When processing polymer with single screw extruder, it is necessary to have three functions of plasticity, mixing and metering pumping, and it is also required to have the comprehensive ability to control the temperature of heating and cooling, to deal with high viscosity materials or to mix raw materials.
For single screw extruders, the pumping method is extrusion drawing. It uses the rotation of the screw to pull and draw the melt pump. Its pumping principle is shown in Figure 1. The two plates at intervals of H are filled with materials, and the lower plates are fixed, and V is moved horizontally at the plate speed. At this point, the material adhering to the upper plate moves with the velocity V of the upper plate, while the material adhering to the lower plate is stationary. Because the material has a certain viscosity, the moving material will affect the adjacent material, its material flow as shown in the force B1 moving. However, due to the back pressure Pb at the outlet, a reverse thrust force B2 is generated for the material. As a result of the interaction between B1 and B2, the material flow moves along the shape of resultant force B3. It can be seen that the extrusion efficiency of the extruder is very low because of the influence of the feed side velocity and the back pressure on the discharge side.