Reversal phenomena of molten immiscible polymer blends during creep-recovery in shear

In this work, the creep- recovery behavior of immiscible poly (styrene)/poly (methyl methacrylate) blends and their pure components in the molten state were systematically investigated. A stationary plateau in the recoverable compliance of pure components is observed. Unexpectedly, for immiscible polymer blends, the recoverable compliances show different phenomena. For blends with a fine co-continuous morphology, the recoverable compliances exhibit a one-reversal phenomenon, whereas a two-reversal phenomenon is found in the blends with a sea-island morphology. Moreover, these reversal behaviors become less pronounced with decreasing temperature, increasing creep stress, increasing annealing time, or incorporation of nanoparticles. Three competitive effects, i.e., the recovery of oriented polymer matrix, the interfacial tension which drives the deformed droplets to their equilibrium shape, and the phase coarsening process, are used here to explain the different behaviors. (C) 2017 The Society of Rheology.