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A mathematical model of strain of a dispersed-phase-polymer droplet in flow of a molten polymer blend from a wide reservoir to a narrow one has been created with the use of the structural-continuum approach. The system of differential equations obtained has numerically been solved by the Runge-Kutta method. The model satisfactorily describes the actual processes of flow of molten polymer blends in the entrance zone of a molding orifice: the values of the droplet strains are a function of the relation of the viscosities of the starting components and their absolute values, the volume concentration of the dispersed phase, the interphase tension, and the elasticity of the droplet. The adequacy of the model created has been confirmed by comparison of the droplet strains calculated using the equations obtained and the theoretical conclusions and experimental results.The use of polymer blends is one efficient method of creating materials with a prescribed set of properties. Polymer blends may be considered as specific colloidal systems whose properties are determined by the type of structure formation and the surface phenomena at the phase boundary [1]. Processing of molten blends offers a new method of molding of ultrafine synthetic fibers (microfibers) of diameter from several fractions to tenths of a fraction of a micrometer. This phenomenon has been called specific fiberization [2]. The empirical approach is dominant in investigating the processes of formation of a structure in polymer dispersions. Romankevich et al. have made an attempt to describe the process of formation of microfibers in the matrix of the other polymer in the case of flow of a molten binary mixture; the emphasis was on the strain of a polymer droplet in the channel of the molding orifice and after the exit from it or in subsequent thermoorientational stretching [3, 4]. The mechanism of the phenomenon of specific fiberization, whose essence is that the fiberization of one polymer in the mass of the other (matrix) polymer is carried out in the field of tensile forces arising in transition from a wide reservoir to a narrow one, has been formulated and experimentally confirmed in [2].The present work seeks to create a mathematical model of strain of a droplet of the dispersed-phase component in flow of a molten polymer blend in the entrance zone of a molding orifice.To describe the processes occurring in dispersion flow one must know of numerous characteristics of the dispersion: the viscoelastic properties of the components, the volume concentration of the dispersed phase, the shape, size, and interaction of particles, etc. It is possible to allow for these indices in detail within the framework of the structural (microscopic) approach which has widely been used in investigating comparatively simple media, such as diluted suspensions with simply shaped particles. The possibility of using the structural method in the rheology of dispersions is limited by their diversity and complex morphology. The structural-continuum method proposed in [5,6] combi...

The influence of the concentration of thermally and organomodified montmorillonite on the processes of structure formation in a blend of polypropylene/polystyrene (PP/PS) was studied. It is established that in nanofilled compositions, as well as in the original, is formed a microfibrillar structure, the dimensional characteristics of which depend on the content of the additive and the method of its modification. The investigated clays by content (0.2–2.0) wt. % by weight of polypropylene have a compatibilizing effect in the blend of PP/PS, which reduces the average diameter of microfibers by 1.6 times and increases the homogeneity of their distribution by diameter: statistical indicators decrease (standard deviation, variance, coefficient of variation). The modifying effect of thermally modified clay is higher—the improvement of the dimensional characteristics of PP microfibers is achieved at its minimum content in the blend (0.2 wt. %). The formation of anisotropic PP structures in the PS matrix and the relaxation of the accumulated stresses at the exit of the molding hole is the main factor that causes high values of the coefficient of swelling of the extrudates (4.0–7.7). The change in the microstructure of the extrudates of nanofilled systems during spinning depends on the composition of the blend and the method of modification of montmorillonite. The average diameters of microfibers decrease from 2.2 μm (in the original blend) to (1.3–2.0) μm (in three-component) depending on the content of additives. The ability to regulate the microstructure of incompatible polymer blends by introducing additives of thermally and organomodified montmorillonite will contribute to the creation of nanocomposites with controlled morphology, as well as new fine-fiber materials with improved filtering characteristics.

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