The functions of Screw elements
Material conveying: The conveying elements can transport the
materials from the feeding port to all processing sections of the
extruder, ensuring the continuous flow of materials within the
extruder. For example, in plastic extrusion molding, plastic
pellets are transported from the hopper to the heating and melting
section.
Mixing and dispersion: The shear elements and mixing elements
achieve thorough mixing of the components in the materials through
shear, stretching, and compression, and disperse agglomerated
particles to improve the uniformity of the materials. In the
production of color masterbatches, it can evenly disperse pigments
in the resin matrix.
Melt plasticization: Under the rotational action of the screw, the
friction between the threaded elements and the materials, as well
as the friction between the materials and the barrel wall, generate
heat, causing the materials to gradually melt and plasticize. For
example, in rubber processing, the block-shaped raw rubber is
melted and plasticized into a flowable rubber compound.
Pressure building and pressure generation: Reverse conveying
threaded elements and some special structure threaded elements can
form certain pressure within the extruder, which is helpful for the
compaction, melting, and mixing of materials, and can also ensure
the quality and dimensional accuracy of extruded products. For
example, in pipe extrusion, sufficient pressure can make the wall
thickness of the pipe uniform and the surface smooth.
