Basic extruder process functions for gas injected foamed products
Twin screw extruders can efficiently sequence sub-processes as required to make foamed extrudates. These sub-processes usually consist of the following: (1) Polymer/additives feeding, (2) Melting and mixing, (3) Dynamic sealing to maintain supercritical gas pressure, (4) Gas injection and dissolution mixing, (5) Cooling of the melt to bring the viscosity up to at target extrusion window condition, (6) Thermal homogenization prior to exit, and (7) Pump with pressures to the adapter/die system.
Example: generic foam screw design