Multilayer coextrusion is a process in which two or more polymers are extruded and joined together in a feedblockor die to form a single structure with multiple layers. These layers should be uniform in thickness across thestructure for best performance. However, layer thickness non-uniformities have been observed in many coextrudedproducts. Previous work has shown these layer thickness variations can occur due to viscosity differences betweenthe polymers in the layers and/or elastic effects that introduce secondary flows. The objective of this work was toexamine the effect of viscous and elastic forces present in polyethylene coextrusion processes.
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