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chemcurious
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Delrin as paraformaldehyde source?
Delrin Acetal Thermoplastic (DuPont) is a linear polyacetal polymer. As far as I can tell, it _is_ 99.5% paraformaldehyde, with the difference being
that the ends of the formaldehyde chains are capped with hydroxyl or other terminations to promote thermal stability. Several patents mention the use
of this material as a formaldehyde generator, using nitric or other acids to catalyze its decomposition into formaldehyde.
Question is whether this material can be used as a substitute for paraformaldehyde in HMX synthesis?? I ask, because Delrin is exceptionally easy to
get OTC, and is cheap in small quantities.
Any experts care to venture a guess?
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obsessed_chemist
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AFAIK, paraformaldehyde can be dissolved in water to yeild formalin-solution.
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chemcurious
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In this case the end-caps prevent depolymerization in water. However, strong acids and strong bases will supposedly unzip the polymer to release
formaldehyde. According to DuPont, even 10% nitric will decompose it.
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not_important
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| Quote: | Originally posted by obsessed_chemist
AFAIK, paraformaldehyde can be dissolved in water to yeild formalin-solution. |
That's unterminated paraformaldehyde, which unzips as easily as a US Congressman.
Delrin can be depolymerised fairly readily, see the attached patent which does work. You may need to try several variations for your particular
application, remember that this board is about experimentation. 8-)
[Edited on 17-4-2007 by not_important]
Attachment: US4740637A1.pdf (518kB)
This file has been downloaded 926 times
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chemcurious
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Yeah, that's the patent that I was referring to. They use an organometallic as a catalyst, whereas another patent refers to using a mineral acid. As
the patent mentions, Delrin is almost completely anhydrous, which for nitration would be better than the usual paraformaldehyde, I would guess.
I tried a 10% ammonia solution at room temp (hoping the resulting formaldehyde would react to form hexamine), but no luck yet. I don' t have any
nitric handy...
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not_important
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Try HCl, start with just enough to cover the plastic, then if it looks to be working at water bit by bit. After that add the ammonia.
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Levi
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| Quote: | Originally posted by not_important
Try HCl, start with just enough to cover the plastic, then if it looks to be working at water bit by bit. After that add the ammonia.
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Won't the Cl attack the hexamine?
Chemcrime does not entail death. Chemcrime is death.
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garage chemist
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With HCl, you'd have lots of NH4Cl in your product afterwards.
I'd try to depolymerize it by simple strong heating under exclusion of air, the resulting fomaldehyde gas forms paraformaldehyde again very easily on
cooling but this time it will be the uncapped variety.
Or better dissolve in water to make formalin.
Uncapped paraformaldehyde is often insoluble in water even at 100°C when the chains are very long. Adding a very small amount of base works as
depolymerization catalyst, allowing dissolution to form formalin.
Paraformaldehyde also rapidly dissolves in aqueous ammonia forming a solution of hexamine.
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chemcurious
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For making HMX or other compounds requiring paraformaldehyde, wouldn't adding the delrin to the nitrating mix be feasible? The nitric or mixed acid
would depolymerize it, similar to what happens with the uncapped variety.
A secondary goal, of course, would be to use delrin to make hexamine.
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not_important
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Trying HCl was if you wanted to make hexamine, shouldn't need much HCl to convert a goodly amount of the plastic. The amount of Nh4Cl formed
shouldn't be a problem.
Wouldn't likely need it for HMX, but you'd want to try on a very small scale to start with.
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DeAdFX
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Is this a cheaper source of formaldehyde compared to trioxane? Trioxane fuel bars are fairly common(US$.50-1.00) and I haven't seen this plastic
before...
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not_important
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| Quote: | Originally posted by DeAdFX
Is this a cheaper source of formaldehyde compared to trioxane? Trioxane fuel bars are fairly common(US$.50-1.00) and I haven't seen this plastic
before... |
Depends. You can buy new acetal stock for a little over ... 2.2 cents US per gram. The large trioxane bars are 30 grams, if you could get them for 66
cents a bar the price would be about the same.
If you can find a source of acetal scrap then the cost could go as low as zero. Plastic gears are often acetal or nylon, junked vacuum cleaners,
mixers, and blenders could yield a little.
If you buy acetal plastic, make sure it is homopolymer and no copolymer.
The raw resin in quantity is much less costly, but most people don't have anywhere to put a railroad car full of plastic resin.
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franklyn
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You have to be kidding , Delrin is as hard as naval seamen on leave.
At the least you will need to powder it with a motorized rotary file before
your "treatment". It's not one of the most utilized plastics without reason ,
and is resistent to almost everything you may subject it to. This is from
Dupont's own assessment:
Zinc Chloride and Chlorine
Delrin acetal resin is not recommended for use in zinc chloride solutions
or environments that may generate zinc chloride. Zinc chloride acts to
depolymerize (corrode) Delrin acetal resin. The extent of attack will
depend on stress, temperature, concentration, and time of exposure.
Performance under exposure to strong acid or alkali is unacceptable.
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not_important
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Uh, the first section of your post is on the physical toughness of acetals, the second is on their easy of destruction by various chemicals. I fail to
see the correlation.
As for the toughness - when I was testing a reaction using acetal I sat the plastic on dry ice for awhile and then dropped it piece by piece through a
pair of gears, from some old piece of big machinery, to crack and crush it; a blender might work as well. There was no need to powder it, the bits
resembled coarse sand or cracked pepper. For what I was trying, it came unzipped under the reaction conditions fast enough to work nicely.
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franklyn
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Not being a chemist I tend to view things as physical systems. The material's
specifications warn of surface degradation and deterioration , that's a looong
way from turning into pulp. This naturally implies some processing beforehand.
Since you have a working method I stand corrected.
Very neat to crush it by cold embrittlement , I have to remember that.
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not_important
as you have the knack to crack the tough nuts, have a go at
the trimer of cyanogen which is triaminotriazine commonly
available as Formica counter tops.
 
| Quote: | Originally posted by chemoleo
Would be nice to find the detailed conditions, or also how to depolymerise thusly produced melamine back to cyanamide... |
http://www.sciencemadness.org/talk/viewthread.php?tid=6717&a...
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jarynth
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| Quote: | Originally posted by franklynhave a go at
the trimer of cyanogen which is triaminotriazine commonly
available as Formica counter tops. |
Melamine is the trimer of cyanamide. The resin by the same name is actually made with melamine and formaldehyde.
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Panache
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| Quote: | Originally posted by jarynth
| Quote: | Originally posted by franklynhave a go at
the trimer of cyanogen which is triaminotriazine commonly
available as Formica counter tops. |
Melamine is the trimer of cyanamide. The resin by the same name is actually made with melamine and formaldehyde. |
By resin are you referring to the fully cured benchtop or the uncured sticky goop that is activated with a 'hardener' and then applied and cures to
the benchtop. I ask as i have a couple of 20L drums of melamine uncured (cytec some LA company) and if it's this trimer and formaldehyde as opposed to
a partially cured copolymer of the two then it requires investigation, otherwise i will laminate my bench with it.
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jarynth
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Melamine is a white solid, no goop. The addition of formaldehyde probably also helps liquefying the mixture, but there might be some other ingredient,
solvent, polymerization inhibitor etc that I don't know of. Hardening must be the result of polymerization.
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kclo4
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Wow, Derlin does look like a pretty good source for Formaldehyde.
I wonder what the most common source of it is? I may have seen it, but never realized it. If it is easily obtainable this would be great! although,
forms of Formaldehyde are not at all hard to get.
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Fyndium
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https://patents.google.com/patent/WO1993024439A1/en
When looking through materials I realized that delrin should be convertable to formaldehyde with ease. It is probably available otc in some form, but
at least companies that specialize in plastics usually sell leftover cuttings and other pieces for very cheaply, starting from few € per kg.
If the patent method works to convert delrin into formaldehyde with 1-2% H2SO4 catalyst added into solution, it would be a great source for
formaldehyde.
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Fyndium
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I got some delrin stock which I machined boss heads for myself, and got a vat-ful of chips and turnings.
Gonna try out churning formaldehyde out of them. I see that one needs a lot more temperature than boiling water to make any use of it, up to 200C, so
unless some other liquid can be used as solvent or water could be salted to make it boil higher. CaCl2 would work, but it reacts with the acid, and
apparently any acid that would be suitable would react, including phosphoric acid.
Other method is to just pyrolyze the plastic. This'd be much more straightforward and does not need anything but a suitable steel pot, and temp from
250 to 450C. A temp buffer from thick steel plate like torch cut barbell plate could be used to evenly heat it instead of creating hotspots from flame
to make it release formaldehyde instead of decomposing to smaller molecules.
Considering formaldehyde is not available for any consumer use or easily produced from such, a commodity such as delrin as a source of formaldehyde
would be great. I understood that paraformaldehyde could be produced by condensing the dry formaldehyde in -19C and lower?
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unionised
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It shouldn't be a problem in dilute solution but, for those who are thinking of using HCl...
https://en.wikipedia.org/wiki/Bis(chloromethyl)_ether
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Fyndium
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Ah, this was that I read around somewhere. Thanks, but no thanks. HCl'd be bad anyway because it would come over with the formaldehyde fumes.
I also thought it around, how about using more concentrated sulfuric acid to bring temp up to 200C? Would it destroy the plastic instead of breaking
it into formaldehyde?
Likely the pyrolysis is the way to go. All it needs is some delrin and a little heat.
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Mateo_swe
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Paraformaldehyde is available on ebay but its quite expensive and small volumes.
If searching for Delrin/Acetal one can get a few kg for quite cheap.
Delrin is very common as a fabrication material for parts used in production machines.
Every plant workshop has lots of it to make parts thats need replacement a.s.a.p. to not cause stop in the production.
Its often used for one of a kind parts and is available at the companys that sell steel, aluminium and other stock materials and online.
A way of converting it to formaldehyde could certainly be useful to know.
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Fyndium
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Delrin can be readily purchased as bar or sheet stock for less than 10€/kg basically everywhere. Wouldn't bother ordering it ebay, unless it happens
to be cheapest there.
I'll try the pyrolysis process asap I get my stuff together. Not sure atm what my stainless steel reactor lid is about, and what connectors I need,
but on general it should work. I would rather try it on smaller scale first, as the reactor is 10 liters volume.
If I'd use an ordinary rbf for the reaction, would it be viable option? I could easily sacrifice one for it, but likely it can be cleaned afterwards
with either acetone or piranha. I can turn the bar stock into filings with lathe or a mill.
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