The invention: A fluorocarbon polymer whose chemical inertness and physical properties have made it useful for many applications, from nonstick cookware coatings to suits for astronauts.
The person behind the invention:
Roy J. Plunkett (1910-1994), an American chemist
Nontoxic Refrigerant Sought
As the use of mechanical refrigeration increased in the late 1930′s, manufacturers recognized the need for a material to replace sulfur dioxide and ammonia, which, although they were the commonly used refrigerants of the time, were less than ideal for the purpose. The material sought had to be nontoxic, odorless, colorless, and not flammable. Thomas Midgley, Jr., and Albert Henne of General Motors Corporation’s Frigidaire Division concluded, from studying published reports listing properties of a wide variety of chemicals, that hydrocarbon-like materials with hydrogen atoms replaced by chlorine and fluorine atoms would be appropriate.
Their conclusion led to the formation of a joint effort between the General Motors Corporation’s Frigidaire Division and E. I. Du Pont de Nemours to research and develop the chemistry of fluorocar-bons. In this research effort, a number of scientists began making and studying the large number of individual chemicals in the general class of compounds being investigated. It fell to Roy J. Plunkett to do a detailed study of tetrafluoroethylene, a compound consisting of two carbon atoms, each of which is attached to the other as well as to two fluorine atoms.
The “Empty” Tank
Tetrafluoroethylene, at normal room temperature and pressure, is a gas that is supplied to users in small pressurized cylinders. On the morning of the day of the discovery, Plunkett attached such a tank to his experimental apparatus and opened the tank’s valve. To
his great surprise, no gas flowed from the tank. Plunkett’s subsequent actions transformed this event from an experiment gone wrong into a historically significant discovery. Rather than replacing the tank with another and going on with the work planned for the day, Plunkett, who wanted to know what had happened, examined the “empty” tank. When he weighed the tank, he discovered that it was not empty; it did contain the chemical that was listed on the label. Opening the valve and running a wire through the opening proved that what had happened had not been caused by a malfunctioning valve. Finally, Plunkett sawed the cylinder in half and discovered what had happened. The chemical in the tank was no longer a gas; instead, it was a waxy white powder.
Plunkett immediately recognized the meaning of the presence of the solid. The six-atom molecules of the tetrafluoroethylene gas had somehow linked with one another to form much larger molecules. The gas had polymerized, becoming polytetrafluoroethylene, a solid with a high molecular weight. Capitalizing on this occurrence, Plunkett, along with other Du Pont chemists, performed a series of experiments and soon learned to control the polymerization reaction so that the product could be produced, its properties could be studied, and applications for it could be developed.
The properties of the substance were remarkable indeed. It was unaffected by strong acids and bases, withstood high temperatures without reacting or melting, and was not dissolved by any solvent that the scientists tried. In addition to this highly unusual behavior, the polymer had surface properties that made it very slick. It was so slippery that other materials placed on its surface slid off in much the same way that beads of water slide off the surface of a newly waxed automobile.
Although these properties were remarkable, no applications were suggested immediately for the new material. The polymer might have remained a laboratory curiosity if a conversation had not taken place between Leslie R. Groves, the head of the Manhattan Project (which engineered the construction of the first atomic bombs), and a Du Pont chemist who described the polymer to him. The Manhattan Project research team was hunting for an inert material to use for gaskets to seal pumps and piping. The gaskets had to be able to withstand the highly corrosive uranium hexafluoride with
Roy J. Plunkett
Roy J. Plunkett was born in 1910 in New Carlisle, Ohio. In 1932 he received a bachelor’s degree in chemistry from Manchester College and transferred to Ohio State University for graduate school, earning a master’s degree in 1933 and a doctorate in 1936. The same year he went to work for E. I. Du Pont de Nemours and Company as a research chemist at the Jackson Laboratory in Deepwater, New Jersey. Less then two years later, when he was only twenty-seven years old, he found the strange polymer tetrafluoroethylene, whose trade name became Teflon. It would turn out to be among Du Pont’s most famous products.
In 1938 Du Pont appointed Plunkett the chemical supervisor at its largest plant, the Chamber Works in Deepwater, which produced tetraethyl lead. He held the position until 1952 and afterward directed the company’s Freon Products Division. He retired in 1975. In 1985 he was inducted into the Inventor’s Hall of Fame, and after his death in 1994, Du Pont created the Plunkett Award, presented to inventors who find new uses for Teflon and Tefzel, a related fluoropolymer, in aerospace, automotive, chemical, or electrical applications.
which the team was working. This uranium compound is fundamental to the process of upgrading uranium for use in explosive devices and power reactors. Polytetrafluoroethylene proved to be just the material that they needed, and Du Pont proceeded, throughout World War II and after, to manufacture gaskets for use in uranium enrichment plants.
The high level of secrecy of the Manhattan Project in particular and atomic energy in general delayed the commercial introduction of the polymer, which was called Teflon, until the late 1950′s. At that time, the first Teflon-coated cooking utensils were introduced.
Impact
Plunkett’s thoroughness in following up a chance observation gave the world a material that has found a wide variety of uses, ranging from home kitchens to outer space. Some applications make use
An important space application for Teflon is its us on the outer skins of suits worn by astronauts (PhotoDisc)
of Teflon’s slipperiness, others make use of its inertness, and others take advantage of both properties.
The best-known application of Teflon is as a nonstick coating for cookware. Teflon’s very slippery surface initially was troublesome, when it proved to be difficult to attach to other materials. Early versions of Teflon-coated cookware shed their surface coatings easily, even when care was taken to avoid scraping it off. A suitable bonding process was soon developed, however, and the present coated surfaces are very rugged and provide a noncontaminating coating that can be cleaned easily.
Teflon has proved to be a useful material in making devices that are implanted in the human body. It is easily formed into various shapes and is one of the few materials that the human body does not reject. Teflon has been used to make heart valves, pacemakers, bone and tendon substitutes, artificial corneas, and dentures.
Teflon’s space applications have included its use as the outer skin of the suits worn by astronauts, as insulating coating on wires and cables in spacecraft that must resist high-energy cosmic radiation, and as heat-resistant nose cones and heat shields on spacecraft.
See also Buna rubber; Neoprene; Nylon; Plastic; Polystyrene; Pyrex glass; Tupperware.
