V.F. Shumskii

Viscosity studies of filled oligo-ester melts☆

Abstract The viscosities of the oligo-ester (OE) melts containing various amounts of aerosil were studied over a wide range of temperatures. The thickness of the boundary layer of the oligomer was evaluated on the solid particles. The analysis of the temperature dependence of viscosity forms the basis of the assumption that glass formation and an “iso-entropic” transition applies to the filled polymers.

The effect of modification of the filler surface on the viscosity of a polyester-aerosil disperse system☆

Abstract 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.

Viscosity and molecular behaviour of narrow polyoxyethylene fractions in melt

Abstract 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.

The thermodynamic and rheological properties of polymer melt mixtures

Abstract 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.

Rheological properties of a polyethylene-polystyrene blend☆

Abstract 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.

Rheological properties of mixtures of amorphous and crystalline polymers using a mixture of polyamide with an acrylonitrile-styrene copolymer☆☆☆

Abstract 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.

The viscoelastic properties of mixtures of crystallizable polymers

Abstract 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.

Investigation of the thickness of adsorbed oligomer layers on solid surfaces

Abstract 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.

High temperature transition in oligourethanes

18. J. E. MARK and P. J. FLORY, Rubber Chem. and Technol. 41: 1140, 1968 19. T. L. SMITH, Rubber Chem. and Technol. 41: 1231, 1968 20. B. M. E. VAN DER HOFF and E. J. BICKLER, J. Macromol. Sei. AI: 747, 1967 21. A. CIFERRI and I. J. HERMANS, J. Polymer Sei. B2: 1089, 1964 22. S. M. GRUMJBELL, L. MULLINS and R. S. RIVLIN, Trans. Faraday Soc. 49: 1495, 1953 23. J. E. MARK and P. J. FLORY, J. Am. Chem. Soc. 86: 138, 1964 24. A. N. GENT, Fourth Rubber Technology Conference London, 1962 25. M. PORTER, J. Appl. Polymer Sci. 11: 2255, 1967 26. E. MAEKAWA, R. G. MANCKE and H. D. FERRY, J. Phys. Chem., 2811, 1965

The structural “memory” of amorphous polystyrene

Abstract 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.