How to solve the plasticizing effect of the extruder screw at high speed extrusion
The plasticization phenomenon of the extruder screw at high speed extrusion, how to solve the plasticizing effect of the extruder screw at high speed extrusion
In order to solve this contradiction, in the past, the general method is to reduce the depth of the groove while increasing the rotation speed, and to increase the plasticization and homogenization of the plastic by increasing the shearing action. But relying on this, some plastics that cannot withstand high shear (such as hard polyvinyl chloride) are easily decomposed and cannot be processed on such extrusions. In order to reduce the possibility of plastic decomposition, it is necessary to strengthen the cooling of the barrel. In addition, it is necessary to pass cold water into the screw. This dependence actually reduces the amount of extrusion, and colleagues waste heat. The reduction in the groove depth H3 causes the positive flow to decrease and thus the amount of extrusion. These phenomena are contradictory to the requirement to increase the rotational speed to increase production.
In order to solve this contradiction, some plastics can also increase the temperature of the barrel to promote the solid phase melting. But this method is limited. Because the temperature of the extruded product will also increase, the burden on the cooling system of the main engine and the auxiliary machine is increased. The efficiency of current cooling systems tends to be a major obstacle to limiting extrusion productivity. Excessive extrusion temperature of a colleague will also cause large internal stresses in the product during cooling, resulting in greater deformation, for those heat sensitive plastics, or extrusion processes that must be processed at lower temperatures (eg, cross-linking, Foaming, etc.) Increasing the barrel temperature is fundamentally undesirable. Therefore, at present, it is actually required to design the screw correctly to reduce the extrusion temperature. This is the so-called “low temperature extrusion screw” introduced by some materials.