Manufacture of Granulated Chitosan

Conditions for dry-wet spinning of spherical chitosan granules 0.5–2.0 mm in diameter into a two-layer spinning bath consisting of immiscible liquids are proposed, where an organic liquid, decane in particular, is the upper layer of the bath while a solution of ammonium hydroxide is the lower layer. The possibility of obtaining chitosan microgranules from 2 to 30 µm in diameter by emulsification of a solution of chitosan in decane or a solution of an anion-active surfactant — sodium dodecyl sulfate — is demonstrated. The effect of the molecular weight and concentration of the solutions on the granule-forming power of chitosan is established. A 6% solution of chitosan with a molecular weight of 200 kD is recommended for further studies.__________Translated from Khimicheskie Volokna, No. 5, pp. 26–29, January–February, 2005.     

Causes of gelation in solutions of acrylonitrile copolymers

The effect of aluminum and some other metals on gelation in spinning solutions in production of the polyacrylonitrile fiber nitron-S was investigated. It was found that gelation in industrial spinning solutions is caused by the aluminum—iron electric pair contained in the filter press so that the aluminum lons formed cross-link the macromolecules of the acrylonitrile copolymers. It was shown that separation of the electric pair reduces gelation and consequently increases the stability of formation and improves the quality of the fiber.All-Russian Scientific-Research Institute of Synthetic Fibers, Tver'. Translated from Khimicheskie Volokna, No. 4, pp. 26–28, July–August, 1992.     

Syntheses and the Main Properties of Fiban Fibrous Ion Exchangers

The works on synthesis and main properties of fibrous ion exchangers are reviewed in the paper. The main attention is paid to the FIBAN materials found practical applications in water treatment and air purification processes. The following methods for preparation of ion exchange fibers have been considered: mechanical mixing of inert fiber‐forming polymer solutions or melts with finely dispersed ion‐exchangers with their following spinning into fibers; preparation of composite fibers containing polymeric reinforcement in the polyelectrolyte body; spinning of specially prepared polymers containing ionizable groups and having fiber‐forming properties; grafting of ionogenic polymers (or polymers in which ionogenic groups can be introduced after grafting) onto polymer chains of the existing polymer fiber; polymer analogues conversion of existing polymeric fibers by introducing in their structure ionizable functional groups. Conditions for preparation of ion exchange fibers with high exchange capacity, optimal swelling and acceptable mechanical properties have been outlined.     

Optimizing the process of filtering spinning solutions

Conclusions The question of optimizing the spinning solution filtration process with respect to a production criterion — the maximum gain in commercial production (profit) — has been examined.It has been shown methodically and experimentally that attainment of the maximum yield of fibre of highest quality as a result of increasing the cleanness of the spinning solution is attended with a deviation from the maximum profit.A procedure has been worked out, and specific example given, for calculating the optimum values of the filtration surface and charge density for typical manufacturing situations. It is recommended to use this procedure in plants which produce viscose, acetate, nitron, or other fibres.Translated from Khimicheskie Volokna, No. 6, pp. 8–12, November–December, 1985.     

Effect of spinning temperature and blend ratios on electrospun chitosan/poly(acrylamide) blends fibers

We report the formation of non-woven fibers without bead defects by electrospinning blend solutions of chitosan and polyacrylamide (PAAm) with blend ratios varying from 75 wt% to 90 wt% chitosan using a modified electrospinning unit wherein polymer solutions can be spun at temperatures greater than ambient up to 100 °C. Electrospinning at elevated temperature leads to further expansion of the processing window, by producing fibers with fewer defects at higher chitosan weight percentage in the blends. Effects of varying blend ratios, spinning temperatures, and molecular weights on fiber formation were studied and optimum conditions for formation of uniform non-woven fiber mats with potential applications for air and water filtration were obtained. Uniform bead-less fiber mats with fiber diameter as low as 307 ± 67 nm were formed by spinning 90% chitosan in blend solutions at 70 °C.     

海藻酸锌纤维

海藻酸锌纤维是一种具有优良生物活性的功能性纤维材料,可以通过湿法纺丝直接制备,也可以通过对海藻酸钙纤维进行离子交换间接制备。在间接法制备海藻酸锌纤维的过程中,可以通过控制海藻酸钙纤维与锌盐的质量比例得到含不同浓度锌离子的纤维。由于纤维中含有对伤口的愈合有促进作用的锌离子,海藻酸锌纤维通过持续释放锌离子在医用敷料的生产中有特殊的应用价值。试验结果表明:海藻酸锌纤维在释放锌离子的过程中可以起到抑制细菌增长的作用,在医疗卫生领域具有特殊的应用价值。     

Mathematical modeling and calculation of the spinning solution filtration process in the manufacture of man-made fibres

Conclusions A generalized filtration equation has been obtained, which permits one to carry out mathematical modeling of a broad class of filtration processes of spinning solutions of fibre-forming polymers; it has low values of the error in approximation.On the basis of the results of mathematical modeling, a procedure has been worked out for evaluating the complex mechanism of the filtration process, using which it is possible to carry out a comparative analysis of the experimental data and to take into account (quantatively) the effect of technological conditions on the filtration process.The extremeness of the behavior of the basic characteristics of filtration equipment as a function of change in filtration rate, which characterizes the operating regime of a filter, has been demonstrated.The use of the magnitude of specific costs as an optimicity criterion in designing and rational construction of filtration schemes is soundly based.Program provision has been devised for calculating and making an analysis of the characteristics of apparatus design in the stage of filtering spinning solutions of fibre-forming polymers using a computer for projected and operating man-made fibre manufacturing.Translated from Khimicheskie Volokna, No. 2, pp. 24–27, March–April, 1985.     

Lignin-based carbon fibers for composite fiber applications

Carbon fibers have been produced for the first time from a commercially available kraft lignin, without any chemical modification, by thermal spinning followed by carbonization. A fusible lignin with excellent spinnability to form a fine filament was produced with a thermal pretreatment under vacuum. Blending the lignin with poly(ethylene oxide) (PEO) further facilitated fiber spinning, but at PEO levels greater than 5%, the blends could not be stabilized without the individual fibers fusing together. Carbon fibers produced had an over-all yield of 45%. The tensile strength and modulus increased with decreasing fiber diameter, and are comparable to those of much smaller diameter carbon fibers produced from phenolated exploded lignins. In view of the mechanical properties, tensile 400–550 MPa and modulus 30–60 GPa, kraft lignin should be further investigated as a precursor for general grade carbon fibers.     

Review of some specific characteristics of conducting chemical fibers

The analysis of the domestic and foreign publications on conducting chemical fibers showed that their electrophysical properties are a function of the method of fabrication (the temperature-mechanical effects to which they are exposed during spinning, finishing, and processing into articles) than of the composition to a much greater degree. For carbon black-filled fibers containing more than 20 wt. % filler, the specific electric resistance differs by several orders of magnitude even for the same polymer support.All-Russian Scientific-Research Institute of Polymer Fibers, Mytishchi. Translated from Khimicheskie Volokna, Vol. 25, No. 1, pp. 25–29, January–February, 1993.     

Purification of spinning baths in production of dyed fibers from solutions of polymers

Possible methods of purification of dyes from spinning baths in production of fibers from solutions of polymers were examined. The outlook for the adsorption method of purification of spinning baths and optimum versions of the equipment formulation were demonstrated.All-Russian Scientific-Research Institute of Synthetic Fibers, Tver'. Translated from Khimicheskie Volokna, No. 4, pp. 22–26, July–August, 1992.     

Polarization-optical methods of investigating structure-formation kinetics in polymer systems

Conclusions Contemporary rapid optical methods have been developed for investigating structural transformations in the precipitation of polymers from solutions, structure study and monitoring during thermal and deformational actions on polymer solutions, films, and fibres.Application of these methods makes it possible to determine basic structural parameters — anisotropy, orientation, size and morphology of supermolecular structures; these characterize operational properties of fibres and films.The experimental assemblies devised on the basis of optical methods with photographic or photoelectric recording of the transmitted and scattered light have improved metrological characteristics; they are universal, and are used to monitor fast-occurring processes of structure-formation in spinning fibres and films without interference into the investigated system.Translated from Khimicheskie Volokna, No. 4, pp. 6–10, July–August, 1986.     

Change in structure of polypropylene during processes of fibre spinning by the high-speed method

Conclusions Conditions for preparing polypropylene fibres from polymers of various structural modifications, orientations, and crystallinities at spinning speeds of 1000–5000 m/min have been studied experimentally.The investigated fibres are characterized by a high degree of crystallinity and orientation of the crystalline regions.Depending on fibre spinning speed, a transition is observed through definite morphological structures — from spherulitic to a typical fibrillar structure, which is formed at very high spinning speeds.Translated from Khimicheskie Volokna, No. 6, pp. 47–49, November–December, 1989.     

Fibers from a mixture of cellulose triacetate and polystyrene

Conclusions The introduction of a nonfiber-forming substance — polystyrene — into cellulose triacetate does not cause the formation of long microfibers in the polymer matrix; the polystyrene is distributed along the fiber axis in the form of stretched-out regions.The addition of polystyrene helps increase the strength figures for triacetate fibers by more than 20%.Translated from Khimicheskie Volokna, No. 4, pp. 37–38, July–August, 1983.     

Technological bases for realizing the preparation of bulk-profiled yarns on LPM-15 modernized industrial lines

Conclusions A fundamentally new type of fibrous materials — bulk fibrillated yarns — can be produced on the basis of modernized LPM-15 lines.The significant possibilities for variation in the make-up of compositions make it possible to use essentially scrap secondary raw material or waste plastics. Prospectively, bulk fibrillated yarns can receive just as wide circulation as film-process fibrillated yarns from polypropylene or other polymers.Translated from Khimicheskie Volokna, No. 5, pp. 47–50, September–October, 1989.     

Formation of melt and solution spun polycaprolactone fibers by centrifugal spinning

Nano‐ and microfibers have a myriad of applications ranging from filtration, composites, energy harvesting, to tissue engineering and drug delivery. Electrospinning, the most common method to produce such fibers, has many limitations including low fiber output and solvent dependency. Centrifugal spinning is a new technique that uses centrifugal forces to form nano‐ and microfibers both from solution and the melt. In this work, the effect of melt temperature, collector distance, rotation speed, and concentration (for polymer solutions) of polycaprolactone were evaluated with respect to fiber morphology, diameter, alignment, and crystallinity. The fiber diameter generally decreased with increasing rotation speed and reduced concentration. Crystallinity for spun fibers decreased compared to the bulk polymer. Fiber alignment was improved with rotation speed for the melt‐spun fibers. The fiber mats were evaluated as tissue scaffolds with neuronal PC12 cells. The cells adhered and extended neurites along the fibers for both melt and solution‐spun scaffolds. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41269.     

Fabrication and characterization of melamine formaldehyde fibers with enhanced mechanical properties and high fire resistance by dry spinning

High-performance melamine formaldehyde (MF) fibers are successfully produced by innovatively utilizing dry spinning with high efficiency and low emission. Three ways are adopted to enhance the mechanical performance of MF fiber. First, MF resin is modified by introducing flexible chain segments into MF three-dimensional network and reducing the network crosslink density. Second, the energy dissipation capacity of the MF fibers is improved through constructing of hydrogen bond networks among modified MF resin, nano-SiO₂, and/or polyvinyl alcohol and forming interpenetrating network structures of modified MF resin and nano-SiO₂. Third, homogeneous and stable spinning solutions without phase separation are prepared, which can reduce interior defects of MF fibers. The chemical changes in the spinning solutions with increasing temperature and the rheology behavior of the solutions are investigated. In addition, the effects of fiber compositions on microstructure, morphology, and the properties of the MF fibers are also systematically studied. The prepared MF fibers possess high fire retardancy (i.e., limiting oxygen index >40%), thermal stability (i.e., T_max >360°C), and mechanical properties (i.e., tensile strength >2.5 cN/dtex).     

Composite Aluminum Oxide Ceramics with Fibrous Components

The reactions between oxides in the Al₂O₃ – ZrO₂ – MgO system in the production of ceramics using fibrous components are studied. It is established that under heat treatment of the ternary systems, the component stabilizing the tetragonal structure of zirconium dioxide reacts with the aluminum oxide matrix and forms spinel interlayers on the fiber – matrix interface. The use of highly disperse fibers as the initial component for producing ceramics and as a fibrous filler additive introduced into a gel-like matrix makes it possible to obtain composite ceramics of elevated strength.     

Filterability of cellulose cuprammonium solutions through media with various pore sizes

Conclusions The Cu/cellulose ratio in a cuprammonium spinning solution considerably affects the viscosity and filterability of the solution. On increase in this ratio, the viscosity of the solution is reduced, the rate of filtration is increased, and the filtration hold-up index is reduced.On storage of cuprammonium spinning solutions for 5 days, the filtration hold-up index is essentially not increased.Filtration of heated solutions, even with subsequent cooling, is impaired at temperatures over 40°C; this is connected with decomposition of the unstable cuprammonium complex and deposition of a precipitate of CuO, which leads to a gradual clogging of the filter medium holes.Translated from Khimicheskie Volokna, No. 4, p. 30, July–August, 1983.     

Effect of the conditions of spinning of polyester fibres on the longitudinal velocity gradient

The velocity gradient changes as a function of the conditions of spinning PETP, and the value can increase from several tens to hundreds of units in the order LSS (low-speed spinning)—MSS (medium-speed spinning)—HSS (high-speed spinning). A combined increase in the longitudinal velocity gradient, orientation, and relaxation time is observed with an increase in the speed of spinning PETP. It was shown that crosslinking of PETP is determined by the character of the strain in the longitudinal velocity gradient field. The features and common points of spinning of PETP monofilament and complex fibre and their cross-linking in a longitudinal velocity gradient field were determined.All-Russian Scientific-Research Institute of Synthetic Fibres, Tver'. Translated from Khimicheskie Volokna, No. 5. pp. 30–33, September–October, 1996.     

A new softening agent for melt spinning of softwood kraft lignin

Kraft lignin obtained from the pulping of wood is an interesting new precursor material for carbon fiber production because of its high carbon content and ready availability. However, continuous spinning of softwood kraft lignin (SKL) has been impossible because of its insufficient softening characteristics and neat hardwood kraft lignin (HKL) has required extensive pretreatments to enable fiber formation. Softwood kraft lignin permeate (SKLP) and hardwood kraft lignin permeate (HKLP), fractionated by membrane filtration, were continuously melt spun into fibers. To improve the spinnability of SKL and HKL, HKLP was added as a softening agent. SKL‐ and HKL‐based fibers were obtained by adding 3–98 wt % HKLP. A suitable temperature range for spinning was 20–85°C above the T_g of the lignin samples, and this range gave a flawless appearance according to the SEM analysis. Smooth, homogeneous fibers of SKLP, HKLP, and SKL with HKLP were successfully processed into solid carbon fibers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013