Women Inventors: How Stephanie Kwolek Created Kevlar

Women Inventors: How Stephanie Kwolek Created Kevlar
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Childhood Traits Instilled

As a young girl, Stephanie Kwolek spent time exploring the woods with her father, John, a naturalist. She was great around animals and knew how to study them on quiet feet. Her father instructed her in noiseless observation. He taught her to examine details, remember to focus and take in everything that happened around her.

Patience paid off. Together they watched spiders, tracked paw prints and collected leaves, seeds and other treasures she carefully pressed into scrapbook pages. Stephanie lost her father when she was only 10 years old, but the lessons he imbued in his daughter would add value to the rest of her life.

History of Protective Wear

As long as men have done battle, they have looked for protective clothing. When the Greeks were marching to the sea in 401 BC, Xenophon, a great warrior, led his army of Greek mercenaries up the Tigris valley. He writes an eyewitness account of meeting the Chalybes, a most warlike tribe. He says, “They had body armour of linen, reaching down to the groin, and instead of skirts to their armour they wore thick twisted cords. They also wore greaves and helmets and carried on their belts a knife about the size of the Spartan dagger.”

The Roman Armies wore chain mail (maille) shirts, which were rings of heavy iron, steel or brass linked together in breastplates. Other large countries such as Persia, India and Japan also developed their own overlapping scales of protection, often utilizing metal, horn, bones, leather and plates of animal skin and rhinoceros hide.

Renaissance Europe had the most prolific armor production in both Northern Italy and the south of Germany. In Milan, one family, the Missaglias, became prominent for their artisanship; they exported armor in all directions. A man who earned fame as a skilled and highly esteemed armorer of his age was Filippo Negroli (1510–1579), a descendant of the Missaglias. His business provided parade armor for the Emperor, hunting plates and protective wear for the duke of Urbino, Francesco Maria I della Rovere.

Metropolitan Museum of Art historians claim that armor was most commonly looted from the battlefield and worn by knights or warriors. However, armor could also be bought at all price points and was often ready-made at markets, trade fairs and city shops. Of course, the king’s armor would have been the craft of celebrated masters, and although it is hard to assess costs, perhaps the phrase, “worth a king’s ransom” is apropos here.

The Big Idea

Stephanie Kwolek’s discovery of Kevlar—protective wear—came about as the result of several factors aligning. Kwolek was born July 31, 1923. She lived through World War II, when American companies were eager to hire women, since millions of men were away at war. Over 6,000,000 women answered the government’s call, many of them taking top jobs in defense industries.

Although Kwolek finished college in 1946 (Margaret Morrison College of Carnegie-Mellon University in Pittsburgh) and soldiers were coming back, she managed to snag a job with the DuPont company in Buffalo, New York because they believed her love for chemistry was genuine. Her plans for medical school fell by the wayside. Her new job was to find new ways to make thread and cloth out of chemicals. She worked for DuPont from 1946 until 1986, staying with them for 40 years.

Physics: How It Works

Items such as soap, TV screens, bulletproof vests and silk all have a degree of crystallinity. Until the mid-twentieth century, scientists tried linking small hydrocarbon molecules together to form synthetic polymer chains. At first, it was haphazard. The size and orientation of the chain molecules were mixed: some short, some long, some branched and some straight. Because the structure of the chains determines how they pack together and how concentrated they become, water molecules cannot penetrate. Knowing how to achieve this special arrangement—the crystallization of polymers—suggests that scientists can make polymers or fabric made from polymers strong. For example, Charles Goodyear discovered how to cross-link the polymer molecules of gum extracted from the Brazil wood tree by heating it with sulfur. This so-called vulcanization process converts soft gum into rubber.

Chemicals Mixed into Synthetics

After the war, there was a gas shortage. A lightweight yet super-strong material was needed to replace the heavy steel cord used inside car tires. Making the tire weigh less would allow the car to run more efficiently because it would be lighter and use less gas.

Kwolek and her team of chemists made thousands of liquid fibers. The process often involved pushing or spinning liquid fibers through tiny holes in a steel plate. Many DuPont chemists had given up on the idea. Not Kwolek. In fact, she even moved to Wilmington, Delaware to work in a more modern laboratory the company had built.

Ten years passed. Not one of the threads was strong enough to replace the steel. Then she made a discovery. A batch of chemicals looked as cloudy and thin as water. Many chemists would have thrown it out. Kwolek looked at it through a microscope and saw that parts of the chemical chains were straight sticks, lined up, “…like spaghetti,” she said. She sent a batch to the spinning room to spin it into threads. The person in charge there refused because he thought it might gum up the machines and make them inoperable. She asked him to reconsider many times, almost daily until he finally agreed.

These synthetic polymers known as aramids had the tensile strength greater than that of steel, but much lighter. In essence, Kwolek had created the first of a group of synthetic fibers of exceptional strength and stiffness; the best known is Kevlar. Kevlar is one of the best candidates so far for tethering a space platform and, of course, as a fabric for bullet-resistant vests.


Kwolek and her boss, Paul Morgan, got a patent for Kevlar in 1966. DuPont was soon strengthening all kinds of products: tennis rackets, skis, work gloves, safety helmets and even space suits. Its fire-resistant qualities and super-strength made it lifesaving. It is used in over 200 products from sails and boats to linings for jet engines to suspension cables for bridges.

Kevlar can be the difference between life and death for police, fire fighters, security guards, combat soldiers and people in high-risk jobs. It is difficult to cut through, resistant to chemicals and will not conduct electricity.

Bullet-resistant Vests

Of course, Kevlar is the stuff that makes personal armor. It really is not bulletproof but it is resistant to ammunition by reducing the penetration of the body from firearm projectiles, shrapnel from explosions and the danger of being stabbed.

The vests are made in layers. The fibers are meant to snag a bullet and change the impact by making it mushroom into a flattened state. The vest itself absorbs the bullet’s energy—by spreading it out—and resists allowing it to enter the body. The bullet will still injure the person because of blunt force trauma, but it will better save a life. Extra protection can be made with the addition of plates and other protective armor.

These upgraded ballistic vests have become standard in military use, as soft body armor vests are ineffective against military rifle rounds. Prison guards and police often wear vests, which are designed specifically against bladed weapons and sharp objects.

Awards for Kwolek

  • National Inventors Hall of Fame (1994)
  • The National Medal of Technology (1996); given by then President Bill Clinton
  • The Perkin Medal, presented by the American Section of the Society of Chemical Industry (1997)


  • Wyckoff, Edwin Brit. Stopping Bullets with a Thread: Stephanie Kwolek and Her Incredible Invention. Berkeley Heights, NJ: Enslow Publishers, Inc., 2008.
  • Ball, Phillip. Stories of the Invisible: A Guided Tour of Molecules. Oxford, England: Oxford University Press, 2001. Book.
  • Kespert, Deborah. Genius! The Most Astonishing Inventions of All Time. New York, NY: Thames & Hudson Ltd., 2015.
  • Carey, John. Eyewitness to History. Cambridge, MA: Harvard University Press, 1987. Book.
  • Woodford, Chris and Jon Woodcock. Cool Stuff 2.0 and How It Works. New York: Dorling Kindersley Ltd., 2007. Book.