Teflon: Its History & How it Works

On this day in 1941, Teflon, the polymer commonly found in non-stick pans, was patented. Its discovery actually occurred a few years previously – here’s a quick look at the story behind it, as well as the science behind its non-stick effect.

What is Teflon?

Teflon is the chemical found in some brands of saucepans that helps to prevent your meal from sticking to them during the cooking process. The brand name is Teflon, but its correct chemical name is polytetrafluoroethene (PTFE).

How was it discovered?

The discovery of PTFE actually happened completely by accident. When working in a team trying to develop non-toxic refrigerants in the 1930s at chemical company Dupont, Dr. Roy Plunkett was using a compound called tetrafluoroethene. Tetrafluoroethene is a gas, so it needed to be stored in small cylinder. Upon opening one of these cylinders, Plunkett found that the gas had disappeared, and in its place was a white, waxy solid. This solid was PTFE.

How did it end up in non-stick pans?

Though PTFE was patented in 1941, the brand name Teflon didn’t follow until 1945, and its first uses didn’t involve saucepans at all. One of its first applications was as part of the Manhattan project, where it was used to coat as a coating for the valves and seals of pipes containing highly radioactive uranium compounds. It wasn’t until 1954 that the first Teflon-coated pans appeared: a Frenchman, Marc Grégoire, had the idea of coating his fishing tackle with the compound, but it was actually his wife who had the brilliant idea of using it to coat pans. They subsequently went on to establish the brand Tefal.

How does it make pans non-stick?

PTFE is a long chain of carbon atoms with two fluorine atoms bonded to each carbon atom in the chain. These carbon–fluorine bonds are exceptionally strong; due to the high electronegativity of the fluorine atoms (they attract the electrons in the bond strongly), the carbon and fluorine atoms end up with partial charges, which attract each other and strengthen the bond further. Due to these strong bonds, PTFE is incredibly unreactive. It’s simply not possible for the molecules in food to form bonds with the carbon atoms in PTFE chains. Even fluorine gas, which is incredibly reactive, doesn’t react with the polymer.

Fluorine’s electronegativity also means that other molecules have a hard time sticking to PTFE, as they’re simply repelled. An oft-cited related fact is that PTFE is the only known surface that geckos are unable to stick to; the van der waals intermolecular forces they rely on to do this simply don’t work with PTFE.

If it’s so non-stick, how come it can stick to pans in the first place?

There are a couple of techniques that can be used to stick PTFE to pans. For one, it can be heated to a high temperature, then pressed into place, though this does usually result in it peeling off after a short duration. Another technique is to bludgeon the polymer molecules with ions at high speed to break away some of the fluorine atoms and make the polymer ‘sticky’.

Is it safe to use?

Some health concerns have been raised about Teflon pans. Though PTFE itself is inert, at high temperatures it can start to degrade, breaking down and releasing toxic fluorine-containing compounds. However, this only occurs above the polymer’s melting point, which is 327˚C; for reference, the recommended maximum safe use temperature for Teflon pans is 260˚C. It’s certainly possible to reach this temperature if the pan is overheated whilst empty, but when cooking food it’s unlikely to surpass this temperature.

Inhalation of the fumes from overheated PTFE, known as ‘polymer fume fever’, has been associated with flu-like symptoms in humans, and can cause death in birds. At present, the long term effects of inhalation of these fumes is largely unknown. Another chemical of concern is perfluorooctanoic acid (PFOA), which can be used in the Teflon manufacture process. Small amounts of this chemical can remain in the pan, and be released when heated. However, Dupont stopped using PFOA to produce Teflon in 2012.

There’s an excellent, more detailed look at the issue here.

 

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References & Further Reading