Extrusion And Compounding
Extrusion compounding, or compounding extrusion is a pre-process for the other process of thermoplastic injection molding. This is the compound and foam extrusion process in which one or more polymers are mixed with additives to get qualitative plastic compounds. The developed product is mostly in pellet form irrespective to the type of feed that may be powder, pellet, and/or liquid. This product is used in various other plastic forming processes like injection molding and further extrusion. The size of the machine which is required for this process ranges from small lab exruder machines to the larger extruders available in the industry.
In this process, generally, the preference is given to twin-screw extruders as these provide improved mixing at the lower melt temperatures. A large number of these extruders have barrels and screws that include smaller segments like venting, mixing, conveying, and additive feeding that allows the design to be changed for meeting production as well as product requirements. However, single-screw extruders can also be used for this process, especially when suitable screw design & static mixers are present after the screw. Further, along with the equipment, the selection of components to be mixed such as viscosities & additive carriers is also very important.
Use carbon dioxide gas, nitrogen, etc. as foaming agents in harmony with the environment, and use their supercritical properties to produce plastic foam products with uniform diameter bubbles. It is also possible to form fine bubbles with cell diameters up to microns.
Main Foam Extrusion Equipment
Co-rotating twin screw extruder + inert gas filler → Melt pump → Single screw extruder (PLC).
Suitable for: PE, PS, PP, TPU, PLA.
Single screw extruder + inert gas filler → Melt pump → Single screw extruder (PLC).
Suitable for: PE, PS, PP.
Co-rotating twin screw extruder + inert gas filler → Melt pump → Melt cooler (PLC)
Suitable for: PE, PS, PP, TPU, PLA.
Auxiliary Foam Extrusion Equipment
● Flat die head → Three-roller setting cooling → Cooling → Cutting edge → Hauling → Winding and cutting
Foaming ratio: 1-3 times
●Tube die head → Splitting and cutting → Auxiliary hauling → Flattening → Cooling → Hauling → Winding
Foaming ratio: 5-15 times
● Bead die head → Strand cooling → Hauling and pelletizing
Foaming ratio: 10-35 times
● Multi-hole foaming die head → Pre-shaping → Cooling and shaping → Deep cooling → Trimming → Planing on both sides → Cutting with fixed-length → Stacking
Foaming ratio: 5-20 times
