Examination of Condition for Fine Structure of Immiscible Polymer Blends by Step Change of Shear Rate
Yoshiaki TAKAHASHI, Masanao SUZUKI and Ichiro NODA
Abstract:Effective flow conditions for making fine structure of a model immiscible polymer blend, I.e., equiviscous immiscible polymer blend was examined by using interrupted flow and combination of step increase and decrease of shear rate. Overshoot peak of first normal stress difference, which corresponds to the existence of most elongated domains, was used as an indicator for changing shear rate. That is, shear rate was decreased (including zero shear rate) just after the overshoot peak of first normal stress difference appeared. Time needed to rupture the elongated domains and also droplet size and distributions thus obtained were compared to the data evaluated by using shear flow with step increase of shear rate. The time needed to rupture the domain with interrupted flow and combination of step increase and decrease of shear rate was shorten to be one fifth and the size of domains and their distribution were almost the same compared to corresponding data for flow with step increase of shear rate. It was concluded that decreasing of shear rate at the most elongated state of domain structure is an effective procedure to make fine structure of immiscible polymer blends. Key Words:Immiscible polymer blend, Fine structure, Overshoot peak, First normal stress difference, Decreasing of shear rate