Stephanie Kwolek

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Stephanie Kwolek (born July 31, 1923) is an American chemist who discovered poly-paraphenylene terephtalamide, better known as Kevlar. Born in the Pittsburgh suburb of New Kensington, Pennsylvania, she joined DuPont as a chemist in 1946, specializing in low-temperature processes for the preparation of condensation polymers.

She received her B.S. in chemistry from the Carnegie Institute of Technology (now Carnegie Mellon University) in 1946, originally hoping to continue to medical school. However, she lacked the money and instead took a job as a research chemist with DuPont.

DuPont was at the forefront of research into synthetic fibers, having discovered and brought to market nylon, Dacron polyester, Lycra spandex, and later Nomex aramid. Kwolek was part of a DuPont team working to find new synthetic fibers of commercial importance. (Her particular mandate was to find a synthetic fiber of use in tire manufacture. Ironically, it would be decades before the fiber she discovered was used this way).

Team members, including Kwolek, had a great deal of latitude in directing their own research. She in particular was working with a class of intractable para-oriented aromatic polyamides. These are composed of rodlike molecules, unlike the very flexible molecules in nylon and other synthetic fibers. The challenge was not only in synthesizing these molecules, but also in finding solvents that would allow DuPont to spin the molecules into thread.

Kevlar in solution did not resemble DuPont's successful molecules — it was cloudy, opalescent upon being stirred, and of low viscosity. The chemist in charge of running the 'spinning' machine at first refused even to test it. However, Kwolek persuaded him to try, and both were surprised to see that the Kevlar solution was easy to spin into thread, and that once it had been spun, the threads were of tremendous strength.

Kwolek knew she had something important even before she ran rigorous tests on the fiber — the individual threads were hard to break by hand. When rigorously tested for tensile strength and other metrics, Kevlar showed itself to be extraordinary. In the years since, a whole new field of polymer chemistry has been built upon Kwolek's discovery.

She holds 17 patents, was inducted into the National Inventors Hall of Fame in 1995, and received the National Medal of Technology in 1996.