Preparation
Plastic scrap or waste comes in all manner of shapes
and sizes such as plastic bottles, bottle crates,
plastic pallets and car bumpers and a variety of
material types.
Often these plastic materials are not compatible
with each other when it comes to recycling so they
have to be identified and separated.
It is also necessary to strip off any extraneous
materials such as metal or foam which will hinder
the recycling process at a later stage.
It may also be necessary to clean the scrap (particularly
if the plastic waste comes from packaging applications
such as plastic milk bottles).
Size Reduction
Before the plastic waste can be melted down and
recycled into plastic pellets for moulding into
new products it must be reduced in size. At its
most basic this is a case of sawing large items
of scrap so that they will fit down the throat of
the granulation machines.
Shredding is a much more efficient way of reducing the size of large scrap plastic items. A shredder basically consists of a large tank that the scrap is fed into, at the bottom of which are heavy duty rotating blades which quite literally rip the plastic to shreds.
The output of the shredding process is irregular sized strips of plastic which will be up to several inches in length (still too big for the compounding process).
Finally comes granulation. Granulation is probably the most common form of plastic recycling and there are many granulation companies dotted around the UK.
The process again involes a set of rotating blades,
but unlike shredding the granulation process chips
the plastic scrap. Grids can also be used with the
granulation machines to control the size of the
resulting regrind (also known as reground). Typically
plastic regrind has a diameter of about 10mm which
is ideal for the compounding process.
Blending
Blending is simply the process of creating a homogenous batch of plastic and can be used at various stages of the plastic recycling process. Material may be blended on arrival at our recycling facilities to aid with testing of the plastic. Many polymer types are incompatible and therefore we need to ensure that incoming batches are not contaminated with different polymer types.
We may also blend several batches of plastic regrind together to create a homogenous batch of material to be extruded into compound. This ensures that the finished batch of compound is consistent throughout.
A blender is essentially a very simple piece of
equipment, it consists of a large container into
which the plastic materials are fed, the bottom
of which is conical in shape to aid with emptying
the material out after the blending process is complete.
A vertical screw feeds the plastic to the top of
the blender where it then spays onto the sides of
the blender where foils further disperse the material.How long this process takes depends on the quantity of material and the speed of the screw.
Compounding / Extrusion
The compounding process is similar to that of an injection
moulding machine. Plastic raw materials and additives
are metered into a hopper at one end of a barrel.
This material is transported along the length of
the barrel by an Archimedes screw and is melted by applying heat from external heater
bands, as well as the heat caused by friction / shear heat.
As the material moves along the screw, special sections of the screw
knead, mix and compound the plastic, additives
and fillers together. At the other end of the barrel, the melted
plastic is passed through a wire screen that filters
out any residual dirt, grit or other contaminants,
and is then pushed through a die plate.
As the material comes
through the die plate, it is cut into pellets
and then cooled by quenching in water. It is then dried and packed into a selection of different packaging types.
|
CK Polymers are specialists
in all aspects of plastic recycling if you have
a requirement for plastic recycling processes or
need assistance with general or plastic waste management
then send us your details through our
contact form or call us on 01472 398960 .
We also buy and sell all types of plastic in all
forms, be it plastic production scrap, post consumer
or post industrial waste, regrind, off-spec compound
and recycled plastic compound. If you are looking
to buy or sell any plastics then please contact
us for competitive pricing and payment terms.
For more information about how we work please click here.
|
|
