Processing via the Elastoplastic State

Blowing can be considered as a special form of stretch forming from annular nozzles producing unbroken, continuous hollow bodies, which are used as such or else cut into film afterward. Blowing also enables hollow products of two components to be produced, e.g., toothpaste tubes, which consist of polyamide outside and poly(ethylene) inside. 

Extrusion blow molding is really a special type of extrusion. The extruder 

---

Figure 36-5. Processing via the elastoplastic state (schematic). (I) Pressure molding, (II) vacuum forming, (III) blow molding, (IV) extrusion blow molding with annular nozzle (see text).

---