4. Extrusion line components

4.1 Extruder

In the vast majority of cases, since rigid PVC is used, a counter-rotating twin-screw extruder is employed. The primary advantage of twin-screw extruders is that they allow PVC to be processed with its additives in powder form (dry blends). This makes it possible to add the desired stabilizers and plasticizers in the desired quantities according to one’s own formulation. The interpenetrating counter-rotating twin-screw extruder is used in most cases because it ensures significant homogenization while avoiding excessively high shear rates. It allows for high throughput and has the property of being self-cleaning (no stagnation points). Due to its excellent homogenization capacity for the extruded material, and despite its higher cost, it is therefore preferred over...