Rheology of immiscible polymer blends and emulsions in steady shear flow

Abstract

Blend properties can be predicted by combination of pure component terms and interface contribution. Interface contribution which is related with morphology change is predicted as excess terms by Park and Lee model. In the model, both excess shear stress (shear viscosity) and excess normal stress are described by two parameters, Κ and λ(1-μ). k represents the ratio of excess normal stress to excess shear stress and λ(1-μ) is a parameter to describe some relaxation of interface. The applicability of Park and Lee model is verified by comparing the predicted and observed rheological behavior for blends of polystyrene(PS)/ polypropylene(PP), etylene-propylene-diene rubber(EPDM) / PP at steady shear flow. Interface contribution which was defined as excess terms is well explained in both PS/PP and EPDM/PP blends with the Park and Lee model. Especially, the excess normal stress difference terms which is related to elastic effect are more apparent than excess shear stress terms. Therefore, it can be concluded that blend properties are well predicted by Park and Lee theory for immiscible polymer blends. In 30PS0/70PP blends, the blend property is mainly determined by pure component``s contribution. On the other hand, the interface contribution is more dominant at 50PS/50PP blends, which may be reflected by the increased interfacial area with volume fraction. However, for EPDM/PP blends which has very elastic dispersion phase, the relative magnitude of interface contribution is small compared with pure component contribution, even though it is still large compared with other blend systems. The blend properties are mainly determined by the pure components contribution because the original difference in first normal stress difference of pure components is too high. Interface contribution which is related with morphology can be separated in emulsion system too. The interfacial tension was large in PIB/PAM1 emulsion where PAM is dissolved by 2wt% than in PIB/PAM2 where PA...