PTFE

Discussion in 'General Engine Discussion' started by Mo deller, Jan 22, 2010.

  1. Jan 22, 2010 #1

    Mo deller

    Mo deller

    Mo deller

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    I have a scrap box of plastic and was wondering if there is a positive way of identifying ptfe.

    Peter ???

     
  2. Jan 22, 2010 #2

    Noitoen

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    PTFE is a dull white, feels soapy, and is denser/heavier then other plastics.
     
  3. Jan 22, 2010 #3

    rickharris

    rickharris

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    FWIW

    Density PTFE (lb/in³)
    unfilled 0.078 25% Glass filled 0.081 25% carbon filled 0.075

    (g/cm³)
    unfilled 2.16 25% Glass filled 2.25 25% carbon filled2.08

    Same for Polyethylene

    Density (lb/in³)
    LDPE 0.033 HDPE 0.035 UHMW 0.034

    (g/cm³)
    LDPE 0.92 HDPE 0.95 UHMW 0.93


    http://www.boedeker.com/ Useful site with lots of information
     
  4. Jan 22, 2010 #4

    Mo deller

    Mo deller

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    I have some that is I would say milky white and does feel a bit slippy to touch. I would guess it is ptfe but I have no experience so wondered if I could be fooled by something similar.

    Rick, I dont know what to do with all the numbers. I guess there must be a formula to work it out from weight and volume but I have no idea how to do it.

    Thanks
    Peter

     
  5. Jan 22, 2010 #5

    Noitoen

    Noitoen

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    The numbers are easy. Just fill a graduated measuring cup with some water, drop a chunk of the material you want to measure, determine the water displacement in cu/in, weigh the piece and calculate the density.
     
  6. Jan 22, 2010 #6

    Mo deller

    Mo deller

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    ;D Yes I can do the drop it in some water and weigh it bit,it's the calc I dont understand. What is the formula?
     
  7. Jan 22, 2010 #7

    Mo deller

    Mo deller

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    Ok I think I have it. Mass divided by volume = density. I get the impression that's very basic and in reality it is more complicated.
     
  8. Feb 4, 2010 #8

    solver

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    How about simple rubbing-test? If it's ptfe, it should be quite slippery against for example brass or steel.
     
  9. Feb 5, 2010 #9

    charlesfitton

    charlesfitton

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    A technican at my place of employ showed me a neat way to identify plastics
    - a burn test.

    Some won't stay lit, some smoke a lot, some drop small burning gobe of fire - I'm sure there's a chart somewhere on the web.

    Marry up the characteristics with the chart and Roberts' married to your Auntie...

    f
     
  10. Feb 5, 2010 #10

    Mo deller

    Mo deller

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    I just had a google and found that if I poke a soldering iron into ptfe it doesn't drip and should smell of burnt hair.
    Added to feeling slippery I think should get some positive id there.

    Many thanks
    Peter
     
  11. Feb 5, 2010 #11

    solver

    solver

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    Burning ptfe isn't recommended, since it forms very hazardous gases.
     
  12. Feb 6, 2010 #12

    Mo deller

    Mo deller

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    I appreciate your concern and I half expected someone to raise the health issue. I am well aware that burning any plastic is not to be reccomended but will a quick prod with a hot object done outside just to verify things be that bad?
     
  13. Feb 6, 2010 #13

    solver

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    If proper precautions are taken, I suppose it can be done.

    Some info about ptfe: http://en.wikipedia.org/wiki/Polytetrafluoroethylene#Safety

    Using respirator mask isn't exaggerated. If you inhale that smoke even bit, it gets you in a quite bad shape almost immediately.

    I have done that mistake, and hope others don't do it. Safety first.
     
  14. Feb 6, 2010 #14

    Mo deller

    Mo deller

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    mmmmmmm I dunno, I think I'll stick to the rub test then.
    This has made me wonder how much it gets heated inside an engine but we could go on and on. It's a small amount but if you happen to be sensitive to it that is irrelevant.
    With all the stuff that is going on in the world I think we are all doomed anyway, doomed,doomed I tell yeee ;D

    Anyway safety issues noted,thanks.
     
  15. Apr 30, 2012 #15

    AdShea

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    I know this is reviving an old thread, but one easy indicator of PTFE over HDPE or PP is that PTFE sinks quickly in water, the others don't (just look at the density).
     
  16. Jun 5, 2012 #16

    Todd...

    Todd...

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    getting ptfe above 300 degrees F will emit a gas and cause "ptfe flu"

    had to do my senior design project using the stuff, easy to machine but a pain to work with non the less
     
  17. Jun 5, 2012 #17

    steamer

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    Yes...the "flu" I suspect is a result of Phosgene gas. PTFE needs to be turned more slowly than most plastics so that it doesn't overheat and break down....but it's not that hard to do. The other by product I believe is Hydrofloric acid.....KenI will be along with a complete and correct assessment... ;D

    DON"T SMOKE WHILE TURNING THIS STUFF!

    Dave
     
  18. Jun 5, 2012 #18

    Blogwitch

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    PTFE machining gases whilst smoking produces phosgene gas. Which in turn forms hydrochloric acid and carbon monoxide in the lungs.

    Burning Viton produces hydrofloric acid, which kills any living cells on or in the body it comes into contact with. Usually it is easier to amputate the whole limb quickly rather than attempting to treat the affected area, as it spreads with ease throughout the body. It also eats it's way through glass.

    These are two of the most dangerous 'plastics' that we can use in our shops.


    John
     
  19. Jun 5, 2012 #19

    Maryak

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    Thanks for that Bogs :bow: I wonder how many of us knew that ??? I sure didn't.

    Mental note to self........"Don't have one last scratch of your privates, when burning Viton." :p

    Best Regards
    Bob

     
  20. Jun 5, 2012 #20

    Tin Falcon

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    Hmm interesting conversation. brings up some interesting points.
    1) know the material you are working with. Know the hazards. that is What MSDS sheets are for they are readily obtainable and available as pdf files. download and print. follow recommended precautions.

    2) smoking in and of itself is not healthy the cigarette companies enhance the tobacco with nasty chemicals . to even call the stuff in cigarettes tobacco is to call sawdust/garbage board aka mdf wood. I would expect burning mdf in a fire expels some nasty gasses as well.

    3) some plastics are made with phosegene,burning it releases phosegene.

    4) phosegene a chemical discovered during world war I. A chemical warfare agent , smells like freshly mown hay.Causes dry land drowning. no antidote. exceed exposure levels it will kill you. made by reacting chlorine (poison) and carbon monoxide) another poison.

    5) OSHA regulations prohibit eating drinking or smoking in work areas that contain potential harmful or hazardous material or chemicals. also these materials are not permitted in designated eating areas/break rooms.
    6) popper practice of industrial hygiene including following recommendations on MSDS sheets prevents chemical exposures.

    7) most of us here machine in our own private space we call a shop. we set the rules and enforce them or not. we are responsible for our own saftey. work safe ladies and gents.
    8) do not forget this is supposed to be fun ;D
    Tin
     
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