Her friend, Rita Vasta, told The Associated Press that Stephanie Kwolek died Wednesday in a Wilmington hospital. Vasta says she doesn't know the cause of death but that Kwolek had been ill for about a week.
DuPont says Kwolek made her discovery in the mid-1960s while working on speciality textile fibers. She invented a liquid crystalline solution that could be spun into exceptionally strong fibers.
Kevlar is widely used in protective equipment by police and the military.
Vasta says Kwolek was proud of her invention and worked to get more women into science.