A New Scale-Up Approach Through the Evaluation of Stress History Within a Twin-Screw Extruder

Abstract

The development of any new product manufactured by extrusion requires initial testing at the laboratory level. Once the behaviors of the product and process are understood, the operation is scaled-up to an industrial grade procedure. Scale-up/down is used in a wide variety of markets such as food processing, food packaging, tubing, and pharmaceutical industries. Product quality is critical to the success of all these applications, but is often made difficult when compounding with additives, fillers, pigments, plasticizers, and other supplemental ingredients. Product quality is achieved when the constituents are well mixed. Stress is a critical parameter in accomplishing good mixing. Through the use of polymeric stress beads, a methodology has been developed to measure residence stress distributions in real time. The methodology has enabled the analysis of both model and industrial grade extruders. Evaluation of both processes has led to the creation of a new scale-up approach for dispersive mixing. The new scale-up rule based on percent drag flow was shown to be a more accurate dispersive mixing scale-up approach for a range of operating conditions compared to the current industry standard.