggests, GORE-TEX is another creation of the Gore family. In 1970, Robert Gore started applying for a series of patents for ePTFE, and in 1976, W.L. Gore started marketing GORE-TEX as a material for outdoor enthusiasts.

The hydrophobic properties of ePTFE make it an ideal material for rain jackets, and this fabric is also windproof while remaining somewhat breathable. Since the 1970s, GORE-TEX has exploded in popularity, and it is now considered the premier material in a variety of different waterproof garments.

While PTFE is inherently impermeable by water, since GORE-TEX is made from stretched ePTFE, it has a microporous structure that allows the passage of water when it is in a gaseous form. When your body sweats, for instance, it emits steam, and this steam can freely move through GORE-TEX. Liquid water in the form of rain, however, cannot pass through this waterproof fabric.

How Is PTFE Fabric Made?

PTFE is polymerized from tetrafluoroethylene (TFE). In turn, TFE is created by combining fluorspar, hydrofluoric acid, and chloroform. To create TFE, these three components are combined under high temperatures through a process called pyrolysis. The resulting substance is in a gaseous form, and it is converted into a liquid under high pressure in low temperatures.

PTFE Filter Mesh Fabrics

TFE is highly volatile, so it isn't commonly transported. Instead, most PTFE manufacturers make their own TFE on site. In the process of creating TFE, small amounts of a number of different chemicals, such as disuccinic acid and ammonium persulfate, may be used as initiators, and large amounts of water are also used in the PTFE production process.

Once TFE has been acquired, PTFE may be made in a variety of different ways, and most manufacturers of this type of fabric have production process trade secrets that they do not share. However, the various production processes used to make PTFE can all be sorted into to basic categories: suspension polymerization and dispersion polymerization.

Suspension Polymerization

In this process, a reaction chamber is filled with purified water and an initiator chemical, and liquid PTFE is then introduced into the chamber. As soon as liquid PTFE comes in contact with the initiator, it starts to polymerize, and it forms solid grains that remain on the surface of the water. Throughout the process, the reaction chamber is moved back and forth to facilitate the circulation of water as a coolant.

Once a certain weight of PTFE is reached, the process is stopped, and the water is drained from the reaction chamber. The resulting PTFE grains are then dried and pulverized with a mill. The resulting substance has a flour-like consistency, and these powdery grains are then made into larger granules since PTFE is hard to work with in this form. The resulting pellets are dried in an oven.

PTFE Staple Fiber

Once the pellets are dry, they can be made into a variety of different forms in the factory, or they may be shipped off in pre-made cylinders called billets. To make PTFE into a certain shape, it is heated above 680 degrees Fahrenheit (360 degrees Celsius) in an oven, at which point it takes on a gel-like consistency.

Dispersion Polymerization

This method does not result in solid grains of PTFE. Instead, it results in a liquified form of this substance that can only be used in coating or finish applications. As in the suspension polymerization method, water, an initiator chemical, and liquid TFE are introduced into a reaction chamber. Instead of being vigorously shaken, however, the reaction chamber is only lightly agitated, which results in tiny beads of PTFE.

Once these beads have formed, a certain amount of water is removed, and a milky substance is formed. While this liquified substance is usually kept in its liquid form, it can also be dried into a fine powder.

Production of ePTFE

While Bob Gore came upon the idea for stretched PTFE early in his career working with his father, he spent endless fruitless hours trying to determine how to stretch this polymer before he created this new technology for the first time.

Bob started by heating PTFE to a high temperature and pulling it slowly from both ends. However, these rods invariably broke. In exasperation, Bob finally tried pulling a rod of PTFE as fast as he could after it had been heated. Incredibly, the rod expanded to 10 times its normal size.

All ePTFE made today, whether it's made by Gore & Associates, Inc. or a different company, is made with this seemingly simplistic method. By heating and rapidly stretching PTFE, this substance takes on unique properties that give it completely different performance characteristics than formal PTFE. In most cases, this substance is made with industrial ovens and stretching machines.

Before they can be sold, PTFE and ePTFE products must meet certain quality control standards. For instance, dispersion PTFE is tested for viscosity and gravity parameters, and if PTFE manufacturers want to market their products as Teflon, they must adhere to certain standards laid down by DuPont since Teflon is a registered trademark of this corporation.

How Is PTFE Fabric Used?

PTFE is used in a wide variety of applications. Nearly 50 percent of the world's PTFE is used in the computer industry since it has high dielectric strength. Since its initial use in the Apollo missions, NASA has used PTFE in many different manned and unmanned space missions, and this substance is also used to make insulation for wires in extreme climates like Antarctica.

Since it has a low coefficient of friction, PTFE is also used in bearings, bushing, gears, seals, and gaskets, and it is commonly used in the production of carbon fiber composites in the aerospace industry. The UV-resistance of PTFE makes it popular in outdoor industrial applications, and PTFE is also commonly used to coat the outsides of flexible architectural materials. For instance, the roof of the Minneapolis Metrodome is covered with PTFE coating to make this structure UV-resistant and easy to clean.

PTFE is used in dozens of other industrial and scientific applications, but the context in which consumers have most commonly come into contact with this polymer is in non-stick pans. While Teflon is a registered trademark of DuPont, a variety of other companies have made similar coatings, and most types of cookware on the market now have Teflon coatings to make them easier to use and clean. Teflon and similar substances have also been used in such diverse applications as gaming mice and 3D printers to help reduce friction.

In the form of GORE-TEX and similar substances, ePTFE is used in a wide variety of different types of apparel. As a general rule of thumb, if a flexible outdoor garment, shoe, or accessory is listed as waterproof, it's most likely that this product incorporates a layer of GORE-TEX or a similar ePTFE fiber. The GORE-TEX in ski jackets and other types of outdoor apparel outperforms other forms of waterproofing, and this substance is even used in many types of hiking shoes to help keep the feet of outdoor enthusiasts clean and dry while on long hikes.

ePTFE is also used in a wide variety of medical applications. For instance, this fabric is used as a filtration membrane in drug delivery, urine collection, and laparoscopic surgery applications, and it is also used to make coatings for intravascular medical devices, which are types of devices that go inside of veins and arteries. ePTFE may also be used to coat medical implants that are designed for permanent installation to protect these devices from breakdown due to contact with bodily fluids.

Due to its resistance to high temperatures, PTFE is often used as a coating for the gear and garments that are worn by first responders such as firefighters. Firefighting gear may also contain layers of ePTFE to improve heat resistance and improve breathability. Furthermore, PTFE and ePTFE are used in gear worn by members of military and paramilitary organizations. PTFE is even used to make consumer items like guitar strings.

Where Is PTFE Fabric Produced?

China is the largest producer of PTFE. In 2016, this Asian nation exported PTFE material worth $154 million, and the USA is China's main competitor since it produced $118 million of PTFE in the same year. After the USA and China, Germany, the Netherlands, Italy, and Japan are the next biggest exporters of PTFE.

Despite producing this substance in large quantities, the USA is also the largest importer of PTFE. This country imported $158 million of PTFE in 2016, and it was followed by Germany at $99 million and Italy at $84 million. While DuPont holds the trademark to Teflon, it allows other manufacturers to make this substance as long as they meet certain manufacturing guidelines.

How Much Does PTFE Fabric Cost?

While the price of PTFE fluctuates substantially, the average cost of this product is approximately $8,800-$16,000 per ton. The price of PTFE also varies by country; for instance, exporting PTFE to countries like China and Germany generally costs somewhat more than exporting this product to the United States or India.

To the end consumer, types of PTFE used in garments, such as GORE-TEX, are not significantly more expensive than other types of raingear. However, the GORE-TEX brand carries significant recognition around the world, so garments that contain this substance may be marketed at higher price points. For instance, a GORE-TEX jacket for men costs an average of $70-$200.

China Ptfe Membrane Fabric

Consumers don't generally have any use for ePTFE when it isn't incorporated into garments, so prices of this substance by the sheet aren't usually relevant in the consumer market. While cookware containing PTFE branded as Teflon or another trade name may be slightly more expensive than other types of cookware, this price discrepancy isn't usually very pronounced.

What Different Types of PTFE Fabric Are There?

In its original form, PTFE is a rigid substance that cannot be made into flexible, fabric-like materials. However, this substance can be added to other types of materials to make a fabric-like substance, and various types of fabrics can also be made with ePTFE, which is the stretched form of this linear polymer.

1. PTFE Fiberglass

Flexible fiberglass sheets can be coated with PTFE to improve their durability and weather resistance. In most applications in which flexible fiberglass is used outdoors, this material is coated with PTFE. This coating makes fiberglass suitable for the permanent, tent-like roofs that stretch over dozens of stadiums and business centers around the world. While PTFE fiberglass doesn't last forever, it does last for about 30 years before it must be replaced.

2. PTFE-Coated Garments

While normal PTFE isn't used to make garments, it is used to coat garments made from other materials. When coated with PTFE, garments have decreased friction, which makes them easier to clean. In addition, this coating makes garments resistant to stains, and it acts as a flame retardant. Therefore, PTFE is commonly used to coat special types of clothing such as uniforms and ceremonial robes.

3. ePTFE

In some cases, ePTFE fabric may be used in outdoor architectural applications instead of PTFE-coated fiberglass. Pure ePTFE has all of the benefits of PTFE fiberglass, but it also lasts longer than other types of flexible outdoor architectural materials. One of the most notable benefits of this architectural material is its light transmission; according to Birdair, ePTFE allows 40 percent more light transmission as compared to PVC.

ePTFE may also be used in garments. While this substance is most commonly branded as GORE-TEX, when it is made by independent manufacturers, it is usually labeled simply as ePTFE or with another trade name. Whether or not ePTFE is labeled as GORE-TEX, it has the same waterproofing and breathability benefits.

4. GORE-TEX

GORE-TEX is a registered brand name of the W.L. Gore corporation, and it is the most commonly used type of ePTFE in consumer garments. While GORE-TEX may also be used in military and industrial applications, it is most commonly used as a waterproof lining in rain jackets, ski jackets, gloves, boots, ski pants, and a wide variety of other apparel applications in which increased airflow and high porosity are desired.

How Does PTFE Fabric Impact the Environment?

The production of PTFE results in a variety of toxic byproducts. For instance, hydrofluoric acid is released in the production of this substance, and this byproduct is highly toxic. Hydrofluoric acid causes serious tissue damage if it comes into contact with either human or animal tissue, and it also causes environmental damage if it is not disposed of properly.

PTFE production also releases carbon dioxide into the atmosphere, which has been identified as a greenhouse gas. The presence of these chemicals can pose serious harm to workers if production areas are not properly ventilated, and bodily harm through exposure to these substances is so widespread that a specific disease has been named to refer to the symptoms of hydrofluoric acid and carbon dioxide exposure in PTFE production plants: polymer fume fever. Some of the waste substances produced in PTFE production can be reused, but since these substances are now widely available, there isn't as much of an incentive for factories to retain these waste products for new products.

A wide body of research has been conducted to determine the effects of PTFE production on the environment, and the National Institutes of Health (NIH) have compiled the results in a comprehensive toxicity dossier. PTFE production involves the release of hydrofluorocarbons, and while these substances don't destroy the ozone layer like chlorofluorocarbons, they have other toxic effects when introduced into the environment.

In addition, the thermolysis (breakdown by heat) of PTFE releases a substance called trifluoroacetate, which is highly toxic to humans and animals. This substance accumulates in the water supplies of urban environments, and it has even been shown to adversely affect the growth of root matter in plants.

Currently, the best way to dispose of PTFE and related substances is in landfills since incinerating this substance releases hydrogen chloride and other toxic substances into the atmosphere. However, if landfills are not properly designed to prevent leaching into the surrounding soil, trifluoroacetate and other substances could contaminate the environment surrounding these designated waste disposal areas.

While PTFE does leach toxic contaminants into the environment, this substance is not biodegradable, which means that it does not break down due to natural processes. Therefore, garments made from ePTFE or GORE-TEX will remain in the environment for thousands of years after their date of manufacture.

PTFE Fabric Certifications Available

Since PTFE and ePTFE are fully synthetic compounds that are made from all-new materials, they are not eligible for recycled or organic certification. However, they are eligible for various types of certification from organizations like the International Organization for Standardization (ISO). For instance, good PTFE or ePTFE fiber will come with ISO 9001 certification, and it will also have ISO 13485 certification if it is being used in medical devices. Furthermore, these substances may be eligible for ISO 14001 certification if their production meets certain environmental standards, and PTFE or ePTFE may also be eligible for OHSAS 18001 certification if facilities producing these substances meet certain workplace safety requirements.