Modeling of structured polyblend flow in a laminar shear field

A new model is proposed for describing the negative deviating behavior, NBD, of polymer blends. The model was derived for a telescopic flow of two Newtonian liquids. flowing through a capillary at vanishing Reynolds numbers. The stress field was considered continuous along the radial position, while the velocity field, due to the slippage, was assumed to be discontinuous at each interface between the two adjacent polymeric layers. A special case of an interphase with its own characteristics, thickness and viscosity, was also considered. The model derived here is applicable for Newtonian fluids or for generalized Newtonian fluids (non-Newtonian) but at constant stress and for morphologies where the phases are structured in oriented layer in the direction of flow or for sheared sandwiches. The capability of the model for describing the NDB behavior was shown on some experimental data of the literature. The main future of the results is that the interlayer slip is caused by the interfacial lubrication due to low viscosity of the narrow interphase. The proposed model was compared with Heitmiller's and Lin's models. Some inconsistencies of Lin's approach have been indicated.