Fluid mechanics of the formation of polymer blends. Part I: Formation of lamellar structures

Abstract This paper deals with the early stages of blend morphology development as occurs in a screw extruder. Using combinations of similar polymers (polystyrene and styrene‐butadiene copolymer) and dissimilar polymers (PS and EVA) as model systems, it has been concluded that during melting the scale of segregation between the blend components is reduced by orders of magnitude within fraction of a second residence time. During the early stages of morphology development, the melting pellets produce fine lamellar structures (thickness of the order of μm) that extend over much of the melting zone before being broken up by capillary forces. The origin and the deformation history of the lamellar structures have been successfully interpreted by a new theory.