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Blown film extrusion

Plastic forming process with extruded plastic is inflated to create a thin plastic film.

Beskrivning
Illustration of Blown film extrusion

The process

Plastic pellets [1] are supplied via a hopper into a rotating screw [2] whose spiral shape moves the pellet forward through a heated chamber [3].The pellets are heated gradually and turns into a homogeneous plastic melt as it approaches the end of the helical screw.

The molten mass is pressed through a die [4] in which the melt is extruded into a thin-walled tube. Inside the tube, air is blown in [5], which means that the pipe is expanding rapidly and thins the tube walls to a thin plastic film which is then squeezed and rolled up on a roll [6].

Blown film extrusion
Advantages and disadvantages
In comparison with alternative methods
Superior mechanical properties of the film
Maximum toughness
High productivity, product breadth checked easily
Lower temperature needs
generally inexpensive production machines
Cooling constraints limits the production rate
Limited film thickness
Poor optical properties compared to some other alternatives