Milestones of Innovation 5: Stephanie Kwolek and Kevlar


Let’s hear it for Stephanie Kwolek, a determined, observant, and playful chemist who died last year at the age of 90. She is the inventor-heroine of an artificial fiber stronger than steel called kevlar, which has saved thousands of soldiers and policemen from fatal bullet wounds and is used in everything from cellphones to skis. This year marks the 50th anniversary of the moment that Kwolek was convinced that she had discovered the real McCoy and could show it to her bosses at E.I. duPont de Nemours and Co. without embarrassment.

Her story, which DuPont celebrated at this year’s X Games Aspen, carries at least three lessons: 1. You must have the intellectual capital—what Edwin Land once called a track record of “structured accomplishments”—organization, and moolah to bring an innovation to scale. 2. You have to have researchers who are ready for a surprise and who stick to their guns. 3. In Kwolek’s view, although more parents are encouraging their daughters to enter science, even today women should be prepared for something short of full equality and do two majors.

Kwolek was the daughter of Polish immigrants: her workman father taught her to love exploring nature, and her seamstress mother encouraged a deep interest in fabrics and fashion. She took a job at DuPont in 1946 as a lab chemist to earn money for medical school, but stayed on because the work was interesting, persevering in spite of the slow promotions granted to women in research and sharing an American Chemical Society prize in 1959 for a widely used classroom demonstration of how students could make nylon in a beaker at room temperature. It was called the Nylon Rope Trick. As Kwolek once said: “All sorts of things can happen when you’re open to new ideas and playing around with things.”

In 1964, she started on a road that “was terribly exciting because it was so unexpected.” A veteran of DuPont’s vast, multi-decade drive for artificial fibers derived from petroleum, she was assigned a problem related to potential shortages of gasoline. DuPont’s idea was to improve gas mileage by paring a car’s weight. One way to do this was to substitute relatively light artificial fiber for steel in belted radial tires.

After a long string of successes, the massive, vertically integrated DuPont was stretching into fibers that could operate in extreme conditions, withstanding high temperatures or massive impacts. This would involve years of heavy capital expense and slogging scale-up. DuPont was going beyond the flexible strings of carbon atoms linked by “amide” bonds in nylon, say, to something more rigid. This included chains of “aromatic” carbon rings that could align tightly, but which were much more difficult to melt.

As Kwolek recalled for American Heritage of Invention and Technology, “I started working with the more intractable para-oriented aromatic polyamides, which are made up of rodlike molecules that are unlike the very flexible molecules you find in nylon.” It was “quite a bit of work” not only to make the molecules but to find the right solvent to dissolve them. She discovered a solvent that could produce an ultra-strong fiber (five times as strong as steel) at a moderate, energy-saving temperature. Her highly technical achievement was crucial to the economics of the new fiber.

“But the solutions turned out to be unlike any we had previously seen in the laboratory,” she said. “They were cloudy, opalescent on being stirred, and of low viscosity.” This stuff resembled buttermilk. It wasn’t the molasses-like liquid everybody at DuPont was used to after 40 years of developing nylon, orlon, and dacron. Some people might have been tempted to throw it out and start over. But not Stephanie Kwolek.

She asked a technician to run the liquid through his shower-head-like spinneret. He objected that the cloudy material contained particulates that could clog the tiny holes in the device. Kwolek persisted. Then, when the resulting threads absolutely would not snap in two, she sent the fibers back, more than once, to the testing lab—to be sure. And the numbers kept coming back about the fibers’ extraordinary strength.

When she showed the results to the higher-ups, all men, it turned out they already had somebody working on a separate project to develop potential body-armor material. And now Kwolek had produced the right type of material. With enthusiasm, DuPont launched a 15-year, $500 million development program for what Fortune magazine once called “a miracle in search of a market.”

Kwolek didn’t know it at first, but she had created the world’s first liquid crystal polymer. Her work eventually brought her induction into the National Inventor’s Hall of Fame in 1995, the National Medal of Technology in 1996, the Perkin Medal of the American Chemical Society in 1997, the MIT Lemelson Prize for lifetime achievement in 1999, and her third honorary degree—from her alma mater, Carnegie Mellon University—in 2000.

As you can imagine, she was one of the few women to attain any of these honors. She also became, so far, the only female employee of DuPont to receive its Lavoisier Medal (named for the founder of modern chemistry). It’s nice that Hale Charch, the man who hired her in 1946 and became a mentor, got a Lavoisier medal, too. She recalled that Charch had his own interests—researching, writing, and attending meetings—and left her “considerable independence.” So, “with this freedom, I was able to be creative and work as hard as I wanted.”

[Editor’s Note: This is the fifth of an envisioned series of notes about major anniversaries in innovation and what they teach us. You’re invited to suggest other milestones of innovation for in the Xconomy Forum. Example: This year will mark the 250th anniversary of James Watt’s brainstorm on a Sunday in Glasgow for a more efficient steam engine.]

Further Reading:

John Kenly Smith and David Hounshell, Science and Corporate Strategy: DuPont R & D 1902-1980, Cambridge University Press 1988, paperback 2006

Stephanie L. Kwolek, interview by Raymond C. Ferguson, May 4, 1986, Chemical Heritage Foundation ($5 fee)

Stephanie L. Kwolek, interview by Bernadette Bensaude-Vincent, Mar. 21, 1998, Chemical Heritage Foundation ($5 fee)

Jim Quinn, Hall of Fame Interview, Stephanie Kwolek, American Heritage of Invention and Technology, Volume 18, Issue 3, Winter 2003


Xconomist and science reporter Victor McElheny of MIT is author of Watson and DNA: Making a Scientific Revolution (2003) and Drawing the Map of Life: Inside the Human Genome Project (2010) Follow @

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One response to “Milestones of Innovation 5: Stephanie Kwolek and Kevlar”

  1. Bill Ghormley says:

    Innovation in chemistry is other-worldly in today’s hardware-software context — Kevlar is a “miracle” fiber! Thanks for its amazing history. BG