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- Chemical
washing.
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- Sometimes,
fortunately in some rare situations, chemical are
needed to improve washing effects, separation among
different materials etc.
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- All
systems can handle chemicals, as long as they are
manufactured out of Stainless Steel, meaning it
is pretty easy to ad chemical to any system thus
improving washing and separation effects.
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- The
other face of the medal is you should be able to
get rid of them before discharging.
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- The
most known and used chemical agent is caustic
soda, mainly used to remove glue from PET bottles
flakes.
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- Caustic
is used together with surfactants helping to trap
the glue and dirt molecules and, sometimes,
to decrease the causticity of the caustic soda itself.
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- To
neutralize caustic soda is a simple job so, you
may say, no big deal; unfortunately the caustic
soda you get after processing it with dirt and glue
has been transformed into glycol, water and salts,
then you have the glue (that didn't disappear) dirt
and all these good stuff.
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- So,
to get rid of this is not an easy job.
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- Moreover,
if a very deep rinsing isn't applied, the oxygen of
the NA2CO3 is more than happy to complete the chain
of the polymer giving as result a very yellow pellet.
(that you may not like)
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- Therefore,
while adding chemicals is a cost, to get rid of
them is a much bigger one.
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- Chemicals are compulsory when washing PET bottles for
food applications; the FDA requires in fact a purity
that cannot be achieved without them but, other
than that, you better stay away from chemicals of
any sort.
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- Unless
you are a very good chemist and you know what you're
doing.
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- Here
a very interesting link where you will find something about
polymers of all kind, with some aspects of recycling:
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- THE
MACROGALLERIA
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- Then,
if you want to deeper into the subject, here some
more:
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- CENTER
OF POLYMER STUDIES
- POLYMER
CHEMISTRY
- POLYMER
CHEMISTRY GLOSSARY
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