Nonlinear viscoelasticity of complex fluids: A kinetic network model

In this work, the rheological behavior of complex fluids is analyzed with a model based on the classical transient network formulation, in which the description of nonlinear viscoelasticity and time-dependent phenomena considers spatial and temporal variations of the entanglement density in the flow region. The entropic law of the segments that join entanglement points of macromolecules (or dispersed phase) is modeled with a Warner spring law with variable extensibility. The structure modification is described with a function that is dependent of a kinetic process that involves the formation of a more entangled microstate on one extreme, and a flow-induced degradation of the transient network with variable entanglement density on the other extreme (disentangled microstate). Predictions of the model under simple shear, inception of shear flow, stress relaxation, interrupted shear, and shear-thickening are compared with those of other models and with experiments.