Mathematical modeling of synthesis processes for polymers which are prepared by the low-temperature polycondensation method

Conclusions A procedure has been proposed for the construction and identification of a mathematical model for the process of a nonequilibrium polycondensation.The method is applicable for the construction of a mathematical model and control algorithms for the control of a process for preparing a thermally resistant polymer.Translated from Khimicheskie Volokna, No. 2, pp. 8–11, March–April, 1985.     

Search for optimum regimes in the imidization of polyamido acid in solution

Conclusions -- A mathematical model of the process of imidizing a polyamido acid in the liquid phase has been developed using the theory of neighboring group effects.-- An identification of the model has been performed using the method of moments.-- The mathematical model of the imidization process of polyamido acids has been used to calculate optimum regimes for preparing polyimide fibres.Translated from Khimicheskie Volokna, No. 1, pp. 22–24, January–February, 1991.     

An adaptive system of automatic control of the quality indices in the process of polyethylene terephthalate

Conclusions -- Principles for constructing an adaptive control system for qualitative indices of the polyethylene terephthalate synthesis process have been examined.-- A mathematical assurance of a control system for the basic technological stages has been developed.-- A control algorithm has been realized in the esterification stage of the synthesis process of an industrial unit, which ensures a degree of completion of the process within assigned limits.Translated from Khimicheskie Volokna, No. 5, pp. 48–49, September–October, 1990.     

Operative control of the polymer solution filtration division

Conclusions An approach to the construction of an optimum control system for multistage schemes for cleaning-up spinning solutions under conditions of appreciably nonsteadiness of the filtration process has been examined.The control problem has been formulated and the basic stages in its solution have been set forth, based on the results of mathematical modeling of the process and formalizing the decisive links.A standard functional structure of the system of operative control of the filtration division as a subsystem of the ACS TP for man-made fibre plants is given.Program and mathematical assurance for realizing the control system examined have been developed, using computer control technique.Translated from Khimicheskie Volokna, No. 5, pp. 29–32, September–October, 1986.     

A mathematical model of the oxidative degradation of alkali cellulose in pre-ripening chambers

Conclusions A theoretical study of the oxidative degradation of alkali cellulose in pre-ripening chambers has been conducted.A mathematical model of the process has been constructed which reflects the change in mean degree of polymerization and temperature of the alkali cellulose along the length of the chamber, with consideration of heat-exchange and hydrodynamic processes.The values of the kinetic and thermal constants of the mathematical model have been refined on the basis of experimental data, and its adequacy for the object has been established.Translated from Khimicheskie Volokna, No. 2, pp. 14–16, March–April, 1985.     

The preparation of fibrous anion-exchange resins based on a graft copolymer of polycaproamide-polyglycidyl methacrylate and polyethylene polyamine

Conclusions -- A mathematical model for the amination reaction of the PCA-PGMA graft copolymer has been constructed which adequately describes the process.-- The problem of optimizing the process of aminating the PCA-PGMA graft copolymer with polyethylene polyamine has been solved. The chemisorbents prepared at the optimum regime have an SEC of up to 3.7 meq/g.Translated from Khimicheskie Volokna, No. 5, pp. 34–35, September–October, 1991.     

Stability to the process of spinning a jet of polyacrylonitrile solution in dimethylformamide

Conclusions An experimental study of stretching resonance in spinning solutions of polyacrylonitrile in dimethylformamide has been performed, and conditions for stable spinning of these solutions has been determined.It has been shown that the mathematical model used to describe theoretically spinning process stability adequately describes this process only on the condition that the rheological characteristics are functions of lengthwise deformation rate and spinning conditions.Translated from Khimicheskie Volokna, No. 4, pp. 16–18, July–August, 1988.     

Analytical control of contaminating components in wastewater from viscose manufacturing operations

Conclusions The world working level of control of the composition of natural waters and wastewater has been analyzed.A mathematical model has been proposed which characterizes the level of environment-protective standardization and the tendency for its development.The information stream of national and international standards with respect to nomenclature and quality has been analyzed. Tendencies have been disclosed which coincide with mathematical calculations.A high completeness in standardization of procedures in performing measurements of the composition of natural waters and wastewater, orderliness in standardization, a tendency toward overall standardization, automatic, and instrumentation of standardized methods of performing measurements are characteristics of the leading countries in the environmental-protective respect (as applied to the needs to viscose manufacturing).The overall model of analytical control which has been made up in the leading countries in the environmental respect can be used in the man-made fibre sub-branch upon appropriate treatment.Translated from Khimicheskie Volokna, No. 6, pp. 21–26, November–December, 1988.     

Determination of the temperature of a moving yarn

Conclusions A mathematical model has been proposed for the process of heat-exchange between yarn and heating chamber which permits one, with reasonable accuracy, to describe the yarn temperature distribution over the length of the heater and beyond its limits. This model affords the possibility of calculating the amount of heat carried off by the yarn from the heating chamber and to estimate heat losses into the environment, and, consequently, to select the most economical heater.By connecting up the dynamics of yarn heating with yarn properties, the mathematical model developed permits one to calculate the optimum temperature profile in a heating chamber. Using this model, one can transfer the optimum conditions for heat-stretching yarns to other temperature-time levels.Translated from Khimicheskie Volokna, No. 2, pp. 54–56, March–April, 1989.     

Some features of moisture exchange by carbon fibres

Conclusions A mathematical model for the moisture exchange of carbon fibres in an atmospheric medium has been proposed.The kinetics of moisture exchange by carbon fibres has been studied. Depending on atmospheric humidity, the dynamics of moisture exchange by carbon fibres is determined by a mechanism of activated, Knudsen, or free diffusion or by a combination of these.Diffusion coefficients have been obtained for the moisture which make it possible to carry out a calculation of the drying process and to select optimum conditions for storing carbon fibres.Translated from Khimicheskie Volokna, No. 1, pp. 36–37, January–February, 1990.     

Method of determining the rheological characteristics of polymers during spinning

Conclusions A method has been proposed for determining rheological characteristics which makes it possible, on the basis of the experimentally measured polymer jet profile and a mathematical model of the spinning process, to estimate rheological parameters which yield difficulty to direct measurement.It has been shown that ambiguity in determination of the viscous and elastic components of jet deformation can be eliminated by using additional experimental data on tensional force or on jet kinematics, determined for other spinning conditions.Translated from Khimicheskie Volokna, No. 2, pp. 7–9, March–April, 1988.     

Thermal and process calculation of a high-temperature shaft furnace

A mathematical model of a high-temperature shaft furnace has been developed. It correlates the kinetic processes of thermal dissociation and sintering of the material being fired with the thermal characteristics of the firing process. Calculations by a program realizing the mathematical model make it possible to determine the principal parameters of the plant to ensure the production of material of specified density with low energy expense.Translated from Ogneupory, No. 3, pp. 17–19, March, 1994.     

A Two-Step Reaction Mechanism of Oxygen Release from Pd/CeO2: Mathematical Modelling Based on Step Gas Concentration Experiments

A mathematical model has been developed to study the transient release of oxygen from a 1wt% Pd/CeO₂ catalyst in the 450–550 °C range based on alternate step concentration switches between CO and O₂. A two-step reaction mechanism that involves the reaction of gaseous CO with the oxygen species of PdO and of the back-spillover of oxygen from ceria to the oxygen vacant sites of surface PdO has been proven to better describe the CO and CO₂ transient response curves. The proposed mathematical model allows the estimation of the transient rates of the CO oxidation reaction and of the back-spillover of oxygen process. It also allows the calculation of the intrinsic rate constant k ₁ (s^–1) of the Eley–Rideal step for the reaction of gaseous CO with surface oxygen species of PdO to form CO₂. An activation energy of 10.1 kJ/mol was estimated for this elementary reaction step. In addition, an apparent rate constant k ₂ ^app (s^–1) was estimated for the process of back-spillover of oxygen.     

Optimizing the processes of recovering dimethylacetamide and isobutanol in the manufacture of man-made fibres

Conclusions The process of recovering DMAc and IBA has been investigated using mathematical modeling.It has been shown that the use of a two-phase adsorption—desorption cycle is possible for recovering DMAc at an original concentration not over 4 g/m³ and for an initial IBA concentration not over 2 g/m³.Translated from Khimicheskie Volokna, No. 1, pp. 52–54, January–February, 1987.     

Use of multiple regression analysis for development of a mathematical model of the resistance of converter linings

Conclusions To construct mathematical models of the process of the failure of converter linings, use can be made of the method of regression and correlation analysis.The content of silicon in the pig iron has a considerably greater effect on the stability of periclase-spinellide products than on the resistance of uncalcined refractories in a resin binder.In comparison with a lining made of resin-dolomite-magnesite products based on Novotroitsk dolomite (basic variant), products based on Zakarpatsk dolomite have the highest resistance (increased by 11.9–13.8%), and those based on ordinary metallurgical dolomite have the lowest resistance (a decrease of 9.9–10.3%).A further improvement of the mathematical model may be achieved by a fuller use of the methods of mathematical statistics.N. A. Aleksandrova participated in the work.Translated from Ogneupory, No.3, pp.44–51, March, 1968.     

Effect of aerodynamic spinning parameters and polymer properties on fibre diameter

Conclusions On the basis of theoretical calculations by a mathematical model of the process of aerodynamic spinning of polymer melts, whose adequacy has been established from experimental data, the sensitivity of final fibre diameters to change in technological spinning parameters and on the thermophysical and rheological properties of the polymer has been determined.It has been shown that among the factors which most significantly affect the final fibre diameter are the velocity of air movement in the ejector, the polymer flow rate, the temperature of the melt, the density of the melt, the viscosity anomaly, and the activation energy of viscous flow.Translated from Khimicheskie Volokna, No. 5, pp. 37–39, September–October, 1988.     

Adaptive system for stabilizing viscose ripeness

Conclusions A control algorithm has been described for the process of viscose ripening, which is based on compensating for current perturbations and predicting their effect using an adaptive mathematical model of the process.The algorithm developed has been realized in the make-up of the ACS TP for viscose tire cord manufacture in the Svetlogorodsk Khimvolokno PO and in cellophane manufacture in the Kiev Khimvolokno PO.Translated from Khimicheskie Volokna, No. 5, pp. 26–29, September–October, 1986.     

Evolution of carbon disulfide in apparatus for the plasticized stretching of artificial fibre

Conclusions It has been found that the evolution of carbon disulfide from a yarn in a plasticized stretching trough over its length obeys the laws for turbulent exchange.A mathematical dependence of the carbon disulfide distribution over the plasticization trough length on the basic parameters of turbulent transfer has been found.Intensification of the process of stripping off carbon disulfide without increasing the volume of air pumped off from the apparatus requires increasing the velocity of the air stream which passes through the apparatus.Translated from Khimicheskie Volokna, No. 4, pp. 56–57, July–August, 1984.     

A mathematical model of heating of the material in a layer with occurrence of processes of its thermal decomposition

Conclusions A generalized mathematical model of heating of materials in a layer with thermal decomposition of them taking into consideration in the interrelationship the heat and mass exchange and kinetic rules of the production operations has been developed. A Fortran computer program used for production heat-exchange equipment has been developed on the basis of the model.Translated from Ogneupory, No. 6, pp. 37–41, June, 1987.     

The discharge behaviour of the porous lead electrode in the lead-acid battery. II. Mathematical model

A mathematical model for the porous lead electrode in the lead-acid battery has been derived in order to explain the limited discharge capacity at high rates of discharge. By comparison with experimental discharge curves the model predicts that the discharge process is ended by a coverage of the electroactive surface of lead by lead sulphate, even at current densities around 1000 A m^–2. Only at concentrations lower than the normal (4–5 M) and very high current densities will depletion of sulphuric acid become a limitation. By using an expression which relates, the local maximum utilization of the active material to the time integral of the local current density in a way which resembles the empirical Peukert equation, final lead sulphate distributions can be predicted with a maximum in the centre of the electrode, which is in agreement, with measurements.