The difference between twin screw extruder and single screw extruder

The difference between twin screw extruder and single screw extruder is mainly reflected in the following two aspects.

 1. Delivery mode of materials


In the single screw extruder, friction drag is used in the solid conveying section and viscous drag is used in the melt conveying section. The tribological properties of solid materials and the viscosity of molten materials determine the conveying behavior. If some materials have poor frictional performance, it is difficult to feed the materials to a single screw extruder if the feeding problem is not solved.In twin-screw extruders, especially meshing twin-screw extruders, the material transmission is forward displacement to some extent, and the degree of forward displacement depends on the close degree of the relative screw groove of one screw and another. The screw geometry of a tightly meshed cross-rotating extruder can obtain high forward displacement conveying

2.Flow velocity field of material

At present, the flow velocity distribution of materials in a single screw extruder has been described quite clearly, but the flow velocity distribution of materials in a twin screw extruder is very complicated and difficult to describe. Many researchers just analyze the flow velocity field of the material without considering the material flow in the meshing zone, but these analysis results are quite different from the actual situation. Because the mixing characteristics and overall behavior of twin-screw extruders mainly depend on the leakage flow in the meshing zone, however, the flow situation in the meshing zone is quite complicated. The complex flow spectrum of the material in the twin screw extruder shows the advantages that the single screw extruder can not be compared with, such as sufficient mixing, good heat transfer, large melting capacity, strong exhaust capacity and good temperature control of the material