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Working principle of PVC twin-screw extruder

Update:23 Nov 2019
Summary:

Although the structure of the PVC twin-screw extruder i […]

Although the structure of the PVC twin-screw extruder is similar to that of the single-screw extruder, there is a big difference between them in the working principle. In the single-screw extruder, the power of material advancement mainly depends on The difference between the material and the coefficient of friction between the barrel and the screw. If the friction coefficient between the material and the inner wall of the barrel is too small, when the screw rotates, the material will hold the screw and rotate together, so that the thread can not play its propulsion role, and the material cannot be transported forward. However, in a twin-screw extruder, the two screws are meshed with each other. At the toothing, the thread of one screw is inserted into the groove of the other screw, so that the continuous groove is divided into C-shaped cells which are separated from each other. When the screw rotates, as the axial movement of the toothed portion moves, the C-shaped chamber also moves along the axial direction. Each time the screw rotates, the C-shaped chamber moves forward by a lead distance, and the material in the C-shaped chamber is due to Due to the thrust of the toothed thread, the tendency of the material to hold the screw to rotate is hindered and pushed forward by the thread. There is no backflow or stagnation during the conveying process, so it has a large forced conveying property.

Because the PVC twin-screw extruder has the characteristics that the material stays in the twin screw for a short and uniform time, it is not easy to cause local degradation and deterioration. This is a heat sensitive plastic such as PVC which is thermally decomposed, solidified or agglomerated when the material stays for a long time. It has unique advantages in coloring, mixing and product production.

Due to the excellent mixing and plasticizing characteristics of the twin-screw extruder, it is mainly used for the modification of polymers, such as blending, packing, reinforced extrusion, etc., and can also directly extrude products such as plates, pipes and profiles.

The twin-screw extruder has a wide range of applications and can be applied to the processing of a variety of materials. It can achieve high output, high quality, high efficiency and other characteristics. Despite its complicated structure, it has received widespread attention and rapid development.

In recent years, with the development of new fields, new products and new technologies such as synthetic materials and fine chemicals, the number of special or special-state polymers to be processed is increasing, and the application of twin-screw extruders is becoming more and more extensive. At present, the trend of twin-screw extruders in the world is to develop toward high torque, high speed and low energy consumption.