Canadian Plastics

Teflon: Refrigerators and the French Connection

By Jim Anderton,technical editor   



In Hollywood, great discoveries and inventions are always dramatic. Isaac Newton's apple, Thomas Edison's light bulb, the Wright brothers' airplane, have all been mythologized as "Eureka!" moments tha...

In Hollywood, great discoveries and inventions are always dramatic. Isaac Newton’s apple, Thomas Edison’s light bulb, the Wright brothers’ airplane, have all been mythologized as “Eureka!” moments that change everything. In our industry, however, very few innovations stir the public’s imagination. That’s too bad, because there are many examples of genius that really did change everything in a single stroke.

Take PTFE, or polytetrafluoroethylene. We know it by DuPont’s trade name, Teflon, but unlike other major polymer innovations such as PA (nylon), PTFE was more inspiration than perspiration.

The story began, strangely enough, at General Motors. GM’s Frigidaire division, eager to capitalize on the market potential for the then-new home refrigerators, searched for a refrigerant to replace dangerous ammonia and propane. Chlorofluorocarbons showed promise, and by the mid ’30s, Freon compounds were so popular that GM formed a joint venture with chemical giant DuPont to mass produce the stuff. But with every drop going to Frigidaire, DuPont wanted their own refrigerant to feed growing demand for the new “icebox”.

The company put 27-year-old Dr. Roy Plunkett on the team, who attempted to synthesize a new refrigerant from tetrafluoroethylene gas. Plunkett and his lab technician, Jack Rebok, made about 100 pounds of TFE gas, which they stored in gas cylinders packed in dry ice. On April 6th, 1938, Plunkett hooked up a cylinder to his reaction apparatus and opened the valve. Nothing happened. Suspecting a clog in the valve, the pair poked wires into the cylinder. Still nothing. Weighing the cylinder, however, showed that the gas was still inside.

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Then Plunkett and Rebok took the step that defines great scientists and engineers everywhere: they cut the cylinder open, just to see what was inside. Inside was a waxy, white substance that melted at very high temperatures, and seemed unaffected by acids, alkalis, water or petroleum products. It didn’t absorb moisture, swell, rot or degrade under sunlight. The gunk lining the cylinder obviously had a future, and by 1939, Plunkett had a process to synthesize PTFE, and DuPont had a valuable patent.

Post war, DuPont looked for civilian uses for PTFE and immediately ran up against a major problem: how do you mold a polymer that can survive temperatures from 600 to 1000F? The answers could fill a book, but coating metals was an obvious use, suitable for everything from bearings to electrical wire. But not cookware. DuPont had experimented with Teflon coatings for commercial bakery equipment, but fear of litigation (sound familiar?) kept the firm from the most famous application of the wonder polymer.

Meanwhile, in much-less-litigious France, an engineer named Marc Gregoire became interested in a colleague’s process for etching aluminum industrial parts, which were then covered with Teflon powder to form a tough mechanical lock between polymer and metal. Gregoire had several uses in mind, but his wife Colette had a radical idea. By 1955, Marc coated the frying pans and Collette sold the increasingly popular cookware on the street. The couple formed the Tefal Corporation in 1956. DuPont could see the writing on the wall and sought FDA approval for domestic food use, but at less than 10 million pounds-per-year of production, Teflon was hardly the “hottest job in the shop”. It took years, an American textile machine manufacturer and a Macy’s department store buyer named George Edelstein to make Teflon fly on this side of the Atlantic.

And Roy Plunkett? He worked for DuPont until 1975 and was inducted into the U.S. National Inventors Hall of Fame in 1985. Plunkett died in 1994. If you ask me, he should have been given a star in the Hollywood “Walk of Fame”.

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