Extruder high shear extrusion technology
Issuing time:2021-05-14 16:51
In the process of extrusion, the material from the glass state to the molten state, in addition to doing well the balance of the heat required for plasticization of the material and the amount of heating, so that the material to complete the ideal plasticization, melting pressure is also a very important control index. The extruder is not under normal pressure due to the influence of die resistance and screw compression ratio. The compression ratio of screw is constant and invariable in different die of single screw extruder.
Under the premise that the extrusion speed remains unchanged, the feeding speed and the feeding section screw material volume change, while the exhaust section material volume remains unchanged. Therefore, the feeding section and compression section change with the compression ratio, and the melt pressure increases or decreases accordingly. Under the premise that the feeding speed remains unchanged, the extruding speed and the screw material volume of the feeding section also change. The material volume of the exhaust section remains unchanged, so the melt pressure of the feeding section and compression section increases or decreases with the change of compression ratio. The feeding speed is raised or decreased synchronously with the extrusion speed. As the feeding section screw material volume remains unchanged, the melt pressure changes due to the increase or decrease of the feeding speed.
It is impossible to increase or decrease the total pressure of melt in the extrusion process. Total pressure adjustment mainly depends on the extrusion speed, feed and W extrusion speed ratio and other technological methods. Adjusting the extrusion speed and the ratio of feed to extrusion speed are not only important measures to adjust the extrusion temperature, but also the main measures to adjust the melt pressure and extrusion efficiency.
As for the temperature control of nose, itd and die, the difference between low-shear plastic extruder and high-shear extruder mainly lies in screw structure, which has little to do with nose, itd and die. At the same time, the setting temperature of the head, itd and die only serves to change the flow direction of the melt material, adjust the flow rate of the material section and the surface finish of the products.
Therefore, there is no big difference in temperature control between the two plastic extruders with different shear properties. According to the shape and appearance of the export type blank color adjustment. For the specific adjustment, please refer to UPVC profile extrusion process and dynamic thermal balance of materials. It should be pointed out that high or low shear extruder should be used in accordance with extrusion profile specifications.