Effect of surface-active substances on the fibre-forming process and properties of nitron fibre

Conclusions The effect of surface-active agents on the surface tension of polyacrylonitrile (PAN) spinning solutions has been studied.It has been found that introducing SAS into the precipitation bath increases fibre-formation stability. The use of SAS as modifying additives to the spinning solution and into the precipitation bath leads to an increase in the uniformity of spun fibre properties.The possibility of reducing the linear density of Nitron fibres on introducing SAS into the spinning solution and the precipitation bath has been demonstrated.Translated from Khimicheskie Volokna, No. 3, pp. 24–26, May–June, 1985.     

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.     

Preparation of polyacrylonitrile fibre by spinning into organic baths

Conclusions -- The spinning of polyacrylonitrile copolymers into organic baths containing dimethyl sulfoxide and isopropyl alcohol has been investigated. It has been found that the optimum DMSO:IPA ratio in the precipitation bath is 60:40% by wt..-- It has been discovered that the strength of the spun yarn is higher the lower the jet stretch.-- The effect of temperature on orientation stretch ratio has been studied. It has been shown that the optimum temperature for heat stretching of PAN yarn lies in the range 155–160°C.-- The dimethyl sulfoxide content of yarn has been determined by technological transitions. In the final yarn it does not exceed 0.3–1.2% by wt.VNIIPV. Translated from Khimicheskie Volokna, No. 3, pp. 15–16, May–June, 1991.     

Investigation of the structure of polyacrylonitrile fibres modified with sodium salts by the method of water vapor or dye sorption

Conclusions Figures for the capillary porosity of polyacrylonitrile fibre which has been modified with salts of alkaline metals have been determined.The introduction of salts of alkaline metals into freshly spun fibre aids in the formation of a more porous structure for it.The nature of both the cation and also of the anion exerts and effect on the porosity of the modified fibres.Translated from Khimicheskie Volokna, No. 2, pp. 35–36, March–April, 1990.     

Acid treatment of polyacrylonitrile tows with subsequent high-temperature washing

Conclusions -- A method has been proposed for combined short-term acid treatment of polyacrylonitrile tow with a sulfuric acid solution of elevated concentration. Intensification of the process of acid diffusion is achieved by subsequent high-temperature washing.-- The process of combined acid treatment and washing of fibre has been studied in which washing begins before completion of acid diffusion to the tow axis. It has been shown that in acid treatment during the course of the reduced time of 0.4 · 10⁴ sec/cm² (which corresponds to 0.5–2 sec) and subsequent washing with water having a temperature of 50–60°C, complete acid treatment of the tow is achieved.Translated from Khimicheskie Volokna, No. 4, pp. 25–26, July–August, 1991.     

Optical bleaching of freshly spun polyacrylonitrile fibres

Conclusions A new effective optically bleaching substance of the cationic type in liquid form has been developed.The advisability of using it to bleach freshly spun polyacrylonitrile fibre by a continuous method has been demonstrated.Translated from Khimicheskie Volokna, No. 2, pp. 42–43, March–April, 1990.     

Structure of twisted polyacrylonitrile fibres modified with cadmium sulfate and ethylenediamine

Conclusions Treatment of freshly spun polyacrylonitrile gel-fibre with CdSO₄ solution leads to an increase in its thermal stability.Treatment with a mixture of CdSO₄ and ethylenediamine solutions causes the development of structure nonuniformity and twisting of the fibre.Translated from Khimicheskie Volokna, No. 2, pp. 34–36, March–April, 1989.     

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.     

Effect of metal salts on the dyeing of freshly spun polyacrylonitrile fibre with acid dyes

Conclusions The effect of the metal cations Al³⁺, Zn²⁺, and Cr³⁺ on the process of dyeing freshly spun PAN fibres with acid dyes has been studied. It has been found that the greatest amount of dye is fixed on the fibre when Al³⁺ ions are introduced into the dye bath.On the basis of analysis of the IR spectra of the dyed fibres, a mechanism has been proposed for the interaction of both the metal cations and also of the dye with PAN fibre. It has been found that the metal cation is bonded with the fibre both by an ionic bond with the—COOH groups and also by a coordination bond with >C=0 groups of the polymer substrate.Translated from Khimicheskie Volokna, No. 6, pp. 13–14, November–December, 1986.     

Change in structure of polyacrylonitrile fibres on treatment with alkali metal salts

Conclusions Treatment of polyacrylonitrile fibre with alkali metal salts helps to change its supermolecular structure.As a result of treatment of the freshly spun gel-fibre with alkali metal salts and subsequent drying in the free condition, the degree of orientation of the structural elements is not reduced.Translated from Khimicheskie Volokna, No. 5, pp. 35–36, September–October, 1989.     

Effect of calcium salts on the thermal properties of polyacrylonitrile fibres

Conclusions -- On interaction of CaCl₂ with polyacrylonitrile fibres, strong chemical bonds are formed between the polymer macromolecules.-- The introduction of Ca(II) into the fibre helps reduce polymer deformation up to a temperature of 200°C and helps increase its thermal resistance.Translated from Khimicheskie Volokna, No. 6, pp. 51–52, November–December, 1990.     

Coagulation Mechanism in Wet Spinning of Fibres

Spinning baths are divided into three types as a function of the coagulating (desolvating) power: hard, soft, and ultrasoft. The concentration of precipitant c_p in hard spinning baths is two times higher than the critical (threshold) precipitation concentration c_cr, i.e., c_p > 2c_cr. Precipitation takes place with formation of a boundary line (precipitation front) which coincides with the critical supersaturation line — spinodal. The fibre is characterized by large fibril size and high porosity. Soft baths are realized when the concentration of precipitant in the bath is less than two and more than one critical precipitation concentration, i.e., c_cr > c_p > 2c_cr. Precipitation takes place according to a frontal mechanism with initial formation of a liquid segment in the spun fibre. In spinning into soft baths, the optimum conditions are created for formation of fibres with a small-fibril structure and elevated physicomechanical indexes. At a concentration of precipitant below c_cr but above c_e (equilibrium), the precipitant accumulates on the fibre and precipitation takes place over the entire volume, without formation of a precipitation front. The fibre obtained is characterized by high porosity. __________ Translated from Khimicheskie Volokna, No. 4, pp. 26–31, July–August, 2005.     

Use of calcium salts as antistatic preparations

Conclusions Treatment of freshly spun polyacrylonitrile fibre with calcium salts affords the possibility of improving the antistatic properties of the fibre without the use of an antistat.In the process of fibre treatment, both physical sorption and also chemical reaction of the fibre with the calcium cations take place.Translated from Khimicheskie Volokna, No. 4, pp. 24–25, July–August, 1986.     

Copolymerization of acrylonitrile,methyl acrylate,and itaconic acid in thiocyanate solutions in the presence of hydrolyzed nitron fibre waste

Conclusions -- The kinetics of the copolymerization process of AN, MA, and IA in the presence of hydrolyzed Nitron fibre characterized by various degrees of hydrolysis has been studied. It has been found that introducing H-PAN into the reaction mixture leads to an increase in degree of conversion in the copolymerization process and to an increase in molecular weight of the copolymer synthesized.-- Fibre has been spun from the products of joint copolymerization of AN, MA, and IA in the presence of H-PAN with various concentrations of these in the solution and various SEC values. Introducing up to 5% by wt. of an H-PAN with an SEC not over 0.2 meq/g into the reaction mixture aids in obtaining fibres with satisfactory properties and opens up the possibility of still another way of solving the question of regenerating wet Nitron fibre wastes.Translated from Khimicheskie Volokna, No. 4, pp. 17–19, July–August, 1991.     

Morphological features of the structure of fibres prepared from solutions of cellulose in methylmorpholine oxide

Conclusions Structural features of fibres spun from solutions of cellulose in N-methylmorpholine-N-oxide into isopropyl alcohol have been studied.It has been found that the structural porosity of these fibres is determined to a considerable degree by the temperature of the precipitant — isopropyl alcohol.Translated from Khimicheskie Volokna, No. 1, pp. 27–28, January–February, 1988.     

Deformation properties of modified polyacrylonitrile fibres

Conclusions Deformation properties of polyacrylonitrile fibres modified with alkali metal salts have been studied.The introduction of alkali metals by treatment of freshly spun gel-fibre with solutions of the appropriate salts aids in loosening fibre structure.Both the form of cation and also of the anion in the salt introduced affect the deformability of the modified fibres.Translated from Khimicheskie Volokna, No. 4, pp. 40–41, July–August, 1989.     

Mechanism of polyacrylonitrile fibre spinning by the thiocyanate method

Conclusions 1. The process of spinning PAN fibres by the thiocyanate method into baths with various precipitating powers has been studied. The mildness and severity of the baths have been varied by varying the NaSCN concentration from 12 to 24%, and also varying the temperature from 5 to 20°C.2. A dependence of the threshold precipitation concentration on polymer content of the spinning solution has been shown. At a polymer content of 13.5%, the threshold precipitant (water) concentration at which precipitation begins is 63%.3. At NaSCN concentrations above 22–24% in the precipitation bath, a precipitant concentration is established on the surface of the forming fibre at the moment of contact between the spinning solution and the precipitation bath which is below the threshold value, and precipitation begins after a certain time, during the course of which, as a result of diffusion, the precipitant concentration is raised to the threshold level.4. On softening the spinning conditions by increasing the NaSCN concentration in the precipitation bath up to a certain limit, a fibre is formed with a more perfect fibril structure, which ensures obtaining a stronger carbon fibre.5. Extreme softening of the spinning conditions leads to an increase in fibre porosity. The suggestion is advanced that this phenomenon is connected with a change in the mechanism of spinning solution phase breakdown where, along with polymer precipitation in the form of a solid phase, partial precipitation in the form of a liquid phase takes place.Translated from Khimicheskie Volokna, No. 5, pp. 3–7, September–October, 1993.     

Laws governing the process of spinning isotropic pitches

Conclusions -- A procedure has been developed for calculating the specific volume of the flowing zone of fibre in spinning from the melt.-- The unequivocal connection between the specific volume of the flowing zone of spun fibre and the strength of the final fibre from pitches indicates that to attain higher strength, it is necessary to create more severe conditions for fibre cooling.-- It has been found that fibres from pitches with a softening point above 200°C are more sensitive to fluctuations in parameters of the spinning process.VNIIPV. Translated from Khimicheskie Volokna, No. 3, pp. 41–42, May–June, 1991.     

Dynamics and kinematics of the process of spinning man-made fibres by the wet method

Conclusions The change in yarn tension has been calculated theoretically as a function of the precipitant concentration in the precipitation bath. For the investigated system (polyoxadiazole), the calculated range in change of tension on transition from mild to severe spinning conditions is 0.45×10^–4<F<0.58×10^–3 N (under conditions of constant rate of take-up).It has been shown that under severe spinning regimes the assigned rate of take-up is attained immediately on exit from the spinneret channel.The effect of yarn tension on expansion (compression) of the polymer jet after exit from the channel has been qualitatively investigated. For polyoxadiazole, the coefficient of jet expansion (compression) varies within the range 0.53<B*<1.77, depending on F.Translated from Khimicheskie Volokna, No. 2, pp. 17–19, March–April, 1989.     

Physicomechanical properties of polyethylene gel-fibers at various stages of orientation stretch

Conclusions Diffusion coefficients of the precipitant in binary and ternary acrylonitrile systems have been determined at a constant temperature and over a wide range of solvent concentrations in the precipitation bath. The threshold precipitant concentration has been evaluated for each polymer-solvent-precipitant system.It has been shown that the dependence of diffusion characteristics and of fibre strength has the character of an indirect correlation.Tashkent Textile and Light Industry Institute. Translated from Khimicheskie Volokna, No. 2, pp. 19–22, March–April, 1992.