Why does nothing stick to Teflon? And how is it applied to pots and pans nonetheless?

Anyone who has ever washed pots and pans, knows that Teflon-coated cookware is one of the easiest to wash by far. It seems that no matter how hard one tries, nothing sticks to such cookware. How does this magic occur?

Teflon is the commercial name of a molecule called Polytetrafluoroethylene, or PTFE. It was discovered accidentally in 1938, by scientist Roy J. Plunkett, who was working at the american company DuPont while trying to create a new substance to be used for refrigeration. The product he created was a polymer (a long molecule composed of repeating units) built as a long chain of carbon atoms attached to fluorine atoms. This molecule possesses several distinctive properties - it does not tend to interact with other materials, it has a high melting point, it is electrically insulated, it has a very low coefficient of friction and things do not tend to stick to it. 

The special properties of teflon stem from its chemical composition and structure: the bonds between the carbon and the fluorine atoms are very strong, implying that a large amount of energy is required to break and replace these bonds with new ones. Therein lies the chemical stability of this material and its indifference to other materials. Additionally, being larger than the carbon atoms, the fluorine atoms “hide” the carbon atoms from external molecules and reduce thus the chance of a chemical reaction. 

Other reasons why materials do not adhere to Teflon are related to its electric properties: PTFE is an electrically neutral molecule, meaning that the sum of its positive charges (the number of protons) is equal to the sum of its negative charges (the number of electrons). Therefore the molecule is neither attracted to charged molecules in its vicinity nor is it repelled by them.  

In principle, neutral molecules can be attracted, albeit more weakly, by Van der Waals forces. These are very weak electric forces that operate within very short ranges (less than a nanometer) between neutral molecules (molecules whose total electric charge equals zero). In order for this to occur, the molecules need to be either polar or polarizable, implying that the electrons are scattered throughout the molecule unevenly, either permanently or due to an external influence. 

Teflon however is a non-polar molecule, nor is it easily polarizable. The reason for this is the symmetrical structure of the Teflon molecule, which results in an even scatter of electrons around it, implying non-polarity. In addition, fluorine strongly attracts electrons from other atoms. These electrons gather around the fluorine atoms and are not easily moved, making the polarization of Teflon molecules difficult. The combination of all of the above reasons makes Teflon a highly smooth material, such that even a gecko is unable to adhere to it.

Strong bonds between the carbon and fluorine atoms and a uniform  electron scatter cause the Teflon molecule to be indifferent | Image: Science Photo Library
Strong bonds between the carbon and fluorine atoms and a uniform electron scatter cause the Teflon molecule to be indifferent | Image: Science Photo Library

A bit of cheating

The relevant question would then be - how is it possible to attach Teflon to pots and pans in spite of its above described properties? The answer is that in order to do so, a small amount of “cheating”, which includes a slight modification of the molecule, is required. This can be done using plasma, i.e. by bombarding the Teflon with charged particles in such a way as to cause the fluorine atoms to detach from the carbon chain. Where this is achieved, the carbon remains unprotected and electron deficient since the electron-attracting fluorine atom has taken the electron along with it. This results in a very unstable chemical state in which the carbon atom will seek to form a chemical bond with any material in its vicinity, such as the metal of which a pan is made.

Another way to break the carbon-fluorine bond is by using a reducing agent, a chemical that will “donate” electrons to the fluorine, breaking the fluorine-carbon bond and making the carbon accessible. The reducing agent thus in fact steals the fluorine from the carbon. Good reducing agents for breaking the fluorine-carbon bond are alkali metals such as sodium, potassium and lithium. 

Ted-Ed video about teflon.