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【文献】Part II: Invention of Expanded Polytetrafluoroethylene


Part II: Invention of Expanded Polytetrafluoroethylene

In 2008, W.L. Gore and Associates celebrated the 50th anniversary of the founding of their company. Ironically, 2008 also marked the 70th anniversary of Roy Plunkett’s discovery of PTFE at DuPont. W.L. Gore is where expanded polytetrafluoroethylene (ePTFE) was discovered and perfected over the years. The discovery stories of PTFE and ePTFE are separate yet intertwined, similar though unique. Both discoveries were the result of the technical brilliance, creativity, curiosity, perseverance, and business savvy of their respective masterminds. Foremost among the common qualities is curiosity, because these scientists were curious enough to recognize an anomaly and pursue with vigor what many might have considered a setback or an odd effect. Both PTFE and ePTFE are still used in the development of innumerable new products that have made vital contributions to humankind for more than half a century. PTFE and ePTFE have also generated tens of billions of dollars’ worth of business.


1.4 A New Type of Polytetrafluoroethylene

W.L. Gore was a successful small company, barely a decade old, when Bob Gore discovered ePTFE, which the company named Gore-Tex. ePTFE transformed W.L. Gore into a multibillion-dollar giant of creativity that has continued to try to find new product development opportunities in which ePTFE plays a key role. Without the discovery of PTFE and fluoropolymers, DuPont would have still been a large corporation, albeit somewhat diminished. In the absence of ePTFE, W.L. Gore and Associates, whatever its fate, would not have been the company that it became, thanks to Gore-Tex. The discovery and evolution of ePTFE is inextricably linked to the history of W.L. Gore as a company, and so this chapter tells that story. W.L. Gore’s unique management style and structure have been credited for its sustained growth through innovation and creativity. Over the past five decades, the company has brought the technology of Gore-Tex into a myriad of applications. The end-use products utilizing ePTFE have enhanced people’s lives beyond imagination. There is some controversy over which company or individual first invented the concept of PTFE expansion. Regardless of the answer to this question, however, it is W.L. Gore that continues to propel ePTFE to new frontiers. Over time, competitors began to produce ePTFE
membranes and products containing them. This book presents the contributions of many of these companies and explores the valuable role that W.L. Gore and its competitors played in the evolution of ePTFE technology.

1.5 Early History of W.L. Gore and Associates

Wilbert (“Bill”) L. Gore was born in 1912 in Meridian, Idaho. He spent most of his formative years in Salt Lake City, Utah. Bill studied chemistry and engineering and received both a bachelor of
science degree in chemical engineering, in 1933, and a Master of Science in chemistry, in 1935, from the University of Utah in Salt Lake City. Bill was a quiet
and modest man with a passion for innovation and tinkering. In 1935, he married Genevieve Walton, who also became Bill’s lifelong business partner. Both Bill and Vieve developed a great love for the outdoors that they bequeathed to their five children. That so many of the Gore-Tex apparel fabrics enhance the outdoor experience for sportsmen, hunters, and others is not surprising. In 1941, Bill Gore was employed by DuPont, where he was assigned to working on advancing the company’s research into polymers, resins, and plastics. During World War II, when PTFE was placed under a secrecy order, DuPont was prevented from developing commercial PTFE products. When the secrecy order was lifted in 1946, opening the way for commercialization of PTFE, Bill Gore worked for the next 12 years on the development of new applications for PTFE. A new plant was built in Parkersburg, Virginia, to produce the new polymer, and a flurry of research and development work got underway at DuPont to find applications for Teflon® PTFE. The focus of this work ranged from solving fundamental problems with polymerization and finishing of tetrafluoroethylene polymers to finding end uses and markets for the product. Bill Gore’s interests were focused primarily on finding new uses for Teflon®. The fundamental properties of PTFE rendered the material useful for many applications. No other material possesses all the properties of PTFE, which include a low dielectric constant (it is a good electrical insulator); high thermal resistance; a low coefficient of friction; low flammability; resistance to UV light, hydrophobicity, and oleophobicity; and chemical inertness. Only imagination could expand the breadth of new applications for this special plastic. Bill Gore was a man who possessed such imagination. DuPont in the 1950s was a basic materials supplier and did not produce many fabricated products; it did not go down the value chain, as they say. The company, which was over 150 years old at this point, had a well-entrenched culture. Corporate environments were (are) hardly fertile ground for nonconformers, mavericks, or those who, like Bill Gore, were possessed of an entrepreneurial spirit and driven to innovate. Bill Gore felt the need to leave the large corporate environment to pursue his interests, and so in 1958 he leave DuPont to establish his own business.

The suggestion that he leave DuPont has been attributed to his wife Vieve. In addition to being the mother of their five children she supported the fledgling company in many ways.
Vieve maintained her active role in the company until the end of her life. When she died in 2005, the annual sales of W.L. Gore and Associates approached 2 billion dollars. W.L. Gore’s first commercially viable were wire and cable insulated with PTFE. Bill Gore’s eldest son, Bob, played an important role in these innovations. Bob, who was at the time a chemical engineering student at the University of Delaware, is credited with coming up with the concept that resulted in Gore’s first patent
[6a] for PTFE-insulated wire and cable [6b]. W.L. Gore’s first order was from the city of Denver, Colorado, for 7.5 miles of insulated ribbon cable (Fig. 1.4). For the company’s first 10 years, these products comprised the core of the W.L. Gore’s sales. Multi-Tet cables, as they were called, were recognized for high performance in the defense industry and in the nascent field of computers. The cables were even used in the Apollo space program for the first moon landing.


1.6 Discovery of Expanded Polytetrafluoroethylene

By the late 1960s, W.L. Gore was a successful wire and cable supplier. Bob Gore, who had earned a bachelor’s degree from the University of Delaware in 1959 and a master’s and a PhD from the University of Minnesota (all in chemical engineering), joined the company’s board of directors in 1961 and began working at the company full time in 1963. As competition grew and other companies began to produce similar cables, Bill Gore looked for ways to reduce costs and to develop new products. Bill thought they might cut costs, and perhaps create a new form of PTFE, if they could find a way to stretch the PTFE insulation [8]. His idea was to introduce air into the polymer structure and basically create a foam form of PTFE. The cost of the cables would be reduced because they would use less polymer for insulation. Because PTFE is a thermoplastic but not melt processible, stretching it is difficult. Bob placed rods of PTFE in an oven and attempted to stretch the heated rods by hand. But the rods broke regardless of the temperature Bob used or the rate at which he stretched them. While they knew that PTFE stretches when it is elongated at very slow rates (<5 cm/min), these rates are not commercially practical; so Bob needed to find a method for stretching it more quickly. The story goes that, late one night in 1969, Bob became frustrated because of his inability to stretch the PTFE rods. As he later explained, “We were having really bad luck with that so I started to experiment with it at high temperatures. The more carefully I tried to stretch the material, the more easily it broke. That seemed counterintuitive to me. One evening, I took a piece that had been treated at high temperature and gave it a fast yank (Fig. 1.5), and was surprised to find that it stretched 1000 percent, rather than the 10 to 20 percent we had been seeing” 

Gore ascertained that the ePTFE (trademarked Gore-Tex) was both “very porous and very strong.” This discovery, of the conditions under which it would stretch to this degree this quickly, set the stage for the creation of hundreds of products and fundamentally altered the trajectory of the manufacturing efforts of W.L. Gore and Associates. “I guess that would be my biggest discovery, the basic Gore-Tex® material,” Bob Gore once noted. The expanded form possesses the basic properties of PTFEdincluding chemical inertness, low friction constant, wide-use temperature range, hydrophobicity, outdoor durability, and biocompatibilitydin addition to porosity, air permeability, and extreme strength. Given this range of properties, the potential applications of the expanded form were limitless. ePTFE is found in thousands of medical, industrial, and fabric products, as well as in electronic products [9]. Bob Gore and his family originally lived in the Rockies, where they used to “hike and go backpacking for several weeks, carrying everything on [their] backs.” Given his family’s love for the outdoors, Bob Gore finds the use of ePTFE in outdoors garments and adventure gear personally rewarding.

Moreover, ePTFE has facilitated new technologies and treatments in the field of medicine because of its biocompatibility. Millions of people have received ePTFE medical implants, which are configured to exclude or accept tissue in-growth depending on the needs of the specific application. Biocompatible ePTFE is used in vascular grafts, cardiovascular and soft tissue patches, facial implants, surgical sutures, and endovascular prostheses. ePTFE was first used as a joint sealant, and since then the number of its applications in the industrial arena has grown rapidly. W.L. Gore still produces sealants and the world’s tightest, most chemically resistant gaskets. The ePTFE membrane is the key to filtration products for a range of particle sizes, from pollutants found in the energy, mineral, metal, and chemical industries to clean room and computer disk drive micro contaminants [9].

The original W.L. Gore product line, which constituted insulated wires and cables, benefited from the discovery of ePTFE. ePTFE combines the chemical, thermal, and flammability characteristics of PTFE with the electrical properties of air. It has greater thermal stability, lower loss tangent, higher velocity of propagation, more flexibility, and a lower dielectric constant than solid PTFE. Figure 1.5 Bob Gore’s depiction of Gore-Tex discovery [7]. Courtesy Motion System Design.

ePTFE has been also used in printed circuit boards, electromagnetic interference shielding material, and fiber optic assemblies. It has diverse applications in the defense industry, industrial automation, computers, telecommunications, and medical technologies.
Today, with more than 2 billion dollars in sales, the company operates over 45 facilities throughout the world and employs thousands of associates. Bob Gore has stated that two fundamental core principles have underpinned the company’s growth.
The first principle is the pursuit of product development through leadership in fluoropolymers, and  particularly ePTFE. The second principle is acommitment to creating a unique, fulfilling work environment. Bob’s parents initiated and articulated this commitment in the early days of the company. Numerous organizations have recognized Bob Gore’s accomplishments. He was awarded the 2005 Perkin Medal by the Society of Chemical Industry, was elected to the National Academy of Engineers, and received the Society of Plastics Engineers award for benefits to society through the use of plastics as well as an award for lifetime achievement in fluoropolymers from DuPont and the WinthropeSears Award from the Chemical Heritage Foundation. In 2006, he was inducted into the National Inventors Hall of Fame. W.L. Gore’s serious commitment to research and development has resulted in a continually broadening range of products. The company’s unique corporate culture, which they refer to as a “flat lattice” structure, stresses freedom, fairness, commitment, and
good judgment in an open and creative work environment. Associates have no titles, communicate directly with one another, and work closely together in teams and task forces. Gore associates believe this unique culture enables the company to respond quickly to changing market developments and that it has been a key element in the company’s success and growth



[1] (a) S. Ebnesejjad, Introduction to Fluoropolymers: Materials, Technology, and Applications, Elsevier, New York, 2013 ch. 3.(b) R.J. Plunkett, US Patent 2,230,654, Assigned to DuPont Co, Februaury 4, 1941.
[2] R.J. Plunkett, The history of polytetrafluoroethylene: discovery and development, in: R.B. Seymour, G.S. Kirshenbaum (Eds.), High Performance Polymers: Their Origin and Development, Proceedings of the Symposium on the History of High Performance Polymers at the ACS Meeting Held in New York, April 1986, Elsevier, New York, 1987.
[3] A. Kinnane (Ed.), DuPont: From the Banks of the Brandywine to Miracles of Science, Johns Hopkins, Baltimore, MD, 2002.
[4] (a) R.J. Plunkett, in: Speech at the American Chemical Society Meeting, New York, April 15
e18, 1986.
(b) S. Ebnesajjad, Fluoroplastics, Volume 1: Non-melt Processible Fluoropolymers, second ed., Elsevier, New York, 2014.
[5] S. Ebnesajjad, Fluoroplastics, Volume 2: Melt Processible Fluoropolymers, second ed., Elsevier, New York, 2016.
[6] (a) US Patent 3,082,292, Assigned to Robert W. Gore, September 22, 1964.
[7] Bill, Bob Gore, Motion System Design Magazine, Penton Media, Inc, 2008.
[8] C.C. Manz, H.P. Sims, Business Without Bosses: How Self-managing Teams Are Building High, John Wiley & Sons, New York, 1993.
[9] University of Delaware, Alumni News, 2008
e2009, May 2, 2015. www.che.udel.edu/ downloads/2009ChEgNewsletter.pdf.
http://dedo.delaware.gov/information/ databook/technology.pdf.
[11] The Culture of W.L. Gore & Associates.
www. gore.com/en_xx/aboutus/culture/index.html.
[12] J.P. Riederer, M. Baier, G. Graefe, Innovation management
dan overview and some best practices, C-LAB Rep. 4 (3) (2005) 9.
[13] G. Hamel, B. Breen, The Future of Management, Harvard Business School Press, Boston, MA, 2007.