lucky123
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plastics and ethanol?
I was wondering is there any plastic that could ever be used for an ethanol still? I have heard hdpe and pp plastics have excellent chemical
resistance. So anyone here have a thought I have seen the polypipe still online and the amazing still and wonder about the safety....
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hissingnoise
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I can't believe you didn't see see the discussion a few threads down.
Unless you have an extreme form of tunnel vision, you haven't even bothered looking. . .
Open your eyes, dammit!
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1281371269
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The issue would be heat resistance rather than chemical resistance - alcohol is often sold in plastic bottles!
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Picric-A
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A PTFE flask would work as a boiling flask if submerged in a waterbath (they are good beyond 120degC)
then rest can be polypropylene. OR for extreme resistance PTFE tubing, it isnt as expencive as it sounds...
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lucky123
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Where?
Really just a few threads down is a discusion about ethanol and plastics? I bad must have tunnel vision!
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1281371269
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It's in miscellaneous (assuming that's the one hissingnoise refers to) - a link I found yesterday on the chemical resistance of plastics. So your
tunnel vision is probably ok  .
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starman
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In the very early days I tried to fashion a fractionation column out of a 3ft length of rigid 3/4 " PE filled with cut up 1/4 " rigid 'sprinkler
riser' PE tubing as a poorman's raschig rings.All this to fractionate ethanol.It was working preyty well and had equilibriated nicely when suddenly
the whole thing went down like a flaccid penis,faster than a bust at a brothel!
Chemistry- The journey from the end of physics to the beginning of life.(starman)
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lucky123
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fractional column
I was thinking of trying this with hdpe pipe packed with pot scrubbers and wonder if it will fall apart as well like you had happen. So I noticed the
other day white drain pipe stamped pp instead of pvc. The compression nuts (white discs for joining pipes when screwing together) I think are ldpe
which I think would be a problem at higher temps with ethanol... Any sugestions what to use to join pipes? That would be resistant and inert?
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blogfast25
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Polypropylene has excellent chemical resistance and an MP of about 165 DC. That should make it safe to use to up to about 140 DC, depending a little
on wall thickness.
PP based conical measuring flasks can be bought on eBay and could be used as boilers for primitive stills below 140 DC. PP isn't very resistant to
paraffinic (alkanes and such like, but OK for alcohols) liquids of course. One foreseeable problem might be the wattage of the boiler: with a steam
bath at say 140 DC (add a boiling point increasing substance to the water: salts, glycol anti-freeze or glycerine for instance) the heat transfer from
bath to boiler may not be very high and it may be hard to fill your column and obtain a distillate...
PVC is pretty chemically resistant too, especially the non-plasticised variety (rigid PVC) which has a fairly high MP, and is cheaply available as
(grey) plumbing pipe. It would be suitable for relatively low temp. still columns (including alcohol): pack with adequate size glass marbles (or glass
or pottery shards, screened to suitable average size) for extra surface and 'column loading'.
Now all you need is a condenser and a timed valve (or similar) for reflux control!
[Edited on 11-11-2009 by blogfast25]
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lucky123
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pvc?
Grey pvc pipe? Is that the electical conduit kind your talking about i see? Also wonder about things like ss sink drain pipes since they screw
together nicely? The inside is golden color though so wonder if it is safe...(I see this in cambells soup cans sometimes too and have told soup
cans are not a good idea.) On a final thought what you think about plastic pex pipe? Since it is already used in hot and cold water supplies...
Would this be an excellent choice along with the most resistant and temp tolerant?
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starman
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What has to be born in mind in plastics is the softening temperature .In the example I gave the faily thick-walled tubing was only at less than
80C,well below melting point.It didn't "fall apart" it went down like a slapped erection.In a later modification I sleeved the HDPE inside a slightly
larger PVC,which solved the "droopy dick" syndrome.In the end I grew oh so weary of stuffing around with plastic and spent the money required for
purpose-built equipment
One thing though,raschig rings,with far better resolution power than marbles or any type of wool are outrageously expensive.For low temp fractionation
cut up small diameter PE tubing is a very cheap alternative that is almost as good.
[Edited on 13-11-2009 by starman]
Chemistry- The journey from the end of physics to the beginning of life.(starman)
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blogfast25
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@ Lucky123:
Not sure what you mean by 'pex': crosslinked PE? That would probably work as the cross links make the product virtually unmeltable (although it will
soften). I've never heard of crosslinked PE tubes for 'domestic. applications though.
No, I'm specifically referring to uPVC pipes for plumbing: grey, cheap and cheerful, although PVC pipes to house electrical domestic wiring would work
too (but that's usually only 1/2 inch diam.).
For a boiler one could also consider a PP or PVC thick walled bottle like the ones used to package shampoo, detergents, washing machine stuff, fabric
conditioner etc. Usually the material is indicated at the bottom. Or use Pyrex kitchen glass ware, like measuring jugs, small sauce pans etc. I use
these all the time for direct flame resistant and chemically resistant containers and reactors.
@ Starman:
Totally agreed on the Raschig rings. Alternative packing could also be silicone tubing used for RC model aircraft fuel lines, cut into small lengths
(L = D). It doesn't resist hot water for very long though due to hydrolysis (silicone ---> silica).
Also rather than one long column, shorter column segments that can be shunted onto each other to make up the required column length are to be
preferred. That also allows to redistribute the down flow back to the centre of the packing: the liquid has a tendency to fan out to the column walls,
thereby reducing resolution of the column.
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watson.fawkes
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Quote: Originally posted by blogfast25  | | Not sure what you mean by 'pex': crosslinked PE? That would probably work as the cross links make the product virtually unmeltable (although it will
soften). I've never heard of crosslinked PE tubes for 'domestic. applications though. |
PEX tubing (yes,
crosslinked polyethylene) is one of the piping materials of choice these days for residential work. The system is PEX tubing, metal crimp rings, and
brass joints. It's advantage is very quick installation, shifting cost from labor to materials for a net decrease, commercially. If your time is cheap
it may not be the best solution. But it's popular; Home Depot sells crimping tools, for example. It's flexible, but has a pretty large bend radius.
It's not the best choice for home-made process piping, though, because the metal joint pieces get pricey and may be too reactive for many
applications.
There's also a specialty PEX-Al-PEX tubing, which has an interior aluminum liner, used for hydronic heating, which is impervious to gas infiltration.
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blogfast25
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Interesting, Watson.
Peroxide cross linked PE (HDPE, I'd assume) would derive it's rigidity from the crystalline domains and the links but above the MP of the crystallites
(about 110 DC) the material would behave very much like a cross linked (cured) elastomer like a high ethylene grade ethylene propylene copolymer - or
a terpolymer with diene insaturation (as used in under the hood auto applications, see Nordel, Vistalon, Dutral etc), including high floppiness...
Probably not suited for alcohol still columns!
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gsd
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http://www.amazingstill.com/
gsd
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blogfast25
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That's essentially a simple (but inventive) one-stage still.
Strand, BTW, also supplies Raschig rings (or at least used to).
=============
Also really interesting design for a copper tubing based fractionation distillation still, here:
http://www.moonshine-still.com/
with an interesting and doable design for valved reflux column head that could be fitted to any suitably sized column:
http://www.moonshine-still.com/page16.htm
[Edited on 14-11-2009 by blogfast25]
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lucky123
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what about ldpe tubing I would think not be satisfactory? Has good resistance but temp wise no good? Also what about cpvc hear has better risistance
and temp than regular pvc....
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lucky123
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pete?
Pete plastic I haven't been able to find a chemical resistance chart on this type of plastic. Would this be satisfactory to use and anyone have a
link to some info on this plastic
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not_important
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PETE (use the all caps form, else it sounds as if you're taking about a person) is also know as PET or Polyethylene terephthalate. The database at
http://nalgenelab.nalgenunc.com/techdata/chemical/index.asp has it listed as Polyethylene Terephthalate (PET), and suggests it is
satisfactory up to 50 C. At 70 C and above you are on questionable ground, both chemical resistance and mechanical properties may be degraded.
Go with metal piping, even ferrous water pipe - can buy it threaded and with fixtures for making the take-off arm and connecting to the still pot..
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Panache
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Are you the dude in X-men 2 who is locked in that prison made entirely of plastic and as such needs a non-metal solution otherwise the prison
authorities won't allow the stil.
Wait, no that guy escaped by using his magnetic mutant ability (that happens to work on all metals not just nickel and iron) to 'suck' the iron out
of a guards body, so it can't be you. Forget the question.
I think his name was Magnetia or Magnet Man or something, he had a funny hat and was played by that super camp british actor who is also Gandalf and
does a funny cameo on an episode of Extra's. Actually every cameo on extra's is funny so that was a tautology, sorry for that and while i'm at it
sorry for this slightly irrelevant post, i'll redeem myself by adding some pertinent information now.
PE stands for polyethylene for those unaware of this abbreviation.
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lucky123
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cling wrap?
Is cling wrap HDPE or LDPE plastic and anyone know of a plastic wrap made of PVDF? Also wonder what you guys think of pex pipe or cpvc since they are
both used for hot water lines seem they would handle the high temps...
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watson.fawkes
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Most such films are polyethylene, with one useful exception: Saran Wrap
is polypropylene. They'll both exclude water just fine, but the PP film also excludes oxygen diffusion. This means it will keep your guacamole green,
by pressing the film down onto the surface.
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lucky123
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I believe according to the website for saran wrap they say:
What ingredients are in Saran wrap
™ Premium Wrap and our Saran
™ Cling Plus® Wrap are made with Polyethylene!
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watson.fawkes
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| Quote: Originally posted by lucky123 | I believe according to the website for saran wrap they say:
What ingredients are in Saran wrap
™ Premium Wrap and our Saran
™ Cling Plus® Wrap are made with Polyethylene! |
Must have changed in the fifteen years since I last
learned this. See the Wikipedia entry. And according to this, it wasn't polypropylene, but PVDF. Apparently my source was wrong.
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not_important
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| Quote: Originally posted by lucky123 | | Also wonder what you guys think of pex pipe or cpvc since they are both used for hot water lines seem they would handle the high temps...
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CPVC generally has various additives in it, which might extract out into the alcohol. Both contamination from codistillation, and embrittlement of the
plastic, are possible concerns.
PEX is less likely to have those problems, but is sensitive to air oxidation in direct or bright indirect sunlight.
Both CPVC and PEX tubing are somewhat flexible, not the best thing for a still column which needs to be straight and vertically aligned.
Polymethylpentene is more likely to work, but isn't as likely to be easily found.
Plastic pot scrubbers used as packing are likely to have issues with both heat and extraction. I suspect the first use would result in a settling and
compression of them to the bottom of the column or into the still pot.
Read that link to still making blogfast25 gave earlier. Metal is the least likely to cause problems, even if it costs more. Check salvage yards as
you may find needed materials more cheaply.
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