Type | Fabric |
---|---|
Material | expanded PTFE |
Production process | Mechanized |
Introduced | 1969 |
Manufacturer | W. L. Gore & Associates |
Gore-Tex is W. L. Gore & Associates's trade name for waterproof, breathable fabric membrane. It was invented in 1969. Gore-Tex blocks liquid water while allowing water vapor to pass through and is designed to be a lightweight, waterproof fabric for all-weather use. It is composed of expanded PTFE (ePTFE), a stretched out form of the PFAS compound polytetrafluoroethylene (PTFE).
External videos | |
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"I decided to give one of these rods a huge stretch, fast, a jerk... and it stretched 1000%", Scientists You Must Know: Bob Gore, Science History Institute |
Gore-Tex was co-invented by Wilbert L. Gore and Gore's son, Robert W. Gore. [1] In 1969, Bob Gore stretched heated rods of polytetrafluoroethylene (PTFE) and created expanded polytetrafluoroethylene (ePTFE). His discovery of the right conditions for stretching PTFE was a happy accident, born partly of frustration. Instead of slowly stretching the heated material, he applied a sudden, accelerating yank. The solid PTFE unexpectedly stretched about 800%, forming a microporous structure that was about 70% air. [1] It was introduced to the public under the trademark Gore-Tex. [2]
Gore promptly applied for and obtained the following patents:
Another form of stretched PTFE tape was produced prior to Gore-Tex in 1966, by John W. Cropper of New Zealand. Cropper had developed and constructed a machine for this use. However, Cropper chose to keep the process of creating expanded PTFE as a closely held trade secret and as such, it had remained unpublished. [3] [4]
In the 1970s Garlock, Inc. allegedly infringed Gore's patents by using Cropper's machine and was sued by Gore in the Federal District Court of Ohio. The District Court held Gore's product and process patents to be invalid after a "bitterly contested case" that "involved over two years of discovery, five weeks of trial, the testimony of 35 witnesses (19 live, 16 by deposition), and over 300 exhibits" (quoting the Federal Circuit). On appeal, however, the Federal Circuit disagreed in the famous case of Gore v. Garlock, reversing the lower court's decision on the ground, as well as others, that Cropper forfeited any superior claim to the invention by virtue of having concealed the process for making ePTFE from the public. As a public patent had not been filed, the new form of the material could not be legally recognised. Gore was thereby established as the legal inventor of ePTFE. [3] [5]
Following the Gore v. Garlock decision, Gore sued C. R. Bard for allegedly infringing its patent by making ePTFE vascular grafts. Bard promptly settled and agreed to exit the market. Gore next sued IMPRA, Inc., a smaller maker of ePTFE vascular grafts, in the federal district court in Arizona. IMPRA had a competing patent application for the ePTFE vascular graft. In a nearly decade-long patent/antitrust battle (1984–1993), IMPRA proved that Gore-Tex was identical to prior art disclosed in a Japanese process patent by duplicating the prior art process and through statistical analysis, and also proved that Gore had withheld the best mode for using its patent, and the main claim of Gore's product patent was declared invalid in 1990. [6] In 1996, IMPRA was purchased by Bard and Bard was thereby able to reenter the market. After IMPRA's vascular graft patent was issued, Bard sued Gore for infringing it.
Gore-Tex is used in products manufactured by many different companies.
Gore's patents on ePTFE based fabric expired in 1997 and ePTFE membrane waterproof fabrics have become available from other brands. [7]
For his invention, Robert W. Gore was inducted into the U.S. National Inventors Hall of Fame in 2006. [8]
In 2015, Gore was ordered by the Federal Circuit Court of Appeals to pay Bard $1 billion in damages. [6] The U.S. Supreme Court declined to review the Federal Circuit's decision. [9] [10]
ePTFE has a porous microstructure composed of long, narrow fibrils that intersect at nodes. Increasing the processing temperature or increasing the strain rate leads to more homogenous expansion with more spherically symmetric pores and more intersections between fibrils. [11] The formation of ePTFE is enabled by the unwinding of PTFE molecules to create large pores within the structure. This favors highly ordered, crystalline PTFE that allows the molecules to disentangle more easily and uniformly when stretched. The porosity is largely determined by the stretching temperature and rate. Changing the stretching rate from 4.8 m/min to 8m/min can increase the porosity from 60.4% to 70.8%. [12]
Due to the high work hardening rate of PTFE, ePTFE is significantly stronger than the unstretched material. On a microscopic level, this work hardening corresponds to the increasing crystallinity of PTFE as the fibrils untangle and orient upon the application of an external stress. ePTFE has a strikingly high ultimate tensile strength (50-800 MPa) relative to its full-density counterpart (20-30 MPa) as a result of its high crystallinity. This behavior also yields a negative Poisson's ratio due to the expansion of ePTFE along all directions, contrasting the more expected reduction in the directions perpendicular to the stress in cases with volume conservation. [11]
ePTFE has tunable porosity based on the processing conditions and can be made permeable to certain vapors and gases. However, it is impermeable to most liquids, including water, a property that is exploited in certain applications such as raincoats. These additional properties in combination with the inherent properties of PTFE-based materials more generally (chemical inertness, thermal stability) make ePTFE a versatile material for a range of applications. [11]
The most common process used to produce large sheets of ePTFE at scale is a tape stretching process through the following steps:
Factors such as strain rate, oven temperature, sintering time, and sintering duration can affect the specific properties of the resulting ePTFE sheet which can be tailored to match particular applications. [14] [11]
PTFE is a fluoropolymer made using an emulsion polymerization process that utilizes the fluorosurfactant PFOA, [15] [16] a persistent environmental contaminant. The International Agency for Research on Cancer has classified PFOA as carcinogenic to humans. [17]
Gore pledged in 2017 to eliminate PFCs such as PFOA by 2023, although the core technology will continue to be based on PTFE, [18] which is a PFAS compound. [19] [20] Many Gore-Tex products have a durable water repellent coating and the version that do not contain PFCs of environmental concerns are marketed as "Gore PFCEC Free DWR". Unlike the "Gore DWR", it lacks any form of oil repellency. [21]
The company intends to replace ePTFE membrane with expanded polyethylene membrane by 2025 in consumer fabrics. [22] The new material, while intended to perform comparably to the existing ePTFE material, will cost more, and require more frequent washing. [23]
in 2023, two lawsuits have been filed against Gore on the matter of PFAS related water pollution around its Cecil County, Maryland manufacturing plant and the Maryland Department of the Environment has ordered an investigation and residents in the monitoring area have been offered bottled water. [24] One of the lawsuits alleges that the company knew about the dangers of PFOA/PFAS since the 1990s. [25]
Gore-Tex materials are typically based on thermo-mechanically expanded PTFE and other fluoropolymer products. They are used in a wide variety of applications such as high-performance fabrics, medical implants, filter media, insulation for wires and cables, gaskets, and sealants. However, Gore-Tex fabric is best known for its use in protective, yet breathable, rainwear.
Before the introduction of Gore-Tex, the simplest sort of rainwear would consist of a two-layer sandwich, where the outer layer would typically be woven nylon or polyester to provide strength. The inner one would be polyurethane (abbreviated: PU) to provide water resistance, at the cost of breathability.
Early Gore-Tex fabric replaced the inner layer of non-breathable PU with a thin, porous fluoropolymer membrane (Teflon) coating that is bonded to a fabric. This membrane had about 9 billion pores per square inch (around 1.4 billion pores per square centimeter). Each pore is approximately 1⁄20,000 the size of a water droplet, making it impenetrable to liquid water while still allowing the more volatile water vapor molecules to pass through.
The outer layer of Gore-Tex fabric is coated on the outside with a Durable Water Repellent (DWR) treatment. The DWR prevents the main outer layer from becoming wet, which would reduce the breathability of the whole fabric. However, the DWR is not responsible for the jacket being waterproof. Without the DWR, the Gore-Tex layer would become soaked, thus preventing any breathability, and the wearer's sweat being produced on the inside would fail to evaporate, leading to dampness there. This might give the appearance that the fabric is leaking when it is not. Wear and cleaning will reduce the performance of Gore-Tex fabric by wearing away this Durable Water Repellent (DWR) treatment. The DWR can be reinvigorated by tumble drying the garment or ironing on a low setting. [26]
Gore requires that all garments made from their material have taping over the seams, to eliminate leaks. Gore's sister product, Windstopper, is similar to Gore-Tex in being windproof and breathable, and it can stretch, but it is not waterproof. The Gore naming system does not imply any specific technology or material but instead implies a specific set of performance characteristics. [27]
Expanded polytetrafluoroethylene is used in clothing due to its breathability and water protection capabilities. Besides use in rainwear ePTFE can now be found in space suits. [28]
Gore-Tex is also used internally in medical applications, because it is nearly inert inside the body. Specifically, expanded polytetrafluoroethylene (E-PTFE) can take the form of a fabric-like mesh. Implementing and applying the mesh form in the medical field is a promising type of technological material feature. [29] In addition, the porosity of Gore-Tex permits the body's own tissue to grow through the material, integrating grafted material into the circulation system. [30] Gore-Tex is used in a wide variety of medical applications, including sutures, vascular grafts, heart patches, and synthetic knee ligaments, which have saved thousands of lives. [31] In the form of expanded polytetrafluoroethylene (E-PTFE), Gore-Tex has been shown to be a reliable synthetic, medical material in treating patients with nasal dorsal interruptions. [32] In more recent observations, expanded polytetrafluoroethylene (E-PTFE) has recently been used as membrane implants for glaucoma surgery. [33]
Gore-Tex has been used for many years in the conservation of illuminated manuscripts. [34]
Explosive sensors have been printed on Gore-Tex clothing leading to the sensitive voltametric detection of nitroaromatic compounds. [35]
The "Gore-Tex" brand name was formerly used for industrial and medical products. [36] [37]
Gore-Tex has been used since the 1980s to make bagpipe (woodwind instrument) bags as an alternative to bags made of animal hides as it was able to hold air while allowing moisture to escape, and did not degrade with exposure to water. [38]
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from DuPont, which originally discovered the compound in 1938.
A raincoat is a waterproof or water-resistant garment worn on the upper body to shield the wearer from rain. The term rain jacket is sometimes used to refer to raincoats with long sleeves that are waist-length. A rain jacket may be combined with a pair of rain pants to make a rainsuit. Rain clothing may also be in one piece, like a boilersuit. Raincoats, like rain ponchos, offer the wearer hands-free protection from the rain and elements; unlike the umbrella.
Wilbert Lee "Bill" Gore was an American engineer and scientist, inventor and businessman who co-founded W. L. Gore and Associates with his wife, Genevieve (Vieve).
Oilskin is a waterproof cloth used for making garments typically worn by sailors and by others in wet areas. The modern oilskin garment was developed by a New Zealander, Edward Le Roy, in 1898. Le Roy used worn-out sailcloth painted with a mixture of linseed oil and wax to produce a waterproof garment suitable to be worn on deck in foul-weather conditions. Oilskins are part of the range of protective clothing also known as foul-weather gear.
Waterproofing is the process of making an object, person or structure waterproof or water-resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environments or underwater to specified depths.
Waterproof fabrics are fabrics that are, inherently, or have been treated to become, resistant to penetration by water and wetting. The term "waterproof" refers to conformance to a governing specification and specific conditions of a laboratory test method. They are usually natural or synthetic fabrics that are laminated or coated with a waterproofing material such as wax, rubber, polyvinyl chloride (PVC), polyurethane (PU), silicone elastomer, or fluoropolymers. Treatment could be either of the fabric during manufacture or of completed products after manufacture, for instance by a waterproofing spray. Examples include the rubberized fabric used in Mackintosh jackets, sauna suits, and inflatable boats.
Durable water repellent, or DWR, is a coating added to fabrics at the factory to make them water-resistant (hydrophobic). Most factory-applied treatments are fluoropolymer based; these applications are quite thin and not always effective. Durable water repellents are commonly used in conjunction with waterproof breathable fabrics such as Gore-Tex to prevent the outer layer of fabric from becoming saturated with water. This saturation, called 'wetting out,' can reduce the garment's breathability and let water through. As the DWR wears off over time, re-treatment is recommended when necessary. Many spray-on and wash-in products for treatment of non-waterproof garments and re-treatment of proofed garments losing their water-repellency are available.
Fluorinated ethylene propylene (FEP) is a copolymer of hexafluoropropylene and tetrafluoroethylene. It differs from the polytetrafluoroethylene (PTFE) resins in that it is melt-processable using conventional injection molding and screw extrusion techniques. Fluorinated ethylene propylene was invented by DuPont and is sold under the brandname Teflon FEP. Other brandnames are Neoflon FEP from Daikin or Dyneon FEP from Dyneon/3M.
Sympatex is a type of fabric that is branded as waterproof but "breathable", made or licensed by Sympatex Technologies GmbH a company founded in 1986. The fabric features a waterproof, windproof and breatheable membrane that is laminated to fabrics either on its inner surface or sandwiched between two fabric layers. The latter system offers greater durability, by better protecting the integrity of the Sympatex layer from abrasion to both the outside and the inside of the garment.
Windstopper is a windproof breathable fabric laminate made by W. L. Gore & Associates. One of its most common applications is a lamination with polar fleece, to compensate for fleece's lack of wind resistance.
W. L. Gore & Associates, Inc. is an American multinational manufacturing company specializing in products derived from fluoropolymers. It is a privately held corporation headquartered in Newark, Delaware. It is best known as the developer of waterproof, breathable Gore-Tex fabrics.
The Extended Cold Weather Clothing System is a protective clothing system developed in the 1980s by the United States Army Natick Soldier Research, Development and Engineering Center, Natick, Massachusetts. The first generation ECWCS consisted of parka and trousers plus 20 other individual clothing, handwear, headwear and footwear items which are used in various combinations to meet the cold weather environmental requirements of the US military. The Extended Climate Warfighter Clothing System, or Gen III ECWCS, is designed to maintain adequate environmental protection in temperatures ranging between −60 and +40 °F.
Ventile, is a registered trademark used to brand a special high-quality woven cotton fabric first developed by scientists at the Shirley Institute in Manchester, England. Originally created to overcome a shortage of flax used for fire hoses and water buckets, its properties were also useful for pilots' immersion suits, but expensive and leaky if exposed to sweat or oils.
Robert W. Gore was an American engineer and scientist, inventor and businessman. Gore led his family's company, W. L. Gore & Associates, in developing applications of polytetrafluoroethylene (PTFE) ranging from computer cables to medical equipment to the outer layer of space suits. His most significant breakthrough was likely the invention of Gore-Tex, a waterproof and breathable fabric popularly known for its use in sporting and outdoor gear.
Breathability is the ability of a fabric to allow moisture vapor to be transmitted through the material.
A non-stick surface is engineered to reduce the ability of other materials to stick to it. Non-stick cookware is a common application, where the non-stick coating allows food to brown without sticking to the pan. Non-stick is often used to refer to surfaces coated with polytetrafluoroethylene (PTFE), a well-known brand of which is Teflon. In the twenty-first century, other coatings have been marketed as non-stick, such as anodized aluminium, silica, enameled cast iron, and seasoned cookware.
Guided bone regeneration (GBR) and guided tissue regeneration (GTR) are dental surgical procedures that use barrier membranes to direct the growth of new bone and gingival tissue at sites with insufficient volumes or dimensions of bone or gingiva for proper function, esthetics or prosthetic restoration. Guided bone regeneration typically refers to ridge augmentation or bone regenerative procedures; guided tissue regeneration typically refers to regeneration of periodontal attachment.
Nikwax Analogy is a two-component fabric system for weatherproof clothing based on "biomimicry" of fur.
A perfluorinated compound (PFC) or perfluoro compound is an organofluorine compound that lacks C-H bonds. Many perfluorinated compounds have properties that are quite different from their C-H containing analogues. Common functional groups in PFCs are OH, CO2H, chlorine, O, and SO3H. Electrofluorination is the predominant method for PFC production. Due to their chemical stability, some of these perfluorinated compounds bioaccumulate.
The global market for chemicals from fluorine was about US$16 billion per year as of 2006. The industry was predicted to reach 2.6 million metric tons per year by 2015. The largest market is the United States. Western Europe is the second largest. Asia Pacific is the fastest growing region of production. China in particular has experienced significant growth as a fluorochemical market and is becoming a producer of them as well. Fluorite mining was estimated in 2003 to be a $550 million industry, extracting 4.5 million tons per year.
The largest single use material within the PFAS compound class is poly(tetrafluoroethylene) (PTFE)