Sciencemadness Discussion Board

Ammonia + PET Bottles = Disaster

Xenoid - 19-2-2008 at 19:45

A few months ago I aquired some laboratory grade ammonia solution from a local online source. When I collected the chemical it was packaged in a small PET (Poly Ethylene Terephthalate) soft drink bottle, and was marked NH4OH (25%). I stored it with various other chemicals on the bottom shelf of my chemicals cupboard. The bottle was in a fairly cool basement area, temperature would not have been above about 20 oC. at any time.

I happened to notice this morning that the container had turned white. When I picked it up, the plastic was very fragile (paper thin, brittle) and the inside was coated with a white powder or finely crystalline material. I was able (just) to get the top off, and filter the ammonia into a glass bottle. If a few more days had elapsed the plastic bottle would have collapsed and high strength ammonia would have gone everywhere. My wife would not have been happy!

Does anyone know what the white material is, I assume it is some sort of ammonia-phthalate compound? I have some other ammonia, purchased at the same time, in small HDPE bottles, these are perfectly OK. On the inside of the lid, on the blue liner, the whitish material appears crystalline, but this would have been in the headspace area.

WARNING do not store ammonia in PET bottles!

Ammonia.jpg - 31kB

Ozone - 19-2-2008 at 20:02

Maybe the ammonium salt of terephthalic acid and perhaps the glycol? Even at 25%, there is a huge amount of water and a decent amount of alkali catalyst.

Interesting,

O3

[Edited on 22-2-2008 by Ozone]

chemrox - 19-2-2008 at 22:04

NH4OH is stored in glass. Next time you do this you will undoubtedly transfer to a glass bottle. People who buy reagents in bulk and resell on ebay don't necessarily know what they're doing. Good lesson learned. I just got some Mg turnings from one of these guys. He wrapped them in plasticwrap bundles. An invitation to oxidation problems. I am transferring them to jars. I am sweeping the jars with N2. It's overkill but makes me feel better.

not_important - 19-2-2008 at 22:08

Several things can happen.

One is a state change: PET in bottles is mostly amorphous, when it goes crystalline it turns white and more brittle. In recycling PET recrystallisation is encouraged by heating the scrape plastic, I think it's to about 200 C; when cooled the microcrystalline PET is easier to crush. Heat is not the only thing that causes recrystallisation, just the fastest and easiest.

The second was already mentioned. PET is a polyester, and like most esters can hydrolyse. Alkalies are the normal agent, and PET is rated as having poor resistance to them.
Quote:
It makes good resistance to mineral oils, solvents and acids but not to bases.
In this case the ammonia may have diffused into the PET, resulting in a much faster overall hydrolysis. The ethylene glycol would dissolve in the water of the aq ammonia, ammonium salts of TPA would form, and you'd have oligomers of PET.

I cringe every time I read a posting here where someone was using a PET bottle to run an alkaline reaction, or with strong acids, or heating it. PET is not glass, or even HDPE, people.

[Edited on 20-2-2008 by not_important]

woelen - 19-2-2008 at 23:39

Storing ammonia in glass bottles also is troublesome. I had 25% ammonia, stored in a clear (colorless) glass bottle. After two years of storage, the glass is covered by a milky layer (it appears frosty on the inside) and when the bottle is shaken, the ammonia is a little turbid. My nice and pure ammonia now is impure with silicate. I transferred the ammonia to a thick hard HDPE bottle, and the glass indeed is attacked on the inside. The bottle cannot be made clear anymore.

YT2095 - 20-2-2008 at 01:05

in a strange way I`m quite pleased to read this thread, the same happened to my glass also, and I was going to post asking about it, but didn`t as I figured you`d all think I was insane!

looking at that PET bottle in the OP, it reminds me a little of these biodegradable plastic bottles, but I`m fairly sure they have some sort of stamp or marking on to say so.

PHILOU Zrealone - 20-2-2008 at 02:07

PET is unsuitable recipient for acids like HNO3 or HClO4, nor for NH4OH.
It is a polyester and as such can hydrolyse to terephtalic acid (or terephtalate) and polyethylene glycol (read alfa-omega alcane diol aka HO-CH2n-OH) or its oxydation products.

PET is more resistant to organic solvents although it has a tendency to shrink...and after a while a good deal of the solvent volatise through the walls...

70% HClO4 eats through quite fast (in a few days), 70% HNO3 (in a few weeks/monthes), 20% NH3 (in a few weeks/monthes); NaOH concentrate (in a few weeks/monthes).
With HClO4 it forms a transparent gelous mass, with all the others you get brittle opaque flakes.

[Edited on 20-2-2008 by PHILOU Zrealone]

jokull - 20-2-2008 at 07:16

Just a comment from my own experience. 5 years ago I stored ~20% ammonia into a small HDPE jar, and some minutes ago I opened it up (I got curious with this thread), the plastic material does not show changes (at least visibles).

Unfortunately I don't have a digital camera to post a picture.

YT2095 - 20-2-2008 at 07:25

there shouldn`t be a change really, HDPE is pretty robust stuff, it`ll take HF(aq) without an issue also.
PET on the other hand (and I`v learned some things about it from this thread that I never knew before) seems to be a bit lousy in comparison.

I`m grateful for the heads-up ;)

not_important - 20-2-2008 at 08:17

For polyolefins like HDPE, you are in effect dealing with wax - alkane hydrocarbon for the most part, with a tiny amount of unsaturation.

Polystyrene - the name says it, an aromatic molecule. Deals with alkali and moderately strong acids, those that react with the aromatic ring will cause problems - HNO3 and H2SO4 for example. Works OK for most aqueous chemistry, except strong oxidisers and free radical stuff can attack the backbone starting with the benzylic hydrogen.

PVCs are the halogenated equivalents, except that most PVCs also are plastised up the ying-yang, waiting to leach stuff out into whatever you put them in contact with. OK for surface coating, a little leaching into a spill isn't important.

Nylons are amides, PET and other polyesters are esters. Polycarbonates like LEXAN are also esters, phenolic carbonates. Strong acid and alkali zap the lot of them.

Polyacrylics like Perspex, Plexiglas, and Lucite, are also esters, but the ester is on the side chain rather than forming the backbone. They do get attacked, but tend to hold their shape better than polyesters.

PTFE (Teflon) is the best, but costs the most. HDPE is the poor person's make-do.

Xenoid - 20-2-2008 at 11:50

PET - what it lacks in chemical resistance, it sure makes up for with physical toughness!

I just made some micrometer measurements of the wall thickness in the central part of the bottle!

Ammonia bottle - .06 mm :o
compared to
80 gsm laser paper - .10 mm
Soft drink bottle - .33 mm

Carrying the bottle was like moving a jelly, I held it by the still rigid lid and supported it underneath with the other hand, it made "crackling" noises as it wobbled!

So I gather from the above discussion that my rescued ammonia solution will be contaminated with ethylene glycol, but I guess it should still be OK for most "inorganic" reactions.

JohnWW - 20-2-2008 at 14:29

Quote:
Originally posted by chemrox
I just got some Mg turnings from one of these guys. He wrapped them in plasticwrap bundles. An invitation to oxidation problems. I am transferring them to jars. I am sweeping the jars with N2. It's overkill but makes me feel better.

You will have to use argon for that! Mg turnings, besides being liable to surface oxidation to MgO and possibly MgO2, also combine directly with N2 to form the nitride, Mg3N2.

12AX7 - 20-2-2008 at 14:33

Curiously, I once poured concentrated H2SO4 into a PET container. The wall immediately turned white. Strong base does little in comparison, though I'm sure it will, given some time.

HDPE slowly reacts with chlorinated solutions (namely, the strong brew resulting from chlorate and perchlorate electrolysis), giving a wide spectrum of, I assume, chlorinated alkanes. In addition to the chlorine odor, my cell liquor has a sort of sweet/solventy/chlorinated smell to it, the kind of thing I associate with chlorinated hydrocarbons. This is a very slow reaction, I've only ever smelled this. I would suppose there is little enough that it remains dissolved in solution, and does not concentrate enough to form droplets or anything, instead evaporating.

Tim

PP the best

Panache - 20-2-2008 at 18:56

The advantage over glass of polymer storage vessels is obviously the reduced weight but more importantly the their ability to take a hit, lol.
Surprising no one has mentioned polypropylene, it is by far the best material for storing chemicals, dissolvable really only by boiling xylene, completely inert under normal conditions and much more robust than hdpe or ldpe. Also it has structural intergrity at 100C which is useful. Something PET also lacks.
PTFE is more inert and heat resistant but hell the damm things keep slipping out of my hand and hasn't even a whiff of the strength of PP oh and everything made from it needs to be sintered or machined making it prohibitively expensive for general use, unless of course you're extremely wealthy then it wouldn't be prohibitively expensive, it probably wouldn't be a problem, a situation however i am inexperienced with, except when i'm asleep, then its all lots of chocolates for me to eat and lots of coal making lots of heat.
That last paragraph was one sentence.
hmm

[Edited on 20-2-2008 by Panache]

not_important - 20-2-2008 at 19:02

I did mention polyproplene, as it is a polyolefins. It's more flexible the PE, but I believe it's also slightly more permeable and a couple of charts I have list it as a bit more reactive, possibly because of the tertiary hydrogens.

Fluorinated PE/PP may be the best, the bulk properties of polyolefin with the increased chemical and solvent resistance of fluorocarbons.

microcosmicus - 20-2-2008 at 22:37

Deciding to make lemonade out of this lemon, I did a little experiment. Seeing how
the alkali wrecked the bottle, this looked like a potentially practical way of obtaining
terepthalic acid. So I picked a pop bottle out of the trash can, cut some of it into little
bits and put it into a boiling concentrated solution of NaOH. After a few minutes it
looked like Xenoid's bottle. After two hours of boiling, the plastic turned completely
into a soapy mush.

Upon adding more water, this mush dissolved except for some brown scum
which I filtered out. Upon adding HCl to the filtrate, it fizzed a bit (presumably
because of CO2 from the air which had made Na2CO3) and the liquid became
white and cloudy, presumably from precipitating C2H4(COOH)2 quickly.

Looking around some, I found some interesting references. First, there
is a patent which describes how terephthalic acid is soluble in
organic salts and how one can purify it by, for instance, dissolving it in a
solution of magnesium acetate and then recrystallizing

U. S. Patent number: 3629328
Purification of Organic Acids
A. L. Stautzenberger and A. F. MacLean

Also, I found an article on recycling PET to make both terephthalic and
oxalic acids:

Conversion of a Used Poly(ethylene terephthalate) Bottle into Oxalic Acid and Terephthalic Acid by Oxygen Oxidation in Alkaline Solutions at Elevated Temperatures

Toshiaki Yoshioka,* Masaki Ota, and Akitsugu Okuwa

Ind. Eng. Chem. Res., 42 (4), 675 -679, 2003. 10.1021/ie010563z

Since I did not want to pay to read it online, I can't comment further on it., so I'll put
this on my list of things to look up when I go to the library.

Also, I found that chromium did pretty much what I did a few
years back and posted pictures:

http://www.sciencemadness.org/talk/viewthread.php?tid=4952&a...

Once you have your teretphthalic acid, here are some ideas what to do with it:

Copper terephthalate and its thermal decomposition products
G. P. Panasyuk, L. A. Azarova1, G. P. Budova1 and A. P. Savost’yanov
Neorganicheskie Materialy, 2007, Vol. 43, No. 9, pp. 1062–1066
http://www.springerlink.com/content/l5068v1122671r01/

According to the abstract, if you mix with CuSO4 and heat to 300 C, you get
phase-pure Cu2O. Another item to look up at the library.

So Xenoid, save the mess in your bottle, acidify it, filter the precipitate,
and purify it according to the procedure in the
patent, and think of this not as an ammonia purchase gone wrong but as a
serendipitous acquisition of terephthalic acid. :)


[Edited on 21-2-2008 by microcosmicus]

not_important - 20-2-2008 at 23:25

Quote:
Originally posted by microcosmicus
...
Also, I found an article on recycling PET to make both terephthalic and
oxalic acids:

Conversion of a Used Poly(ethylene terephthalate) Bottle into Oxalic Acid and Terephthalic Acid by Oxygen Oxidation in Alkaline Solutions at Elevated Temperatures

Toshiaki Yoshioka,* Masaki Ota, and Akitsugu Okuwa

Ind. Eng. Chem. Res., 42 (4), 675 -679, 2003. 10.1021/ie010563z

...


Looked that one up awhile ago, summary is
Quote:
Because sparingly soluble sodium terephthalate in concentrated NaOH solutions was stable to the oxidation, the TPA yield was approximately 100 mol % under all conditions. In contrast, EG was oxidized to oxalate and CO2, and the maximum oxalic acid yields were 60.7 mol % using flakes from the bodies of transparent bottles and 65.9 and 71.4 mol % using commercial transparent flakes and a mixture of transparent and green flakes from PET, respectively.
...
The air was then replaced with N2, and the beaker was heated to 160-250 °C at 3 °C/min in an electric furnace. After reaching the prescribed temperature, the oxygen oxidation was started by pressurized oxygen at 1-10 MPa, and this time was defined as the reaction start.


This is an long time known oxidation of alcohols to acids by oxygen in the presence of base. That's 10 to 100 atmospheres of O2 pressure, the pressure being used to get more oxygen to dissolve in the reaction mix. By using pure O2 in a sealed system losses of the glycol through evaporation is avoided. Pumping air through the mixture and using a reflux condenser works, but with noticeably lower conversions, more glycol being unchanged and a higher percentage being converted to CO2 and H2O. The CO2 reacts with the NaOH, unless the condenser is used as a fractionation column to allow the water to escape the dilution off the reaction mix seems to further hinder conversion to oxalic acid.

Attachment: Conversion of a Used PET Bottle into Oxalic Acid and Terephthalic Acid.pdf (88kB)
This file has been downloaded 1998 times

bfesser - 21-2-2008 at 10:51

Quote:
Originally posted by microcosmicus
Also, I found that chromium did pretty much what I did a few
years back and posted pictures:

http://www.sciencemadness.org/talk/viewthread.php?tid=4952&a...


Have you seen this page?
http://www.sciencemadness.org/member_publications/index.html

Ozone - 21-2-2008 at 14:22

That's great! Xenoid got me thinking about making this into a "lab" exercise for a course I am planning to teach (or a really nice Science fair project--I judged at a science fair today, So I am thinking that way). Chromium has provided an excellent manual ( If parts are used, I will of course cite as such)!

It's the little things,

O3

MagicJigPipe - 21-2-2008 at 17:45

I admit that I didn't read this entire thread. Sorry, if this has been mentioned.

I know from personal experience that Coke bottles will not store concentrated H2SO4 for more than a week or so. It's been a while since this happened to me but, from what I can remember, it turned the acid milky white and small beads of acid started to form on the outside of the bottle.

Personally, I wouldn't use PETE for even slightly reactive chemicals. Maybe non-alkali, non-oxidizing salt solutions but that's it. HDPE is cheap and readily available, so there's not reason to use PETE except for the few cases where it is preferred.

Panache - 21-2-2008 at 17:54

Quote:
Originally posted by not_important
I did mention polyproplene, as it is a polyolefins. It's more flexible the PE, but I believe it's also slightly more permeable and a couple of charts I have list it as a bit more reactive, possibly because of the tertiary hydrogens.


Quite right, apologies for suggesting your summary was somehow incomplete.

8)

bio2 - 22-2-2008 at 12:00

A check of the chemical resistance would have shown that PET is incompatible with
inorganic bases and strong inorganic acids among others.

http://www.nalgenelabware.com/techdata/chemical/index.asp

That being said, and knowing that NaOH hydrolysis PET as I once used 50% NaOH
to do this, I put some 5% NaOH in a PET bottle intending to use it within a day or so.

Anyway I forgot about it on the back shelf and a couple months later I went to pick
up the bottle to use the dilute NaOH and it disintegrated in my hand.

PET is great for organic hydrocarbons, much better than PE or PP.

Morgan - 18-8-2016 at 08:42

One time I bought a 6 pack of what I thought was heavy duty HDPE 4 liter IP2 packing bottles like these on eBay for cheap.
http://www.calpaclab.com/nalgene-hdpe-heavy-duty-ip2-packagi...
But they were LDPE so the seller told me to keep them and sent me the correct HDPE as well. But the HDPE bottles yellowed over time while the LDPE are still pristine looking.

byko3y - 18-8-2016 at 14:42

PET is the last thing I consider when choosing the container. In my region even good suppliers may use crappy containers which are filled right before selling the stuff to you and can survive week or two, the rest is not their problem.