Mainly reflected in the following two aspects.
Material delivery method
In the single-screw extruder, the solid transport section is friction drag and the melt transport section is viscous drag. The frictional properties of the solid material and the viscosity of the molten material determine the transport behavior. If the friction properties of some materials are not good, if you do not solve the feeding problem, it is more difficult to feed the material to a single-screw extruder. In twin-screw extruders, in particular in intermeshing twin-screw extruders, the material is conveyed to a certain extent by forward displacement. The extent of positive displacement depends on the screw thread of one screw and the other screw. The relative proximity of the groove. The close engagement of the screw geometry of the counter-rotating extruder results in a highly positive displacement transport characteristic.
Material flow velocity field
The flow velocity distribution of the material in the single-screw extruder has been described quite clearly at present, and the distribution of the flow velocity of the material in the twin-screw extruder is rather complex and difficult to describe. Many researchers only analyze the material flow velocity field without considering the material flow in the meshing area, but these analysis results are quite different from the actual situation. Because the mixing characteristics and overall behavior of a twin-screw extruder depend primarily on leakage flow occurring in the meshing zone, the flow conditions in the meshing zone are rather complicated. The complex flow spectrum of the materials in the twin-screw extruder shows macroscopic advantages that cannot be matched by the single-screw extruder. For example, sufficient mixing, good heat transfer, large melting capacity, strong exhaust capacity, and good control of material temperature, etc. .