Study of non-Newtonian polymer blends using large amplitude oscillatory shearing flow
Large amplitude oscillatory shear (LAOS) was carried out on non-Newtonian minor phase in Newtonian matrix phase polymer blends. The blend consists polybutadiene (PBD) as the droplet phase and polydimethylsiloxane (PDMS) as the matrix phase. The PBD droplet phase was an elastic “Boger” fluid prepared by dissolving a high-molecular-weight PBD into a low-molecular-weight Newtonian PBD. Different percentages of the high-molecular-weight PBD were used to prepare different types of Boger fluids that resulted in blends with different viscosity ratios from lower than unity, to unity and higher than unity. Furthermore, the LAOS results of the blends were analyzed by using the Fourier Transform (FT) technique. From a theoretical point of view, the constrained volume model (CV-model) for Newtonian components is adapted to the case of a Newtonian matrix phase and non-Newtonian Boger fluid droplet phase by taking into account stresses that arise in the Boger fluids. The adapted model and the Newtonian CV-model were compared to the experimental results of FT-LAOS for checking the predictability of the model against the rheological properties. The adapted model shows some reasonable qualitative and quantitative agreements at high strain amplitude values.