, 片材设备（图示） 由高分子物理学知道，高聚物存在三种物理状态，即玻璃态、高弹态和粘流态，在一定条件下，这三种物理状态会发生互变。 Sheet extruder and sheet equipment (pictured) are known from polymer physics. There are three physical states of polymers, namely glass state, highly elastic state and viscous fluid state. Under certain conditions, these three physical states The state will change. After the solid plastic enters the barrel from the hopper, it moves forward with the rotation of the screw toward the head. During this process, the physical state of the plastic is constantly changing. According to the change of three physical states of the plastic in the extruder and the working requirements of the various parts of the screw, the screw of the extruder is usually divided into a feeding section (solid conveying section), a compression section (melting section) and a homogenizing section. (Melt transfer zone) Three stages. For conventional gradually threaded screws, the extrusion process of plastics in the extruder can be described by the basic functions of each section of the screw and the physical state of the plastics in the extruder, as shown in Figure 5. 1. The feeding section plastic enters the barrel of the extruder from the hopper. Under the rotation of the screw, it moves forward due to the friction between the inner wall of the barrel and the surface of the screw. In this section, the function of the screw is mainly to compact the plastic to provide forward power, and the material still exists in a solid state, although due to the strong frictional heat, the plastic that is in contact with the inner wall of the barrel is close to or close to the end. When the viscous flow temperature is reached, the surface of the solid particles starts to stick, but the melting has not yet started. This area is called the hysteresis zone, which refers to the viscous flow state from the end of the solid transport zone to the beginning of melting. 3. Homogenization section The material that enters the homogenization section from the melting section is the viscous fluid that has been completely melted. The viscous fluid conveyed forward is under the resistance of the die of the machine head, part of the reflux is further mixed and plasticized, and part of the viscous fluid is extruded from the die of the machine head at a constant pressure. , 片材设备（图示） Sheet extruder , sheet equipment (pictured)
From the working principle of the above single-screw extruder, it is not difficult to see that plastic is plasticized in the extruder and squeezes forward. The main driving force comes from the solid transport in the feeding section. The uniformity of plasticization is largely due to Reflow caused by the structure of the homogenization section and the resistance of the die. There have been many new structures in improving the screw mixing structure, but they are often suitable for polymers with good thermal stability, but not suitable for the production of PVC resins, which will not be introduced one by one.
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