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Plastic. It's what
our modern world is
built from.
Plastic
Products have many uses
in today's society,
including some which are
considered
indispensable. However
there is a down side to
plastic: One third of
all plastic is used for
items with a lifespan of
less than one year and
very little plastic is
recycled. For example in
San Francisco less than
2% of the 40,000 Metric
Tons of plastic they use
every year is recycled
(see the October 2005
Forbes article,
Junk Into Money).
There are 200 types of
different plastic resins
but most plastic
consumer products fall
into one of six
categories.
Plastics
have developed
an amazing
presence in our lives.
From the most
commonplace tasks to our
most unusual needs
plastics increasingly
have provided the
performance in products
that consumers want.
Just consider it a
moment; if you woke up
tomorrow and there were
no plastics you would be
in for quite a shock.
From your toothbrush to
your Tylenol, life would
be much more expensive
and much less
comfortable. And many of
the conveniences you had
come to take for granted
would be gone entirely.
Mostly, though, you
would be surprised at
the sheer numbers of
products that had
vanished -- things you
had never thought of as
being plastic. That's
because in just a few
decades consumers have
come to consider the
extraordinary properties
of plastics as nothing
out of the ordinary.
Plastics' popularity and
wide usage can be
attributed to one basic
fact: Because of their
range of properties and
design technologies,
plastics offer consumer
benefits unsurpassed by
other materials. Let's
take a look at the
different types of
plastics, usually
referred to as "resins,"
and see how they are
made and used.
Plastics
generally are organic
high polymers
(i.e., they consist of
large chainlike
molecules containing
carbon) that are formed
in a plastic state
either during or after
their transition from a
small-molecule chemical
to a solid material.
Stated very simply, the
large chainlike
molecules are formed by
hooking together
short-chain molecules of
chemicals (monomers:
mono = one, mer = unit)
in a reaction known as
polymerization (poly =
many). When units of a
single monomer are
hooked together, the
resulting plastic is a
homopolymer, such as
polyethylene, which is
made from the ethylene
monomer. When more than
one monomer is included
in the process, for
example, ethylene and
propylene, the resulting
plastic is a copolymer
What do these
numbers mean?
The society for the
Plastics Industry came
up with a labeling
system for plastics a
number of years ago.
This system, which used
the numbers from 1 to 7
(7 is used for anything
that doesn't fall into
the 6 common categories)
surrounded by recycling
arrows, was designed to
identify the different
types of plastic resins
so that they could be
more easily recycled
when recycling systems
came into place. The six
common resins are :
- 1.Polyethylene
Terephthalate (PET);
- 2.High Density
Polyethylene (HDPE);
- 3.Polyvinyl
Chloride (PVC);
- 4.Low Density
Polyethylene (LDPE);
- 5.Polypropylene
(PP);
- 6.Polystyrene
(PS); and others
The plastic
Types more clearly
defined as:
Thermosets
and Thermoplastics
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