History of Scientific Women

Main achievements: Inventor of the Kevlar.

Stephanie Louise Kwolek was an American chemist who invented poly-paraphenylene terephthalamide—better known as Kevlar. She was born in the Pittsburgh suburb of New Kensington, Pennsylvania. Kwolek won numerous awards for her work in polymer chemistry.

Kwolek was born to Polish immigrant parents in New Kensington, Pennsylvania, in 1923. Her father, John Kwolek (Polish: Jan Chwalek), died when she was ten years old. He was a naturalist by avocation, and Kwolek spent hours with him, as a child, exploring the natural world. She attributed her interest in science to him and an interest in fashion to her mother, Nellie (Zajdel) Kwolek.

In 1946, Kwolek earned a degree in chemistry from Margaret Morrison Carnegie College of Carnegie Mellon University. She had planned to become a doctor and hoped she could earn enough money from a temporary job in a chemistry-related field to attend medical school. In 1946, Hale Charch, a future mentor to Kwolek, offered her a position at DuPont's Buffalo, New York, facility. Charch had initially told Kwolek that he would contact her within two weeks, but after Kwolek said she had to answer another job offer and insisted on a faster reply, Charch immediately offered her the position. Although Kwolek initially only intended to work for DuPont temporarily, she found the work interesting enough to stay and not pursue a medical career.

She moved to Wilmington, Delaware, in 1950 to continue to work for DuPont. In 1959, she won a publication award from the American Chemical Society. While working for DuPont, Kwolek invented Kevlar. In 1964, in anticipation of a gasoline shortage, her group began searching for a lightweight yet strong fiber to be used in tires. The polymers she had been working with at the time, poly-p-phenylene terephthalate and polybenzamide, formed liquid crystal while in solution that at the time had to be melt-spun at over 200 °C (392 °F), which produced weaker and less-stiff fibers. A unique technique in her new projects and the melt condensation polymerization process was to reduce those temperatures to between 0–40 °C (32–104 °F). As she later explained in a 1993 speech: “The solution was unusually (low viscosity), turbid, stir-opalescent and buttermilk in appearance. Conventional polymer solutions are usually clear or translucent and have the viscosity of molasses, more or less. The solution that I prepared looked like a dispersion but was totally filterable through a fine pore filter. This was a liquid crystalline solution, but I did not know it at the time.” This sort of cloudy solution usually was thrown away. However, Kwolek persuaded technician Charles Smullen, who ran the spinneret, to test her solution. She was amazed to find that the new fiber would not break when nylon typically would. Not only was it stronger than nylon, Kevlar was five times stronger than steel by weight. Both her supervisor and the laboratory director understood the significance of her discovery, and a new field of polymer chemistry quickly arose.

By 1971, modern Kevlar was introduced. Kwolek learned that the fibers could be made even stronger by heat-treating them. The polymer molecules, shaped like rods or matchsticks, are highly oriented, which gives Kevlar its extraordinary strength. Kwolek was not very involved in developing practical applications of Kevlar. Once senior DuPont managers were informed of the discovery, they immediately assigned a whole group to work on different aspects," she said. She also did not profit from DuPont's products, as she signed over the Kevlar patent to the company. Kevlar is used to build cellular telephones; Motorola's Droid RAZR has a Kevlar unibody. Kevlar is also used for sports rackets and bullet-proof vests. During the week of Kwolek's death, the one millionth bullet-resistant vest made with Kevlar was sold. For her discovery, Kwolek was awarded the DuPont company's Lavoisier Medal for outstanding technical achievement: at the time of her death, she is still the only female employee to receive that honor.

Source: Wikipedia