Modelling of the Nonlinear Behavior of Compatibilized Polyethylene/Polyamide Blends in Shear and Extensional Flows

We have studied the effect of the amount Φ_c of a reactive compatibilizer on the rheological properties of a polyethylene/polyamide blend, under steady shear and transient extensional flows. Here, we propose to describe the viscosity η(γ) and the first normal stress coefficient γ₁(γ) using a Carreau‐type power‐law model, which is a three‐parameter model. A single model is sufficient to express the behavior of γ₁(γ) On the other hand, the complete η(γ) curve is described by the superposition of two Carreau models, in relation to the presence of two relaxation mechanisms. Moreover, the extentional viscosity η_E(?), estimated using the end pressure drop observed in capillary flow experiments, is expressed by a two‐parameter power‐law model.