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Domain structures and rheological properties of immiscible polymer blends composed of components having almost the same viscosities in a parallel-plate (PP) geometry are studied in comparison with those in a coneplate (CP) geometry. Both steady states and transient states after step increase of shear rate are examined. At steady states, it was confirmed that the domain size becomes smaller inversely proportional to the distance from the center (i. e., shear rate) along the radial direction of PP, consistent with the data in CP compared at the same shear rate. The related rheological data are also consistent. At transient states after the step increase of shear rate, there was no apparent long-range interference in the transient behaviors undergoing in different time scales at different positions along the radial direction of PP. The structure change and the related excess stresses of immiscible polymer blends with the nearly same viscosities under shear flow in PP are consistent with those in the CP geometry.

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