Investigation of the Two-Channel Feedblock Zone in Co-Extrusion of Polymers

Abstract

A process when different materials are combined to produce a product with multiple layers is called co-extrusion. During this process, polymers are melted in separate machines and then extrudate from different die channels. Once these channels converge, the polymers meet and flow through a single channel. The surface where the two fluids face is called “interface”. It is crucial to maintain the interface's uniformity and stability in order to achieve the desired multi-layered structure. Most of the issues in co-extrusion are related to issues that can be classified into two categories such as polymer encapsulation/interfacial distortion and die swell. To solve these problems, designers focus on improving the interface's stability. This paper examines effects of cross-section modification of the two-channel feedblock on the interface location and velocity and pressure distributions of the flow. The ANSYS software was used to simulate the co-extrusion of polymers, LLDPE and HDPE, in two-channel feedblock with rectangular, circular, and straight slot cross-sections. The results show that sharp corners increase the thickness of dead zones, while rounding them decreases the thickness. Additionally, stadium-shaped (or straight-slot) cross-section channels can move the flow with a higher maximum velocity and thinner boundary layer combining the results of rectangular and circular feedblocks.