Experimental and numerical analysis of micro/nanolayer coextrusion

Coextrusion is a common method used for producing multilayer films and sheets. Coextrusion is a process in which two or more polymers are extruded and joined together in a feedblock or die to form a single structure with multiple layers. This technique allows the processor to combine the desirable properties of multiple polymers into one structure with enhanced performance characteristics. The coextrusion process can be used to produce multilayer sheet, blown film, cast film, blow molding parts, tubing, wire coating and profiles. It is important to understand the effects of material and equipment parameters on the final micro-/nanolayer structures. Layers normally should have uniform thicknesses throughout the structure for optimal performance. However, layer thickness non-uniformities have been observed in many coextruded structures. It is a very complex and challenging problem due to coupled material and processing variables. This paper will discuss experimental programs as well as numerical modeling of the coextrusion process. The topics that will be covered include rheological measurements of coextruded structures as well as flow of coextruded structures through layer multipliers and dies.