Carbon and fluorine. Polymers and PTFE. Chemical bonds and energy. And why non-stick pans work so well.
Don’t be so sticky! Food sticks to pans because of the chemical bonds that form between the food and the metal pan (read all about the science in the 1-Minute NomNom “Yes it’s true, yes it’s true, I’m so happy to be stuck with you“). Hence one way to prevent this is to use non-stick pans.
Many of these non-stick pans are made with a non-stick coating such as polytetrafluoroethylene (PTFE). One example is Teflon®, which has become synonymous with non-stick pans.
PTFE is a large molecule made up of smaller molecules that repeat themselves (see diagram below). The smaller molecules are tetrafluoroethylene (TFE i.e. C2F4). When C2F4 repeats themselves, the large molecule formed is called a polymer – represented by the “n” at the bottom – and hence the “poly” in PTFE.
Why is PTFE such a great material for non-stick pans? It has to do with single bonds that are unavailable for bonding (e.g. with food)!
Look at the chemical diagram above again and you can see PTFE has only carbon-carbon single bonds, and carbon-fluorine single bonds. These single bonds are very strong and must first be broken before they become available for food to form new and sticky chemical bonds (such as covalent bonds) with the pan.
In fact, the carbon-carbon bond is known to be an unusually strong bond. And the bonds that fluorine form are known to be very stable. This is because fluorine is one of the most reactive elements – it “reacts with almost anything instantly” – and when it bonds with other elements,
“… a large amount of energy is released… The resulting compounds are very stable because the same large quantity of energy must be put back in if you want to tear them apart. This energy must be supplied by some yet-more-reactive substance, of which… there are precious few.” (Source: The Elements)
Most cooking conditions also do not have enough energy to do that. However cooking at at very high temperatures does. This is usually beyond 260°C/500°F. The polymer begins to break down into toxic fumes. If you do need to cook safely at those temperatures, why not use a wok (see the 1-Minute NomNom “Hei, wok’s up?“) and enjoy some wok hei while at it!
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photos: in order – depositphotos/eelnosiva;weyo; logos2012; blueringmedia; boule1301