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PTFE / PCTFE / Viton / EPDM characteristics and applications

  1. Aug 4, 2011 #1
    Hi all

    I want you to give a comparison between PTFE / PCTFE / Viton / EPDM O-ring considering these points :

    • nonflammability
    • excellent chemical resistance to all inorganic corrosive fluids
    • Thermal resistance
    • friction
    • practically zero moisture absorption
    • excellent electrical properties

    Does PCTFE has same characteristics as PTFE?

    What are the characteristics of Viton (VS. PTFE)?

    What are applications for PTFE / PCTFE / Viton / EPDM?

    I want to use these items in high-purity pipeline (In-Vitro Fertilization lab) and the last thing I want to happen is gas contamination or chemical reaction

    Please advise and give comparison and provide recommendation?


    Regards
     
  2. jcsd
  3. Aug 4, 2011 #2
    Basically these are all called fluorinated materials. In other words, fluorine atoms surround carbon atoms and this gives the chemical resistance (since fluorine is inert).

    These materials are broken down into what is called fully fluorinated and partially fluorinated. The full ones have all carbon atoms surrounded by fluorine and the partial ones have some besides fluorine.

    PTFE is the original DuPont Teflon fully fluorinated material.

    PFA is basically also pure Teflon but is injection moldable.

    Viton and EPDM are partially fluorinated elastomers but much less expensive than PTFE.

    BTW, pure PTFE o-rings are usually sold by the trade names Kalrez (DuPont product) and Chemraz (GreenTweed product).

    So if you need the full chemical resistance and Teflon properties, go with PTFE. If not, the Viton or EPDM will be much less expensive.

    Another good choice is called TEV which stands for Teflon Encapsulated Viton. It is basically an inner ring of Viton in a Teflon tube. Much cheaper than than PTFE and almost as good in most cases.
     
    Last edited: Aug 4, 2011
  4. Aug 4, 2011 #3

    Thank you very much edgeflow for you continuous assistance, these info are very helpful

    What about PCTFE?

    I have to pipelines, One for CO2 and the other is special mix gas (89% nitrogen , 6% CO2 , 5% Oxygen) for (IVF lab) and I use stainless steel for whole installation and PCTFE, but there are Non-return valves that have EPDM or Viton O-Ring. I am afraid using other material other than PTFE would lead to moisture absorption (bacteria) and other gas contamination.So what should I do? The non-return valve manufacturer has only two choices;Viton or EPDM, should I just take one of them (may be Viton) and they will do a good job or should I go and find another manufacturer that has PTFE Or-ring on their non-return valve?
     
    Last edited: Aug 4, 2011
  5. Aug 4, 2011 #4
    The PCTFE should be fine - it is known for high compressive strength and low deformation.

    I think Viton is good for this gas mixture. If it was just oxygen, I would recommend the Teflon o-rings, but if the gas stays mixed in the ratios you mentioned, I think Viton is OK. Double check with some o-ring companies, however.
     
  6. Aug 4, 2011 #5
    Among the plastics you cite, only EPDM (which isn't fluorinated) and Viton are elastomers. This should tell you their roles as seal parts.

    EPDM has good resistance to chemicals, as a hydrocarbon, but poor resistance to heat. Impossible to sterilize for instance.
    PTFE creeps horribly. Permanent worry for seals. Compressive strength says little about a polymer.

    Developing seals is a difficult job needing months and years. Very few materials fit, and a seal uses to consist of several parts made of different materials. So if one company doesn't have the product you'd like, you may try a few other companies, but don't hope to obtain good rings from a material nobody uses.
     
  7. Aug 5, 2011 #6
    Hi

    Thank you all for contribution. Here are more info :

    http://fluorotherm.com/Properties-PCTFE.asp" [Broken]

    http://fluorotherm.com/Properties-PTFE.asp" [Broken]

    http://www.wisegeek.com/what-are-elastomers.htm"

    http://www.pspglobal.com/sab.html" [Broken]

    http://www.pspglobal.com/viton-properties.html" [Broken]
     
    Last edited by a moderator: May 5, 2017
  8. Mar 15, 2012 #7
    Sorry for resume an old post, but google sent me here.
    Is this still an issue?
    Carlo
     
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