JOHN YANG: The fiber Kevlar is stronger than steel, and it's revolutionized everything from body armor for the military and police to sports equipment.

Its inventors the subject of tonight's hidden histories for Women's History Month.

Here's Ali Rogin.

ALI ROGIN (voice-over): Skis, brake pads, racing sails, spacesuits.

MAN: I think this is just a fantastic looking suit.

ALI ROGIN (voice-over): And perhaps most famously, the bulletproof vest.

These products and many others are made with Kevlar, a strong lightweight fiber invented by researcher Stephanie Kwolek in 1965.

It all began when DuPont Chemicals asked researchers to make a fiber that could withstand extreme conditions.

STEPHANIE KWOLEK, Chemist: The solution was very, very fluid.

I mean, it was almost like had the consistency of water.

ALI ROING (voice-over): Synthetic fibers start in liquid form and are spun into a strand.

STEPHANIE KWOLEK: So when I asked the technologists to help me with the spinning, he refused, because he said, this will never spin.

It's too fluid.

It's it probably has particulate matter in a because it's cloudy and so forth.

ALI ROGIN (voice-over): But Kwolek was convinced it would work and persuaded him to give it a try.

STEPHANIE KWOLEK: Well, the results came back and they were sort of unbelievable.

ALI ROGIN (voice-over): The fiber was lightweight, heat resistant, and five times stronger than steel.

STEPHANIE KWOLEK: There of course, was immediate excitement.

Because everybody realized the potential of this discovery.

ALI ROGIN (voice-over): But Kwolek did not set out to become an inventor.

Growing up outside Pittsburgh, she considered fashion inspired by her mother who sewed.

Later as a bright student, she thought about teaching.

By the time she started college in the midst of World War II, she was determined to go to medical school.

She chose to major in chemistry at Carnegie Tech, now called Carnegie Mellon University.

But when she graduated, her plans changed again.

STEPHANIE KWOLEK: Since I could not afford to go to medical school at that time, I had to go out and seek employment.

ALI ROGIN (voice-over): She got several job offers, but one stood out for its interesting work, and for paying men and women the same starting wage.

STEPHANIE KWOLEK: And so I took the job with the DuPont Company.

The only problem was that I became so enamored of the work that I totally lost interest in medical school.

ALI ROGIN (voice-over): When she started DuPont Research Laboratory was in the middle of a race to discover fibers that would revolutionize not just fashion but war and space travel.

MAN: Miss Gloria Glamour fields for the ultimate in hosiery.

ALI ROGIN (voice-over): Just a few years earlier, the company had created the first synthetic fiber nylon.

MAN: No baggy needs all the forming wrinkles during the life of a nylon stocking.

ALI ROGIN (voice-over): That fiber success and wartime rationing of natural materials like silk and rubber will set off and intense competition between companies like DuPont and Monsanto.

STEPHANIE KWOLEK: There was tremendous interest in new fibers, and new ways to make fibers.

ALI ROGIN (voice-over): Over the next few decades, the group created the methods and techniques that would be used to make spandex.

MAN: That's one small set for men.

ALI ROGIN (voice-over): New polyester and acrylic fabrics.

MAN: These curtains are made of Dacron polyester fiber.

ALI ROGIN (voice-over): And the flame resistant Nomex.

But there was another stiffer stronger fiber waiting to be discovered.

Kevlar.

In 1964, Kwolek's research group was tasked with finding a fiber to make durable, lightweight tires to improve fuel efficiency in cars.

STEPHANIE KWOLEK: It got to be a race, but it was a very, very, very secretive race.

So that very few people outside of our laboratory knew what was going on.

But it still was a lot of fun, particularly if you want.

ALI ROGIN (voice-over): And they did.

Kwolek crack the problem in 1965, discovering a version of the polymer that could be spun up into a fiber.

Fiber B as it was known internally became Kevlar, the basis for a whole family of products.

Kwolek spent the rest of her career at DuPont.

She mentored other women in her field and worked to introduce young people to science, writing letters and giving lectures.

STEPHANIE KWOLEK: I really did not think of the bulletproof vests.

We had Dr. Joe Rivers, who at that time, was already looking for fibers to use to and making bulletproof vests.

And I remember the very first time that I spun the one for B that he came over and he said if you can possibly spare a tiny bit of that fiber, I would like to test it and see if it'll be useful and a bulletproof vests.

ALI ROGIN (voice-over): She was named on a total of 28 patents and won several awards for her work, including the National Medal of Technology.

Kwolek was inducted into the National Inventors Hall of Fame in 1995.

At the time, she was only the fourth female inductee, but to Kwolek her crowning achievement was making Kevlar possible.

STEPHANIE KWOLEK: I was fortunate enough to do something that would be a benefit to mankind.

It's been an extremely satisfying discovery.

I don't think there's anything like saving someone's life to bring you satisfaction and happiness.

ALI ROGIN (voice-over): Kwolek died in 2014 at the age of 90, but her greatest invention is still saving lives today.

For PBS News Weekend, I'm Ali Rogin.