Effect of precipitation bath composition on the swelling of viscose textile yarn

Conclusions The dependence of the degree of swelling of freshly spun viscose textile yarn (primary swelling) and of the finished yarn (secondary swelling) on precipitation bath composition has been investigated by the mathematical planning method, using a three-factor experiment.The optimum precipitation bath composition has been found, which ensures a minimum degree of swelling of viscose textile yarn and, consequently, a more uniform distribution of yarn properties over the cake layers, which has made it possible to increase cake weight.Translated from Khimicheskie Volokna, No. 4, pp. 26–28, July–August, 1985.     

Acoustical method of studying structural changes during the swelling of fibres in liquids

Conclusions A procedure has been developed for direct study of the kinetics of structural changes in fibres during swelling in various liquids which used ultrasound.The possibility of using the ultrasonic method to study structural changes in fibres of various chemical structures during swelling has been demonstrated.Translated from Khimicheskie Volokna, No. 3, pp. 58–59, May–June, 1987.     

Effect of precipitation bath composition on the primary swelling of yarns prepared from highly concentrated viscoses

Conclusions The magnitude of the primary swelling of viscose yarns prepared from highly concentrated viscoses in various stages of spinning has been determined as a function of the composition of the precipitation bath. The magnitude of forced syneresis has been calculated.Translated from Khimicheskie Volokna, No. 6, pp. 32–34, November–December, 1987.     

Swelling of aromatic polyamide fibres in active media

Conclusions The method of swelling in active media, with the aid of optical microscopy, has been used to discover fine structural differences in aramide fibres. The method is informativeTranslated from Khimicheskie Volokna, No. 1, pp. 33–34, January–February, 1987.     

Some special features in the precipitation of hydrocellulose from cuprammonium solutions

Conclusions The effect of precipitation baths with varying precipitation power on the composition and swelling of gels precipitated from a cuprammonium cellulose solution has been examined.The degree of decomposition of the cellulose cuprammonium complex in aqueous-organic systems depends but little on the nature of the organic compound, but the degree of swelling of the freshly spun gel in aqueous-organic systems decreases with increase in the proportion of the organic component in the precipitation bath.Translated from Khimicheskie Volokna, No. 3, pp. 37–39, May–June, 1983.     

Temperature and concentration limits of cellulose solubility of cuprammonium complex solution

Conclusions The solubility of cellulose in cuprammonium complex solution has been studied over a wide range in concentration and temperature, and it has been shown that these solutions have a lower critical mixing temperature.Concentration limits of cellulose solubility and swelling have been determined in mixtures of cuprammonium complex with diethylene glycol; these depend to a considerable extent on the Cu/cellulose/NH₃ proportions.Translated from Khimicheskie Volokna, No. 5, pp. 36–37, September–October, 1989.     

Some peculiarities of the copolymer precipitation in spinning a strongly-acid chemisorptive fibre

Conclusions The existence of polyelectrolyte swelling (self-elongation of the fibre on change of medium) has been established in strongly acid undrawn gel-fibre.It has been shown that cementing of the strongly-acid fibre after drying, when the fibre has been wet-spun into aqueous-organic baths, is caused by the presence of solvent which is strongly retained on the fibre.A possible mechanism for the retention of solvent by the strongly-acid gel-fibre has been advanced.Translated from Khimicheskie Volokna, No. 4, pp. 32–34, July–August, 1987.     

Morphological and structural features of polyacrylonitrile fibres spun by the dry-wet method

Conclusions -- A technological regime for the preparation of polyacrylonitrile fibres from binary and ternary copolymers has been chosen; these differ from known specimens in having a more uniform cross-sectional structure and a smoother elementary filament surface.-- A considerable difference in crystalline structure of fibres from binary and ternary copolymers which have been spun into a dimethyl sulfoxide—water bath has been shown.-- Fibres from the binary or ternary copolymer which have been spun into a precipitation bath having a large dimethyl sulfoxide content in water are characterized by a lower degree of swelling.-- Shrinkage of fibres from the binary copolymer in the temperature range 200–220°C is twice as small as the shrinkage of fibres from the ternary copolymer.Deceased.VNIIPV. Translated from Khimicheskie Volokna, No. 3, pp. 19–22, May–June, 1991.     

The swelling of Nigma fibres

Conclusions -- It has been found that the primary swelling of fibres prepared from solutions of cellulose curpimonium complex has an extremal dependency on the composition of the aqueous—organic precipitation bath.-- The character of the dependence of the swelling of the finished CuC and HC fibres on composition of the mixed precipitant indicates a structural memory of the fibre during the transition CuAC CuC HC.-- The extremal character of the temperature dependence of swelling of HC fibres in a solvent + precipitant mixture is probably brought about by several oppositely directed processes, including complex formation, change in solubility, ionization, etc.Translated from Khimicheskie Volokna, No. 1, pp. 56–58, January–February, 1991.     

Some special features of the dissolution of cellulose in the dimethylacetamide-lithium chloride system

Conclusions The effect of the character of the activating treatment on change in cellulose crystalline structure, its degree of polymerization, swelling, and thermodynamic parameters of the spinning solutions has been investigated.A probable mechanism for the activation has been suggested, which consists of an unblocking of the capillary walls of the cellulosic material, and not of the capillaries themselves, which is confirmed by data from the experimental studies.Translated from Khimicheskie Volokna, No. 2, pp. 10–11, March–April, 1989.     

Mathematical model for swelling in a liquid emulsion membrane system

Application of the liquid emulsion membrane (LEM) technology to the industrial scale is hindered by the challenges imposed by stability of the emulsion during the transfer of the solute (pertraction). One of the important factors which leads to the instability is swelling. Emulsion undergoes swelling due to the osmotic gradient across the membrane as well as due to the occlusion of the external phase into the membrane phase; the latter is caused by the hydrodynamic deformation of the membrane globules. In the present work, we have studied swelling of the emulsion phase in a water-in-oil-in-water type LEM system. Nitric acid is the internal aqueous phase and is encapsulated in organic membrane phase composed of DEHPA–kerosene-SPAN80. Demineralised water is used as the external phase. The effect of the composition of the system and the hydrodynamic condition on the rate of swelling has been studied. A mathematical model has been developed to describe the effects of the relevant parameters on swelling of the emulsion. The globules of the emulsion are viewed as having a core-shell structure, based on the visual evidence. The model takes into account both the osmotic and the occlusion modes of swelling and also the leakage of the internal phase. The predictions of the model are found to be in good agreement with the experiments. The model would be useful for evaluating the rate of pertraction of a solute through the membrane–strip combination used in the present study. The study would also be useful for tuning the design and the operating parameters in LEM pertraction to achieve minimum swelling of the emulsion.     

Effect of surface-active substances and of carbon disulfide in the viscose manufacturing precipitation bath on the chemical resistance of rubber materials

Conclusions As a result of this study, it has been found that the effect of surface-active substances, solutions of sulfuric acid, or of a model precipitation bath on the chemical resistance of rubbers is slight.The carbon disulfide contained in a real precipitation bath exerts the greatest effect; this causes swelling of the material and a significant loss in strength and elongation.These results must be taken into account in selecting materials for rubberizing reservoirs in chemical manufacturing operations.Translated from Khimicheskie Volokna, No. 6, pp. 32–33, November–December, 1985.     

Effect of intensive drying of viscose fibres on their properties

Conclusions Experimental data are given on the effect of moisture evaporation rate in drying viscose yarns on the strength and elongation, sorptive capacity for water vapor from the air, swelling, shrinkage, and wear resistance of yarns.It has been found that, by regulating the drying temperature, it is possible to affect the capillary-porous structure of a yarn to a considerable degree. Raising the temperature and the drying rate leads to an improvement in wear resistance and yarn elasticity. However, due to the decrease in internal surface area, one may expect a decrease in the sorptive capacity of the yarn in dyeing. A decrease in drying temperature helps increase the degree of swelling, and helps improve the absorption of dye by the yarn.Translated from Khimicheskie Volokna, No. 2, pp. 46–47, March–April, 1984.     

Effect of electromagnetic treatment of viscose on stability of the spinning process and quality of technical yarn

Conclusions The effect of electromagnetic treatment of viscose during spinning on the stability of yarn preparation and quality of the final viscose yarns has been studied.It has been shown that electromagnetic treatment of viscose permits one to increase yarn strength, resistance to repeated deformation, and shear modulus, to increase the degree of orientation of the polymer macromolecules in the yarn, and to reduce its degree of swelling.It is recommended to carry out electromagnetic treatment of the viscose directly on the spinning machine, before delivery of the viscose to the spinneret.Translated from Khimicheskie Volokna, No. 4, pp. 39–40, July–August, 1989.     

Viscose fibres from hydroxyethylcellulose of low degree of substitution

Conclusions The effect of introducing small quantities of hydroxyethyl groups into cellulose (=6–10) on the structure and properties of various types of viscose fibres has been studied. The structure and properties of cord fibre and cord are not affected, but the properties of textile yarn deteriorate sharply. There is a significant change in the structure of polynosic fibre and in some of its properties: the brittleness is reduced, simultaneously with an increase in alkali solubility and swelling in water.All-Union Scientific-Research Institute for Synthetic Fibres (VNIIV). Translated from Khimicheskie Volokna, No. 4, pp. 55–57, July–August, 1969.     

Properties of chemically resistant carbon-reinforced plastics

Conclusions The thermal behavior and character of swelling of three carbon-reinforced plastics based on various grades of phenolic resins have been studied in the original state and after service in aggressive media.It has been shown that the molecular weight of the binder exerts an effect on the temperature range and thermal effect of chemical reactions and degradation processes in these materials.The thermal analysis method permits one to determine the difference in properties of carbon-reinforced plastics on change in technological conditions for their preparation, and also to follow the development of degradation processes in carbon-reinforced plastics after service in aggressive media.Translated from Khimicheskie Volokna, No. 1, pp. 13–15, January–February, 1989.     

Styrene-Divinylbenzene Copolymers: Influence of the Diluents on Absorption and Desorption Properties

Styrene-divinylbenzene copolymers with porous structures were prepared by seeded suspension polymerization using toluene and heptane as diluents. The influence of each diluent on the formation of porous structure and the swelling ratio was investigated. The styrene-DVB beads are capable of absorption and desorption of organic solvents having solubility parameters in the range of 17.6–19.6 (MPa)1/2. Styrenic imbiber beads were swelled in toluene and the kinetics of absorption was studied. The imbiber bead could absorb toluene completely within 90 min and yielded a maximum swelling ratio of 12.7. The diffusion coefficient values of these beads were in the range of 1.55 × 10–5 to 3.68 × 10–5 cm2 · s–1.     

Sorptive properties of heat-resistant fibers based on aromatic polymers

Conclusions -- A comparative study has been made of the sorptive properties (isotherms and kinetic sorption-desorption characteristics for water vapor and swelling in water) of aromatic heat-resistant and difficultly combustible fibers.-- The sorption isotherms of the fibers Terlon, Fenilon, SVM, Togilen, Oksalon, and Aramid-T have an S-shaped form, which is characteristic of polymers containing hydrophilic functional groups which are able to be hydrated. In the case of Lola fiber, the isotherm has a convex form, which is typical for polymers of low polarity with a porous structure.-- For most of the fibers, the kinetic sorption-desorption curves are characterized by the presence of a section of rapid moisture exchange with subsequent departure onto a plateau. SVM fiber has some differences, where the sorption-desorption process takes place over hundreds of hours because of structural changes (amorphization of structure) on swelling in vapor.-- Polyamidobenzimidazole fibers of the type of Togilen and SVM have the best hygroscopic properties. Among all the forms of aromatic heat-resistant fibers, Togilen is close to cotton, wool, and viscose fibers in hygroscopic properties.-- The structural causation of differences in the sorptive properties of aromatic thermally stable fibers has been examined.Translated from Khimicheskie Volokna, No. 2, pp. 37–39, March–April, 1993.     

Mass and heat transfer analysis of SAS: effects of thermodynamic states and flow rates on droplet size

The supercritical antisolvent (SAS) process entails attainment of extremely high supersaturation in an atomized solution droplet by a very rapid increase in the antisolvent CO₂ mole fraction in it during its flight through a CO₂ continuum. In this work the droplet dynamics has been studied for a single droplet of CO₂–acetone solution falling in a flowing CO₂ environment in terms of variations in its concentration, temperature and size due to the two-way mass transfer of CO₂ and solvent. A model based on the SAS mechanism of simultaneous mass and heat transfer has been simulated to study the effects of the thermodynamic states and the individual flow rates of CO₂ and solution. The hydrodynamics of the droplet and the convective mass and heat transfer have been combined in the model to ascertain the individual number of moles of CO₂ and solvent transferred and their directions at any instant of time during the flight. The effects of process parameters have been analyzed for the initial droplet size of the solution. The swelling or shrinking of the droplet has been analyzed with time till the solvent is completely evaporated, in the pressure range of 71–350 bar, temperature range of 313–333 K, SC CO₂ flow rate of 0.1136–1.136 mol/s and the ratio of the volumetric flow rates of CO₂-to-solution in the range of 100–1000. The mole fraction of CO₂ attained inside the non-isothermal droplet has been analyzed with time, which is needed in the design of supersaturaton and nucleation kinetics in the SAS process.     

Relationship between the structure and the swelling of polyvinyl alcohol fibres

Conclusions 1. The kinetics of the swelling of PVA fibres in aqueous sodium sulphate solution can be characterised fairly accurately by a first-order kinetic equation.2. The anisotropy of swelling and the initial rate of swelling of PVA fibres depend on the orientation and the supermolecular structure of the fibres. These magnitudes can be used as characteristics of the structural changes in the fibres caused by their drawing.3. The coefficients of the rate of swelling of transverse sections of PVA fibres not subjected to heat treatment are in direct relationship with the strength of the fibres.S.M. Kirov Leningrad Institute for the Textile and Light Industries. Translated from Khimicheskie Volokna, No. 2, pp. 23–25, March–April, 1969.