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?obsessed_chemist - 17-4-2007 at 15:29
AFAIK, paraformaldehyde can be dissolved in water to yeild formalin-solution.chemcurious - 17-4-2007 at 15:37
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.not_important - 17-4-2007 at 15:41
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 928 times
chemcurious - 17-4-2007 at 15:54
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...not_important - 17-4-2007 at 16:57
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.Levi - 17-4-2007 at 17:09
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.
Won't the Cl attack the hexamine?garage chemist - 17-4-2007 at 17:25
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.chemcurious - 17-4-2007 at 18:19
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.not_important - 17-4-2007 at 19:20
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.DeAdFX - 17-4-2007 at 19:55
Is this a cheaper source of formaldehyde compared to trioxane? Trioxane fuel bars are fairly common(US$.50-1.00) and I haven't seen this plastic
before...not_important - 17-4-2007 at 21:04
Quote:
Originally posted by DeAdFX
Is this a cheaper source of formaldehyde compared to trioxane? Trioxane fuel bars are fairly common(US$.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.franklyn - 18-4-2007 at 01:06
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.
.not_important - 18-4-2007 at 08:12
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.franklyn - 18-4-2007 at 17:19
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.
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...
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.Panache - 9-10-2008 at 17:20
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.jarynth - 9-10-2008 at 18:11
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.kclo4 - 9-10-2008 at 20:25
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.Fyndium - 31-1-2021 at 01:08
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.Fyndium - 10-2-2021 at 11:35
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?unionised - 11-2-2021 at 02:24
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 Fyndium - 11-2-2021 at 11:21
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.Mateo_swe - 11-2-2021 at 12:19
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.Fyndium - 11-2-2021 at 14:12
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.draculic acid69 - 11-2-2021 at 18:20
Is there a possibility that it can it be used in a grignard to yeild
primary alcohols?Fyndium - 12-2-2021 at 11:07
Possibly if a catalyst is used with sufficient temp, it could form formaldehyde in situ. If the pyrolysis works well though, I'd opt for just making
formaldehyde and use it, because plastics, especially colored ones, can have additives, which could either react or need extra step for purification.
Not sure what the coloring agent is, but the black one makes your hands black when you handle it.
I wonder how much the plastic mass will foam when degenerating it with heat? I probably should fill the flask first pretty conservatively to see how
it behaves.
Also, if formaldehyde gas is lead into cold receiver(cold, as below -19C of formaldehyde bp), should it form paraformaldehyde? Possibly a flask could
be immersed in CaCl2 bath at -35C and lead a tube into it to condense it as pure form? This could be beneficial if it is intended to be stored, as
formalin takes a lot more space and is possibly not as stable.Fyndium - 25-2-2021 at 13:35
It sort of works.
The delrin decomposes upon heating, forming white mass that coats every surface of the apparatus. It generates very stingy, burnt-rubber like smell,
and it's completely different from formaldehyde smell. I've got a little paraformaldehyde which I know the odor.
Adding a little NaOH made the white mass slowly dissolve, and the solution gave off formaldehyde odor, so it's supposedly paraformaldehyde. ABEK
respirator does little to nothing to stop the odor.
I'm thinking how to create an apparatus that allows the recovery of it? Possibly by directing the reactor fumes with stillhead directly to a 3-neck
flask that also acts as the suckback reservoir for the final bubbling apparatus.
The bubbler seemed like it put all the bubbles straight through the water, but no odor of formaldehyde was detected, so is there a possibility it was
some other gas formed by the plastic?
It appears that the major product is paraformaldehyde which immediately sticks. MP appears to be on point too, with heat gun and IR temp meter.
I used only salt ice for the cold trap as formaldehyde BP is -19C so CaCl2 bath should be used instead. This could possibly be used to trap all
products into one vessel as paraformaldehyde.
Sorry if text is a bit messy, I'm tired AF and will look into this later with some pics I took. Please comment and ideas are very welcome.enlight - 27-2-2021 at 08:48
Could you just wash your apparatus with water and filter, then add methanol? Seems like your paraformaldehyde just never made it to the bubbler.
Perhaps you can charge your apparatus (a three-neck flask) with a stream of air to force the paraformaldehyde into your trap. The loss of material
then depends on the surface area of your apparatus.
I believe the Delrin you're looking for is the white homopolymer, as I'm not sure what the black Delrin consists of. Find a supplier that is willing
to supply a material test report.
I would opt for turning Delrin rod in a lathe to increase its surface area (acetal plastic makes large stringers from what I remember). Otherwise, buy
large 1mm thick sheet and break it into smaller pieces.
Also consider using a warm water bath around your trap to increase solubility.Fyndium - 27-2-2021 at 10:51
The sublimate was very sparsely soluble to water, and only adding a little NaOH made it dissolve by time. The water was cold, though. I had better
luck with stronger NaOH and hot water when I washed the glassware after.
Does formaldehyde dissolve better in hot than cold water? I used cold water in the trap. I weighed the water initially to 630g and final weight was
660g, this including few grams of NaOH, and some losses when using the water to wash all the parts that I was able to. The bubbles did little to
absorb though, I've bubbled all kinds of gases like NH3 to water, formic acid, HCl gas to all kinds of things etc and the bubbles just disappear at
once. These came through like nothing.
I was using black POM plastic turnings which were left from me after turning some clamps in lathe and mill. By tightly packing, I was able to fill
200g of turnings into 1L rbf. If these were not so cheap, I'd opt for purchasing 10mm rods and cutting them to short prills with wire cutters as they
would allow a significant weight charge over turnings which are very lightweight, a small bucket was filled by those 200g of turnings. Afaik all
polyacetal are the same, they might have some minor additives and that might explain the stingy smell which came through ABEK like nothing. The very
distinctive formaldehyde odor, which I've associated with corpses, morgues and rotten stuff even I'm not aware what those smell actually, was present
at times when handling it, especially when wet. The mere white stuff was of little odor.
I was first thinking of using my chromatography reservoir as the sublimate vessel to be placed upon the pyrolysis flask, but the issue is that the
polywhatever-white stuff doesn't seem to stick at any specific place, no matter if it's warm or cold, it just melts and evaporates with heat gun, and
it eventually covers the whole apparatus in uniformly thick layer, and no more seems to sublime on that same spot. It will eventually clog any small
ways, like the distillate takeoff adapter tube which I used to connect it to the cold trap flask. It didn't condense anymore of the white stuff, even
when the temp was -20C.
I was expecting that it would steadily sublime to the spots that are cold, and stop there, and I would collect a lot of it in that flask, but nope, it
just went through it like everything else.
I would like to develop a working apparatus to extract (para)formaldehyde in useful quantities from delrin, so any ideas for input are willingly
appreciated and tested if deemed potential.
I would argue that it kinda doesn't considering a yield of virtually nil. Max solubility in water is 37% @1.09, that should be more than soluble
enough for a simple bubble trap.
First suggestion would be a liquid medium. Low thermal contact means high temperatures and low heat flux, not exactly ideal conditions.
unionised - 27-2-2021 at 16:08
I may have missed a detail. Did you add an acid catalyst to promote decomposition?Fyndium - 27-2-2021 at 16:51
Thermal decomposition only.
The patents referring to acids also include elevated pressures up to 10bar.unionised - 28-2-2021 at 02:12
I worked in a lab looking at measuring formaldehyde in air.
One option was to draw the air through a filter coated with dinitrophenylhydrazine and an acid catalyst.
We had problems with filter holders made from acetal.
So I'm pretty sure that, even at room temperature, phosphoric acid attacks acetal.
At elevated temperatures I'm sure it would be even better. Obviously the use of higher pressures lets you raise the temperature of an aqueous acid
further. But it also actually impedes the reaction.
It would be interesting to do a repeat experiment but to rinse the shavings with, say, 5%, phosphoric acid firstFyndium - 1-3-2021 at 04:12
I'll give phosphoric acid a try. Should sulfuric acid work also? Compatibility charts give them all a severe effect at all concentrations, so I
suppose so.
[Edited on 1-3-2021 by Fyndium]Fyndium - 3-3-2021 at 13:14
Did not got phosphoric acid, but sulfuric acid so I thought to give it a try. I put a keck clip as a sacrifice and added sulfuric acid. 1% at boiling
did pretty much nothing, and gradually adding more neither, so I poured a good one, and likely the concentration rose to 30%-ish. Now the plastic
creates constant flow of bubbles, and formaldehyde odor is clearly noted.
The green gunk appears to be the coloring agent for the plastic, left from decomposition. During the process, bubbles were formed on the plastic in
rapid manner, looking like boiling stones, but the liquid was not boiling itself.
As I don't want to waste anymore of my high € per kg keck clips, I'll wait till I get back to my workshop to do an actual test run now that I have
proof of concept and I will rerun it with delrin turnings and bubble it through a water trap. I weight the flask prior and after, and same for the
water trap to see how much gas was dissolved. Formaldehyde gas absorbs into cold water as usual, but paraformaldehyde dissolves better in hot water,
just for the record as earlier was suggested to place the trap in warm bath.
I have lots of conc sulfuric acid so I'll likely use it, but I also want to test out phosphoric acid, because it is much easier available. It seems
that very dilute solutions decompose the plastic slowly, although keck has very little surface area compared to turnings, and applying concentrated
hot acid can cause too rapid decomposition, blasting the gas through the trap, so I'll start with dilute acid and add more if the reaction appears too
slow. As the acid's supposed to act as catalyst and only little traces are left within the liquid, the mother liquor should be able to be reused
multiple times after the depolymerization is complete, and temporarily cooling down and refilling the reactor should allow for quick generation of
useful quantities of formaldehyde.
[Edited on 4-3-2021 by Fyndium]draculic acid69 - 22-3-2022 at 21:29
Delfin is what bic lighters are made of so this provides a never-ending source of plastic that can be recycled into a saleable product.the h2so4
method sounds best if all that is required is a reflux
