L. N. Mizerovskii

On the procedure of constructing phase diagrams of partially crystalline polymer-liquid systems

The procedure of constructing phase diagrams of partially crystalline polymer-liquid systems, which is based on a difference in refraction indexes of a pure liquid and its solutions in partially crystalline and high-elasticity polymer was proposed.

State diagrams of partially crystalline polymer-good solvent systems: The isotactic polypropylene-m-xylene system

In the development of concepts according to which partially crystalline polymers are, in terms of phase state, microheterogeneous metastable liquids, a state diagram of the isotactic polypropylene-m-xylene system is obtained and discussed. It is shown that, in the absence of the limiting line in the diagram that reflects the temperature dependence of the liquid solubility in the partially crystalline polymer, no correct interpretation for the thermodynamic meaning of the temperature dependence of complete amorphization of such a polymer on the initial composition of a binary system (the liquidus curve) is possible.

The phase diagram of the high-density polyethylene-m-xylene system

A phase diagram of the high-density polyethylene (HDPE)-m-xylene system has been plotted and discussed in the context of the concept according to which semicrystalline polymers are three-dimensionally structured liquids with thermotropic grid nodes in the form of crystallites from the thermodynamic point of view. It has been shown that the specific feature of the semicrystalline-polymer-good-solvent systems is the change in the number of phases in them that is exclusively due to the reversible process of dissolution of the low-molecular-mass component in the amorphous regions of the polymer. It has been proposed that the coordinates of the imaging point that corresponds to the minimum temperature of the complete amorphization of the polymer in the presence of the liquid in the phase diagram of these systems can be used as a characteristic for the level of the thermodynamic affinity of the semicrystalline polymer and the liquid.

Phase equilibrium of a semicrystalline polymer-liquid system: Isotactic polypropylene-dibutylphthalate

A hypothesis proposed for semicrystalline polymers as metastable, microheterogenous, three-dimensionally structured liquids with crystallites as grid sites is developed. The phase diagram of the isotactic polypropylene (PP)-dibutyl phthalate system obtained via this approach is discussed in detail. Additional arguments for the thermodynamic nonequivalence of the liquidus line in this and similar systems, on one hand, and in the systems of low-molecular-mass crystalline-liquids, on the other hand, are given. The appearance of a boundary curve, reflecting the transition of the original two-phase system into a single phase, such as a liquid-solution in a polymer, on the phase diagram of the semicrystalline polymer-liquid system is shown to fundamentally change the technological meaning of the diagram, thereby clarifying the mechanism of microporous-membrane formation from solutions of semicrystalline polymers via thermally induced phase separation.

Reaction of Cellulose with Aqueous Solutions of Orthophosphoric Acid

Experimental data were obtained that suggest that total amorphization of hydrated cellulose is attained in 79-80% aqueous solutions of H3PO4. The reaction of cellulose with aqueous solutions of H3PO4 is accompanied by selective sorption of molecules of the acid. Aqueous, especially concentrated, solutions of H3PO4 are characterized by low wetting power with respect to natural and hydrated cellulose.

Phase diagram of the high-density polyethylene-1,2,4,5-tetrachlorobenzene mixture

The full phase diagram of a high-density polyethylene-1,2,4,5-tetrachlorobenzene (TeCB) mixture, which includes the solubility curve of TeCB in the polymer, is constructed for the first time by the optical method. It is shown that TeCB crystals are dissolved in polyethylene via vapor phase mechanism on heating, which leads to the polymer amorphization. The eutectic mixture composition corresponds to the situation when the crystallization of TeCB out of its solution in polyethylene is accompanied by the crystallization of elementary units of macromolecules. As a result, the polymer acquires a gel structure with crystallites as crosslinks and amorphous regions saturated with TeCB.

Melting of binary mixtures of low-density polyethylene and alkylbenzenes

Regardless of the dependence on the thermal history and structure of the alkylbenzene the melting point of the LDPE—alkylbenzene binary system is a linear function of the composition for a concentration of the lowmolecular-weight component of up to 0.9–0.95 mass fraction. Annealing of LDPE — alkylbenzene binary systems at temperatures below their melting point leads to differentiation of solvents with respect to the level of thermodynamic affinity. The heat of fusion of LDPE crystals is 293±15 J/g.

On the kinetics of the reversible repolyamidation of polycaproamide below the melting point of the polymer

It is shown that from a kinetic standpoint the reactions of reversible and irreversible repolucondensation of polycaproamide below the melting point of the polymer obey kinetic regularities of reactions in which kinetically nonequivalent particles participate. The limiting stage is the formally monomolecular process of dehydration of ion pairs —NH3+, —OOC—. It is seen from the experimental results that the use of acidic catalysis in the solid-phase repolyamidation of polyamides is basically inefficient.

Prospects for Perfecting Production Technology for Polycaproamide Used in Production of Textile and Industrial Fibres. Part I

The correlation between the strength indexes of polycaproamide (PA-6) fibres with the molar mass of the polymer and degree of nonlinearity of its macromolecules is discussed. The causes of breaking of branched PA-6 chains in modern technology for synthesis and preparation of the fibres for spinning are analyzed. Possible directions in improving these technologies are advanced.

Dissolution of Dimethylformamide in Aramids: Effect on the Structure and Properties of the Fibres

Swelling of the aramid fibres Kevlar, Armos, SVM, and VMN in dimethylformamide at 298 K is accompanied by an increase in the proportion of ordered regions inaccessible to liquids and a decrease in the molecular orientation in accessible, less ordered regions of the polymer. Addition of small amounts of a thermodynamically active liquid to a solution of binder allows both effectively acting on the overall level of solubility of the composite in the unordered regions of aramid fibres and on the degree of selective sorption of its components.