Kevlar

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Kevlar is a synthetic para-aramid fiber and one of the most consequential materials ever produced in the state of Delaware. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s as a replacement for steel in racing tires. Born from research conducted at DuPont's Wilmington laboratories, Kevlar went on to transform industries ranging from law enforcement and military defense to aerospace, automotive manufacturing, and telecommunications. Kevlar is a material used in protective vests as well as in boats, airplanes, ropes, cables, and much more — in total about 200 applications. The fiber's invention stands as one of Delaware's most enduring contributions to modern science and technology, and its story is inseparable from the history of the DuPont Company and its Experimental Station on the banks of the Brandywine Creek.

Discovery and Invention at DuPont's Wilmington Laboratories

Stephanie Kwolek was working in a Wilmington, Delaware, research lab for the textile division of the chemical company DuPont, which had invented another fiber called nylon 30 years earlier. Fearing a looming gas shortage — one that arrived in earnest in 1973 — DuPont was searching for a synthetic material that could make tires lighter and stronger, replacing some of their steel and improving overall fuel efficiency.

Kwolek was in her 40s when she was asked by DuPont to scout for the next generation of fibers capable of performing in extreme conditions. This assignment involved preparing intermediates, synthesizing aromatic polyamides of high molecular weight, dissolving the polyamides in solvents, and spinning these solutions into fibers.

She unexpectedly discovered that under certain conditions large numbers of the molecules of these rodlike polyamides become lined up in parallel — that is, form liquid crystalline solutions — and that these solutions can be spun directly into oriented fibers of very high strength and stiffness. These polyamide solutions were unlike any polymer solutions previously prepared in the laboratory.

The person in charge of the spinning equipment initially refused to spin the first such solution because he feared that the turbidity was caused by the presence of particles that would plug the tiny holes (0.001 inch in diameter) in the spinneret. He was finally persuaded to spin, and much to his surprise, strong, stiff fibers were obtained with no difficulty. Following this breakthrough, many fibers were spun from liquid crystalline solutions, including the yellow Kevlar fiber.

It then took six years to produce Kevlar commercially, finally reaching the market in 1971. Kwolek's discovery was the product of a broader research culture at DuPont that had already yielded nylon, neoprene, and Teflon, reinforcing Delaware's standing as the nation's preeminent center of polymer chemistry.

Stephanie Kwolek: Delaware's Pioneering Chemist

Stephanie Kwolek (1923–2014) is the central human figure in Kevlar's Delaware story. Unable to fund medical school, she took a job at DuPont's textile fabrics laboratory as a chemist in Buffalo, New York. When DuPont's Pioneering Research Laboratory opened in 1950 in Wilmington, Delaware, Kwolek moved her work there.

Kwolek is the only woman in the history of DuPont to ever win the company's Lavoisier Medal for outstanding technical achievement. The honors extended well beyond the company. For her invention of Kevlar and her 40-year career at DuPont, Kwolek earned many awards, including the Kilby Award and National Medal of Technology in 1996. Kwolek was only the fourth woman to be inducted into the Inventors Hall of Fame in 1994 out of its 113 members. She also received the Perkin Medal from the American Section of the Society of Chemical Industry in 1997, and the 1999 Lemelson-MIT Lifetime Achievement Award.

She retired from DuPont in 1986. After her retirement, Kwolek spent time on various hobbies, such as sewing and gardening. She gave many lectures on her life and inventions and tutored high school students in chemistry.

Kwolek passed away at the age of 90 on June 18, 2014, in Wilmington, Delaware. On the day of her death, DuPont announced the sale of the 1 millionth bullet-proof vest made of Kevlar. Her personal papers, photographs, and artifacts were later acquired by the Hagley Museum and Library in Greenville, Delaware, where they are preserved as part of the museum's permanent collection.

From the Laboratory to the Marketplace: The Team Behind Kevlar

While Kwolek's 1965 discovery provided the scientific foundation, bringing Kevlar from a laboratory curiosity to a commercially viable product required the efforts of a substantial team of scientists and engineers, all working within Delaware's DuPont network. Through many surprising twists, the team worked to make Kevlar serve the occasionally contradictory interests of the DuPont Company, scientific inquiry, the marketplace, and the general public.

Herbert Blades developed a commercially viable process to spin fibers economically and at high speeds from the polymer to make Kevlar. Wesley Memeger, Jr. solved a major problem in making Kevlar. Donald Sturgeon used his PhD in engineering mechanics to evaluate the properties of Kevlar fibers for composite structures. He developed weight-saving Kevlar composites for the aircraft industry, bullet-resistant vests, and non-cut fabrics.

Bob Wolffe, who had a PhD in chemical engineering, said in his interview that the most important application for Kevlar was in ballistics. He also worked on products for the aircraft industry, with the first applications for interior, non-structural uses.

Ted Merriman was instrumental in developing a pulped form of Kevlar fiber suitable for automobile brake lining after it was discovered in the late 1970s that the standard material, asbestos fiber, caused lung cancer. Brake pads with even very small amounts of Kevlar had good wear characteristics and were quieter than other types. In the early 1980s, Merriman was named the Kevlar product steward to ensure there were no health or safety problems for DuPont's customers.

The full scope of this collaborative effort is documented in Kevlar R&D: An Oral History, a 13-hour video produced by the Hagley Museum and Library in Wilmington. "The history of technology shows that innovation is a team effort, and the stories documented by 'Kevlar R&D' reveal the work done by many talented individuals to bring Kevlar out of the laboratory and into our lives," said Gregory Hargreaves, Hagley Oral History Project manager.

Properties and Applications

Kevlar's utility flows directly from its extraordinary physical properties. Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. The chemical structure of Kevlar consists of long, rod-like polymer chains that are highly oriented and hydrogen-bonded, creating a rigid and tightly packed fiber. This molecular arrangement gives Kevlar its extraordinary strength and heat resistance.

Kevlar has many applications, ranging from bicycle tires and racing sails to bulletproof vests, due to its high tensile strength-to-weight ratio; by this measure it is five times stronger than steel. It is inherently heat-resistant up to 850 degrees Fahrenheit, and, unlike most plastics, Kevlar fibers won't melt or burn.

Kevlar is produced in multiple grades for different end uses. The most common types include Kevlar 29, used primarily for ballistic protection in body armor, helmets, and vehicle armor; Kevlar 49, used in structural applications such as reinforcement in composites, ropes, and cables; Kevlar 119, known for its high elongation properties, used in fiber optics and industrial fabrics; and Kevlar 129, which offers enhanced ballistic protection and is used in bulletproof vests and helmets.

Kevlar has gone on to save lives as a lightweight body armor for police and the military; to convey messages across the ocean as a protector of undersea optical-fiber cable; to suspend bridges with super-strong ropes; and to be used in countless more applications from protective clothing for athletes and scientists to canoes, drumheads, and frying pans.

One significant limitation of the material is its vulnerability to sunlight. The ultraviolet component of sunlight degrades and decomposes Kevlar, a problem known as UV degradation, and so it is rarely used outdoors without protection against sunlight. Kevlar production is also expensive because of the difficulties arising from using concentrated sulfuric acid, needed to keep the water-insoluble polymer in solution during its synthesis and spinning.

DuPont, Kevlar, and Delaware's Chemical Legacy

Kevlar's invention is embedded in the broader story of E. I. du Pont de Nemours and Company and its outsized role in Delaware's economic and scientific identity. Among the most notable figures in that story was French immigrant Éleuthère Irénée du Pont de Nemours, founder of the gunpowder-producing DuPont company founded near Wilmington in 1802. Over the succeeding century and a half, DuPont's research facilities along the Brandywine produced a string of synthetic breakthroughs, of which Kevlar is among the most enduring.

In 2025, DuPont announced a significant transaction involving the brand. DuPont moved to unload its celebrated Kevlar brand to a Georgia company. Arclin announced it entered into a definitive agreement to acquire DuPont's Aramids business, which includes the Kevlar and Nomex brands, for approximately $1.8 billion. "DuPont is proud of the legacy of the Kevlar and Nomex brands," said Lori Koch, CEO of DuPont. "We are confident that under Arclin's leadership, these businesses will continue to thrive and expand their impact in new industries and applications."

The planned acquisition expands Arclin's portfolio to include aerospace, electrical infrastructure, electric vehicles, personal protection, and defense, while building on its strong positions in construction, infrastructure, weather and fire protection, and transportation.

Despite the change of ownership, the scientific and cultural origins of Kevlar remain firmly rooted in Delaware. The fiber was invented by a woman working in a Wilmington laboratory, commercialized by a Delaware corporation, and documented for posterity by a Delaware museum. By one estimate, Kevlar has saved at least 3,000 police officers from bullet wounds in the years since its introduction. That impact — measured in lives protected and industries transformed — is a defining chapter in Delaware's long and distinctive industrial history.

Preservation and Memory in Delaware

The Hagley Museum and Library, located along the Brandywine in Wilmington, serves as the principal repository of Kevlar's history. After Dr. Kwolek's death, Hagley was fortunate enough to receive her collection of documents, photographs, and artifacts. It made sense, said Erik Rau, director of Library Services at Hagley, to cover the spectrum of Kevlar's development, from the laboratory to finished products.

The oral history project, produced in cooperation with Hagley, gathered first-person accounts from chemists, engineers, and executives who collectively moved Kevlar from a test tube in Wilmington to factories, police precincts, and aircraft hangars around the world. The order of the interviews follows the development of Kevlar from a laboratory oddity to the production line.

Kwolek's story has also entered the realm of children's literature. In 2013 her story was told in a children's book by Edwin Brit Wyckoff, The Woman Who Invented the Thread That Stops the Bullets: The Genius of Stephanie Kwolek. Her legacy is further commemorated through her induction into the National Inventors Hall of Fame and through ongoing educational programs at the Science History Institute in Philadelphia, which holds additional materials related to her career.

See Also

• DuPont Company
• Stephanie Kwolek
• Hagley Museum and Library
• Wilmington, Delaware
• Delaware Chemical Industry