Simple granulation can be done using a single-screw extruder, which has a low cost.
A twin-screw extruder has better mixing effects compared to a single-screw extruder and can complete the compounding and granulation process in one step; it is generally used for powder material production.
Material conveying principles differ:
1. Single-screw extruder - Drag-induced type
- Solid conveying section: Friction drag (feeding section and compression section)
- Melt conveying section: Viscous drag (compression section and homogenization section)
Therefore, the efficiency of conveying depends on the friction properties of the solid material and the viscosity of the melt.
In short: Material conveyance in a single-screw extruder relies on the difference in the friction coefficient between the material and the barrel and screw for advancement.
2. Twin-screw extruder - Positive displacement type