The structure and rheological behavior of a reactive oligomeric ionic liquid (OIL) have been studied. The OIL has a linear structure and contains ionic fragments of two types at both ends of oligo(ethylene oxide) chain. The ionic fragments are represented by secondary amino groups and nitrogen-containing heterocycles protonated with ethane sulfonic acid. The results obtained using rotational rheometry in different dynamic regimes indicate that, in the linear region of deformation at temperatures T < 20°C, this OIL exhibits the behavior of an elastic solidlike body. The components of the complex shear modulus (G ' ~ 107 Pa and G '' ~ 106 Pa) are independent of frequency ω and temperature. At the same time, its complex dynamic viscosity is independent of temperature and decreases with an increase in ω (in logarithmic coordinates, the dependence is linear and has a slope close to unity, which is a formal sign of the existence of a yield stress). At T ≤ 20°C in the nonlinear region of periodic deformation, a crossover is observed in the amplitude dependences of G ' and G '', which indicates that the critical shear stress is reached. As a result, the OIL passes into the liquid state (G '' > G '). The boundary, which is located at nearly 30°C, is characterized by equality between G ' and G '' in a wide range of strain amplitudes. The structural transformations induced by thermal and mechanical energies have been explained using a hypothesis of the existence of micellar structures and a “normal micelle–reverse micelle” transition in the OIL, as well as changes in micelle shapes. The analysis of the temperature dependences for the viscoelastic characteristics and scattered light intensity, as well as the data of DSC and optical microscopy, has led to the hypothesis that at, T = 21–28°C, the OIL may occur in an ordered state similar to the liquid-crystalline one.

The relationship between the rheokinetics of the in situ formation of a linear poly(methyl methacrylate)–crosslinked polyurethane blend in the presence of various amounts of an oligomeric azo initiator containing polyurethane chain fragments and groups able to initiate the radical polymerization of methyl methacrylate and the process of phase separation, the morphology, and the mechanical properties of the final products is studied. It is shown that the times of phase separation and gelation are interrelated and depend on the concentration of the azo initiator in a simple manner. This initiator affects the structural and rheological transitions in the system and leads to the formation of morphologies with smaller domains. The most stable system with the best dispersion of polyurethane in poly(methyl methacrylate) is the blend containing 0.002 mol/L azo initiator that possesses the optimum mechanical properties.

Изучена связь реокинетики формирования in situ смеси линейный полиметилметакрилат–сшитый полиуретан в присутствии разного количества олигомерного азоинициатора, содержащего фрагменты полиуретановой цепи и группы, способные инициировать радикальную полимеризацию метилметакрилата, с процессом фазового разделения, морфологией и механическими свойствами конечных продуктов. Установлено, что время фазового разделения и гелеобразования взаимосвязаны и находятся в простой зависимости от концентрации азоинициатора. Такой инициатор влияет на структурно-реологические переходы в системе и приводит к образованию морфологии с более мелкими доменами. Наиболее стабильной системой с лучшим диспергированием полиуретана в полиметилметакрилате является смесь, содержащая 0.002 моль/л азоинициатора, которая обладает оптимальными механическими свойствами.

The process of the in situ formation of a linear poly(methyl methacrylate)-crosslinked polyurethane blend in the presence of different amounts of an oligomeric azo initiator containing fragments of a polyurethane chain and groups capable of initiating the radical polymerization of methyl methacrylate has been studied. It has been shown that the use of an azo initiator providing for the formation of block copolymers retards the phase separation in the system and favors the formation of a finer blend structure that is characteristic by a domain size several times smaller than that of the pristine blend, without the azo initiator. The optimum azo initiator concentration that results in a better dispersion of polyurethane in poly(methyl methacrylate) has been determined.

The rheological properties and morphology of flow during the in situ formation of linear polyurethane and poly(methyl methacrylate) blends of various compositions are studied. At a certain conversion of the components, the initial homogeneous blend undergoes phase separation, as evidenced by the nonadditive dependence of the logarithm of viscosity on blend composition. For individual components, the gel points correspond to appreciably different conversions. For components in blends of various compositions, this difference is less pronounced and associated with the kinetic conditions of blend formation. The morphology of flow of the reaction blend over the time (or conversion) between the onset of phase separation and gelation during flow with a high shear rate is determined by the blend composition and the ratio between the viscosity of the dispersion phase and the matrix.

The effect of multi-reprocessing on the phase structure and characteristics is studied for thermoplastic elastomers based on recycled high-density polyethylene (HDPE), ethylene-propylene-diene rubber (ternary copolymer of ethylene, propylene, and 5-ethylidene-2-norbornene) (EPDM), and recycled ground tire rubber (RGTR). Analysis of the viscous flow characteristics of thermoplastic elastomers shows that, independently of the number of processing cycles, all samples are characterized by the required flow characteristics at elevated temperatures. Processing of thermoplastic elastomers is accompanied by the competing processes of crosslinking and degradation of macromolecules in a polymer mixture. The results of DSC study and dynamic mechanical thermal analysis show that, as the number of processing cycles is increased, phase separation between amorphous and crystalline phases in thermoplastic elastomers decreases. Insignificant intermolecular crosslinking induced by the processing of thermoplastic elastomers appears to have almost no effect on the physicomechanical characteristics of the final material.

The stream morphology and viscoelastic properties of isotropic and liquid-crystal line regimes of solutions of hydroxypropyl cellulose, low-molecular-mass polyisobutylene, and their blends are studied in the steady-state flow and low-amplitude oscillating shear modes. All systems studied obey the Cox-Merz rule. The isotropic 25% solution of hydroxypropyl cellulose exhibits Newtonian behavior at low shear rates. The anisotropic 50% solution of hydroxypropyl cellulose behaves in an essentially non-Newtonian fashion throughout the studied range of shear rates. It was demonstrated that both dissipative and elastic characteristics of the blends are increased compared to the starting components at small shear rates and frequencies. A reduction in the scale of positive deviations of mixture viscosities from additive values at high shear rates is assigned to a decrease in the contribution of interphase boundaries to dissipative losses. Normal stresses for isotropic and anisotropic solutions appear to be commensurable at low shear rates. At high shear rates, the macroelasticity of the isotropic solution becomes much higher than that of an LC solution. The rheological behavior of systems with isotropic and anisotropic matrices is treated in terms of similarity and difference in the behavior of the network of entanglements and the hypothetical network of defects (disclinations).

Rheological properties of the blends of polysulfone with an LC copolyester were studied both in the absence or presence of short glass fibers. Plots of viscosity of the melts of binary blends versus blend composition showed a positive deviation from the additivity pattern at a low content of the copolyester; the deviation was negative at high contents of the copolyester. Filling the blend with glass fiber to a 20% content reduced the amplitude of deviations, that is, the glass fiber did not enhance the interfacial interaction between the components. Introduction of glass fiber reinforced the copolyester, whereas the mechanical properties of polysulfone were almost independent of the content of the glass fiber, When blended matrices were used, the reinforcement was observed in a narrow range of glass fiber contents (5-7%) and the extent of reinforcement was greater for matrices in which the copolyester was the dispersion medium.

Coagulation structure forms upon filling polypropylene and low density polyethylene with carbon black in a melt of composite at low content of filler (phi almost-equal-to 2 vol %). This structure is a spatial frame of carbon black particles, separated by thin interlayers of polymer. As a result, flow limit appears, that is independent of the polymer type. Increase in the concentration of filler at the percolation threshold phi(c), brings about the formation of condensation structure with the contacting particles of carbon black, resulting in an avalanche-like growth of electric conductivity of composite. Filler concentration phi(c), necessary for the appearance of condensation structure, depends on the type of polymer (5 vol % for PP and 9 vol % for LDPE), because of the differences in polymer interaction with the surface of carbon black particles. On the strength of percolation model, the equation is suggested for the description of concentration dependence of electric conductivity. The model includes the parameters of concrete systems PP-carbon black and LDPE-carbon black, that describe, in particular, the interaction between polymer and carbon black.

Coagulation structure of a filler is formed upon filling polypropylene and LPDE with carbon black in a melt at low filler content (φ ≃ 2 vol %). This structure consists of a spatial framework of carbon black particles, separated by thin layers of polymer. As a result, a yield point appears that is indepentdent of the polymer matrix. An increase in the concentration of filler at the percolation threshold φ c causes a condensation structure to form with the contacting particles of carbon black, which results in an avalanchelike growth in the conductivity of th composite. Because of the differences in polymer interaction with the surface of carbon black particles, filler concentration φ c , necessary for the appearance of a condensation strucutre, depends on the type of polymer (5 vol % of carbon black for PP and 9 vol % for LDPE)

It was found that the rheological behavior of liquid-crystalline copolyesters based on poly (ethylene terephthalate) and p-hydroxybenzoic acid reinforced with silica and talc is determined by structural changes which take place in the melt due to the presence of a filler. It seems that polymer at 240-260°C becomes structurally nonhomogeneous due to the appearance in the melt of a network consisting of local crystalline nodes. Viscoplastic behavior (existence of the yield point) of copolyester melt is intensified owing to the presence of the structural network

Rheological and physico-mechanical properties of LC copolyester on the base of PETP and p-hydroxybenzoic acid containing aerosil and talc have been studied. Features of the rheological behaviour of LC copolyester are related with structural changes of melts. Nonhomogeneous state of the material in the 240-260-degrees range is characterized by the high value of the flow activation energy, by the high value of viscosity, its weak dependence on the concentration of disperse fillers and the nonessential effect of the shear rate on the character of this dependence. Viscoplastic behavior (existence of the yield stress) of copolyester in these conditions is reinforced by the presence in the melt of the structural network with local crystallites in the lattice sites. The low values of viscosity, flow activation energy, the strong dependence of viscosity on the content of active small-disperse fillers above 260-degrees correspond to the nematic LC state. The applicability of the concentration-frequency reduction method for systems under study is shown for all the concentration-frequency range. An increase of the orientation of LC copolyester in the presence of small amount of a filler in the course of capillary flow is assumed resulting in decrease of viscosity of the system and increase of the modulus of elasticity of the composition.

Data on the temperature dependence of effective viscosity, specific volume, compressibility and thermal conductivity of the melt, kinetics of enthalpy relaxation in the glass transition range and heats of solution of amorphous polystyrene (PS) samples with various prehistories have been analyzed. It was conducted the incomplete restoration of the initial tangled network in a sample prepared from good solvents is perhaps due to the appearance of a fraction of rheologically less active entanglements.