The Long, Strange History of Teflon, the Indestructible Product Nothing Seems to Stick to | Smithsonian

Oct 24, 2024

Chemists accidentally discovered the material in 1938, and since then it has been used for everything from helping to create the first atomic bomb to keeping your eggs from sticking to your frying pan

Rudy Molinek

Mass Media Fellow, AAAS

On April 6, 1938, a group of chemists at DuPont gathered around part of their latest experiment: a plain metal cylinder. It supposedly contained tetrafluoroethylene, a colorless, odorless gas. But when they opened the valve, no gas came out. Something was wrong. For a while, they were stumped. The cylinder weighed more than it should if it were empty, but it really didn’t seem like anything was inside. Eventually, someone realized they needed to cut the cylinder open to see what was going on. They found the interior of the metal unexpectedly coated with a slippery white powder.

“Somebody asked me in the past, ‘What was your reaction?’” said DuPont chemist Roy Plunkett in a 1986 oral history interview, “My reaction was, ‘Well, we have to start over now.’”

But, instead of discarding the seemingly defective cylinder, Plunkett decided to conduct some tests. He found the gas had spontaneously “polymerized” into a mystery material that didn’t seem to break down at high temperatures. The material also didn’t react to or dissolve in any of the highly corrosive chemicals Plunkett threw at it, including acids strong enough to eat into your bones. The technical name for this super substance is a mouthful: polytetrafluoroethylene, or PTFE. But you probably know it by another name: Teflon.

According to Plunkett, “the next question was, ‘What are you going to do with this stuff?’”

Initially, scientists at DuPont didn’t have a good answer to that question, but now the material is ubiquitous in everyday objects. Since it was discovered 86 years ago, Teflon and its chemical descendants, per- and polyfluoroalkyl substances, or PFAS, have spread everywhere. We use them to make nonstick pans and scientific equipment, to waterproof raincoats, to grease-proof fast-food wrappers, and even sometimes to squeak-proof piano keys. These molecules are so common that a 2015 study found the chemicals in 97 percent of Americans’ blood. And once they make it into our bodies, medical researchers are finding that the long-lasting chemicals could be wreaking havoc.

But the answer to that question about what to do with Teflon, and its subsequent journey from that DuPont lab to our kitchens, closets and bodies, didn’t come overnight. The story of Teflon’s rise starts with the development of refrigeration in the early 20th century and goes through the Manhattan Project’s quest to change the world with atomic weapons before making its way into myriad consumer products, starting with the iconic nonstick skillet. At first, though, it seemed like this material might not go anywhere, since it was expensive to manufacture and didn’t have a clear use.

Teflon’s origin story starts about a decade before its discovery. In the late 1920s, the refrigeration industry was on the ropes after a spate of deadly accidents where dangerous gases used as coolants exploded in dramatic fashion or leaked into unsuspecting homes. Headlines like “Ice Machine Gas Kills 15 in Chicago; Leaks in Refrigeration Plants in Homes Held Cause of Mysterious Deaths” splashed across the New York Times. The problem was that the chemicals being used to extract heat from the inside of a refrigerator and cool it down were either highly toxic, flammable, or both.

Advertisements from early refrigerators that used sulfur dioxide coolant touted them as “self-alarming” because the strong smell would warn home users of a leak before it became too dangerous. Manufacturers of fridges based on carbon dioxide boasted that their systems had no odor and no explosions. “If you’re advertising your refrigerant as no explosions,” says Mark McLinden, a chemical engineer at the National Institute of Standards and Technology, “that maybe is an indication that there was a problem with some of the other competitors.” Though carbon dioxide was safer, it was not particularly efficient for home applications, because it needs much higher pressures to operate, which raises costs and increases the chance of leaks.

Amid the bad press and peculiar advertising, refrigerator manufacturers needed to make a change. At General Motors, head of research Charles “Boss Kett” Kettering talked to the chief of engineering at Frigidaire, and then called Thomas Midgley, who had made his name at the company by adding lead to gasoline to stop engine knocking. “We came to the conclusion,” Kettering told Midgley, “that the refrigeration industry needs a new refrigerant if they ever expect to get anywhere.”

What Kettering needed was a refrigerant that worked at reasonable temperatures and pressures while being inexpensive to produce, non-corrosive to common materials, nontoxic and not highly flammable. Midgley, in his search for this Goldilocks molecule, turned to the upper right-hand corner of the periodic table. These elements, he knew, tended to form compounds that could cool home refrigerators to the ideal temperature. Quickly, he zeroed in on fluorine.

On its own, fluorine seems an unlikely choice. The acid form of fluorine, called hydrofluoric acid, is notoriously nasty. If it gets into your body, it can not only dissolve your bones, but also aggressively bond to calcium in your blood to the point that it stops your heart. But, once fluorine bonds with a carbon atom to form a compound, it undergoes a total personality change.

“They key thing about fluorine is the carbon-fluorine bond is the strongest bond in chemistry,” says McLinden. “So when you put fluorine into a molecule, it’s tough to get it off, and that makes it basically stable. Stable, nonreactive, it kind of goes hand in hand with low toxicity.”

Within three days of getting the assignment from Kettering, Midgley had hit on a potential winner that would be used widely until the 1980s: a chlorofluorocarbon, or CFC, that we now call Freon. Given the human and environmental health impacts of lead in automobile gasoline, and the depletion of the ozone layer due to CFCs, McLinden says, Midgley was “the king of unintended consequences.”

But it would be decades before the dangers of CFCs to the environment were discovered by scientists. In the meantime, it seemed like a miracle refrigerant compared to the toxic and flammable alternatives available in the 1930s. During a demonstration of his newly discovered Freon, Midgley inhaled a lungful of the gas and breathed out, extinguishing a candle to dramatically prove its lack of toxicity and flammability.

The development of an apparently safe refrigerant led to an explosion of consumer uses—iceboxes, car air conditioners, heat pumps and more. But according to Plunkett’s 1986 oral history interview, “early in 1938, a crisis arose.”

Frigidaire, then a subsidiary of General Motors, maintained proprietary ownership of Freon, and other refrigerator manufacturers wanted in on the game. They turned to DuPont to create new refrigerants with the benefits of Freon—and the assignment went to Plunkett’s team. Before long, they ended up, like Midgley, searching for compounds based on fluorine. This hunt led to the fateful, defective cylinder of tetrafluoroethylene, a gas molecule with two carbon atoms surrounded by four of fluorine. The polymerization of the gas hooked those small molecules together into a long chain and solidified into the fluoropolymer PTFE.

The substance that would later be named Teflon was at first shelved, and the scientists returned to their quest for new refrigerants. At the time, the researchers couldn’t envision a profitable use for such an expensive-to-manufacture substance. That all changed just a few years later with the United States’ entry in World War II and the Manhattan Project’s push for atomic weapons. As viewers of 2023’s hit movie Oppenheimer will remember, one of the most critical endeavors in creating the world’s first atomic bomb was refining enough uranium and plutonium, apocryphally represented with scenes of scientists at Los Alamos slowly and dramatically filling a glass bowl with marbles to represent the progress toward explosivity.

According to Gordon Fee, a nuclear engineer and the retired president of Lockheed Martin Energy Systems, scientists and engineers at a government facility in Oak Ridge, Tennessee, stepped up to the task of refining uranium. They settled on a process, called gaseous diffusion, that forced a gas called uranium hexafluoride through miles and miles of pipes containing thousands of filters that sorted out the explosive isotope from the rest of the substance.

The problem for the scientists at Oak Ridge and the general who directed the Manhattan Project, Leslie Groves, was that uranium hexafluoride is highly corrosive. The gas was eating up the gaskets and the valve seals that helped contain and regulate the flow of the rare and crucial material.

What exactly happened next isn’t totally clear, given the secrecy and compartmentalization inherent to the Manhattan Project and the continued classification of documents. But we do know, says Fee, that lots of DuPont employees were working in Oak Ridge, mostly in a separate plant used to refine plutonium.

The DuPont employees knew that Groves had miles of piping he had to seal, says Fee, who began working at the gaseous diffusion plant at Oak Ridge in 1956. “They said, ‘Gee, we have this unique family of materials, we think it would make a good corrosion resistant gasket.’”

From its discovery in 1938 until that moment, likely in 1942, polytetrafluorethylene—it wouldn’t be officially registered as Teflon until after the war—bounced around DuPont as a curious laboratory product.

The nearly unlimited resources of the Manhattan Project gave DuPont its first industrial use for the new material. Scientists and engineers at Oak Ridge, like Fee, used PTFE to protect the facility’s pipes from corrosive gases until the plant was shut down decades later. “There was never a substitute considered as far as I know,” says Fee, “and so it had a lifetime in the Manhattan Project, you might say, until 1985.”

According to Plunkett, these resources and the demand for PTFE during the war gave DuPont the opportunity to continue evaluating the new material and find other uses for it. At first, these applications were mostly in industry and the military.

For example, Plunkett recalled a manufacturing plant that needed to pump high concentrations of nitric acid. Once a week, he said, the pump failed and had to be rebuilt. When the workers tried using Teflon in the pump, though, it worked so well for over six months that they decided to disassemble it anyways to see how it was holding up. Inside, they found, everything was still pristine.

But Teflon was still far from the household name it is today. Until, that is, inventors figured out they could use it to make nonstick cookware. In 1952, Plunkett, in one of the first public recognitions of his discovery, received the John Scott Medal. This honor given to scientists and inventors by the city of Philadelphia for improving the “comfort, welfare and happiness of mankind” has also been awarded to the Wright brothers, Thomas Edison, Marie Curie and Nikola Tesla. But at the ceremony for Plunkett, everyone went home with a special gift.

“It was the first time that anybody in this country saw any cooking utensils lined with Teflon,” said Plunkett in the 1986 oral history, “They made muffin tins lined with Teflon and gave them out as favors. … Some of those muffin tins are still in existence. I have one of them at home.”

A few years later, in the early 1960s, such implements became available to regular cooks. Inventor Marion Trozzolo came up with the first Teflon-coated skillet, called the Happy Pan, in 1957 and began selling it in 1961. For the 25th anniversary of the skillet, in 1986, Trozzolo gifted an original Happy Pan to the Smithsonian’s National Museum of American History.

Since then, Teflon has spread everywhere. In 1969, Wilbert and Bob Gore used a form of PTFE to make a waterproof, breathable fabric they called Gore-Tex that’s now omnipresent in raincoats and hiking boots. Inventors have also put Teflon in dental floss, plumbing thread-seal tape and medical devices like artificial heart valves, among many other applications.

The development and widespread use of Teflon also spurred the creation of a new class of chemicals, called per- and polyfluoroalkyl substances, or PFAS. These utilized the same unique properties that made Teflon so handy for so many purposes. In their simplest form, PFAS molecules all have a chain of carbon atoms surrounded by very strong bonds to fluorine. This part of the molecule is hydrophobic and doesn’t mix with water. Many PFAS also have what chemists call a “head group” attached to that chain. This bundle of atoms is hydrophilic, so one side of the molecule does like to get wet. These chemicals tend to be highly durable and repel water, grease and heat.

But those same properties make PFAS potentially dangerous. Since the carbon-fluorine bond is so strong, PFAS don’t break down easily by natural processes, leading to the moniker “forever chemicals.” Their dual nature of both liking and repelling water makes them highly mobile in wet environmental conditions, since the molecule can easily get picked up by moving water, and just as easily get deposited onto surfaces the water flows through.

And PFAS’s widespread use means they’re everywhere, and once they enter our bodies, the chemicals can cause trouble. According to the Environmental Protection Agency, PFAS can reduce fertility; mess with children’s development; increase risk of prostate, kidney and testicular cancer; interfere with the immune system; and make vaccines less effective.

In response, the European Union and some U.S. states are moving to ban or restrict the sale and use of PFAS, while impacted communities are turning to lawsuits to remedy damages. Often, though, these regulations only focus on a few of the more than 6,000 different PFAS compounds and leave the industry lots of wiggle room.

Not all of this is necessarily true for Teflon itself and other plastics made of fluoropolymers. Because PTFE’s chain of carbon and fluorine atoms in its molecular structure is really long, it’s not as easy for our bodies to absorb it. Producers say this means new and proposed regulations for shorter-chain PFAS shouldn’t include the polymers like Teflon, which they argue is a “polymer of low concern.”

But Rainer Lohmann, an environmental chemist at the University of Rhode Island, says that “if you really look at the entire life cycle from production to the end of life, a very different story emerges.”

That’s because the manufacturing process for fluoropolymers like Teflon often requires companies to use other, short-chain PFAS. Scientists and public health officials are also learning more about how plastics, including fluoropolymers, break down into microparticles and interact with human bodies. Long-chain PFAS can break down into shorter-chain molecules over long periods of time in environments like landfills, where many Teflon-coated consumer products end up. Despite these growing concerns, “there’s always a business interest in sticking to the status quo,” says Lohmann.

Currently, that status quo means annual worldwide Teflon sales to the tune of about $3 billion. That total is projected to grow to more than $4 billion by 2027.

Roy Plunkett died in 1994, before concerns about PFAS toxicity reached the mainstream and became parts of daily news reports like they are now. In 1986, he said that “the discovery of PTFE has been variously described as an example of serendipity, a lucky accident or a flash of genius.” He regarded the discovery, 48 years earlier, as a high point of his career. “I’m proud of my participation in this development,” he said, “proud of the company with whom I’ve worked, proud of what has happened, and most of all I’m proud of the benefit to mankind from this original invention.”

Lohmann thinks that spirit of invention and discovery needs to happen again now, as more and more dangers of PFAS are discovered and regulations begin to outlaw their use.

Industries that rely on fluorine chemistry have been through this before. In the 1980s and 1990s, it became clear that the chemical ancestor of Teflon, chlorofluorocarbon refrigerants, posed a serious threat to the environment because of the damage they caused to the ozone layer. A series of international treaties, including the Montreal Protocol, successfully banned the substances worldwide. The hole in the ozone layer is no longer an urgent concern.

That effort had one important advantage over current progress to remove PFAS from many applications, though. “Really key to the Montreal Protocol,” says McLinden, “was that there were alternatives available that would not compromise on safety or efficiency.”

Currently, no miracle substitutes exist for the myriad and incredibly useful applications of PFAS. But as Plunkett discovered in 1938, that doesn’t mean scientists should stop trying. In fact, given recent reporting that companies like 3M ignored or covered up warnings from scientists about the dangers of PFAS, Lohmann thinks that perhaps the scientists should be given a seat at the head of the table.

“The science part worked. But then, of course, it was somewhere higher up at those companies that [scientists] were sidelined and siloed and silenced,” he says. “Maybe it would never have reached these proportions if scientists had been in charge.”

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Rudy Molinek | READ MORE

Rudy Molinek is Smithsonian magazine's 2024 AAAS Mass Media Fellow.