The material of the Conical twin screw barrel must have high mechanical strength, be able to withstand huge torque, and have the performance not to deform under high temperature and high pressure conditions. The rotation of the extruder screw in the barrel is performed under high temperature, high pressure and high torque. Because it pushes the material forward during the rotation, it also needs to withstand strong friction and corrosion from the decomposition of plastics and corrosive gases.
Therefore, the extruder screw must have these advantages. During the rotation of the extruder screw, the plastic is mainly sheared and plasticized through the edge of the screw, and then the plastic is pushed forward, so the edge of the screw will bear huge shear stress and friction. Due to long-term work under severe conditions, the screw ribs are worn, the screw ribs become smaller and the gap between the same barrel increases, so the amount of plastic extrusion will decrease, and in severe cases, plastic backflow and plasticization.
The effect will be reduced, and grains will appear, and the productivity will be severely reduced. The process of melt extrusion is to feed the pre-mixed materials from the feed port into the extruder barrel. The first part of the barrel is the feed part. The material does not melt at this stage, but is driven by the extruder screw. Bring the material into the second part, the compressed part. This stage is the heating stage. The materials begin to melt, and the friction between the materials increases, forming a high-viscosity object.
Continue to use the extruder screw drive to enter the third stage of high shear is the homogenization stage. This stage will make it very effective to separate the pigment aggregates and achieve sufficient dispersion. Currently, the extruder equipment used for powder coatings is twin extruder screw extruder, single extruder screw extruder and star extruder screw extruder. Although the type of extruder is different, the internal structure is different, but the design purpose is the same, that is, the material is dispersed to the greatest extent.