The effect of feeding mode on dispersive mixing efficiency in single‐screw extrusion

Abstract

Abstract In the case of dry color compounds, where polymer pellets are coated with a pigment powder, the latter tends to form agglomerates during extrusion, owing to the hydrostatic pressure that prevails in the screw channels. In single‐screw extruders, this pressure is due to the Coulombic fricional transport in the solids conveying zone. The formation of agglomerates can be prevented to a considerable extent by operating the extruder in an underfed mode . This result has emerged from a study of the problems encountered when dispersing pigments in poly(butylene terephthalate) (PBT), but can also be applied in the case of numerous compounds where a fine dispersion of solids in polymers is required.