Chemistry - Is there ANY chemical that can destroy PTFE, or Teflon?
Solution 1:
Corrosion Resistant Products, Ltd., with the help of Dupont, has established this source of information on what can and cannot eat teflon.
Here's a list:
- Sodium and potassium metal - these reduce and defluorinate PTFE, which finds use in etching PTFE
- Finely divided metal powders, like aluminum and and magnesium, cause PTFE to combust at high temperatures
These reactions probably reduce PTFE in a manner that starts:
$$\ce{(CF2CF2)_{n} + 2Na -> (CF=CF)_{n} +2NaF}$$
- The world's most powerful oxidizers like $\ce{F2}$, $\ce{OF2}$, and $\ce{ClF3}$ can oxidize PTFE at elevated temperatures, probably by:
$$\ce{(CF2CF2)_{n} + 2nF2 -> 2nCF4}$$
Similar things can occur under extreme conditions (temperature and pressure) with:
- Boranes
- Nitric acid
- 80% NaOH or KOH
- Aluminum chloride
- Ammonia, some amines, and some imines
Solution 2:
Just to add a bit to Ben's excellent answer...
- A number of fluorinating agents also react with PTFE, $\ce{XeF2}$ and $\ce{CoF3}$ being examples
- Ben mentioned the reaction of magnesium metal. Typically with metals, they must be in intimate contact with the PTFE surface, so molten metals or metals dissolved in anhydrous solvents will react.
The magnesium reaction is of special interest because it serves as the basis of the thermite flare. A pyrotechnic device commonly used in the countermeasures aircraft use to evade heat-seeking missiles. The reaction of metals with PTFE is given by the following equation (I think this is the general description for the reaction of metals with PTFE; I'm suspect of the reaction proposed by Ben involving the formation of poly-perfluoroacetylene).
$$\ce{2Mg + -(C2F4){-} → 2MgF2 + 2C}$$
The formation of $\ce{MgF2}$ is extremely exothermic. The heat given off along with the carbon soot provides a new, much hotter, target for the attacking missile to lock onto.
As to whether there is anything more resistant, I suspect that is unlikely. The $\ce{C-F}$ bond is shorter (135 pm) than the $\ce{Si-F}$ bond (160 pm) and therefore better serves to encase and protect the carbon backbone. While there are some other polymers that have better mechanical or thermal properties, I am not aware of any that have better chemical resistance. In Polymers for Electronic & Photonic Application from 2013, the author states, "PTFE is the most chemically resistant polymer known".
Solution 3:
I am aware that this answer does not describe a ‘chemical that can destroy PTFE’. However, since you are also asking ‘is there anything that can destroy Teflon through only chemical means?’, and in order to complete the other answers, I would like to add that PTFE can be easily destroyed by means of radiation chemistry. (Radiation chemistry is the study of the chemical effects of radiation on matter. It is not to be confused with radiochemistry, which is the chemistry of radioactive materials.)
PTFE is exceptionally sensitive to radiation. PTFE experiences significant damage at lower radiation exposure levels than other polymers. In general, PTFE is considered usable without any significant restrictions only for absorbed doses of up to $100\ \mathrm{Gy}$.
The general radiation effects on polymers are formation of gas, cross-linking of polymer chains, and scission of polymer chains. In contrast to most other polymers, all hydrogen atoms in PTFE are substituted by fluorine atoms; therefore, the elimination of hydrogen or hydrogen fluoride and the corresponding formation of double bonds do not occur. The elimination of fluorine due to $\ce{C-F}$ bond break is possible; however, since $\ce{C-C}$ bonds are clearly weaker than $\ce{C-F}$ bonds, $\ce{C-C}$ bond break predominates. Therefore, the primary effect of radiation on PTFE is the scission of the polymer chain (breaking of the large polymer molecule into smaller parts). Due to the absence of π-electrons, the excited states are not particularly stabilized, resulting in high radiation-chemical yields. Because of the absence of unsaturated bonds, the absence of functional groups that can be easily eliminated, and the general chemical inertness, PTFE cannot be cross-linked like an elastomer. Therefore, the scission of the polymer chain is not compensated for by the formation of new bonds. With advancing chain scission, the molar weight of the polymer is dramatically reduced from an initial value of about $6\times10^6\ \mathrm{g\ mol^{-1}}$. It is divided by $4$ after $250\ \mathrm{Gy}$ exposure and by about $20$ for a dose of $1000\ \mathrm{Gy}$.*
The effect of molecular weight reduction is primarily on mechanical properties. Tensile strength is reduced by $25\ \%$ after $500\ \mathrm{Gy}$ exposure and by $50\ \%$ for a dose of about $900\ \mathrm{Gy}$. For doses above $1500\ \mathrm{Gy}$, imminent material failure has to be assumed because of a brittle behaviour with unstable crack propagation.
If possible, PTFE components should be avoided in high radiation environments (nuclear power plants, nuclear fuel cycle facilities, irradiation facilities, or particle accelerators).
* Fayolle, B.; Audouin, L.; Verdu, J.: Radiation induced embrittlement of PTFE. In: Polymer 44 (2003) 2773–2780.
Solution 4:
A PTFE surface can be chemically altered for bonding to other materials by solvated electrons in liquid ammonia (leaving the bulk PTFE intact). Classically alkali metals have been used for this, but a more controlled reaction is obtained from an electrolytically generated magnesium solution. See Ref. 1. From the abstract:
Solutions of solvated electrons in the presence of magnesium offer many advantages for the surface treatment of PTFE when compared to the classical solutions of solvated electrons in the presence of alkalis: the polymer remains white instead of black, its surface is not destroyed and presents a controlled hydrophilic character.
Reference
1. K. Brace, C. Combellas, M. Delamar, A. Fritsch, F. Kanoufi, M. E. R. Shanahan and A. Thiébault, "A new reagent for surface treatment of polytetrafluoroethylene", Chem. Commun., 1996, 403-404.
Solution 5:
Similar polyflourines have been decomposed by ball-milling PTFE with dry potassium hydroxide. There s an interesting article by Zhang et al. [1] which is really informative and makes me thing that PTFE would respond similarly. Everything breaks down to the mineral elements with no nasty interims formed. The energy and pressure of the steel balls smashing the KOH into the polyflourines causes the reactions to go with no aqueous stage needed. It could be the answer to reducing the PTFE waste impact on the environment.
References
- Zhang, K.; Huang, J.; Yu, G.; Zhang, Q.; Deng, S.; Wang, B. Destruction of Perfluorooctane Sulfonate (PFOS) and Perfluorooctanoic Acid (PFOA) by Ball Milling. Environ. Sci. Technol. 2013, 47 (12), 6471–6477. https://doi.org/10/gf5w4f.