Blown film is manufactured from dry blends containing PVC and additives or pellets (PVC composites), fed to a extruder for melting and homogenization. This molten mix feeds a circular die in which a continuous tube is formed (parison), that is inflated in the moment it leaves the headstock. The air volume stretches the tube in the desired width, this balloon is closed with the help of two rolls, from which the cutting and coiling of film begin. Thickness is regulated by extrusion rate and coiling rate.
Extruded Film (Flat Die Extrusion)
In a similar way to the blown film, PVC dry blend or pellets (PVC compounds) are also fed to an extruder. The difference is that the film forming die is flat. This film is led to a cooling cylinder and is readily coiled. Usually, it presents the same optical properties as a blown film and can be manufactured at faster speed. The main disadvantages include high level of scrap generation due to rims and a too small orientation in the transversal direction.
