--- In Homebrew_PCBs@yahoogroups.com, "John Popelish" <jpopelish@...>
wrote:
> > I store FeCl3, cupric chloride and NaOH in used plastic milk
> > containers.
>
> Then you are asking for trouble. Milk bottles are designed to work
> well for more than the life of the product they contain. And that
> isn't very long. I have had many such thin polyethylene bottles
> spring leaks after sitting on the shelf for a year or less,
> especially if one of the fragile corners has been dented.
>
> The best recycled plastic bottles I have seen lately are the gallon
> bottles used to sell Diet Lemon Iced Tea from Nestea (and probably
> othe variation, though this is what my wife has been buying). These
> can be hard to find, but are very sturdy, compared to milk
> containers, especially with respect to strong corners and bottoms.
> They are stamped PP compatible (recycle plastic group 5) and group 7
> (other).
>
> Of course, there are lots of very good Nalgene and other laboratory
> grade plastic bottles available from eBay. Etchant is such viscous
> stuff that it is worth getting good bottles to store it. A single
> spill can cost way more than you will ever spend on bottles.
I just checked and my plastic milk containers are recycle #2 (HDPE).
The bottle my FeCl3 came in is also marked #2. HOWEVER, it has _much_
thicker walls than the milk containers and doesn't have nearly as many
visible ridges/seams from the manufacturing process (just ONE along
the bottom). The 3% H2O2 bottle is also HDPE, not quite as thick as
the FeCl3 bottle, but much thicker than the milk container (and it's
_opaque_ which brings up the question of whether or not a premixed
solution of CuCl etchant in storage should be kept in an opaque
container or at least in a dark area to prevent decomposition of the
H202).
A sturdy, 1 gallon (3.785L) plastic container of cheap white vinegar
that I bought for $1.50 (about 1 UK pound) is also #2, but it's
considerably thicker than the milk container and has far fewer mold
lines. I had seen mention here of HDPE being OK for use with CuCl
etchant (IIRC), so I picked this item up while shopping. I had to
clean my home coffee and expresso machines anyway and will just dump
the rest of the vinegar down the drain.
The shallow (3.5"[8.9cm]x7"[17.8cm]x7"), translucent food storage
containers I plan to use for etchant tanks are all be made of
thick-walled polypropylene (PP) which, as I mentioned in my first
message, seems to be OK for this purpose according to PP's documented
HCl resistance data. The ones I own have blue lids marked LDPE (#4).
I searched via Google and found that Nalgene lab bottles are LDPE with
leakproof polypropylene (PP) screw closures. Wikipedia has this on
the differences between LDPE and HDPE (emphasis >" "< mine):
Low density polyethylene (LDPE): This was the first grade of
polyethylene, produced in 1933 by ICI using a high pressure process
via free radical polymerisation. It is defined by a density range of
0.910 - 0.940 g/cc. It is unreactive at room temperatures, except by
strong oxidizing agents, and some solvents cause its swelling. It can
withstand temperatures of 80 °C continuously and 95 °C for a short
time. It is translucent or opaque, quite flexible, and tough to the
degree of being almost unbreakable.
It is widely used for manufacturing various containers, dispensing
bottles, wash bottles, tubing, and > various molded laboratory <
equipment. Its most common use is in plastic bags.
LDPE has more branching (on about 2% of the carbon atoms) than HDPE,
so its intermolecular forces (instantaneous-dipole induced-dipole
attraction) are weaker, its tensile strength is lower, its ductility
is higher, and as its molecules are less tightly packed and less
crystalline because of the side branches, its density is lower. It is
manufactured by free radical polymerization.
High density polyethylene (HDPE): HDPE has little branching, giving it
stronger intermolecular forces and tensile strength than lower density
polyethylenes. The lack of branching is ensured by an appropriate
choice of catalyst (e.g. Ziegler-Natta catalysts) and reaction
conditions. HDPE is resistant to many different solvents and has a
wide variety of applications, including:
* Containers
o Tupperware
o Laundry detergent bottles
o Milk cartons
* Plastic bags
* > Containment of certain chemicals <
* > Chemical-resistant piping systems <
* Geothermal heat transfer piping systems
Looks like a thick-walled container made of HDPE (#2) or LDPE (#4)
with a minimum number of visible mold ridges from the manufacturing
process and with a screw-on, leak resistant cap should be OK.
As a backup, I'd then store this in a plastic bucket or a large deep
plastic tray with handles as suggested by Stefan Trethan in another
post in this thread.
Stefan also mentioned heavy-walled PET drinks bottles of the
thick-walled variety that you are supposed to return for recycling
and, not sure of what he was talking about since we don't return any
plastic containers for recycling in this state (Colorado) that I know
of, I looked up PET at Wikipedia and found this:
http://en.wikipedia.org/wiki/Polyethylene_terephthalate
Stefan also stated that this was the type of plastic used in the
chemical manufacturer's original HCl containers, so the thick-walled
variety must be OK to use for CuCl etchant. My 259ml water bottles
and 2 liter soda bottles are PET and are marked PETE (#1), but are not
thick-walled.
WB