Back in 1965, Stephanie Kwolek stumbled upon something incredible—synthetic fibers so tough, even steel bullets couldn’t get through them. While studying long molecule chains at low temperatures, she noticed something unusual: polyamide molecules lining up in a way that created super-strong liquid crystalline solutions. This discovery led her to develop industrial fibers that save lives to this day, with the most famous one being Kevlar®. Kevlar is a heat-resistant material that’s five times stronger than steel but lighter than fiberglass, and it’s used in all sorts of things—bulletproof vests, spacecraft, helmets, tennis racquets, tires, and protective gloves, to name a few.

Kwolek grew up in New Kensington, Pennsylvania. Her dad, who died when she was 10 years old, was a naturalist and 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. Her mom, a homemaker, inspired her love of fabrics and sewing. Kwolek also had a knack for chemistry, teaching, and medicine.

After graduating from the women’s college at Carnegie Mellon (Margaret Morrison Carnegie College), Kwolek started applying for jobs as a chemist, including one at DuPont. Her interview with W. Hale Charch—who, fun fact, invented the process to make cellophane waterproof—was pretty unforgettable. He told her it would take about two weeks to decide whether she got the job, but Kwolek, not wanting to wait that long since she had another offer on the table, asked if he could speed things up. Right then and there, Charch called in his secretary and dictated an offer letter in front of her! Looking back, Kwolek believed her confidence played a big role in getting that offer.

Once she started at DuPont she realized chemistry was her jam. She ditched her med school plans and spent her career developing petroleum-based synthetic fibers that could handle extreme conditions. Her work involved synthesizing high-strength polymers, dissolving them in solvents, and spinning them into fibers.

One day, she made a surprising discovery—under certain conditions, polyamide molecules aligned to form cloudy, liquid crystalline solutions. Most researchers would’ve dismissed the cloudy, fluid texture, but Kwolek wanted to dig deeper. The guy running the spinning equipment was hesitant to spin the first solution. He was worried the cloudy appearance meant there were particles that could clog the super tiny spinneret holes (only 0.001 inch wide). But after some convincing, he gave it a shot—and to his surprise, it worked perfectly! The fibers came out strong and stiff without any issues. This breakthrough led to many more fibers being spun from liquid crystalline solutions resulting in products designed to withstand bullets, tears, heat, and more, including the iconic yellow Kevlar fiber.

Kwolek led polymer research at DuPont’s Pioneering Lab until she retired in 1986. She received many awards for her invention of the technology behind Kevlar fiber, including induction into the National Inventors Hall of Fame in 1995. In 1996 she received the National Medal of Technology, and in 1997 the Perkin Medal, presented by the Society of Chemical Industry. 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. Quite the legacy!

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.

Sources:

American Chemical Society. Stephanie Kwolek (1923–2014). https://www.acs.org/education/whatischemistry/women-scientists/stephanie-kwolek.html Accessed: Mar 7, 2025.

Science History Institute Museum & Library. Stephanie L. Kwolek -In a polymer research lab at DuPont, Kwolek discovered the super fiber known as Kevlar. https://www.sciencehistory.org/education/scientific-biographies/stephanie-l-kwolek/ Accessed: Mar 7, 2025.

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