Strain recovery of model immiscible blends without compatibilizer

The rheological properties of blends of immiscible homopolymers have received much attention in recent years (Tucker and Moldenaers 2002). Several publications have been devoted to examining the relationship between the rheology and morphology of two-phase blends. A key strategy employed by many researchers was to conduct experiments on ‘‘model’’ blends that were comprised of rheologically-simple polymers. This gave the enormous advantage that any non-Newtonian behavior of the blend could be ascribed unambiguously to interfacial effects, and thus correlated quantitatively with the morphology of the blend. We are presently studying the effects of added compatibilizer on the rheology of such model immiscible blends. As a part of this research we conducted several ‘‘baseline’’ measurements on blends without compatibilizer, some of which are of interest in their own right. Here we summarize some observations of the creep recovery after cessation of shear of model uncompatibilized blends with droplet-matrix morphologies. These results add significantly to the data on creep recovery of immiscible blends, in particular, we are unaware of any previous publications that detail the effects of volume fraction and viscosity ratio of the immiscible phases on the creep recovery. The effects of added compatibilizer are discussed in the accompanying paper.