More polyethylene is produced than any other polymer. It
can be processed (and reprocessed) into many different products.
Polyethylene
is ideal for the manufacture of film products which are used for a wide range
of purposes because of its physical properties...
- Soft & supple
- Tough, hard & sturdy
- Strong, safe & versatile
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The blown film process is the method by which
the vast majority of all polythene products are manufactured.
Polythene
granules are fed into an extruder. As the granules are transported
down the extruder screw, they are continuously heated and eventually
become molten.
The melt passes through a narrow slit forming a tube
which is extruded vertically until it can be clamped at the top
nip rollers, which continuously pull the tube from the die.
Once clamped
the tube is inflated to create the desired width, the speed of the
nip rolls determines the film thickness. The film is air cooled to
set the film dimensions.
The tube is then collapsed prior to the nips
to form a layflat tube to a set width and thickness. The flat film
is passed through path rollers to a floor mounted winder.
Further processing can take place during this section
for example: Slitting, Trimming, Perforation or treatment for print. |
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In the cast film process the material is forced through
a slit die to form a sheet. The sheet is (as with blown film) drawn
off via nip rolls again the wall thickness is determined by the speed
at which the material is drawn off.
Cast film is cooled as it exits the die via large water
cooled chill rolls which also leave a micro embossed pattern on the
film. |
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The most basic blown film product - formed by collapsing and
flattening the bubble / tube.
All other blown film products are derived from the layflat. |
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This is a layflat tube with one edge fold removed by either
a trim or an edge slit. |
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Again both edges of the edge fold are removed. In this
instance the two sheets of film are separated and are wound up simultaniously.
As with double wound sheet (DWS), the roll can now be slit
down into multiple rolls by inserting slitting Blades.
Because cast film is extruded through a 'slit die' the
final product is exclusively Single Wound Sheet. |
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Both edge folds of the layflat are removed leaving two
single sheets of film wound onto one core.
The roll may now be slit down into multiple rolls by
the addition of slitting blades. |
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Gusseted film is formed by using a pair of wooden (or
metal triangles) to alter the shape of the bubble as it passes through
the collapsing frame. |
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This is a layflat tube with one trim removed from a section
from the edge fold to a specified width on the upper or lower web. |
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