There are many differences between single screw extruder and twin screw extruder in plasticizing capacity, material conveying mode, speed and cleaning.
As the name implies, the single screw is a screw, the twin screw is two screw, are driven by a motor, the power is different because of the screw. Twin screw compressor host force is not smooth, affected by axial force radial force, axial force must be by constant piston, bearing life is short, screw bite when high-frequency noise; Single screw unit operation noise is small, but the single capacity is small, twin screw unit cooling capacity range is large, unit performance is basically similar, so the current market twin screw unit used more. In general, the main differences are as follows:
1.Different plasticizing properties: single screw is suitable for polymer plastic extrusion and granular material extrusion, polymer shear degradation is very small, but the material stays in the extruder for a long time; Compared with single screw extruder, twin-screw extruder has better mixing, exhaust, reaction function, and the residence time in the extruder is short, suitable for powder processing.
2.Different material transport mechanisms: the material transport in the single screw extruder is drag flow, the solid transport process is friction drag, and the melt transport process is viscous drag. The friction coefficient of solid material and metal surface and the viscosity of melt material largely determine the transport capacity of the single screw extruder.
3.Cleaning at different speeds: The speed distribution of the single screw extruder is clear and easy to describe, while that of the twin screw extruder is more complex and difficult to describe, mainly due to the meshing area of the twin screw extruder.
4.Different self-cleaning: the shear speed of the twin screw extruder is fast, because the spiral bar and spiral groove in the meshing area of the opposite speed, the relative speed is fast, any accumulated material attached to the screw can be scraped off, the material has a good self-cleaning effect, the material residence time is short, not easy to local degradation. Single screw extruders do not have this function.
Screw extruders have different working principles and application fields. Twin-screw extruders are widely used in physical and chemical modification of matrix resins, such as filling, strengthening, toughening and reactive extrusion. Single screw extruder is mainly used in pipe, plate, plate and profile fields.
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