K. V. Pochivalov

Phenomenological and Thermodynamic Aspects of Melting and Formation of Polymer Crystals in the Presence of Liquids

Based on the results of a phenomenological and thermodynamic analysis of melting and crystal formation in polymers in the presence of liquids, it was hypothesized that crystalline equilibrium in amorphous crystalline polymer—liquid systems does not obey the phase rule. A new interpretation of the phase diagram of such a system was given within the framework of this concept.

Air Permeability of Fabrics Manufactured from Monofilaments as a Function of Their Structure

A mathematical model of removal of low-density polyethylene formed in processing synthetic leather base with alkylbenzene vapors and condensate was obtained. The model allows calculating the number of base compression cycles required for exhaustive removal of LDPE as a function of the initial concentration of the polymer in the material and the relative deformation of the material.

Phase equilibrium in low-density polyethylene — Normal alkanes systems

The crystalline equilibrium diagrams were obtained for eigh LDPE—n-alkane systems with the cloud point method. A point of view was formulated in which there is a major difference between crystal separation in lowmolecular-weight systems and systems containing flexible macromolecules, and it derives from differences in the essence of the phase transitions that take place in these systems.

Effect of Ultrasound on the Kinetics of Extraction of the Polymer Component from a Porous Composite Material

It was experimentally demonstrated that the kinetic nonequivalence of particles of low-density polyethylene (LDPE) gel which appear under the effect of a solvent in different microvolumes of the pore space of a new generation of synthetic leather (SL) base is caused by the difference in their polymer contents. It was shown that excitation of ultrasound vibrations in a solvent with a frequency of 18 kHz can reduce the duration of extraction of LDPE from the SL base as a consequence of intensification of separation of macromolecules from the surface of the gel and due to an increase in the area of this surface as a result of its fragmentation. It was hypothesized that very efficient extraction of LDPE from a SL base can also be created with the traditional method of conducting it in a large volume of extractant with an appropriate design solution of the problem of delivering the US vibrations to the treated material.

Kinetics of Limited Dissolution of Liquids in Polymers: Theoretical Aspects of the Problem

The characteristics of limited dissolution of liquids in polymers in the highly elastic state are formulated. A rigorous expression was obtained for the rate of the change in the average degree of swelling of the elastomer in the form of an unlimited plate of arbitrary thickness with a linear law of distribution of the driving force of the process in it, equal to the difference in the chemical potentials of the diffusant in and outside of the polymer matrix. Calculation of the diffusion coefficient of a low-molecular-weight liquid in a polymer based on data on the swelling kinetics is only possible when very thin samples are used, where the gradient of the driving force of the process over the thickness of the material approaches zero.

Kinetics of Limited Dissolution of Liquids in Polymers: Dissolution of Methylbenzenes in Polyether Urethane

The applicability of an equation describing the kinetics of swelling of a polymer for calculating the diffusion coefficient of a liquid into a polymer was confirmed in the assumption that the chemical potential gradient of the diffusant approaches zero after some critical value of the relative degree of swelling is attained. It was found that the critical value of this parameter is equal to 0.5 for the polyether urethane based on ester diol—methylbenzene systems. The molar rate constant of mass transfer, correlated with the diffusion coefficient by the relation k = D/RTV1, is determined by the equation k = 5.1·10-18exp(12.2Q∞0.25) in the case of dissolution of methylbenzenes in polyether urethane at 323-373 K.

Mathematical Model of Removal of a Polymeric Component from a Porous Composite by Capillary Gel Flow

A mathematical model of removal of low-density polyethylene formed in processing synthetic leather base with alkylbenzene vapors and condensate was obtained. The model allows calculating the number of base compression cycles required for exhaustive removal of LDPE as a function of the initial concentration of the polymer in the material and the relative deformation of the material.

Kinetic characteristics of extraction of the polymer component from a porous composite material

In a polychronic model of washing of LDPE out of a synthetic leather (SL) base with a selective solvent, the “kinetic nonequivalence” parameter of the polymer gel particles is the reflection of the characteristics of the materials pore structure and is not a function of the thermodynamic quality of the extractant. A decrease in the thermodynamic quality of the extractant is accompanied by an increase in the “strength” of the LDPE gel formed in the pores of the SL base. In extraction of LDPE from a SL base according to the mechanism of “capillary flow of gel,” the gel should be moved over the pores of the material in a sufficiently efficient regime of “hydrodynamic entrainment” by the stream of extractant.