1281371269 - 15-5-2009 at 14:28
Firstly, Hello everyone, I'm Mossy 
I wonder if anyone here can give me an explanation for this...
I have some H2SO4 based drain cleaner, it's called one shot and claims it is 91% acid. The stuff's purple and syrupy and the ingredients are here:
http://www.frontiersd.mb.ca/safety/MSDS/Imperial%20Soap/One%...
I don't have much sulphuric, and to try to stop myself wasting it I poured a small amount into a plastic sprite bottle to use for some various
experiments. There was a bit of water in the bottle so it got a bit hot but I watched it and it seemed to have cooled and settled down nicely, so I
set to work adding some to various old coins to try work out what they were made of etc. Then I heard a hissing...looked up, nice area of desk covered
with the acid. This was about 30mins after I added it to the bottle. On examination of the bottle after clearing the mess with Soda Crystals I found
there were about 6 quite big holes. But surely it shouldn't go through plastic? Any explanations?
UnintentionalChaos - 15-5-2009 at 15:11
You used a PETE (polyester) bottle. Ester bonds are sensitive to acidic hydrolysis.
DJF90 - 15-5-2009 at 15:13
Plastic bottles are made of PET - PolyEthyleneTerephthalate. PET is an ester. Sulphuric acid is a strong acid, and so is more than capable of
hydrolysing an ester. Of course you need water for hydrolysis so that probably explains why the whole bottle didnt "dissolve"; just some holes instead
(either that or the acid leaked out before it could claim the rest of your bottle...).
1281371269 - 15-5-2009 at 15:27
Many thanks I guessed it would have to be something along those lines as the
bottle says it's suitable for PCV pipe and so on. Incidentally it can be purchased in plenty of small stores in the UK at about 6.99 a litre although
purifying it will need a fully glass distiallation kit and a brave chemist. There's also this one:
http://www.shop-com.co.uk/Bullitt_Drain_Cleaner_1Ltr-4518033...
96% and dirt cheap...before I found out about these I used to get my H2SO4 from car battery acid which cost about £5 for a litre, which only yeilds
200ml or so of conc. And the postage was hellish high too...
Formatik - 15-5-2009 at 15:33
On the bottom of the container you'll see the acronyms for the type of plastic usually. In this case it should be, PETE or PET. HDPE has good
compatability with conc. H2SO4 and that's what the drain cleaner plastic is made of. Normally, you can easily find a chemical compatability chart for
the plastic. Though I can't find one for PETE.
JohnWW - 15-5-2009 at 15:42
Re polyethylene terephthalate - for a summary of its properties, see http://en.wikipedia.org/wiki/Polyethylene_terephthalate
Other polyester materials, such as Dacron/Mylar and polycarbonates, are probably also liable to hydrolysis by strong acids or alkalis. The same would
apply to polyamides, such as the Nylons and Qiana and Kevlar.
A bottle made of something like polyethylene, polytetrafluoroethylene (PTFE), polypropylene, or polyvinyl chloride(PVC) or fluoride (PVF), would be
fully resistant to hydrolysis by strong mineral acids and alkalis, except possibly oxidizing acids like nitric acid.
not_important - 15-5-2009 at 15:49
Note that PETE/PET is also susceptible to hydrolysis by strongly alkaline solutions, even strong aqueous ammonia will react over a period of weeks.
Neutral salt solutions usually aren't a problem, same for moderately dilute acid or base, at least for short term storage of a day or three. Alcohols
are OK, as are oils and alkanes like pet ether. Halogenated and aromatic hydrocarbons, ketones (acetone, MEK), and esters are problematic to strictly
no-no.
There are several types of PETE containers, food grade being different than general storage ones, so even a chart should be interpreted with caution.
One chart that has PET included is http://www.curbellplastics.com/technical-resources/pdf/chemi...
Formatik - 15-5-2009 at 15:53
Actually, according to the compatability chart below conc. H2SO4 has a severe effect on PVC:
http://www.rutlandinc.com/industrial/RPT.PVC.Chemical.Compat...
Though that also shows PVC is much more resistant to aqueous sulfuric acid. Fluorinated polymer plastics usually have the highest resistance to
chemicals, especially PTFE.
not_important - 15-5-2009 at 16:38
PVC is going to be tough to cover in a single simple listing, as the amount and type of plastisers used vary widely with rigid PVC generally have
lesser amounts of plastisers.
Polyolefins such as polythene and polyopropylene are just about plain aliphatic hydrocarbons and so resemble white mineral wax in their resistance.
Acids and bases are OK, while halogenated and aromatic solvents do the most damage.