It is mainly reflected in the following two aspects.

Material Transportation Method:

In single-screw extruders, the solid conveying section experiences frictional drag, while the melt conveying section experiences viscous drag. The frictional properties of the solid material and the viscosity of the molten material determine the conveying behavior. If certain materials have poor frictional properties, it can be challenging to feed them into a single-screw extruder without resolving the feeding issues. In twin-screw extruders, particularly intermeshing twin-screw extruders, the material transfer is to some extent a positive displacement transfer, with the degree of positive displacement depending on the proximity of the threads on one screw to the relative grooves on the other screw. The screw geometry of tightly intermeshed, oppositely rotating extruders can achieve a high degree of positive displacement conveying characteristics.

Material Flow Velocity Field

The flow velocity distribution of materials in single-screw extruders has been described quite clearly, whereas the distribution in twin-screw extruders is quite complex and difficult to describe. Many researchers analyze the flow velocity field of materials without considering the flow in the intermeshing zone, but these results significantly deviate from reality. This is because the mixing characteristics and overall behavior of twin-screw extruders mainly depend on the leakage flow occurring in the intermeshing zone, which is quite complex. The complex flow patterns of materials in twin-screw extruders exhibit macroscopic advantages that cannot be matched by single-screw extruders, such as thorough mixing, good heat transfer, high melting capacity, strong exhaust capability, and excellent material temperature control.