The extrusion screw is the most important part of the p […]
The extrusion screw is the most important part of the plastic machine equipment, which is directly related to the plasticizing effect and output of the plastic machine.
Advantages of extrusion screw
The material of the extruder screw must have high mechanical strength, withstand large torques and have no deformation under high temperature and high pressure conditions.
The reason is: the rotation of the extruder screw in the barrel is carried out under high temperature, high pressure and high torque. Because it strongly pushes the material forward during the rotation, it also has to withstand strong friction and plastic decomposition corrosion. Gas erosion, so the extruder screw must have these advantages.
Common problems with extruder screws
During the rotation of the extruder screw, the plastic is mainly sheared and plasticized by the screw edge, and the plastic is pushed forward, so that the screw edge will bear huge shear stress and friction.
Due to the long-term working under severe conditions, the rib wear and the screw ribs become smaller, and the gap with the barrel increases, which leads to a decrease in the amount of plastic extrusion. In severe cases, plastic reflow occurs, and the plasticizing effect is reduced, and crystal grains appear. And the phenomenon of severe decline in production capacity.
Briefly introduce the process of melt extrusion
The melt extrusion process involves the premixed material entering the extruder barrel from the feed port. The first section of the barrel is the feeding section, the material will not melt at this stage, but will be driven by the screw of the extruder; the material is brought into the second section as the compression section, the stage is the heating stage, the material begins to melt, and the material The friction between the two increases to form a high-viscosity; the third section that continues to drive with the screw of the extruder into the high shear is the homogenization section, which makes it very effective in separating the pigment aggregates for the purpose of full dispersion.
The quality of the extruder directly determines the degree of dispersion of the material.
At present, the extruder equipment used in powder coatings is a double extruder screw extruder, a single extruder screw extruder, and a star extruder screw extruder, although the type of extruder, The internal construction is different, but the design is consistent, that is, the material is evenly dispersed.