Viscoelastic properties of immiscible polymer blends under steady and transient shear flows

Abstract

Viscoelastic properties of binary blends of immiscible polymers with almost the same viscosity were studied under steady and transient shear flows in the light of the scaling relations in the constitutive equation of textured materials presented by Doi and Ohta. Samples used were blends of polydimethylsiloxane (PDMS) and polybutadiene (PB) with the composition ratios of 3:7, 1:1, 7:3, and 9:1 for PDMS:PB by weight. It was found that both shear stress σ12 and primary normal stress difference N1 at steady state are proportional to shear rate γ except N1 of 9:1 blend, and the rescaled transient stresses after stepwise increase of shear rate compose a single line in terms of strains if the step ratios of shear rates are constant, in accordance with the scaling relations. For the 9:1 blend, in which the contribution of N1 of component polymers cannot be neglected because the interface is small, however, the extra primary normal stress difference at steady state after subtracting N1 of component polymers from the measured one was found to be proportional to γ in accordance with the scaling relations. © 1994, The Society of Polymer Science, Japan. All rights reserved.