Rheology and dynamics of two-phase system with interfaces

Abstract

The fundamental problems in two immiscible polymer blends, such as deformation, break-up and coalescence of the dispersed phase, were considered. Instead of formulating a single droplet problem, it was assumed that there is a kind of structure of the interfaces, in which the interfacial area(Q) and its anisotrpy($q_ij$) are equilibrated due to the competition between flow and interfacial tension. Relaxation mechanism of the interfaces in heterogeneous systems were phenomenologically considered so that a more general constitutive equation was proposed, which can be used not only for arbitrary volume fractions but also for arbitrary flow fields. Also, the effect of simple shear flow on the morphology of polystyrene(PS)/linear low-density polyethylene(LLDPE) blends was experimentally investigated. Wherease most works along these lines have been done visually in a flow cell, our samples were quenched after steady shear and their resulting structures were analyzed by scanning electron microscopy. In order to achieve a better understanding of morphological effects on polymer blending processes, the semiphenomenoligical expressions describing the interface contributions of immiscible polymer blends were formulated and compared with dynamic shear experiments of PS/LLDPE blends. Also, the morphology and rheological properties of copolymer modified blends of PS/LLDPE/SEBS(styrene-ethylene/butylene-styrene) were presented. To characterize the efficiency of the copolymer as a compatibilizer, the morphological structures in the blends were related to rheological behavior with the model suggested. As a result, the theoretical predictions were found to be appropriate for copolymer modified immiscible polymer blends as well as unmodified one. Based on this model predictions, it was important to give one an insight into the interfacial contributions increased by the compatibilization. On the other hand, it was considered that how the blends rheology is affected by the different...