Kwolek, who worked for the DuPont chemical company for four decades starting in 1946, died in Delaware after a short illness. The company confirmed her death.
"We are all saddened at the passing of DuPont scientist Stephanie Kwolek, a creative and determined chemist and a true pioneer for women in science," DuPont Chief Executive Ellen Kullman said in a statement. "Her synthesis of the first liquid crystal polymer and the invention of DuPont Kevlar highlighted a distinguished career."
The 4-foot-11 Kwolek was working to find a fiber to strengthen radial tires when she came across a thin, milky solution of polymers that showed real promise.
She told the News Journal newspaper in Wilmington, Delaware, in 2007 that it was not exactly a "eureka moment." But it led to the development of Kevlar, now a critical part of bulletproof vests, helmets and other body armor components as well as a range of other applications like tires, firefighter suits, boat hulls, fiber optic cables, fuel hoses, airplane and spacecraft parts and skis.
Kevlar is lightweight but extremely strong - five times tougher than steel.
"At least, I'm hoping I'm saving lives," Kwolek told the newspaper. "There are very few people in their careers that have the opportunity to do something to benefit mankind."
She was careful to take credit for only the initial discovery of the technology that led to the development of Kevlar and credited the work of others involved in the efforts.
In the 2007 comments, she said she was afraid to tell her managers and conducted repeated tests just to make sure.
"I didn't want to be embarrassed. When I did tell management, they didn't fool around. They immediately assigned a whole group to work on different aspects," she said.
Kwolek was born on July 31, 1923, in New Kensington, Pennsylvania, graduated from Carnegie Institution of Technology with a chemistry degree and was hired by Dupont a year after the end of World War Two.