The working principle of single screw extruder and twin screw extruder has the following obvious differences:
The single screw rotates in a cylindrical barrel. After the material enters the barrel from the hopper, it is gradually pushed forward by the thread with the rotation of the screw. During the push process, the material is heated by a heating device outside the barrel to gradually melt it. At the same time, the material is subjected to the extrusion, shear and friction of the screw thread, and plasticized and mixed. Finally, the molten material is extruded through the head and die under the pressure of the screw head.
For example, in the production of simple PE pipes, the single-screw extruder, through its continuous push and plasticization, converts the PE particles into a uniform molten state and extrudes the pipe shape that meets the requirements.
It is suitable for the production of simple plastic products, such as general plastic pipes (such as PVC, PE, etc.), plates and films.
For some products with low mixing requirements and good material processing performance, such as ordinary plastic lines and simple plastic profiles, single-screw extruders can meet the production needs.
In the case of relatively simple production process, large output and product performance requirements are not particularly complex, it has a cost advantage.
For example, common household plastic water pipes are often mass-produced using single-screw extruders, which can reduce costs while maintaining quality.
The two screws of the twin-screw extruder mesh with each other. After the material enters from the feeding port, it is subjected to strong shearing, stirring and mixing in the meshing zone of the two screws. Because the rotation direction and speed of the two screws can be different, the movement of the material in the screw groove is more complicated. At the same time, the screw groove of the twin-screw extruder usually has better sealing, which can achieve better exhaust effect and reduce bubbles and volatiles in the material.
For example, when modifying engineering plastics, twin-screw extruders can more effectively disperse various additives evenly in the plastic matrix, improving the modification effect.
In general, the single-screw extruder mainly relies on the push and extrusion of the screw to achieve the conveying and plasticizing of the material, while the twin-screw extruder achieves a more intense shearing, mixing and exhaust effect through the meshing and complex movement of the two screws.
It is often used in situations where the mixing, dispersion and plasticization of materials are required, such as the modification of engineering plastics (such as strengthening, toughening, filling, etc.).
It is suitable for the production of high performance plastic composite materials, such as glass fiber reinforced plastics, nano composite materials, etc.
Excellent in processing heat-sensitive materials, where precise control of the reaction process (such as reactive extrusion) is required, and where good exhaust results are required to remove volatile components.
For some products that need to blend a variety of materials with different properties, such as plastic films with special functions, plastic parts for automotive, etc., twin-screw extruders can achieve a more uniform blending effect.
For example, in the production of plastic parts with special performance requirements for automotive interiors, twin-screw extruders can fully mix a variety of additives and plastics of different properties to achieve the required performance indicators.
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