A.Ye. Nesterov

The introduction of a filler and consequent increase in the thermodynamic compatibility of binary polyblends

A reversed gas chromatography method has been used to investigate the influence of a filler on the thermodynamics of interaction (characterized by the thermodynamic interaction parameter χ23) in incompatible binary polyblends of types polyurethane-high-density PE and PMMA-polybutylmethacrylate. Investigations were carried out over a wide range of concentrations for the polyblends and the filler (kaolin). The introduction of the filler to a blend of two incompatible polymers enhances the thermodynamic stability of the system. In addition, the system becomes thermodynamically compatible in a definite range of temperature. Complex relations between the thermodynamic interaction parameter χ23 and the filler concentration were observed with various compositions of the PE-polyurethane polyblend. The complex relations are attributed to selective adsorption of one of the polyblend components on the filler surface.

Methods of investigation study of the compatibility of oligomers and polymers by gas chromatography

Abstract A chromatographic method is proposed to determine the compatibility of polymers by measuring excess free energy, enthalpy and entropy of mixing. The method is used to determine several mixtures: polystyrene with polyethylene glycol and polyethylene glycol adipate and several oligomer systems. Compatibility with different component ratios in the mixture was studied for a polystyrene-polyethylene glycol adipate system. It was shown that polystyrene does not mix with both polymers in the temperature range studied. Variations of thermodynamic parameters of oligomer mixtures are similar to those of polymer mixtures.

Use of gas chromatography to study polymers

Abstract Glass temperatures and thermodynamic parameters (heat of mixing and the Flory-Huggins parameter of thermodynamic interaction χ) were determined by gas chromatography for polystyrene and polymethyl methacrylate using substrates of different surface energies (glass and Teflon), according to the thickness of the film applied. It was shown that, when using gas chromatography to study polymers, both the type of the substrate itself and the thickness of the film applied need to be considered. It was found that the properties of films applied on a solid substrate depend on the type of substrate and vary considerably with thickness of the film.

Effect of surface-active substances on the formation of crosslinked polyurethanes☆

When using a number of methods to study kinetics and structural features of the formation of crosslinked polyurethanes in a system containing surface-active substances (SAS) it was found that the presence of the latter causes a marked change in reaction rate, the size of microheterogeneities formed during solidification, degrees of conversion at which crosslinked gel-formation begins and an polymer morphology. Results of investigations suggest that the effect of SAS on crosslinking is observed at the initial stage of gel-formation and involves the localization of SAS in the interfacial range, which separates microvolumes with a developed three-dimensional network from the overall reactions mass.

The thermodynamic compatibility of melted components and the crystallinity of the polymer blends produced from them

Reversed gas-chromatography has been used to establish the Flory-Huggins parameter ξ23 for the thermodynamic interaction between the melted components of polyethylene glycol (PEG-15,000) and oligoethylene glycol adipate (OEGA-2000), oligopropylene glycol (OPG-1055) and oligostyrene (PS-3040), and of paraffin with M-270; the same was also established for OEGA-OPG, PEG-2000-PEG-40,000 blends and those of low density PE with polyoxymethylene. The concentration dependence of the crystallinity of all the above systems has been found to be identical with that of their ξ23. The conclusion drawn is a larger crystallinity for the dynamically less stable melt blends in the solid state, while those more stable have a lower crystallinity after cooling.

Thermodynamic and sorption properties of interpenetrating polymer networks based on a polyurethane and a styrene-divinyl benzene copolymer☆

The methods of inverse gas chromatography and the sorption of the vapours of low molecular substances have been used to investigate a system of interpenetrating polymer networks (IPN), namely, a polyurethane with a styrene-divinyl benzene copolymer. The thermodynamic properties of the IPN were first assessed. The existence of a transition region in the IPN was established experimentally and the proportion of it was assessed, together with the excess enthalpy of mixing as a function of composition. On the basis of the experimental data for the sorption of benzene vapour, the diffusion coefficient in IPN and in the individual components was calculated for various relative pressures of the sorbate vapour. The free volume fraction was calculated for the diffusion process by Fujitas method. It was established that the free volume fractions in IPN were not additive.

Temperature dependence of some properties of polyurethanes in solution and in bulk

O~E of the main problems of modern polymer physics is the determination of relationships between the properties of individual macromolecules and the properties of macromolecules in a sohd body Although theories of structure and properties of macromolecules in dilute solutions are now being actively developed, their results cannot be applied to the properties of bulk polymers firstly because the effects of molecular interaction are not taken into account in dilute solutions. Molecular influences the behaviour of chains and their conformations in a solid polymer, which differ substantially from the conformations of individual chains. From this point of view considerable interest is at tached to the explanation of the problem of how the properties of individual macromolecules are transferred to the properties of a polymer body and how this occurs. Relatively little information of this kind is available in the literature. I t was reported in some studies [1-9] that, in addition to the main changes involved in glass transition, further temperature transitions in polymers were observed as anomalies in the temperature dependence of some properties. Similar transitions were observed both in pure polymers and in solutions [2, 3, 8, 9] Thus, an additional conformation transition, for example for bulk-polymerized polystyrene appears as: a diffuse maximum near 50 ° on the curve of differential thermal analysis (DTA) [7], clear drop in internal pressure (i e cohesive energy) [5], an increase in the Bragg distances between the phenyl groups [6], a discontinuity in dilatometric linearity [4]. In solutions similar transitions were shown in the form of anomalous dependence on temperature [3] of intrinsic viscosity and globule dimensions (~2)1/2 [3, 9], tangent of dielectric loss angle [1, 2], decrease in chain anisotropy, decrease in surface tension [8] and appearance of a discontinuity in the dilatometric linearity [4]. Daane and Barker [4] found transitiSn temperatures for cellulose esters and concluded that these temperatures arc subject to a variation in the molecular mechanism of macromolecular motion. Thus, a minimum number of possible conformations corresponds to the lower

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.

Some features of the thermodynamic reactions between components in oligomer-polymer homologue mixtures as functions of concentration and temperature☆

Abstract Reverse chromatography has been used on some two-component oligomer systems with specific interactions between the components and on polymer-homologue mixtures of polyethylene glycol and polystyrene to study the temperature and concentration dependences of the thermodynamic reaction parameters. A number of anomalies have been detected in the thermodynamics which can be described within the terms of the Flory theory, but also those of the new Huggins theory. Where the polymer homologue mixtures have fairly contrasting thermal expansion coefficients of the components these can be said to be thermodynamically incompatible unless there exist specific reactions between the components.

A birefringence study of molecular and supermolecular structure in polyether urethane-ureas☆

Abstract Polyether urethane-ureas with alternating flexible and stiff-chain segments were studied by static and time-dependent birefringence. Four temperature regions characterized by different molecular mobility have been identified. The hard segments are assumed to be segregated to form domains embedded in a matrix of the soft, polyether segments. The stiff-chain segments inside the domains are oriented perpendicularly to the largest domain dimension. The length of the statistical segment in the stiff-chain blocks is A ⩾ 13 nm.