Saturday, May 28, 2016

Stephanie Kwolek, Chemist and Inventor

Stephanie Kwolek was a chemist working at DuPont when she was assigned to discovering the next high-technology material. She invented Kevlar, a lightweight material five times stronger than steel. 

"All sorts of things can happen when you are open to new ideas and playing around with things."~ Stephanie Kwolek

Stephanie Kwolek was born in 1923 in New Kensington, Pennsylvania. Her father John was a scientist, and her mother Nellie was a seamstress. Stephanie spent many hours with her father exploring the woods and fields near their home and filling scrapbooks with her observations, though he would die prematurely when Stephanie was only 10.

From her mother, Stephanie gained a love of sewing and fabric construction, and at one point she even considered a job as a designer."I did not start out to be a chemist. As a child, I thought I might be a fashion designer. I spent an awful lot of time drawing various types of clothing and sewing."

Sewing provided a creative outlet for Stephanie and she learned the satisfaction of crafting something with her own hands, though her mother warned her that she would starve if she were a designer, as she was such a perfectionist. Stephanie pursued teaching for a while, then decided on medicine and chemistry as fields of study.


Stephanie's work in high school earned her a scholarship to study biology in college, and she enrolled in Carnegie Institute of Technology, now Carnegie Mellon, in 1942. She was frequently invited to present her research work and papers, which she found flattering and encouraging. She subsequently switched to chemistry, and in 1946 she graduated with a BA degree.

After graduation, she applied to DuPont to work as a chemist, and was interviewed by research director W. Hale Church, who had invented the process to make cellophane waterproof.

At the end of the interview, Church told her she would be hearing back from them in two weeks, letter him know if she got the job, but she asked if he could get back to her sooner. She had another offer she had to make a decision on, she explained.

Church called his secretary into the room and dictated an offer letter for Stephanie right then and there, in her presence. She always believed her assertiveness paid off for her in that instance, nudging the decision in her favor.

Working at Dupont

At Dupont, Stephanie joined a team of chemists called the Pioneering Research Laboratory. Dupont had recently invented the world's first synthetic fiber, nylon, and the research Stephanie was engaged in was so fascinating that within a few years she had given up her idea of going to medical school, she was just enjoying what she was doing so much.

In 1965, the American government and industries feared a gasoline shortage. In their exploration of ways to improve fuel economy, DuPont challenged their chemists to come up with the next high-performance fiber to take the place of steel wire in tires, because lighter tires would mean better fuel economy.

The research involved preparing samples, synthesizing polyamides of high molecular weight, dissolving them in solvents, and spinning the solution into fibers. Stephanie was working with long-chain polymers that were very difficult to dissolve, but she found the right solvent.

What that left her with was a "very thin solution, very watery." It was opalescent and "peculiar, not the typical polymer solution." Exploring this solution further, Stephanie had a breakthrough when she discovered that under the right conditions, large numbers of the molecules of the long-chain, rod-like polyamides would line up in parallel, forming liquid crystalline solutions that could be spun into oriented fibers of very high strength and stiffness.

To transform the polymer solution to a fiber took a process called spinning. The liquid would be poured into a spinneret, which would force the liquid through tiny holes to create strands, then spins them in a method that is similar to how cotton candy is made.

Stephanie knew they were looking for a new material and was not put off by the fact that the liquid she was working with looked different, but the operator of the spinneret was. What Stephanie took to be an opalescent feature of the liquid, the spinneret operator took to be particles.

"This solution is too thin; it’s too watery," she recalled him saying, "Furthermore, it has particles in it, and it’s gonna plug up my equipment.”

Stephanie persevered, however. "I filtered this solution, and I knew there were no particles in it, and he still refused to spin it. So I think eventually after a few days — he had a guilty conscience or something — and he came and said he would spin that thing. We spun it, and it spun beautifully."

"It was very strong and very stiff-unlike anything we had made before. I knew that I had made a discovery. I didn't shout "Eureka!" but I was very excited, as was the whole laboratory excited, and management was excited, because we were looking for something new. Something different. And this was it."

Looking back on it later, Stephanie recalled: “I knew the direction in which to go, but I will tell you this: I never expected to get the properties I did the first time I spun it.”

She describes the discovery as “a case of serendipity,” but the liquid might never have been spun if she had not pushed the equipment operator to do it. He simply was not looking for a liquid that had that kind of appearance, and Stephanie was.

Uses of Kevlar

Today Kevlar is used in hundreds of household and industrial applications. Valued for being lightweight and incredibly strong (five times stronger than steel), it is best known for its use in ballistics and stab-resistant body armor, and is credited with saving the lives of thousands of people around the world.

In Iraq in 2009, soldiers utilized Kevlar helmets and vests instead of their standard steel helmets because the Kevlar stopped the shrapnel more effectively, up to 40% better. Today's ground troops and journalists must wear helmets and vests lined with Kevlar to protect their vital organs.

Besides body armor, it can be found in over two hundred applications, ranging from fiber optic cables to vehicles and tires (the original application it was created for), to city roads.

Recognition and retirement

While receiving professional acclaim, Stephanie never profited directly from the invention of Kevlar, as she had signed over the patent royalties to Dupont. She led the team in polymer research until her retirement in 1986, and obtained 17 individual patents for work she did alone, and another 9 patents for work with teams.

After retiring, Stephanie tutored high school students in Chemistry, focusing particularly on young women with an interest in the sciences, and serving as a mentor. In 1994 she was induced to the National Inventors Hall of Fame, where she was only the forth woman, of 113 members.

In 1996 Stephanie received the National Medal of Technology, and in 1997 the Perkin Medal, both rarely awarded to women. She was also induced in the National Women's Hall of Fame, and the Plastics Hall of Fame.

Another way Stephanie is well known in the classroom is through her paper, "The Nylon Rope Trick," published in 1959. This paper describes how to demonstrate condensation polymerization in a beaker at atmospheric pressure and room temperature, and has become a popular and common demonstration in classrooms nationwide.

She died on June 18th, 2014, in Wilmington, DE. She was 90 years old.

Even when she knew they were on to something completely different, Stephanie did not foresee all these applications. "I guess that's just the life of an inventor, what people do with your ideas takes you totally by surprise."


"I seem to see things that other people do not see."

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

  • Stephanie L. Kwolek, Chemical Heritage Foundation,, 2016.
  • Stephanie Kwolek (b. 1923), American Chemical Society,, 2016.
  • Stephanie Kwolek, the Great Idea Finder,, 2016.
  • Stephanie Kwolek: A Great Woman in Sewing, Whipstitch editor,, 2016.
  • Stephanie Kwolek: Film Transcript. Chemical Heritage Foundation,, 2016.

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