Stephanie Kwolek

Remembering Stephanie Kwolek, Gerry Conlon, Johnny Mann

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• published: 15 Jul 2014
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The Woman Who Stopped Bullets KEVLAR, THE GUILDFORD FOUR, AND THEODORE Stephanie Kwolek was one of the most important female inventors of the 20th Century. As a chemist for DuPont, she discovered a polymer that was stronger than steel. Her discovery, Kevlar, became the basis for bulletproof vests, helmets and countless other items where lightweight strength and durability is critical in saving lives and preventing injury. Gerry Conlon was unjustly imprisoned for nearly 18 years after being wrongly convicted of an IRA bombing. The story was immortalized in the 1993 movie In The Name Of The Father, starring Daniel Day-Lewis, Pete Postlethwaite, and Emma Thompson. Johnny Mann was the Hollywood composer and conductor who was also the voice of Theodore for Alvin and the Chipmunks. Stephanie Louise Kwolek (July 31, 1923 -- June 18, 2014) was an American chemist, whose career at the DuPont company covered over forty years.[1] She is best known for inventing the first of a family of synthetic fibers of exceptional strength and stiffness: poly-paraphenylene terephthalamide—better known as Kevlar.[2][3] For her discovery, Kwolek was awarded the DuPont company's Lavoisier Medal for outstanding technical achievement. As of June 2014, she was the only female employee to have received that honor.[4] In 1995 she became the fourth woman to be added to the National Inventors Hall of Fame.[5] Kwolek won numerous awards for her work in polymer chemistry, including the National Medal of Technology, the IRI Achievement Award and the Perkin Medal. While working for DuPont, Kwolek invented Kevlar.[9] In 1964, in anticipation of a gasoline shortage, her group began searching for a lightweight yet strong fiber to be used in tires.[9] The polymers she had been working with at the time, poly-p-phenylene terephthalate and polybenzamide,[13] 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).[9] 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."[14] 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.[9] 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.