8
$\begingroup$

I don't know much about polymers but recently teflon made me get addicted to study their properties and nature.

As far as I know, the teflon polymer contains fluorine which is one of the most reactive elements but in the polymer state it is totally stable and moreover, it is applied as a coating to kitchen-wares and many utensils which are exposed to very high temperatures.

How did a reactive element like fluorine got such an exciting stability?

$\endgroup$
12
$\begingroup$

Teflon (PTFE, polytetrafluoroethylene) is prepared by the polymerization of tetrafluoroethylene as shown below. If we took polyethylene and replaced all of the hydrogens with fluorines, we would have PTFE.

enter image description here

Here is a Table that compares the strengths of some single bonds involving a methyl group.

\begin{array}\hline Experimental ~Bond~ Enthalpies for~ CH_3 - X~ (kcal/mole)\\ \hline \end{array} \begin{array}{|c|c|c|}\hline I & 57.6 \\ \hline Br & 72.1 \\ \hline Cl & 83.7 \\ \hline CH_{3} & 90.1 \\ \hline H & 104.9 \\ \hline F & 115.0 \\ \hline \end{array}

The $\ce{C-F}$ bond is one of the strongest bonds to carbon known. As you add additional fluorine atoms to the carbon, the bond strength increases even further. While the $\ce{C-F}$ bond is a covalent bond, it has considerable ionic character making the carbon positively polarized and the fluorine negatively polarized. This bond polarization results in a strong electrostatic attraction between carbon and fluorine which accounts for the high bond strength observed. It is this very high bond strength that makes fluorocarbons so stable (unreactive). There are not many conditions that can supply enough energy to break this very strong bond.

$\endgroup$
  • 2
    $\begingroup$ One condition for breaking these bonds is cooking. Cooking with teflon at even ordinary temperatures can cause the "Teflon flu," in which gases from the pyrolysis of teflon are breathed in. Birds, which have extremely high respiratory rates, have died in the kitchens of owners with teflon. $\endgroup$ – Dissenter Jun 29 '14 at 20:06
  • 1
    $\begingroup$ @Dissenter wrote, "One condition for breaking these bonds.." Why do you assume that the $\ce{C-F}$ bond in PTFE is involved? Is "Teflon flu" due to the PTFE breaking down or decomposition of some other material used in the manufacture and coating of PTFE that happens to be carried along with the PTFE? If it is the PTFE breaking down, is it the $\ce{C-C}$ or $\ce{C-F}$ bond that is breaking? $\endgroup$ – ron Jun 29 '14 at 20:20
  • $\begingroup$ @ron will the same thing be applicable to pvc [poly vinyl chloride] $\endgroup$ – agha rehan abbas Jun 30 '14 at 14:46
  • $\begingroup$ No, PVC has the structure $\ce{-[CH_{2}-CHCl]_{n} -}$. Both the C-Cl and C-H bonds can react. I don't believe that poly-(tetrachloroethylene), which would be the chlorine analogue of PTFE, exists. I think I once read that steric hindrance from the bulky chlorines prevents polymerization - however copolymers exist. $\endgroup$ – ron Jun 30 '14 at 15:35
  • $\begingroup$ @ron i cant understand what bulky chlorine means as chlorine and fluorine belong to the same group so there must not be such a big difference in those $\endgroup$ – agha rehan abbas Jun 30 '14 at 18:18

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.