What did Stephanie Louise Kwolek invent?

Stephanie Louise Kwolek (July 31, 1923 – June 18, 2014) was an American chemist of Polish heritage, whose career at the DuPont company spanned over 40 years. She is best known for inventing the first of a family of synthetic fibres of exceptional strength and stiffness: poly-paraphenylene terephthalamide—better known as Kevlar. For her discovery, Kwolek was awarded the DuPont company's Lavoisier Medal for outstanding technical achievement. As of February 2015, she was the only female employee to have received that honor. In 1995 she became the fourth woman to be added to the National Inventors Hall of Fame. Kwolek won numerous awards for her work in polymer chemistry, including the National Medal of Technology, the IRI Achievement Award and the Perkin Medal.

In 1964, in anticipation of a gasoline shortage, her group began searching for a lightweight yet strong fibre 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 fibres.

This sort of cloudy solution was usually 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.