Extruders designed to manufacture powder coatings employ a single screw or twin-screw mechanism. Single screw types have flights along the circumference of the screw. These flights convey the mixture into pins that radiate from the interior of the barrel. This creates shearing of the material that in turn melts the mass and affects the distribution and dispersion of the components. The molten mass exits the barrel and is then cooled and broken into flakes.
requires the dispersion of pigment agglomerates. Most pigments are supplied in their natural agglomerated form. The powder coating extrusion process endeavors to disperse these agglomerates. By dispersing the pigment agglomerates, a more consistent and intense color is developed. Incomplete pigment dispersion results in uncontrolled color consistency.
Twin-screw extruders operate on a very similar principle; however, they use the shearing action of two co-rotating, intermeshing screws encased in a smooth barrel. Work is exerted into the mixture by the kneading blocks on the screws. The coordinated rotation of the screws pushes the material from screw to screw as it travels the length of the barrel. The heat generated during this process allows the resinous components to melt. The shearing action intimately melt mixes raw materials and disperses the pigments.