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Compatibility comparison: ethyl alcohol vs. denatured alcohol

  1. Jul 16, 2010 #1
    I have plastic, metal and rubber parts that are compatible with ethyl alcohol (they are regularly washed in a bath of ethyl alcohol). I’m looking for a substitute solution to wash these parts and I am considering denatured alcohol, however, I’m concerned that the denaturing ingredients will harm the parts.

    The denatured alcohol I’m considering is about 86% ethyl alcohol. It also contains the following:
    methyl alcohol 3.6 %
    methyl isobutyl ketone 1.9 %
    ethyl acetate 1.0 %
    naphtha solvent 0.8 %

    Does anyone know if a denatured alcohol with the above composition will be any more harmful to metal, plastic and rubber parts than would a pure ethyl alcohol solution?

  2. jcsd
  3. Jul 19, 2010 #2


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    Welcome, OfficeSpace. Metal is no real problem regardless, but plastic and rubber can have problems with some solvents. If they're fine with ethanol, then it's very unlikely most of the mentioned chemicals will have much effect, since they're chemically quite similar.

    Except the naphta. (Which is basically paint thinner) That's a pretty good non-polar solvent (the others are fairly polar) which makes it rather different. So there's no guarantee a rubber or plastic which is ethanol-resistant will also resist the naphta. On the other hand, the concentration is fairly low. (Also, your numbers don't add up to 100%, so there's something else in there as well?)

    I'd look around for a denaturated ethanol without the naphta.
  4. Jul 19, 2010 #3
  5. Jul 19, 2010 #4


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  6. Jul 19, 2010 #5
    And so can ethyl acetate and methyl isobutyl ketone -- from the OP!!

    Hence why I said
    Everything depends on the concentrations of denaturants involved, not just their compositions.
    (Unfortunately, Walgreens does not specify concentrations...)

    If the OP can well handle ethyl acetate & methyl isobutyl ketone,
    is a bit of acetone really that dangerous?

    Exactly what rubber or plastic is the OP using anyway?

    Here are some online guides for gauging chemical resistance of common materials:
    Last edited: Jul 19, 2010
  7. Jul 19, 2010 #6


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    I didn't say they couldn't. I said it's not as likely if the material is impervious to ethanol.

    As well as temperature and exposure time and qutie a number of factors in fact.

    Yes, acetone damages more plastics and rubbers than those two.

    If he'd said, I'd have made a more detailed recommendation.
  8. Jul 20, 2010 #7
    Why not? Ethyl acetate and methyl isobutyl ketone are pretty nonpolar solvents.
    Several rubbers and plastics impervious to ethanol are easily damaged by both of these solvents.

    The OP said "regularly washed in a bath of ethanol", so I assumed
    exposure time = indefinite ("bathed" in the ethanol)
    temperature = close to room temperature (unless otherwise specified)
    (although hot and/or cold washes are not uncommon)

    I would be interested in seeing your sources for this.

    Probably what should've been asked in the first place
    Last edited: Jul 20, 2010
  9. Jul 20, 2010 #8
    Thanks for the responses to my post, I appreciate the input.

    The parts and the use are fairly pedestrian: an automatic cleaning system for an electric razor. The cleaning system pumps fluid from a reservoir to a portion of the base station where the razor is cleaned in the fluid. I’m not sure of the composition of the parts, but because they include the pump components, the base station and the razor head, I summarized them as plastic, metal and rubber – essentially a best guess.

    Combining information from the box and the MSDS, the original cleaning solution is “60-100%” SD ethanol 40-B, “<0.5%” Limonene, Citral, Fragrance and most likely some water. After consulting the Code of Federal Regulations, SD ethanol 40-B is 99.875 % ethyl alcohol, 0.125 % tert-butyl alcohol, and effectively a trace amount of denatonium benzoate.

    I’m looking for an alternate cleaning solution that (obviously) will not damage the parts. Ethyl alcohol and glycerol (as a lubricant in lieu of the two oils in the original formula) would work. The problem I’ve encountered is that SD ethanol 40-B does not seem to be available for consumer purchase, and there are a wide range of denaturants used in “regular” denatured alcohol but these are not listed on the containers (which means checking the MSDS for each commercially available solution and thinking about compatibility with parts of unknown composition).

    In my original post, the listed denatured alcohol was the “best” regular denatured alcohol that I found; it has the highest concentration of ethyl alcohol, and the fewest additives (again from those that I came across). I have also considered isopropyl alcohol, however I’m uncertain if that would be a good candidate.

    Thanks again for your thoughts.
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