The odd, cloudy batch of polymers that DuPont chemist Stephanie Kwolek mixed up in 1964 might have seemed like a mistake to another researcher. Usually, a polymer solution was clear and viscous. This one was thin and cloudy, almost as if it was contaminated. But Kwolek was more intrigued than disappointed, and continued to work with the chemicals. Her diligence paid offthat milky batch of chemicals led to the development of Kevlar, a super-strong, super-stiff fiber that has saved thousands of lives.
Kevlar is now virtually synonymous with high-tech materials. Heat-resistant, five times as strong as steel, and lighter than fiberglass, it is used in hundreds of products, from protective gloves, helmets, and boots to tires, brake pads, and cables. It's used on spacecraft and to build bridges. Its most famous role, though, is in bulletproof vests, which contain several layers of a fabric woven from Kevlar fiber. According to the Kevlar Survivors Club, at least 2,000 lives have been saved by the bullet-stopping fiber.
With such a big role in the invention of one of the world's best-known synthetic fibers, it's ironic that Kwolek didn't intend to become a chemist. She wanted to be a doctor. Kwolek was born in New Kensington, Pennsylvania, in 1923. Although her father died when she was only 10 years old, he had an early influence on her interest in science. "I remember trudging through the woods near my house with him and looking for snakes and other animals," she says. "We also studied the various wild plants and leaves and seeds." At the same time, she adds, "I was very much interested in designing fashions. That interest came from my mother. I spent many hours creating clothes for my dolls." It was a happy coincidence that the group she later joined at DuPont was devoted to fibers and textiles.
Opportunities for Women Scientists
When Kwolek graduated from Margaret Morrison Carnegie College (now Carnegie Mellon University) in 1946, she realized she couldn't afford to study medicine. She had majored in chemistry, and decided to get a job in that field to save enough money to eventually go to medical school. Technical fields like chemistry had just opened up to women. During World War II, women had entered the work force in unprecedented numbers. When the war ended, many men weren't available, since they had spent the previous five years fighting, not studying. She knew that DuPont was the leading chemical company, and that it was interviewing prospective chemists. Dr. Hale Charch, later a mentor to Kwolek, met with her. After some forceful insistence on Kwolek's part, Charch offered her a job on the spot, and she soon joined DuPont's Buffalo, New York, research facility.
Kwolek began working at DuPont only eight years after the first synthetic fiber, nylon, had been created. With a team of chemists called the Pioneering Research Laboratory, she began exploring new polymer fibers and new ways to make them. These methods allowed her team to make and test hundreds of thousands of new polymers.
In 1964, her group decided to search for a new high-performance fiber. They had a specific use in mind for it: there were predictions of a gasoline shortage, and they thought that a strong, lightweight fiber could be used to reinforce car tires. Lighter, stiffer tires would use less gasoline. "A number of people had been asked to take up this project and no one seemed to be particularly interested," Kwolek explains. "So I was asked if I would do it."
"I made a discovery"
"In the course of that work I made a discovery," she says modestly. Under specific conditions, the polymers she was working with would form liquid crystals in a solution, which no polymer had ever done before. And instead of the usual "bent" polymer moleculesshe likens them to spaghettithese were straight, like match sticks. When the cloudy solution was "spun"forced through the tiny holes of a device called a spinneretthe straight fibers lined up parallel to each other. This made the new fiber very stiff and very strong.
It was not easy for Kwolek to get the polymer solution into the spinneret. "That solution was very different from the standard polymer solution," she recalls. "It had a lot of strange features. I think someone who wasn't thinking very much or just wasn't aware or took less interest in it, would have thrown it out." Kwolek filtered it to see if the cloudy solution was contaminated. It wasn't. Still, she continues, "when I submitted it for spinning the guy refused to spin it. He said it would plug up the holes of his spinneret, because he assumed that [it had] solid particles. So it was a while before he consented to spinning it. I think either I wore him down or else he felt sorry for me."
The Creation of Kevlar
When a chemist spins a fiber, she sends it to a lab to test its strength, stiffness, and other properties. This new fiber came back from the lab with a stiffness at least nine times greater than anything she'd made before. "I was very hesitant about telling anyone," she says. "I didn't want to be embarrassed if someone had made a mistake. So I sent the fiber down several times. The numbers always came back in the same vicinity." Only then did she announce her results, and DuPont realized it had a fiber with great potential. After much more work and refinement by the group, Kevlar was introduced in 1971. The fiber has since found more than 200 applications.
"I love doing chemistry," Kwolek says. "And I love making discoveries." Her careful, dedicated approach to research helped her throughout a 40-year career at DuPont. "I discovered over the years that I seem to see things that other people did not see," she explains. "If things don't work out I don't just throw them out, I struggle over them, to try and see if there's something there." It was just that will to carefully observe, struggle, and stay the course that led to her famous fiber. Today, police officers and others whose lives depend on Kevlar often come up to her to tell of their experiences. One Viriginia police officer even had Kwolek autograph his bulletproof vest, which had saved his life. "I feel very lucky," she says. "So many people work all their lives and they don't make a discovery that's of benefit to other people."