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Wire insulation safety

Discussion in 'Electronic Design' started by Richard Henry, Apr 5, 2007.

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  1. I am not allowed to use PVC-insulated wire on a current project due to
    hazardous chemical components in the smoke should there be a fire.
    Teflon-insulated wire is ok.

    My question is about radiated olefin insulation. Where does this fit
    in the chemical exposure/safety spectrum?
  2. Robert Baer

    Robert Baer Guest

    Ohhh..when Teflon gets really hot, you want to ba *far* away.
    Have you heard of Phosgene?
    Consider the flurine version; *much* worse!
  3. the coated pan on dry heating was less than that of fumes given off by
    ordinary cooking oils".
  4. Glen Walpert

    Glen Walpert Guest

    The MSDS however says "During a fire, irritating and highly toxic
    gases may be generated by thermal decomposition or combustion."
    Wikipedia would not be one of my top 100 sources for toxicity data.
    There is a lot of reliable data on the toxicity of fumes produced by
    burning teflon which can be easily found, just not on wikipedia.

    Usually when the contribution of wire insulation to smoke from a fire
    is a concern some particular standard is invoked and wire must pass
    the appropriate tests in order to be used. Guessing what the smoke
    contribution of particular compounds would be is a rather poor way to
    spec wire insulation IMO.
  5. The specification we are following is from the US Army. They have
    more funding to pursue these tests than we do. Specifically it says
    PVC=No, Teflon=Yes. My guess would be that PVC is toxic at a lower
    temperature or in a higher lethality than Teflon.

    But my original question was about irradiated polyolefin insulation.
    Where does that fit on the safety spectrum?
  6. Glen Walpert

    Glen Walpert Guest

    (Sure, Phosgene is manufacturered in large quantities for use in the
    manufacture of certain plastics, and shipped around the country in
    tank trucks with the standard "corrosive" placard. I did some lab
    testing on a phosgene compressor seal long ago, and the co-worker who
    installed it in the field reported that phosgene makes cigarettes
    taste terrible.)
    I would guess that polyolefins, consisting only of hydrogen and
    carbon, would be fairly good as far as smoke toxicity. But this is
    precisely the sort of guess I don't think you should be basing design
    decisions on. What does the Mil-Spec say? I would expect major wire
    manufacturers to be able to answer questions about what insulations
    meet your specifications; possibly you could call Belden or your
    preferred wire supplier and discuss the matter with their applications
    engineering department.
  7. Try burning PVC sometime. HCl will make you cry - and rust.
  8. There's a movement afoot to get rid of PVC entirely, at least in
    applications where there are reasonable substitutes. Hard to believe,
    considering all the PVC extrusions that are all around us.

    Best regards,
    Spehro Pefhany
  9. I worked in a molding factory. PVC and acetal would explode if mixed and
  10. Robert Baer

    Robert Baer Guest

    What do they know?
    Besides, frying pans are cold relative to the decomp temp of Teflon.
  11. Robert Baer

    Robert Baer Guest

    It does seem to withstand a 200C environment.
  12. Yes, you have to purge the machine barrel with something else (eg. PE)
    when you are switching resins.

    Best regards,
    Spehro Pefhany
  13. One of our guys didn't and stuck his head over the hopper to see what was
    happening. He looked like he had the worst case of measles for a few weeks.
    Lucky it missed his eyes!
  14. Tim Shoppa

    Tim Shoppa Guest

    Much more complicated when you're comparing Army/AF/mil-specs with UL/
    CSA or building codes.

    The worst case army environment has several soldiers in a tiny tank
    compartment (OK, not as tiny as they used to be) filled with dozens
    and dozens of electronic subsystems, a turbine for propulsion, live
    ammo stashed in all kinds of places, and depleted uranium as the
    preferred projectile. I'd rather NOT HAVE A SHORT that might spark an
    explosion, rather than use something like PVC :).

    Note that European building codes are often different than US/Canada,
    and in some cases ban PVC while allowing Teflon in the same situations

    Flame dynamics can be ridiculously nonlinear in response to a small
    change in parameters.

  15. legg

    legg Guest

    If the same reservations were held to all other components in the
    assembly, I doubt few would be acceptible. Why the emphasis on wire
    insulation alone?

  16. The PVC ban applies to all components used. I have no problem finding
    usable components.
  17. MassiveProng

    MassiveProng Guest

    You didn't even come close to answering the question he asked.
  18. Nor he mine. I was asking about radiated polyolefin.
  19. Ian

    Ian Guest

    Interesting that PTFE is considered as ok in a fire: PTFE .pdf

    "at temperatures greater than 350 deg C for emissions of noxious
    fluorine compounds (including HF and COF2)"

    My recollection was the temperatures required were higher than this,
    but any chance of releasing HF is a Bad Idea.

  20. joseph2k

    joseph2k Guest

    For far more than you ever wanted to know toss "wire insulation fire
    toxicity" to a search site / engine.
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