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A geometrical method of comparing steady-state flow in uniaxial tension and in simple shear is proposed. This method is based on a comparison of the deformation regimes relative to the principal axes.

The rheological properties of binary blends of suspension PS and low-density PE have been studied over a wide range of temperatures. Treatment of the temperature dependence of the viscosity in terms of the Vogel-Tamman equation has shown that the effect which is observed when the terminal phase separation occurs in the system, namely, a sharp reduction in the viscosity of PS at a very small PE concentration, is related to an increase in the free volume in the blend. It is suggested that the change in the glass temperature of PS when small amounts of PE are introduced into it is connected with a change in the conditions under which relaxation processes occur in the system.

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.

Rheological properties of acrylonitrile-styrene copolymer and P-6 polyamide mixtures were examined in the entire range of composition at different temperatures. It was shown that on adding to this copolymer small amounts of P-6 solid particles, viscosity is subject to irregular reduction while the maximum Newtonian viscosity of the system is noticeably reduced. Experiment proves that molecular interaction is intensified on the phase interface of the two component polymer mixture. None of the well known theoretical relations gives a description of the experimental course of the curve showing viscosity vs. composition in the entire range of concentration.

A study was made of the thermal and thermo-mechanical behaviour of thermo-elastoplastic polyurethane semicarbazides (PUS) of segmental structure by DTA, dynamic dilatometry, thermomechanics and using a torsional pendulum. It was shown that the complex structural changes taking place in PUS as a result of the action of heat are reflected both by physical and chemical and physical and mechanical properties of polymers. One of the methods of influencing these characteristics may be by a slight change in the structure of rigid unit, which predetermines the structure of rigid domains functioning in PUS as physical network units.

The viscosity of a polyester and of a styrene solution of the latter containing different amounts of modified and unmodified aerosil has been investigated over a wide range of shearing rates at different temperatures. Modification of the aerosil by grafting onto its surface molecules by glycols of the same homological series resulted in a marked change in the viscosity characteristics of the filled oligomeric systems. This change is due to the presence of a continuous structural network of the filler in these systems. The yield point for a polyester solution where the modified aerosil is used as the filler is higher by one order than that observed for the system containing the unmodified aerosil. The thickness of the polyester boundary layer was evaluated on the solid particles.

Melts of polymer mixtures have been found to possess a correlation between their rheological properties and thermodynamic stability. Regardless of the phase of the mixture components (both crystalline or amorphous, or one crystalline, the other amorphous), a low thermodynamic stability of the system will mean a substantial reduction of the viscosity below that of additivity, and vice versa. An attempt is being made to explain the observed mechanism by the type of phase separation mechanism of such systems.

Investigation of the viscosity and high elastic properties of mixtures of low pressure polyethylene with isotactic polypropylene, over a wide range of compositions, stresses, shear rates and temperatures, has shown that the viscoelastic properties of these mixtures in different strain routines in the temperature region below the melting point of the higher melting component, are similar to those of polymer systems filled with active mineral fillers. Molten mixtures of these polymers display a sharp change in viscoelastic properties in the region where their concentrations are comparable. In the region of low concentrations of PP (up to 2%) mixtures of PE and PP melts undergo an anomalous variation in properties.

The possibilities and conditions of correlation are determined for the principal rheological characteristics of single-phase polymer systems measured for one-dimensional shear deformation in steady-state flow regimes, on transition from rest to steady-state flow, and in harmonic vibration regimes. Special significance attaches to the quantitative results of measuring the high-elastic properties of the polymer systems. It is shown that the Lodge theory, describing the flow behavior of high-elastic media, is well-founded in the linear region of deformation, i.e., for the limiting case of shear rates and shear stresses tending to zero, whereas the Mooney-Rivlin-Weissenberg theories are not in accord with the experimental data even in this limiting deformation regime.

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A study was made of the temperature dependence of viscosity and the glass transition points were measured of narrow polyoxyethylene (POE) fractions and low molecular weight homologues with terminal hydroxyl groups or chlorine atoms. From thermodynamic considerations it was shown that the “actual” glass transition point of high molecular weight POE is ∼ 216°K. Parameters of the Vogel and Adam-Gibbs equations were determined. It was found that the characteristic temperature T 0 , which corresponds to the disappearance of free volume of the system and T 2 at which the conformation and excess entropy of POE becomes zero ( T 0 = T 2 = 180°K) are identical. The “critical” molecular weight corresponding to the formation of a “structural network of contacts” in a POE melt ( M cr = 3500), was determined. It was shown that the abnormal dependence of the viscosity of POE oligomers on molecular weight in the range of M M cr is due to the existence of associates, in which macromolecules are linked with intermolecular hydrogen bonds.

Rheological investigation of epoxide oligomers and their solutions in DMFA filled with glass powder has shown that, in such systems, a spatial fluctuation network is formed. From the results of viscometric investigations, the thickness of the epoxide layer adsorbed on the glass powder in the transfer of oligomer molecules from the oligomer phase to the solid surface in the absence of the solvent has been calculated. On the basis of structure-formation data and the fact that the thickness of the adsorbed layers is independent of concentration and temperature, conclusions have been drawn concerning the migration of aggregates of oligomer molecules during their adsorption on to the solid surface, the special features of the flexibility of the oligomers being taken into account.