Gore-Tex
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). Gore-Tex products free of "PFC of environmental concerns" repellent coating lacks the ability to repel oil that "Gore DWR" provided.
History
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:
- U.S. patent 3,953,566, issued April 27, 1976, for a porous form of polytetrafluoroethylene with a micro-structure characterized by nodes interconnected by fibrils
- U.S. patent 4,187,390, issued February 5, 1980
- U.S. patent 4,194,041 on March 18, 1980 for a "waterproof laminate", together with Samuel Allen
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Cropper chose to keep the process of creating expanded PTFE as a closely held trade secret and as such, it had remained unpublished.[3][4]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
Following the Gore v. Garlock decision, Gore sued
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
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]
Structure
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]
Properties
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]
Processing
The most common process used to produce large sheets of ePTFE at scale is a tape stretching process through the following steps:
- A lubricating agent (often an oil) is added to fine PTFE powder until a paste is formed.
- The paste is extruded into a sheet that is calendered to obtain a specific, uniform thickness.
- The PTFE sheet passes through an oven set to an elevated temperature (often around 300C) while simultaneously undergoing an applied stress that dramatically stretches the material. While heating during this step is not necessary for expansion, it improves the uniformity of expansion.
- The ePTFE is sintered to increase its strength. This typically involves heating it to a temperature just above the melting temperature of unexpanded PTFE (340C) so that molecules can diffuse across the boundaries between grains in the material. This reduces the gaps in the ePTFE that might have formed during the stretching step.[13][11]
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]
Environmental and health concerns
PTFE is a
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]
Pollution lawsuit
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]
Applications
Gore-Tex materials are typically based on thermo-mechanically expanded PTFE and other
Use in rainwear
Before the introduction of Gore-Tex, the simplest sort of
Early Gore-Tex fabric replaced the inner layer of non-breathable PU with a thin, porous fluoropolymer membrane (
The outer layer of Gore-Tex fabric is coated on the outside with a
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]
Use in other clothing
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]
Other uses
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
Explosive sensors have been printed on Gore-Tex clothing leading to the sensitive voltametric detection of nitroaromatic compounds.[35]
The "Gore-Tex"
Gore-Tex has been used since the 1980s to make
-
Gore-Tex membrane under an electron microscope
-
Gore-Tex Medical Devices Sample Kit, Science History Institute
See also
References
- ^ a b "Robert W. Gore". Science History Institute. June 29, 2016. Retrieved March 20, 2018.
- ^ Clough, Norman E. "Innovations in ePTFE Fiber Technology" (PDF). W. L. Gore & Associates, Inc.
- ^ a b W. L. Gore Associates v. Garlock, Inc, 721 F.2d 1540. 220 U.S.P.Q. 303 (Fed. Cir. 1983).
- ^
Schechter, Roger; Thomas, John (2008). "16.3.2.8 First Inventor Defense". Schechter and Thomas' Intellectual Property: The Law of Copyrights, Patents and Trademarks (Hornbook Series). West Academic. ISBN 9781628105186.
- ISBN 9780143571957.
- ^ a b "Bard Peripheral Vascular, Inc. v. W.L. Gore & Assocs., Inc., No. 14-1114 (Fed. Cir. 2015)". Justia Law. Justia. Retrieved November 30, 2017.
- ISSN 1059-1028. Retrieved December 6, 2023.
- ^ "Robert W. Gore". National Inventors Hall of Fame. Retrieved September 20, 2015.
- ^ "W.L. Gore & Associates, Inc., Petitioner v.Bard Peripheral Vascular, Inc., et al., No. 15-41". SCOTUSblog. United States Supreme Court. October 5, 2015. Retrieved November 30, 2017.
- ^ "Docket for No. 15-41, W.L. Gore & Associates, Inc., Petitioner v. Bard Peripheral Vascular, Inc., et al." (TEXT). www.supremecourt.gov. United States Supreme Court. October 5, 2015. Retrieved November 30, 2017.
- ^ ISBN 978-1-4377-7855-7.
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- ^ "IARC Monographs evaluate the carcinogenicity of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS)". www.iarc.who.int. Retrieved April 13, 2024.
- ^ "Gore to drop waterproofing PFCs". Chemical & Engineering News. Retrieved November 27, 2023.
- ^ "Global brands lied about toxic "forever chemicals," new study shows - CBS News". www.cbsnews.com. June 2, 2023. Retrieved December 1, 2023.
- PMID 37154713.
The largest single use material within the PFAS compound class is poly(tetrafluoroethylene) (PTFE)
- ^ "FAQ | GORE-TEX Brand". www.gore-tex.com. Retrieved November 27, 2023.
- ^ Helms, Hayley (October 24, 2023). "How Patagonia and Gore-Tex Are Making Waterproof-Breathable Earth-Friendly Too". Gear Patrol. Retrieved December 6, 2023.
- ^ Leuven, Chris Van (May 9, 2023). "We Tested First GORE-TEX Products With ePE Membrane". Men's Journal. Retrieved December 6, 2023.
- ^ Wheeler, Timothy B. (July 19, 2023). "Maryland investigating 'forever chemicals' near industrial plant in Cecil County". Bay Journal. Retrieved December 6, 2023.
- ^ "Gore has known of the dangers of PFAS since the 1990s, lawsuit says". WHYY. Retrieved December 6, 2023.
- ^ "Durable Water Repellent". W. L. Gore & Associates. Retrieved April 24, 2024.
- ^ "Fall 2008 Fabrics and Technologies". Ames Adventure Outfitters. October 18, 2007. Archived from the original on July 11, 2011.
- ^ Keats, Jonathon. "The Accidental Origins of an Outdoor Clothing Essential". Wired. Retrieved March 24, 2019.
- ^ Simonovsky, Felix. "Biomaterials Tutorial Polytetrafluoroethylene (PTFE)". University of Washington Engineered Biomaterials. Retrieved March 24, 2019.
- Chemical Heritage Foundation. Archived from the originalon July 12, 2016. Retrieved October 22, 2013.
- ^ "Wilbert L. "Bill" Gore". Plastics Academy Hall of Fame. Archived from the original on April 2, 2015. Retrieved October 22, 2013.
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