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Kevlar® Inventor, Stephanie Kwolek

June 23, 2014

Founded in 1802, Dupont (more properly, E.I. du Pont de Nemours and Company), is one of the world's largest chemical companies. It has about $35 billion in annual revenue, and its major business has been chemistry; so much so, that its slogan from 1935-1982 was "Better Things for Better Living...Through Chemistry. The short form, "Better Living Through Chemistry," was used as the title of a recent movie.[1]

Dupont has developed many important materials, several of which are known to the general public. These include nylon, Corian, Teflon, Mylar and Lycra. Vespel, neoprene, Nomex and Tyvek, are some of its other materials known to most engineers.

Kevlar chemical structure

Kevlar derives its strength from the inter-chain bonds shown here.

(Via Wikimedia Commons.)


One of Dupont's materials is Kevlar, the para-aramid polymer, poly-paraphenylene terephthalamide, composed of chains of the chemical unit, -CO-C6H4-CO-NH-C6H4-NH-. Because of inter-chain bonding, as shown in the above figure, Kevlar has a ratio of tensile strength per weight (specific strength) that's five times that of steel. Not only that, it's a useful material from cryogenic temperature up to about 150 °C. Inventor of Kevlar, Stephanie Kwolek, died on June 18, 2014, at age 90.[2-5]

Stephanie Louise Kwolek (1923-2014)

Stephanie Louise Kwolek (July 31, 1923-June 18, 2014)

(Still image from a YouTube Video by the Chemical Heritage Foundation.[6]


Stephanie Louise Kwolek was born on July 31, 1923, in a suburb of Pittsburgh, Pennsylvania. Her parents were both Polish immigrants to the United States. The family name was anglicized from Chwałek. Her father was an amateur naturalist, and she attributed her interest in science to her Nature expeditions with him.

Kwolek's initial ambition was to become a physician, so after getting a degree in chemistry from what is now Carnegie Mellon University in 1946, she took a job with Dupont in order to save money for medical school. She discovered, however, that she enjoyed the work, and she eventually relocated from the Dupont facility in Buffalo, New York, to Wilmington, Delaware, in 1950. She worked at Dupont's Wilmington, Delaware, research facility for forty years, where she was head of polymer research at her retirement in 1989.[2,4]

Figure caption

At home in the laboratory, both early in her career and later. Note the absence of safety glasses in the older photograph. Laboratory safety practices have improved over the years, but gloves were still absent in the more modern image. (Still images from a YouTube Video by the Chemical Heritage Foundation.[6]


In 1964, Kwolek was doing research on new polymer materials as a lightweight replacement for steel wires used for automobile tire reinforcement. While investigating polymers that could be processed at lower temperatures, a condition that leads to higher strength, her research team found that the Kevlar material had unique mechanical properties. This research led to Dupont's manufacture and sale of Kevlar for many applications.[5]

The Kevlar material was unique, since it was spun from a liquid crystal solution that was so unusual that most chemists would have discarded it as useless.[2] It was very thin solution, and it had a cloudiness that resembles solutions containing suspended solids. Such solids would block the fine holes in the spinneret used to make polymer fibers.[6]

Kwolek, in a 2007 interview in The News Journal, a Wilmington, Delaware, newspaper, said that Kevlar was so unusual that she needed to do repeated confirmatory experiments to convince herself of the results. When she was certain that she wouldn't embarrass herself to Dupont's management, she presented her results, and Dupont immediately assigned many people to develop the material. Kwolek was always careful to acknowledge her collaborators in Kevlar development.[3]

Kevlar's been used in a plethora of products, including insulation for underwater optical-fiber cables, tire cord, drumheads, baseball bats, ship hulls, skis, and space suits.[3,5,8] One application has been in so-called "bullet-proof" vests, more properly called "lightweight body armor," for both police and military.

Figure caption

An Improved Outer Tactical Vest (IOTV).

The difference in soldier dress between World War II and one of our many, present wars is amazing.

(Via Wikimedia Commons.)


By Dupont's estimate, more than 3,100 law enforcement officers have escaped death or serious injury through use of Kevlar body armor.[5] Kwolek is quoted by the Chemical Heritage Foundation as saying, "I don't think there's anything like saving someone's life to bring you satisfaction and happiness."[8] Dupont just announced the sale of more than a million bullet-resistant vests made from an advanced Kevlar material since it was produced in 2008. The army of the Republic of Korea was the recipient of the millionth vest.[9]

In 1995, Kwolek became the fourth woman to be added to the National Inventors Hall of Fame, and she was awarded the National Medal of Technology in 1996. Kwolek was also awarded the 1997 Perkin Medal from the American Chemical Society, and she was a named inventor on 28 patents (the "Kevlar" patent is 71 pages long).[4] She was elected to the National Academy of Engineering in 2001.

References:

  1. Better Living Through Chemistry (2014, Geoff Moore and David Posamentier, Directors) on the Internet Movie Database.
  2. Camila Domonoske, "Stephanie Kwolek, Chemist Who Created Kevlar, Dies At 90," NPR, June 20, 2014.
  3. Will Dunham, "Stephanie Kwolek, American chemist who invented Kevlar, dies at 90," Reuters, June 21, 2014.
  4. USA: zmarła Stephanie Kwolek, wynalazczyni kevlaru, Radio Poland, June 21, 2014.
  5. Randall Chase, "5 Things To Know about Kevlar," Bismark Tribune, June 20, 2014.
  6. Women in Chemistry: Stephanie Kwolek, Chemical Heritage Foundation, YouTube Video, September 10, 2012.
  7. Stephanie Louise Kwolek,"Wholly aromatic carbocyclic polycarbonamide fiber having orientation angle of less than about 45°," US Patent No. 3,819,587, June 25, 1974.
  8. Stephanie Kwolek, Chemical Heritage Foundation Web Site.
  9. DuPont Announces Millionth Vest Made with DuPont™ Kevlar® XP™, Dupont Press Release, June 18, 2014.

Permanent Link to this article

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