Polytetrafluoroethylene

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Polytetrafluoroethylene
PTFE thread seal tape.jpg
PTFE seal tape.
Names
IUPAC name
Poly(1,1,2,2-tetrafluoroethylene)
Other names
Fluon
Poly(tetrafluoroethene)
Poly(difluoromethylene)
Poly(tetrafluoroethylene)
PTFE
Syncolon
Teflon
Properties
(C2F4)n
Molar mass 100.015·n (n=100-10,000)
Appearance White slippery solid
Odor Odorless
Density 2.200 g/cm3
Melting point 327 °C (621 °F; 600 K) (displays decomposition)
Boiling point Decomposes
Insoluble
Solubility Insoluble in all solvents
Vapor pressure ~0 mmHg
Hazards
Safety data sheet SpectrumChemical
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Polytetrafluoroethylene or PTFE or Teflon is a synthetic fluoropolymer of tetrafluoroethylene, well known for its chemical inertness and very low coefficient of friction.

Properties

Chemical

PTFE is extremely resistant to chemical attacks, being only affected by molten alkali and strong fluorinating agents such as cobalt(III) fluoride and xenon difluoride. Teflon strips appear to burn in air, but it's most likely that the pyrolysis products are the one that catch fire. It will however enter a reaction that resembles burning when mixed with magnesium powder; see below on the mechanism of this reaction.

High temperatures cause PTFE to decompose into lower perfluorocarbons, some of which are very toxic. Reactions with moisture in the air also cause a small amount of HF to form.

Very high temperatures cause PTFE to liberate elemental fluorine, which makes it useful as an oxidizer for flash powders, in which the fluorine immediately and very energetically reacts with a metal such as aluminium or magnesium. The burning of metals in hot fluorine produces enormous heat which is used to decompose more PTFE, causing a chain reaction. This reaction may also be useful as a relatively safe method of fluorinating various substances which normally require the extremely dangerous fluorine gas to fluorinate.

Physical

PTFE is a white solid at room temperature, with a melting point of 327 °C. Its density is 2.2 g/cm3. PTFE maintains mechanical properties down to temperatures of 5 K (−268.15 °C), and has good flexibility at temperatures above −79 °C. Teflon materials however have poor mechanical properties and are susceptible to creep. When melted, PTFE has the consistency of paste which slowly decomposes, so items can only be cast via injection or made via machining blocks of PTFE.

Availability

PTFE is cheaply available as thread seal tapes. Many lab items, such as stoppers, gaskets, sleeves, magnetic stirrers are made from Teflon and can be easily procured online. However, items made of PTFE are expensive, as PTFE cannot be molded like the more common type of plastics.

Most frying pans also contain PTFE, but it's impractical to extract it.

Preparation

PTFE is made via polymerization of tetrafluoroethylene. This process is nigh-impossible for the amateur chemist to perform due to the high reactivity of tetrafluoroethylene and difficulty of producing this compound from scratch.

Projects

  • Container for hydrofluoric acid (PTFE beakers and bottles)
  • Magnesium/PTFE flash powder
  • Ytterbium/PTFE emerald green composition with high IR output

Handling

Safety

PTFE, being chemically inert, is non-toxic. Its pyrolysis is detectable at 200 °C, giving off fluorocarbon gases, that in large quantities can be dangerous for humans and are very toxic to wildlife, such as birds.

Storage

No special storage is required.

Disposal

Teflon materials can be safely dumped in the trash.

Being chemically inert, PTFE poses hazard to the environment, as it cannot be digested by wildlife.

References

Relevant Sciencemadness threads