Extrusion blow molding is used to manufacture hollow recipients such as vials, bottles, pots, fuel tanks, agricultural and industrial tanks. On leaving the extruder, and while it is still hot a tube is enclosed in a mold and blown with compressed air, so that it takes on the shapes of the mold once it has cooled. On coming into contact with the walls of the mold the material will solidify. Then the hollow recipient is ejected.


The Extrusion Process

This is an ongoing process allowing granules to be manufactured and powders and granules to be transformed into tubes, jackets, profiles, seals, films and plates with no limit on the length.
PVC extrusion consists of obtaining an even, viscous mass which then flows through a die to give it the desired shape from a compound in powder or granule form made up of PVC resin and various additives. The transportation, melting, mixing and pumping are carried out by the extruder using a screw or a series of plasticating screws revolving inside a heated plasticizing cylinder.

By superimposing various layers of materials, co-extrusion means that a product with multiple properties can be produced (e.g. specific surface treatment).

The Extruder

Extruders can include one or more screws (there are usually two).
The best yield and quality results are only obtained by carefully choosing the type of machine and screw geometry. This choice has to be made depending on the nature of the product to be machined and the profile section.
"Dual screws" are very frequently used for work on rigid materials and mainly for PVC. In particular they make it possible to obtain the finished product from powder because they give very good results when it comes to homogenizing the material. They are also perfectly suitable for extruding profiles with thick walls.

The applications described below are all carried out by means of extrusion, only the shape of the die changes, thus giving products as different as profiles or very fine films.