ИСТИНА

The analysis of literature and own experimental data have shown that high deformation rates in flow of viscoelastic polymer systems lead to the flow-to-rubbery-like transition. It is the limit of the strong nonlinear behavior of viscoelastic liquids. As a result, different effects including instability (elastic turbulence, spurt, stick-slip, etc) and even self-ordering of the structural and the phase elements were observed. In the particular case of nanocomposite precursors based on polymer matrices, the regular phase separation in rotational flow with high shear rates was observed, that resulted in formation of the concentric circles of nanoparticles. Namely in this region of shear rates such effects as non-Newtonian decrease of viscosity in the filled polymer melts appear the most brightly. To explain a whole set of experimental data and some theoretical predictions of polymer behavior in intense shear flow, the novel model is proposed considering polymer melt in this region as the granular medium deforming pure elastically. The proposed conception is based on the refusal from continuum field approach and serves as a model of behavior (similar to the tube model) of viscoelastic liquid in the strong non-linear region. The behavior of the structure elements in this model is determined by their elastic deformations (transition from spherical to ellipsoidal shape of elements and their orientation, as well as elastic interaction at collisions). The computer simulation has demonstrated that this model really describes the whole consequence of elastic instabilities as the chaos-to-order transition. The experimental data confirm the main model predictions.