The Chemical Resistance of FLUOROPOLYMERS

Fluoropolymers are produced from alkenes (aka: olefins) which are unsaturated hydrocarbons. Unsaturated hydrocarbons are more reactive than saturated (alkanes) since they contain at least one double bond between carbon atoms in the molecular structure.

The presence of double or triple bonds means there is room for additional atoms to be added to the chain, thus making them more highly reactive.

Understanding the chemical structure of fluoropolymers gives an understanding of the chemical resistance of the finished product. Let’s start with the most common fluoropolymer, PTFE or Teflon®.

PTFE is a fully fluorinated homopolymer made by reacting fluorine with simple ethylene producing tetrafluoroethylene and then polymerizing to become PTFE. The resulting polymer is fully fluorinated, lending itself to the highest level of chemical resistance possible.

Like PTFE, PVDF is a fluorinated homopolymer that uses simple ethylene as a base polymer, but only two of the four hydrogens are replaced with fluorine. The resulting polymer is a less chemically inert polymer that offers increased mechanical toughness.

Chemical resistance is influenced highly by the function of the weakest bond in the polymer matrix. PTFE only has two types of bonds, C=C and C-F. Both of these bonds are extremely stable, and thus PTFE has the highest chemical resistance within the fluoropolymer family. 

With all the benefits of PTFE, the downfall is the ability to melt process. Thus a copolymer version of the fully fluorinated polymer was invented thru the reaction of ethylene and propylene to make FEP. The inertness of the material was preserved; however, resulting thermal properties were sacrificed. PTFE has a melting point of 621°F while FEP is at 518°F.

PVDF, PFA, ECTFE, and ETFE all followed in development as copolymers; however, all are onlypartially fluorinated systems. The more these polymers deviate from the full fluorination of PTFE, the less chemical resistance they display.

Compared to traditional polymers, all these polymers offer exceptional chemical resistance, flame retardancy, and purity, making them extremely useful in Semiconductor applications. Each product has unique mechanical properties giving designers and engineers many choices to select for use in the process tools.

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