Multilayer annular flow of a recycled/virgin material combination

One processing alternative for the use of recycled polymer feedstocks is multilayer extrusion. This option allows one to hide the inferior properties of a recycled feedstock as an inner layer, while employing a virgin material as the outer layer. Coextrusion blow molding is one processing alternative that is increasing in importance with regard to recycled polymer feedstocks. Several manufacturers are employing an inner layer of recycled materials in containers, such as motor oil bottles and detergent packaging. The multilayer flow resulting from the coextrusion through an annular die is the primary stage of the coextrusion blow molding process. Therefore, the results of this stage affect the remaining phases; inflation, cooling and solidification. The objective of this work is to obtain a better understanding of the flow behavior, especially the swell dynamics, of a virgin/recycled material combination. The emphasis of the work is on experimental results, however, some theoretical predictions based on viscoelastic models are presented.