Learning from InvENtors: Stephanie Kwolek

Learning from InvENtors: Stephanie Kwolek

In honor of her birthday, this Learning from InvENtors post will highlight the career and accomplishments of Stephanie Louise Kwolek.

Stephanie Kwolek was an American chemist whose career at the DuPont company spanned over 40 years.

In 1965, Kwolek made an unexpected discovery that led to the creation of synthetic fibers so strong, not even steel bullets could penetrate them. The best-known member is poly-paraphenylene terephthalamide—better known as Kevlar®, a heat-resistant material that’s five times stronger than steel, but lighter than fiberglass.

Early Life

Stephanie Kwolek was born in New Kensington, Penn. Her father, who died when she was 10 years old, was a naturalist by avocation. She spent many hours with him exploring the woods and fields near her home and filling scrapbooks with leaves, wildflowers, seeds, grasses, and pertinent descriptions. From her mother, first a homemaker and then by necessity a career woman, Kwolek inherited a love of fabrics and sewing. At one time she thought she might become a fashion designer, but her mother warned her she would probably starve in that business because she was such a perfectionist. Later Kwolek became interested in teaching and then in chemistry and medicine.

College and DuPont

Lacking the funds for medical school, Kwolek applied for a position as a chemist with the DuPont Company (among other places) after graduating from the women’s college (Margaret Morrison Carnegie College) of Carnegie Mellon University.

Her job interview with W. Hale Charch, who had invented the process to make cellophane waterproof and who was by then a research director, was a memorable one. After Charch indicated that he would let her know in about two weeks whether she would be offered a job, Kwolek asked him if he could possibly make a decision sooner since she had to reply shortly to another offer. Charch called in his secretary and in Kwolek’s presence dictated an offer letter. In later years she suspected that her assertiveness influenced his decision in her favor.

At DuPont, the polymer research Kwolek worked on was so interesting and challenging that she decided to drop her plans for medical school and become a lifetime chemist. Kwolek worked with great determination, because she loved the work, but also because she did not want to lose her laboratory position, as many women did, when World War II ended. She soon earned a transfer to DuPont’s Pioneering Research Laboratory in Wilmington, Delaware, when it opened in 1950. Here, with the support of Charch, the first Director of the Lab, Kwolek has a string of successes in the search for new and better polymers.

Discovering Kevlar®

Assigned to finding the next generation of fibers that could withstand extreme conditions, Kwolek’s work involved preparing intermediates, synthesizing aromatic polyamides of high molecular weight, dissolving the polyamides in solvents, and spinning these solutions into fibers.

Unexpectedly, she discovered that under certain conditions, large numbers of polyamide molecules line up in parallel to form cloudy liquid crystalline solutions. Most researchers would have rejected the solution because it was fluid and cloudy rather than viscous and clear. But Kwolek took a chance and spun the solution into fibers more strong and stiff than had ever been created.

Kevlar Reaction

DuPont put its Pioneering Lab to work finding a viable commercial version of Kwolek’s new crystalline polymers, the potential applications for which were obvious. The result was Kevlar® (first marketed in 1971), a fiber five times stronger ounce for ounce than steel, but about half the density of fiberglass.

Stephanie Kwolek and others of the DuPont group that developed Kevlar. Left to right: Kwolek, Herbert Blades, Paul W. Morgan, and Joseph L. Rivers Jr.

Kevlar® is best known to the public as the material from the which bulletproof vests are made; and in this use alone Kwolek’s discovery has saved thousands of lives. In fact, Kevlar® has dozens of important applications, including radial tires and brake pads (a replacement for asbestos), racing sails, fiber optic cable, water-, air- and spacecraft shells, and mooring and suspension bridge cables. It is now used to make skis, safety helmets, and hiking and camping gear. In commercial terms, Kevlar® generates sales of hundreds of millions of dollars per year worldwide.This breakthrough opened up the possibilities for a host of new products resistant to tears, bullets, extreme temperatures, and other conditions.

Speaking about her discovery, Stephanie Kwolek noted,

“I don’t think there’s anything like saving someone’s life to bring you satisfaction and happiness.”

Stephanie Kwolek headed polymer research at DuPont’s Pioneering Lab until her retirement in 1986.

Recognition and Patents

Kwolek’s research efforts have resulted in her being the recipient or co-recipient of 17 U.S. patents, including one for the spinning method that made commercial aramid fibers feasible, and five for the prototype from which Kevlar® was created.

Kwolek received many awards for her invention of the technology behind Kevlar® fiber among them…

In 1980, she received the Chemical Pioneer Award of the American Institute of Chemists.

In 1994, she was inducted into the National Inventors Hall of Fame, only the fourth woman member of 113 at the time and she also became a Kilby Laureate.

She was awarded the DuPont company’s Lavoisier Medal for outstanding technical achievement in 1995. To date, she is the only female employee to have received that honor.

In 1996 she received the National Medal of Technology, and in 1997 the Perkin Medal, presented by the Society of Chemical Industry, the highest award in American industrial chemistry.

In 1999, she was awarded the Lemelson-MIT Lifetime Achievement Award.

In 2003 she was inducted into the National Women’s Hall of Fame.

Kwolek served as a mentor for other women scientists and participated in programs that introduce young children to science. One of Kwolek’s most cited papers, written with Paul W. Morgan, is “The Nylon Rope Trick” (Journal of Chemical Education, April 1959, 36:182–184). It describes how to demonstrate condensation polymerization in a beaker at atmospheric pressure and room temperature—a demonstration now common in classrooms across the nation.

In 2013 her story was told in a children’s book by Edwin Brit Wyckoff, The Woman Who Invented the Thread That Stops the Bullets: The Genius of Stephanie Kwolek.

Kwolek died in Delaware at the age of 90 in 2014.


Stephanie Kwolek was not a woman who took “no” for an answer. Her determination and passion yielded one of the most powerful materials we have in the world today. We hope her story inspired your next idea!


 Sources:

https://www.acs.org/content/acs/en/education/whatischemistry/women-scientists/stephanie-kwolek.html

https://www.famousscientists.org/stephanie-kwolek/

http://www.ideafinder.com/history/inventors/kwolek.htm

https://www.sciencehistory.org/historical-profile/stephanie-l-kwolek

http://www.women-inventors.com/Stephanie-Kwolek.asp

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