Polystyrene bottle and NaOH
micha...@aol.com
polystyrene). I am seeing a white precipitate forming. Is the
polystyrene breaking down?
Thanks
Frank
Your bottle is probably PET and it is breaking down.
Frank
Ernie
<micha...@aol.com> wrote in message
news:1162512704.7...@f16g2000cwb.googlegroups.com...
encountered a polystyrene water bottle.
In my opinion the water bottle is likely to be one of five polymers:
US recycle code
Look for number in
triangle
usually on bottom of
container
Polyethylene Terephthalate (PETe) 1
High Density Polyethylene 2
Low Density Polyethylene 4
Polypropylene 5 (less likely)
SAN (styrene/acrylonitrile) 7
2, 4, and 5 should be ok for NaOH; 1 will be degraded; 5 will be attacked
but slower than 1.
You did not say how long it took for the white precipitate to appear. If
the concentrated solution has been in plastic for years, the precipitate
could be related to CO2 diffusing through the plastic, or water diffusing
out of the plastic. On the other hand, if the container is PET (sane as
PETE) the precipitate is likely to be sodium terephthalate.
Ernie
Uncle Al
1) Invert the bottle and read its composition in the recycle
symbol.
2) Na2CO3 is insoluble in concentrated NaOH.
3) Polyolefins and polymers above their Tg in general are
CO2-permeable.
4) Polyesters, polyurethanes, polyamides, (meth)acrylates, etc.,
will not tolerate strong base.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz3.pdf
Bob M
Water bottles are almost universally PET polyethylene terephthalate.
PET is hydrolysed by caustic soda to sodium terephthalate and ethylene
glycol.
The jar of terepthalic acid on my lab shelf was prepared by digesting
chopped up PET water bottles in sodium hydroxide and precipitating the
terephalic acid from solution with acid.
Why did I prepare terepthalic acid I needed it to prepare a GLC column
and the wait for imported material was just too long.
Bob M