The difference between the twin-screw extruder and the single-screw extruder is mainly reflected in the following two aspects.
Material delivery method
In the single-screw extruder, the solid conveying section is friction dragging, and the melt conveying section is viscous dragging. The friction properties of the solid material and the viscosity of the molten material determine the transport behavior. If some materials have poor friction properties, it is more difficult to feed the material to a single-screw extruder if the feeding problem is not solved. In a twin-screw extruder, especially an intermeshing twin-screw extruder, the transfer of material is transferred to some extent by forward displacement. The degree of forward displacement depends on the screw edge of one screw and the other screw. The proximity of the relative groove. The screw geometry of the tight meshing counter-rotating extruder provides a high degree of positive displacement transport characteristics.
Material flow velocity field
The current flow rate distribution of materials in a single screw extruder has been described quite clearly, while the flow velocity distribution of materials in a twin screw extruder is quite complex and difficult to describe. Many researchers only analyze the flow velocity field of materials without considering the material flow in the meshing zone, but the results of these analyses are quite different from the actual situation. Because the mixing characteristics and overall behavior of the twin-screw extruder are primarily dependent on the leakage occurring in the meshing zone, the flow conditions in the meshing zone are quite complex. The complex flow spectrum of the material in the twin-screw extruder shows the advantages that the single-screw extruder can't match, such as sufficient mixing, good heat transfer, large melting capacity, strong exhaust capacity and good control of material temperature.