Modeling of the rheological properties of multinanolayer films in the presence of compatibilized interphase

Abstract

Rheological behavior of nanolayered films of polyethylene/polyamide 6 (PE/PA6) compatibilized in situ during the coextrusion process has been studied at a temperature between the melting temperatures of PE and PA6. Thanks to the high number of interfaces, a drastic increase in dynamic moduli has been measured when increasing the interphase volume fraction in the films, and a solid-like behavior for the interphase was identified. Different models are compared to capture the complex viscosity of nanolayered films as a function of angular frequency. A model considering interphase and bulk viscosities and a single fitting parameter, namely, the thickness over which the viscosity decreases linearly from the interphase to the bulk one, captures the complex viscosity of all samples. This thickness is comparable to the PE layer thickness up to values about 1 μm before a significant bulk region has to be added to capture the behavior for thicker layers. This suggests that the melt rheology is impacted by the presence of a nanometric interphase over very large (micronic) length scales.