Application of the turbidity spectrum method to construct experimental phase diagrams for polymer-solvent systems

Conclusions Phase conversions in solutions of modified PPTA and PABI have been investigated by the turbidity spectrum method.Fragments of experimental phase diagrams have been given for PPTA-M and PABI in sulfuric acid.Translated from Khimicheskie Volokna, No. 4, pp. 15–16, July–August, 1986.     

Effect of aqueous treatment on the relaxation properties of fibres based on an aromatic polyamide

Conclusions The effect of water treatment on the relaxation properties of heat-treated fibre based on poly-p-phenylenebenzimidazole (PABI) has been studied by the dynamic mechanical loss method.It has been shown that water treatment leads to a disordering of the highly-oriented state of PABI fibre.The suggestion has been made that the amorphous polymer structure is heterogeneous.Translated from Khimicheskie Volokna, No. 2, pp. 33–34, March–April, 1988.     

Investigation of fibres based on rigid-chain polyamides by the wide-line nmr and ultrasonic acoustics

Conclusions -- A dependence of the second moment of the NMR line on the angle between the fibre axis and the magnetic field has been given; the structural coefficient C ₀, C ₂, and C ₄ have been calculated for fibres based on poly-p-phenyleneterephthalamide and poly-p-benzamide at temperatures of –196 and +20°C and for Kevlar-49, from –196 to +400°C.-- The intramolecular structural coefficients C ₀ ^im, C ₂ ^im, and C ₄ ^im have been calculated theoretically, and the orientation parameters and and the acoustic orientation factor f have been obtained, values for which indicate a high degree of orientation of the macromolecules in fibres.-- The smaller values of the second moment of the NMR line for PABI as compared with fibres based on PPTA in the temperature region 250–380°C indicate a more mobile structure for the PABI.-- In the range from –196 to +20°C thermal action leads to a more important change in the coefficient C ₀ for Kevlar-29 and Kevlar-49 as compared with PABI; this is apparently connected with thermal expansion in planes having a predominant concentration of van der Waals bonds for Kevlar-29 and Kevlar-49.Translated from Khimicheskie Volokna, No. 4, pp. 23–26, July–August, 1990.     

High-modulus,high-strength carbon fibre based on polyacrylonitrile

Conclusions -- The effect of the method of preliminary heat treatment and of the structure of fibre being subjected to boronation on the strength of high-modulus carbon fibres has been shown.-- A moreoriented structure of the fibre subjected to boronation and stress relaxation during the heat-treatment process aid in bringing about an increase in strength of high-modulus carbon fibre up to 3.0–3.5 GPa at an elastic modulus greater than 700 GPa.All-Union Scientific Research and Project-Technological Institute of Electrical Carbon Articles, Élektrougli. Translated from Khimicheskie Volokna, No. 3, pp. 29–30, May–June, 1991.     

Polyelectrolyte swelling of polyamidobenzimidazole

Conclusions An extreme character of the swelling of PABI fibres in DMAc-water mixtures has been detected. The maximum is observed in the region of a 10% water content.The peculiarity in swelling has been explained by the manifestation of a polyelectrolyte nature of the polymer.Translated from Khimicheskie Volokna, No. 5, pp. 34–35, September–October, 1987.     

Specifics of the thermal oxidative decomposition and burning of fabrics from fibre mixtures

Conclusions It has been shown that on introducing up to 12% by wt. PCA into a fibre from a mixture of two polymers (PPTA and PCA), a marked increase in the fire-protective characteristics of the fibre is observed.Differences have been established in the mechanism of fire-protective action of the phosphorus-containing combustion retarder for materials from a mixture of cellulosic fibre and PPTA and fabrics from a mixture of cellulosic fibre and a fibre from a mixture of PPTA and PCA.Translated from Khimicheskie Volokna, No. 2, pp. 40–42, March–April, 1990.     

Fabrication of fibres from sulfuric acid solutions of copolyamides containing polyamide—Benzimidazole units and their heat treatment

Fibres based on the aromatic rigid-chain polyamides PABI/PPTA, PABI/PPTA-Cl, and PABI/PPTA-Cl/PPTA with a strength of 130–150 cN/tex were fabricated by spinning from LC sulfuric acid solutions through an air gap, demonstrating the induced elastic character of deformation with tensile stress greater than 50 cN/tex. The fibres obtained can be strengthened significantly as a results of heat treatment, and the best variant is preliminary thermal drawing at 90–175°C with subsequent heat treatment without tension. This heat treatment increases the strength of the fibres to 240–266 cN/tex and the modulus of elasticity to 145 GPa. Termotex, Terlon, Mytishchi. Translated fromKhimicheskie Volokna, No. 1, pp. 8–11, January–February, 1999.     

Effect of defects in high-modulus viscose fibres on their physicomechanical properties

Conclusions -- As a result of microscopic investigation of high-modulus viscose fibres, it has been found that the various types of defectiveness in them amounts to 90%.-- Four characteristic groups of fibre defects have been determined: breakdown in morphological structure - 25%; gas-bubble content - 20%; mechanical contaminants from the viscose - 25%; and mechanical contaminants from the precipitation bath - 20%.-- It has been shown that the presence of defects in the fibre reduces its strength characteristics from 7.7 to 33%, depending on the form of defect and increases nonuniformity in these figures.Translated from Khimicheskie Volokna, No. 4, pp. 49–51, July–August, 1991.     

Structural features and properties of fibres based on mixtures of an ethylene-vinylacetate copolymer with a copolyamide

Conclusions By x-ray analysis, we have confirmed the previously expressed hypothesis of a forced deformation of SÉVA on flow of an SÉVA—SPA mixture as a result of specific interaction of the components at the interface: the degree of orientation of the SÉVA macromolecules in the microfibres is higher than in a monofilament from the starting polymer.It has been shown that ultrathin SÉVA fibres are characterized by a porosity, caused by micro- and macro-hollows, which causes a decrease in their strength as compared with the strength of ordinary SÉVA fibres.Kiev Technological Institute for Light Industry. Translated from Khimicheskie Volokna, No. 2, pp. 39–41, March–April, 1992.     

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.     

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.     

Preparation of reinforced composite yarns based on polymer mixtures

Conclusions The possibility has been demonstrated of preparing self-reinforcing composite fibres on spinning the following mixtures from the melt: polycaproamide—polyoxymethylene; copolyamide—polyoxymethylene; or an ethylene—vinylacetate copolymer—polyoxymethylene, due to the formation of ultrathin polyoxymethylene fibres in the bulk of the other polymer on flow of the mixture melt. Because of the presence of microfibres, an increase in the orientation stretch ratio of the composite fibre is observed, plus a synergistic increase in its strength and initial modulus.In articles from polymer mixtures with a well-developed interfacial layer and a strong interaction of the components in it, the maximum reinforcement will take place only at a low (up to 10%) content of the disperse phase polymer. In the absence of a strong interaction, the maximum reinforcing effect is observed when there is a predominant formation of ultrathin fibres of continuous length by the disperse phase polymer.The presence of films decreases the rise in strength and modulus of the composite fibre to a greater extent than the presence of short fibres.Translated from Khimicheskie Volokna, No. 3, pp. 35–37, May–June, 1984.     

Structure of carbon fibres

Conclusions -- Carbon fibres have been examined as carbon band oriented amorphous-crystalline polymers.-- Characteristic regions in the formation of the structure of carbon fibres have been established, plus the interconnection between structural parameters.-- The components of preferential orientation of carbon fibres have been marked out, and a systematization of orientation in the transverse section of fibres has been presented.-- The character of change in axial component of texture with change in treatment temperature has been given, plus the connection between it and the elasticity and strength of fibres.-- A characteristic has been proposed for evaluating the activity of the surface of carbon fibres.Combustible Minerals Institute. Translated from Khimicheskie Volokna, No. 3, pp. 26–29, May–June, 1991.     

Effect of tow shrinkage in the setting zone on properties of high-modulus viscose fibre

Conclusions In the manufacture of HMV fibre, it is advisable to use a two-zone apparatus for plasticized stretch; in the first zone of this, plasticized stretch is carried out; in the second, a structure setting at an assigned shrinkage.The use of this apparatus makes it possible, at practically unchanged strength indices, to regulate the elongation of the fibre produced, and also, to a definite degree, its twist, which is important in producing fibres of various assortments. The output of the flow line is increased by 10–12%.Translated from Khimicheskie Volokna, No. 2, pp. 38–39, March–April, 1989.     

Modification of the surface of polyacrylonitrile fibres before oxidation with a dispersion of technical carbon

Conclusions -- The possibility of using dispersions of technical carbon in a medium of ethylene glycol, an aqueous solution of a binder of the Sokrat-binder type, or an alcoholic solution of polyvinyl butyral for the modification of polyacrylonitrile fibres before thermo-oxidation, which ensure obtaining a stable and uniform carbon-containing film on the fibre surface has been established.-- The use of ethylene glycol as the dispersion medium leads to retention of the strength of fibres after heat treatment at the level of the starting fibres and reduces the specific bulk electrical resistance.-- Application of aqueous solutions of the Sokrat-binder aids in preserving fibre strength during thermo-oxidation. The linear density of the fibre and its ability to be oxidized are increased, but the specific bulk electrical resistance and elongation are reduced.-- The use of alcoholic solutions of polyvinyl butyral makes it possible not only to preserve fibre strength but also to considerably increase it during the thermo-oxidation process. Thereupon, the linear density of the fibres is significantly reduced, and at a dispersion content of 10% by wt. technical carbon, one can obtain electrically-conducting oxidized fibres.Translated from Khimicheskie Volokna, No. 4, pp. 36–37, July–August, 1991.     

Effect of the structure of nonwoven outdoor materials on their thermally protective properties

Conclusions The thermal resistance of needle-punched, nonwoven, outdoor textile materials (NTM) of various fibre composition, surface density, and thickness has been studied. The concentration of a polymeric binder based on SKS-65GP latex has been varied within a broad range.It has been found that the thickness of an NTM exerts the greatest effect on its thermal resistance; surface density and fibre mix composition exert a smaller effect. The chemical nature and structural factors of the fibre show up in its packing in a unit volume of the NTM.The binder concentration markedly affects the thermal resistance of an NTM. It is suggested that a change in the type of fibre adhesion with increase in binder concentration leads to a change in the structure of the fibre-air cell.Translated from Khimicheskie Volokna, No. 6, pp. 36–38, November–December, 1987.     

Structure of hydrocellulose fibres prepared from cuprammonium solutions by the spin probe method

Conclusions The structure of hydrocellulose fibres has been investigated by the spin probe method.Broad possibilities of this method for investigating the dependence of fibre structure on preparation conditions have been demonstrated.Translated from Khimicheskie Volokna, No. 1, pp. 28–30, January–February, 1988.     

Accelerated determination of the viscosity of poly-p-phenylene terephthalamide

Conclusions A procedure has been proposed for determining the viscosity of dilute PPTA solutions which is based on dissolving the reaction mixture formed in the polymer synthesis process in sulfuric acid.The procedure makes it possible to considerably shorten (by a factor of 10) the time for determining the viscosity of PPTA solutions.Translated from Khimicheskie Volokna, No. 3, pp. 31–32, May–June, 1985.     

Modification of polyacrylonitrile fibres to improve the properties of carbon fibres prepared from them

Conclusions -- It has been found that treatment of acrylonitrile fibres obtained by the wet dimethyl formamide method before thermal oxidation with inorganic salts considerably changes the properties of the thermally oxidized fibres.-- On treatment of the fibres with an aqueous solution containing copper ion in a reducing medium, their sorptive powers are considerably impaired, the fibre diameter is increased, and the electrical conductivity is increased, plus processes of cyclization and oxidation are accelerated.-- On treatment with a solution of aluminum chloride in the presence of orthophosphoric acid, the fibre structure is made denser and its strength is increased.-- Sodium thiosulfate as a modifier considerably changes the functional composition of polyacrylonitrile fibres; thereupon, a process of structural amorphization takes place.Translated from Khimicheskie Volokna, No. 5, pp. 48–50, September–October, 1991.     

Structural-morphological features of yarn spun from a polyarylenesulfone oxide-polyamidobenzimidazole mixture

Conclusions -- The structural-morphological features of yarns spun from a mixture of fusible polyarylenesulfone oxide (PASO) and polyamidobenzimidazole (PABI) have been studied.-- It has been shown that in yarn containing from 1 to 15% by wt. of PABI belongs to two-phase disperse systems of the matrix type in which the birefringent PABI phase is dispersed in an isotropic matrix consisting of the fusible PASO component.-- It has been found that in freshly spun PASO-PABI yarn at a weight ratio of 60:40 or 50:50, the PABI retains a high degree of molecular orientation, but the PASO is in a weakly oriented state.VNIIPV, Mytishchi. Translated from Khimicheskie Volokna, No. 3, pp. 14–17, May–June, 1992.