What are fluoropolymers?

What are fluoropolymers?

Since the first discovery of PTFE polymer, scientists have strived to develop new materials that have all the good attributes, but are more economical and can be processed by conventional melt processing techniques. PTFE has to be cold pressed and sintered. 

Origins

PTFE or Polytetrafluoroethylene is the original fluoropolymer, it was accidentally discovered in 1938 by Dr. Roy Plunkett of the Dupont company, who was experimenting with tetrafluoroethylene (TFE) for the synthesis of new refrigerants, the “accident” basically consisted when, one morning, when checking the pressure in a TFE gas cylinder that he had left the night before to use in an experiment, he discovered that there was no gas, verifying that he detected that there were no leaks in the valve and that the cylinder had not leaked weight, removing the valve and shaking the cylinder he discovered that the container now contained a white pasty substance, which was basically the first polymer of TFE.

Details of the product

Currently, the only material whose chemical, thermal and electrical properties match those of PTFE is PFA or perfluoroalcoxi, however its cost is higher than that of PTFE. Attempts to search for similar substances have generated a whole family of materials, some of which have been successfully accepted in the industry. This family of fluoropolymers is divided into two groups:

  1.  Fully fluorinated materials or perfluoropolymers.
  2.  Partially fluorinated materials containing hydrogen and/or chlorine

The group of fully fluorinated materials has almost completely formed molecules that are carbon and fluorine atoms, their characteristics are:

  • Excellent chemical resistance
  • Excellent electrical properties
  • Management of good service temperature ranges
  • low friction,

However, mechanically they are weak and difficult to process, making them more expensive. Within this group of fully fluorinated materials are:

  • PTFE
  • PFA
  • FEP (fluorinated ethylene propylene).

Partially fluorinated materials have molecular structures where a significant number of fluorine atoms found in PTFE are replaced by chlorine and/or hydrogen atoms, this improves their mechanical resistance and their way of processing, in general they are cheaper than fully fluorinated materials and in most cases are more easily processed using conventional thermoplastic techniques.

Partially fluorinated materials have some limitations (especially when compared to fully fluorinated materials), such as lower chemical resistance, which leads to certain limitations in industrial processes, and lower service temperature ranges.
Within this group are:

  • PVDF (polyvinylidene fluoride)
  • ETFE (Ethylene-Tetrafluoroethylene Copolymer)
  • PP (Polypropylene)

TABLE 1. TEMPERATURE SPECIFICATIONS OF FLUOROPOLYMERS

fluoropolymerTemperature ranges
PTFE (polytetrafluoroethylene)-20 to 500°F (-29 to 260°C)
PFA (perfluoroalkoxy)-20 to 500°F (-29 to 260°C)
PVDF (poly vinylidene fluoride)0 to 275°F (-18 to 135°C)
ETFE (ethylene tetrafluoroethylene copolymer)-20 to 300°F (-29 to 149°C)
PP (Polypropylene)0 to 225°F (-18 to 107°C)
FEP (fluorinated ethylene propylene)-20 to 300°F (-29 to 149°C)

Temperature specifications, in accordance with ASTM F1545

Reference

-Ariawan, Alfonsius, Ebnesajjad, Sina and Hatzikiriajos, Savvas. Properties of Polytetrafluoroethylene (PTFE) Paste
Extrudate. Polymer Engineering and Science. June 2002, Vol. 42.


-Sperati, Carleton A. Physical Constants of Fluoropolymers. Parkersburg. Dupont, 1981.
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