Stephanie Kwolek, Inventor of Kevlar

Plastics News report

Stephanie Kwolek, the inventor of Kevlar — the aramid-fibre body armour that has saved countless lives of soldiers, police and other safety personnel — died 18 June, following a brief illness. She was 90.

A low-key industrial chemist at DuPont Co. who achieved international fame, Kwolek discovered Kevlar in the mid-1960s. DuPont commercialised it in 1971. Kevlar most famously goes into bulletproof vests, but it also is used to make super-strong rope, protective gloves for meatpackers, fibre-optic cables and as a reinforcement for composites used in a host of products.

Kwolek was inducted into the Plastics Hall of Fame in 1997 — she is still the only woman in the hall today. That same year, she received the prestigious Perkin Medal from the Society of Chemical Industry’s American Section. Kwolek entered the National Inventors Hall of Fame in 1995. She also is a member of the Engineering and Science Hall of Fame. In 1996, she received the National Medal of Technology in a White House ceremony.

The International Association of Chiefs of Police reports that more than 3,100 law enforcement officers have been inducted into the IADP/DuPont Kevlar Survivors’ Club. The organisation documents when a bulletproof vest saves a life. Many of these survivors met Kwolek and poured out their emotions and thanks.

Kwolek did her work quietly, in the laboratory. She had joined DuPont in 1946. DuPont already was a well-known fibre innovator thanks to nylon, Dacron polyester and Lycra spandex when Kwolek began her work leading to Kevlar. At first, the researchers wanted to develop a lightweight fibre for tires that would boost gas mileage in cars, she recalled in a Plastics News profile when she entered the Plastics Hall of Fame.

Kwolek was trying to find a good solution for spinning the fibres. She hit on dissolving PBA in amide/salt solvents. She described the details of invention in a 1993 speech: “The solution was unusually (low viscosity), turbid, stir-opalescent and buttermilk in appearance. Conventional polymer solutions are usually clear or translucent and have the viscosity of molasses, more or less.

"The solution that I prepared looked like a dispersion but was totally filterable through a fine pore filter. This was a liquid crystalline solution, but I did now know it at the time.”

The researchers were surprised when the fibres appeared to be super-strong. “Lest a mistake had been made, I did not report these unexpected results until I had the fibres retested several times,” she said.

Kwolek learned that the fibres could be made even stronger by heat-treating them. The polymer molecules, shaped like rods or matchsticks, are highly oriented, which gives Kevlar its extraordinary strength.

Kwolek gave frequent talks to students, encouraging them to get into science. Tire-makers eventually adopted cheaper steel-belted radials, deciding against Kwolek’s invention.

Kwolek was “exceptional”, said Jay Gardiner, president of the Plastics Academy, which administers the Plastics Hall of Fame. Kevlar is an example of a super-tough material that shows the public that plastics are far more than “cheap” and disposable, he said.

DuPont Chairman and CEO Ellen Kullman said in a statement: “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. … She leaves a wonderful legacy of thousands of lives saved and countless injuries prevented by products made possible by her discovery.”