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Plastic
identification; recycling code
When working with
plastics there is often a need to identify which particular
plastic material has been used for a given product. Most
consumers recognize the types of plastics by the numerical
coding system created by the Society of the Plastics Industry in
the late 1980s. There are six different types of plastic resins
that are commonly used to package household products. The
identification codes listed below can be found on the bottom of
most plastic packaging.
PETE Polyethylene Terephthalate (PET) - Soda & water containers, some waterproof
packaging. Recycling PET is similar to the polyethylenes (PE).
Bottles may be color sorted and are ground up and washed. Unlike
polyethylene, PET sinks in the wash water while the plastic caps
and labels are floated off. The clean flake is dried and often
repelletized.
Recycled PET
has many uses and well established market for this
useful resin. By far, the largest usage is in textiles.
Carpet companies can often use 100% recycled resin to
manufacture polyesther carpets in a variety of colors
and textures. PET is also spun like cotton candy to makr
fiber filling for pillows, quilts and jackets. PET can
also be rolled ito clear sheets or ribbon for VCR and
audio cassettes. In addition a substantial quantity goes
back into the bottle market.
HDPE High-Density Polyethylene - Milk, detergent & oil bottles,
Toys and plastic bags. HDPE is called natural since that is it's
natural color, and it is the most valuable because it can be
made into any color when it is recycled. Other products are
often packed in brightly colored bottles whiched are mixed
together at recycling plants into mixed color or rainbow bales.
Most of this material is later dyed black after it is processed.
Recycling
HDPE is a pretty simple process. The bales are broken
aprt and ground into small flakes. These flakes are then
washed and floated to removed and heavy (Sinkable)
contaminants. This cleaned flake is then dried in a
stream of hot air and may be boxed and sold in that
form. More sophisticated plastic plants may reheat these
flakes, add pigment to change the color and run the
material through a pelletizer. This equipment forms
little beads of plastic that can then be reused in
injection molding presses to create new products. Some
end uses for recycled HDPE are plastic pipes,lumber,
flower pots, trash cans, or formed back into non food
application bottles.
V Vinyl/Polyvinyl
Chloride (PVC)
- Food wrap, vegetable oil bottles, blister packages.
LDPE Low-Density Polyethylene - Many plastic bags. Shrink wrap,
garment bags. It ic chemically similar to HDPE but it is less
dense and more flexible. Most polyethylene film is made from
LDPE which you often see as plastic bags and grocery sacks. This
scrap may be clear or pigmented and it is hand sorted and baled
at recycling processing plants.
Recycling
LDPE is verry similar to HDPE except special grinders
are used to handle the thin films. The films are often
washed and repelletized or used directly to make new
products. Some end uses for recycled LDPE are plastic
trash bags and grocery sacks, plastic tubing,
agricultural film, and plastic lumber.
PP Polypropylene - Refrigerated containers, some bags, most
bottle tops, some carpets, some food wrap.
PS Polystyrene - Throwaway utensils, meat packing, protective
packing.
OTHER Usually layered or mixed plastic. No recycling potential
- must be land filled.
These symbols are meant to indicate the type of plastic, not
its recyclability. Types 1 and 2 are commonly recycled. Type 4
is less commonly recycled. The other types are generally not
recycled, except perhaps in small test programs. Common plastics
polycarbonate (PC) and acrylonitrile-butadiene-styrene (ABS) do
not have recycling numbers. Chemical engineers will say that
there are many more types and uses for polymers. But most debate
in recycling focuses on these seven categories.
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