Stephanie Kwolek

Stephanie Louise Kwolek (July 31, 1923 – June 18, 2014) was an American chemist best known for inventing Kevlar. Her career at the DuPont company spanned more than 40 years. She discovered the first of a family of synthetic fibers of exceptional strength and stiffness: poly-paraphenylene terephthalamide.

For her discovery, Kwolek was awarded the DuPont company's Lavoisier Medal for outstanding technical achievement. As of August 2019, she was the only female employee to have received that honor. In 1995 she became the fourth woman to be added to the National Inventors Hall of Fame. Kwolek won numerous awards for her work in polymer chemistry, including the National Medal of Technology, the IRI Achievement Award and the Perkin Medal.

Early life and education
Kwolek was one of two children born to Polish immigrant parents in the Pittsburgh suburb of New Kensington, Pennsylvania, in 1923. The grade school she attended was small enough to require her classroom be shared by two different grades, which she found to be an advantage. As Kwolek's love of science grew, she easily outpaced even the older children across the room. Her father, John Kwolek, died when she was ten years old. He was a naturalist by avocation, and Kwolek spent hours with him, as a child, exploring the natural world. They would spend afternoons together exploring the woods nearby, collecting plants and observing animals that they would later name and characterize in a scrapbook Kwolek kept, as a child. She attributed her interest in science to him and an interest in fashion design to her mother, Nellie (Zajdel) Kwolek, who worked as a seamstress. Her mother told her that she was too much of a perfectionist to work a career in fashion, so Kwolek decided to become a doctor.

In 1946, Stephanie earned a Bachelor of Science degree with a major in chemistry from Margaret Morrison Carnegie College of Carnegie Mellon University. She had planned to become a doctor and hoped she could earn enough money from a temporary job in a chemistry-related field to attend medical school.

DuPont career
William Hale Charch, a future mentor, offered Kwolek a position at DuPont's Buffalo, New York, facility in 1946. During her interview with DuPont, Dr. Charch had said the company would reach out to her in about two weeks to tell her whether she had secured the job. Kwolek asked if they could possibly respond sooner because she had to notify another company if she would accept their offer. Charch then called in his receptionist to dictate Kwolek's offer letter in front of her.

As a chemical company, Dupont was trying to find a petroleum-based polymer fiber that would be lighter and harder-wearing than steel in radial tires. The firm had vacancies, given that many men had been overseas fighting in World War II. Dupont had introduced nylon shortly before the war, and that business boomed and blossomed into several textile applications. At the same time, the protracted second World War emphasized the need for a lightweight, wearable armor to protect personnel and equipment. As the war raged overseas, soldiers engaged in battle had to do without body armor because there was no material strong enough to stop a rifle bullet but light enough to wear in battle. Steel was the only armor material available, and its weight limited its use to armored vehicles. Even then, steel could be pierced by specialized armor-piercing ammunition.

Kwolek intended to work for DuPont temporarily, in order to raise money for further study. At DuPont, the polymer research she worked on was so interesting and challenging that she decided to drop her plans for medical school and make chemistry a lifetime career. Her research group moved to Wilmington, Delaware, in 1950. In 1959, she won a publication award from the American Chemical Society (ACS), the first of many awards. The paper, The Nylon Rope Trick, demonstrated a way of producing nylon in a beaker at room temperature. It is still a common classroom experiment, and the process was extended to high molecular weight polyamides. In 1985, Kwolek and coworkers patented a method for preparing PBO and PBT polymers. Because Dupont was at the cutting edge of polymer technology and innovation, Kwolek never outgrew the position and spent her whole career doing research at Dupont. Over her 40-year career, Kwolek would file 28 patents. In addition to Kevlar, she contributed to products such as Spandex (Lycra), Nomex, and Kapton. She continued as a consultant to Dupont after her retirement in 1986, and became the first woman to earn the company’s Lavoisier medal for research in 1995.

She was engaged in the search for new polymers as well as a new condensation process that takes place at lower temperatures around 0 to 40 C. The melt condensation polymerization process used in preparing nylon, for example, was instead done at more than 200 C. The lower-temperature polycondensation processes, which employ very fast-reacting intermediates, make it possible to prepare polymers that cannot be melted and only begin to decompose at temperatures above 400 C.

Kevlar
Kwolek is best known for her work during the 1950s and 1960s with aramids, or "aromatic polyamides", a type of polymer that can be made into strong, stiff, and flame-resistant fibres. Her laboratory work in aramids was conducted under the supervision of research fellow Paul W. Morgan, who calculated that the aramids would form stiff fibres owing to the presence of bulky benzene (or "aromatic") rings in their molecular chains but that they would have to be prepared from solution because they melt only at very high temperatures. Kwolek determined the solvents and polymerization conditions suitable for producing poly-m-phenylene isophthalamide, a compound that DuPont released in 1961, as a flame-resistant fibre with the trade name Nomex. She then extended her work into poly-p-benzamide and poly-p-phenylene terephthalamide, which she noted adopted highly regular rodlike molecular arrangements in solution. From these two "liquid crystal polymers" (the first ever prepared), fibres were spun that displayed unprecedented stiffness and tensile strength. The innovative polymer Poly-p-phenylene terephthalamide, as invented by Kwolek, was released commercially under the name Kevlar. In 1964, in anticipation of a gasoline shortage, Kwolek's group began searching for a lightweight yet strong fiber to replace the steel used in tires. The polymers she had been working with, poly-p-phenylene terephthalate and polybenzamide, formed liquid crystal while in solution that at the time had to be melt-spun at over 200 C, which produced weaker and less stiff fibers. A unique technique in her new projects and the melt-condensation polymerization process was to reduce those temperatures to between 0 and 40 C.

As she explained 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 not know it at the time.

This sort of cloudy solution was usually thrown away. Kwolek was denied the use of the spinneret for her solution because it was thought the solution would clog the machine. However, Kwolek persuaded technician Charles Smullen, who ran the spinneret, to test her solution. She was amazed to find that the new fiber would not break when nylon typically would. Not only was it stronger than nylon, Kevlar was five times stronger than steel by weight. Both her supervisor and the laboratory director understood the significance of her discovery, and a new field of polymer chemistry quickly arose. By 1971, modern Kevlar was introduced. Kwolek learned that the fibers 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 continued research of thermotropic Kevlar derivatives containing aliphatic and chlorine groups.

Applications of Kevlar
Kwolek was not much involved in developing practical applications of Kevlar. Once senior DuPont managers were informed of the discovery, "they immediately assigned a whole group to work on different aspects", she said. Still, Kwolek continued research on Kevlar derivatives. She did not profit from DuPont's products, as she signed over the Kevlar patent to the company.

Kevlar is used in more than 200 applications, including tennis rackets, skis, parachute lines, boats, airplanes, ropes, cables, and bullet-proof vests. It has been used for car tires, fire fighter boots, hockey sticks, cut-resistant gloves and armored cars. It has also been used for protective building materials like bomb-proof materials, hurricane safe rooms, and bridge reinforcements. During the week of Kwolek's death, the one millionth bullet-resistant vest made with Kevlar was sold. Kevlar is also used to build cell phone cases; Motorola's Droid RAZR has a Kevlar unibody.

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.

Awards, honors, and legacy
For her discovery of Kevlar, Kwolek was awarded the DuPont company's Lavoisier Medal for outstanding technical achievement in 1995, as a "Persistent experimentalist and role model whose discovery of liquid crystalline polyamides led to Kevlar aramid fibers." At the time of her death in 2014, she was still the only female employee to receive that honor. Her discovery generated several billion dollars of revenue for DuPont, being her employer at the time, but she never benefited directly from it financially.

In 1980, Kwolek received the Chemical Pioneer Award from the American Institute of Chemists, and an Award for Creative Invention from the American Chemical Society. In 1995, Kwolek was added to the National Inventors Hall of Fame. In 1996, she received the National Medal of Technology and the IRI Achievement Award. In 1997, she received the Perkin Medal from the American Chemical Society. In 2003, she was inducted into the National Women's Hall of Fame.

She has been awarded honorary degrees by Carnegie Mellon University (2001), Worcester Polytechnic Institute (1981) and Clarkson University (1997).

The Royal Society of Chemistry grants a biennial 'Stephanie L Kwolek Award', "to recognise exceptional contributions to the area of materials chemistry from a scientist working outside the UK".

Kwolek is featured as one of the Royal Society of Chemistry's 175 Faces of Chemistry.

Later life
In 1986, Kwolek retired as a research associate for DuPont. Toward the end of her life, she consulted for DuPont, and served on both the National Research Council and the National Academy of Sciences. During her 40 years as a research scientist, she filed and received either 17 or 28 patents.

She often tutored students in chemistry. She also devised and wrote about numerous classroom demonstrations that are still used in schools today, such as the Nylon Rope Trick.

Kwolek died at the age of 90 on June 18, 2014. Her funeral was at St Joseph on the Brandywine.