A chemist, Kwolek went to work at DuPont in 1946, researching textiles. In 1964, the company thought there would be a gasoline shortage, so she was assigned to work on coming up with a lightweight, strong fiber to reinforce automotive tires, rather than using “steel belts.” In her research on (take a deep breath) poly-p-phenylene terephthalate and polybenzamide, she created a polymer solution of “unusually [low viscosity],” she remembered later. “Turbid, stir-opalescent and buttermilk in appearance. This was a liquid crystalline solution, but I did not know it at the time.” Usually, when such solutions came out milky, they were considered failures and thrown away, but Kwolek asked a technician to test it anyway. He ran it through a spinneret to isolate the fibers, and Kwolek found they were exceptionally strong. “It formed very strong fibers and the stiffness was absolutely spectacular,” she said. “That’s when I said ‘Aha.’ I knew then and there it was an important discovery.” The fibers were, in fact, five times stronger than steel by weight, and they could be made even stronger with heat treatments. The material was also heat-resistant, and would definitely work to reinforce car tires. DuPont called the fiber “Kevlar”. By then, Kwolek had worked for DuPont for 15 years, and had never been promoted.
DuPont poured an estimated $500 million into developing Kevlar, introducing it commercially in 1971 for not only tires, but to reinforce everything from bridges to hockey sticks. It’s best known for making “bulletproof” vests for police officers and soldiers, where its light weight is a major plus. Even my smartphone has a Kevlar body, helping it to survive if dropped. DuPont has made billions on the material, but because she created it on company time, Kwolek didn’t get a percentage of the sales. She was, however, promoted, leading DuPont’s efforts in a new field, polymer chemistry. She retired from the company in 1986, and tutored high school chemistry students, keeping a special eye out for gifted girls and encouraging them to pursue careers in science. DuPont’s CEO called Kwolek “a true pioneer for women in science,” and she surely helped shape DuPont, too: that CEO is a woman, Ellen Kullman. Kwolek was awarded the company’s Lavoisier Medal for outstanding technical achievement in 1995, as a “Persistent experimentalist and role model whose discovery of liquid crystalline polyamides led to Kevlar aramid fibers.” Kwolek is still the only female employee at the company to receive that honor. Outside the company, she was also well recognized. In 1980, Kwolek received the Chemical Pioneer Award from the American Institute of Chemists. In 1995, she became only the fourth woman to be inducted into the National Inventors Hall of Fame. In 1996, she received the National Medal of Technology, and in 1997 she received the Perkin Medal from the American Chemical Society. The day she died, in hospice care at age 90 on June 18, DuPont announced the one-millionth ballistic Kevlar vest had been sold. The vests have been credited with saving thousands of lives.