Wet Spinning Process Research Articles

Thermochromic luminescent fiber based on yellow thermochromic microcapsules: preparation, properties, and potential application areas

Luminescent fibers are widely used in textile fields because of their excellent luminescence performance. However, the lack of its sensing property limits the fiber’s application. In this work, two rare earth luminescent materials, SrAl2O4:Eu2+, Dy3+ (SAOED) and Sr2ZnSi2O4:Eu2+, Dy3+ (SZSO), were used as luminous sources, and a yellow thermochromic microcapsule (YTM) was used as a light conversion agent to prepare a thermochromic luminescent fiber (TLF) through wet spinning. The micro-morphology of the TLF was analyzed using scanning electron microscopy (SEM). Three particles were uniformly incorporated in the cellulose fibers, which provide the fibers with a rough surface. Interestingly, the YTM content had no negative effect on the breaking strength of the TLF. Nevertheless, as the concentration of YTM increased from 3 to 10 %, the elongation at break tended to decrease. X-ray diffraction (XRD) results indicate that the cellulose matrix and the wet spinning process did not destroy the phase of rare earth luminescent materials in the fiber. The thermodynamic stability and dynamic phase structure were investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The TLF was stable below 100 °C. The fluorescence spectra and absorption spectra measurements show that TLF exhibits good thermochromic luminescence performance. The TLF appeared white at room temperature (25 °C) and emitted green light, but when the temperature increased (50 °C), the fiber faded and emitted indigo light. Herein, the potential application areas of the TLF can be used in optical materials and thermal sensors.

Assembly of Nanofluidic MXene Fibers with Enhanced Ionic Transport and Capacitive Charge Storage by Flake Orientation.

MXenes are an emerging class of highly conductive two-dimensional (2D) materials with electrochemical storage features. Oriented macroscopic Ti3C2Tx fibers can be fabricated from a colloidal 2D nematic phase dispersion. The layered conductive Ti3C2Tx fibers are ideal candidates for constructing high-speed ionic transport channels to enhance the electrochemical capacitive charge storage performance. In this work, we assemble Ti3C2Tx fibers with a high degree of flake orientation by a wet spinning process with controlled spinning speeds and morphology of the spinneret. In addition to the effects of cross-linking of magnesium ions between Ti3C2Tx flakes, the electronic conductivity and mechanical strength of the as-prepared fibers have been improved to 7200 S cm-1 and 118 MPa, respectively. The oriented Ti3C2Tx fibers present a volumetric capacitive charge storage capability of up to 1360 F cm-3 even in a Mg-ion based neutral electrolyte, with contributions from both nanofluidic ion transport and Mg-ion intercalation pseudocapacitance. The oriented 2D Ti3C2Tx driven nanofluidic channels with great electronic conductivity and mechanical strength endows the MXene fibers with attributes for serving as conductive ionic cables and active materials for fiber-type capacitive electrochemical energy storage, biosensors, and potentially biocompatible fibrillar tissues.

Preparation and characterization of nanoclay loaded polyacrylonitrile hollow fiber membranes

New Polyacrylonitrile (PAN) nanoclay hollow fiber membranes were successfully fabricated through the dry-jet wet spinning process. The effects of adding the nanoclay on the hollow fiber mechanical properties and permeation performance and dye removal from water were investigated. Direct red 80, Direct orange 26 and Direct brown 2 dyes were used for dye removal experiments. Field emission scanning electron microscopy (FESEM) was used to analyze the cross-sectional and surface morphology and porosity. X-ray diffraction (XRD) has been used to compare crystalline structure of the fabricated hollow fiber membranes. The results showed that permeation is increased by adding nanoclay to the spinning dope. In addition, hollow fibers spun with lower nanoclay content showed lower hydraulic permeability and higher dye removal efficiency. Tensile strength increased from 1.09 to 2.06 with 3 wt% nanoclay loading.

Thermo‐responsive mixed‐matrix hollow fiber membranes

AbstractUp to date, preparation of thermo‐responsive mixed‐matrix membranes (MMM) has only be described as small scale flat membranes or multi‐step processes for hollow fiber membranes. In this work, the development of thermo‐responsive MMM hollow fibers composed of polyethersulfone as membrane polymer and poly(N‐isopropylacrylamide) (PNIPAM) microgel particles via the wet spinning process is presented. PNIPAM particles are synthesized with (NP‐S, zavg 20°C = 105 nm) and without (NP‐L, zavg 20°C = 250 nm) sodium dodecyl sulfate and their thermo‐responsive behavior is characterized by dynamic light scattering. Particle size (NP‐S, NP‐L), particle content (10%, 15%) and the extrusion pressure in the wet spinning process (1.0–3.0 bar) are investigated as experimental parameters. Reversible thermo‐responsive behavior of the hollow fibers is demonstrated by water permeability measurements at different temperatures (20 and 50°C). The largest switching factors (R) are observed for the hollow fibers containing NP‐L. For 15% NP‐L and 1 bar extrusion pressure, water permeances between 0.5 and 6.0 L m−2 h−1 bar−1 are observed, corresponding to R = 12 and a dextran (500 kDa) rejection of 91% at 25°C.

Preparation and properties of high-performance polyimide copolymer fibers containing rigid pyrimidine and benzoxazole moieties with hydrogen bonding

The utilization of 5-amino-2-(2′-hydroxy-4′-aminophenyl)-benzoxazole (HBOA) as third monomer was beneficial for the introduction of OH-type H-bonding into polyimide (PI) matrix through the copolymerization with 2,5-bis(4-aminophenyl)pyrimidine (PRM) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA). And high-performance PI fibers were successfully fabricated via the dry-jet wet spinning process. The FTIR spectra confirmed that the strong interactions of intramolecular and intermolecular H-bonding existed simultaneously in PI fibers. Moreover, the glass transition temperatures (Tg) of all fibers were within 276–318 °C, and the temperatures at 5% weight loss (T5%) ranged from 574 °C to 604 °C, revealing the remarkable thermal stability of PI fibers. The two-dimensional wide-angle X-ray diffraction (2D WAXD) results illustrated a U-shaped change in the crystallinity (from 32.1% to 12.2% until 33.4%) of PI fibers with increasing HBOA content, which was also reflected in the density variation of fibers. The two-dimensional small-angle X-ray scattering (2D SAXS) patterns demonstrated that the micro-defects in all co-PI fibers profitably decreased in comparison with those in homo-PI fibers. Furthermore, the orientation factor of fibers presented an improvement from 0.843 to 0.899 after incorporating HBOA moiety. When the molar ratio of PRM/HBOA was 7/3, the co-PI fiber exhibited optimum mechanical properties with tensile strength and modulus as high as 4.15 GPa and 125.93 GPa, respectively. Interestingly, the variation in fiber orientation was in line with the same trend as that of mechanical properties of PI fibers, indicating orientation was also a crucial factor to improve the mechanical properties. The relationship between structure and mechanical property was also investigated.

Study on the mechanical and flame retardant properties of a novel carrageenan fiber-CAF-K,Al

Herein, Potassium-Aluminum carrageenan fiber-CAF-K,Al was prepared via wet spinning process with KCl as coagulation bath, AlCl3 as stretch bath and carrageenan solution as spinning dope. The mechanical properties of CAF-K,Al were tested with a mechanical tester and the result indicated that the mechanical strength of CAF-K,Al was higher than that of the control groups CAF-Ba,Ba and CAF-K,Ca. The flame retardant properties of CAF-K,Al were tested by limiting oxygen index, cone calorimeter, thermogravimetric analysis. The results showed that the flame retardant performance of CAF-K,Al was better than those of CAF-Ba,Ba and CAF-K,Ca.

Fabrication of High Specific Electrical Conductivity and High Ampacity Carbon Nanotube/Copper Composite Wires

AbstractA challenge is to integrate Cu with carbon nanotubes (CNTs) and form a free‐standing composite wire. This is achieved by first making a CNT filament using high concentration (20 g L−1 ) CNT dispersion, an acid‐free wet spinning process and then by replacing the polymer with copper using heat based polymer decomposition and periodic pulse reverse electroplating. It is demonstrated that indeed the specific conductivity and the current‐carrying capability (or ampacity) are increased manifold. The multiwalled CNT (MWCNT)/Cu composite wires developed in this paper have electrical conductivity σ ≈ 5.5 × 10 5 S cm−1. These MWCNT/Cu wires are 2/3rd the weight of bulk Cu wires. Their specific electrical conductivity is σρ ≈ 9.38 ×10 4 S cm2 g−1 which is 45% higher than International Annealed Copper Standard Cu. These composite wires have an ampacity of A ≈ 20 × 105 and 4 × 105 A cm−2 for 1.5 and 17 mm gauge length wires, respectively, which is four to six times higher than pure Cu depending on the wire lengths. MWCNTs volume percentage in the MWCNT/Cu wire is about 40%.

Metal salt modified PEDOT: PSS fibers with enhanced elongation and electroconductivity for wearable e-textiles

Continuous wet-spinning process is essential for the further application of intrinsically conductive polymer fibers. Especially, moderate stretchability for poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) materials with inherit rigid chains is an insurmountable challenge. In this work, we report a facile strategy for the continuous preparation of conductive PEDOT: PSS fibers with enhanced elongation and electroconductivity for potential applications in wearable e-textiles. Various metal salts were employed for the electrostatic complexation with PSS in a coagulation bath of water and ethanol. Interestingly, resultant PEDOT: PSS fibers with the assistance of Li+ possess a breaking elongation of more than 50%, which is the highest value reported to our best knowledge. Special anisotropic structure was detected inside the composite fibers, providing it outstanding electroconductivity. Moreover, resultant fibers revealed a good sensitivity and high capacitance which provides new inspirations for the development of wearable electronics.

Preparation and luminescence performance of thermochromic luminescent fiber based on reversible thermochromic red pigment

SrAl2O4: Eu2+, Dy3+ (SAOED) and Y2O2S: Eu3+, Mg2+, Ti4+ (YOS), as two kinds of important rare earth luminescent materials, are widely used in fibers due to their excellent luminescent properties. However, the lack of sensing property limits the application areas of the fibers in intelligent materials. In this work, the thermochromic luminescent fiber (TLF) was prepared by wet spinning from the cellulose acetate (CA)/dimethyl formamide (DMF) spinning solution. The rare earth luminescent materials serviced as the luminescent sources and thermochromic pigments (TP) acted as the thermochromic agent in this color changing system. The absorptivity curves and fluorescence spectra were recorded at 25 and 45 °C to investigate the thermosensitive characteristics of the fiber. The scanning electron microscope (SEM) observation presents that the TLFs were cylindrical with the diameters of 300–400 µm and three kinds of particles were evenly distributed in the cellulose matrix. X-ray diffraction (XRD) results confirm that cellulose matrix and the wet spinning process did not destroy the phase of rare earth luminescent materials in the fiber. Thermal stability of TLF was illustrated by differential scanning calorimetry (DSC) and thermal gravity analysis (TGA). Absorptivity and emission spectra measurement indicates that the TLF had perspicuous thermochromic luminescence properties. Decay curves showed that the TLF glowed continuously. This work exploits a new type of intelligent luminescent fiber that can respond to ambient temperature, which broadens its application in sensors.

Study on production technology and surface morphology of carbon fiber

Since the 21st century, China’s carbon fiber industry has begun to develop rapidly. The research and development of carbon fiber is a major project related to national strategic security. Carbon fiber production technology has been mature, among which PAN based carbon fiber has the largest capacity. However, compared with the imported carbon fiber materials, there is still a certain gap in the performance of domestic carbon fiber materials. The purpose of this paper is to compare the properties of domestic carbon fiber and its composites. Firstly, the production process of carbon fiber is introduced, including monomer polymerization, spinning, oiling, preoxidation, carbonization, graphitization and other steps. Then, the T700 Carbon Fibers of Toray, Japan and two kinds of domestic T700 Carbon Fibers of Hengshen and Weihai were characterized and analyzed, and the surface morphology of three kinds of carbon fibers was compared. It is found that the domestic carbon fiber of Weihai adopts the similar technology of thousand spray wet spinning, and the fiber surface is smooth. However, Hengshen carbon fiber adopts the wet spinning process. There are grooves on the surface of the fiber, which will increase the mechanical meshing force between the fiber and the resin, and have a positive significance for the interface performance of the composite. However, it will increase the probability of fiber defects, such as fine lines, and have a negative impact on its tensile properties and other mechanical properties.

Polyimide Aerogel Fibers with Superior Flame Resistance, Strength, Hydrophobicity, and Flexibility Made via a Universal Sol-Gel Confined Transition Strategy.

Aerogel fibers with ultrahigh porosity, large specific surface area, and ultralow density have shown increasing interest due to being considered as the next generation thermal insulation fibers. However, it is still a great challenge to fabricate arbitrary aerogel fibers via the traditional wet-spinning approach due to the obvious conflict between the static sol-gel transition of the aerogel bulks and the dynamic wet-spinning process of aerogel fibers. Herein, a sol-gel confined transition (SGCT) strategy was developed for fabricating various mesoporous aerogel fibers, in which the aerogel precursor solution was first driven by the surface tension into the capillary tubes, then the gel fibers were easily formed in the confined space after static sol-gel process, and finally the mesoporous aerogel fibers were obtained via the supercritical CO2 drying process. As a typical case, the polyimide (PI) aerogel fiber prepared via the SGCT approach has exhibited a large specific surface area (up to 364 m2/g), outstanding mechanical property (with elastic modulus of 123 MPa), superior hydrophobicity (with contact angle of 153°), and excellent flexibility (with curvature radius of 200 μm). Therefore, the aerogel woven fabric made from PI aerogel fibers has possessed an excellent thermal insulation performance in a wide temperature window, even under the harsh environment. Besides, arbitrary kinds of aerogel fibers, including organic aerogel fibers, inorganic aerogel fibers, and organic-inorganic hybrid aerogel fibers, have been fabricated successfully, suggesting the universality of the SGCT strategy, which not only provides a way for developing aerogel fibers with different components but also plays an irreplaceable role in promoting the upgrading of the fiber fields.

Polyelectrolyte Complex Tubular Membranes via a Salt Dilution Induced Phase Inversion Process

Tubular membrane geometries are key elements of many industrial filtration applications and artificial organs. Established processes to fabricate polymeric membranes require the use of organic solvents, which are prone to be phased out due to stricter regulations. In the quest of developing solvent‐free alternative fabrication processes, polyelectrolyte complex (PEC) membranes are recently discovered, offering a promising alternative. While flat sheet PEC membranes are successfully fabricated, tubular or hollow fiber geometries remain a material engineering challenge. For the first time, the organic solvent‐free fabrication of PEC tubular membranes in a dry‐jet wet spinning process is demonstrated. The aqueous polymer solution comprising the polyanion—poly(sodium‐4‐styrenesulfonate) (PSS), the polycation—poly(diallyldimethylammonium‐chloride) (PDADMAC), and KBr is extruded with the water‐based bore fluid through a single‐orifice spinneret, passing an air‐gap before immersed into an aqueous coagulation bath. The phase inversion kinetics are influenced to form a defect‐free lumen separation layer through the addition of glycerol to the bore fluid. The resulting tubular membranes show reproducible nanofiltration membrane properties. They have a molecular cut‐off of 320 Da, are positively charged and retain salts with a characteristic salt retention hierarchy. This promising material engineering strategy motivates to continue the quest for smaller tubular dimensions toward hollow fibers.

Simultaneous removal of binary mixture dyes using mn - Fe layered double hydroxide coated chitosan fibers prepared by wet spinning

In this study, the carbohydrate polymer chitosan (CS) fibers were prepared successfully by a simple wet spinning process and subsequently coated by manganese iron layered double hydroxide (Mn-Fe LDH) through hydrothermal technique. The properties of the Mn-Fe LDH/CS composite were identified by various techniques such as FESEM, EDS, FT-IR, BET and element mapping analyses. The simultaneous removal of indigo carmine (IC) and sunset yellow (SY) as anionic dyes from aqueous solutions using an as-prepared composite were studied. In binary solutions, the first order derivative spectrophotometric approach was used for the simultaneous measurement of IC and SY. Four operational variables, concluding initial concentration of IC and SY, adsorbent amount and contact time were selected to investigate by central composite design (CCD) coupled with response surface methodology (RSM). In the optimum conditions, kinetic study was performed and the pseudo second order model for both IC and SY were found the well fitted model compared to other models, whereas the adsorption isotherm of dyes followed the Langmuir isotherm model with a maximum adsorption capacity of 17.85 and 11.37 mg g −1 for IC and SY, respectively. The thermodynamic analysis highlighted that the adsorption process of dyes onto the Mn-Fe LDH/CS fibers was an endothermic process.

Theoretical and experimental investigation of the wet-spinning process for mechanically strong carbon nanotube fibers

The orientation factor is significantly important for producing highly strong conductive carbon nanotube (CNT) fibers. Highly oriented CNT fibers can be obtained by the wet-spinning of CNTs in a superacid. We present a theoretical model for obtaining well-aligned CNT fibers, which may have superior properties. Our model predicts the minimum draw ratio (DR0) at various Deborah numbers (De) for CNT fibers with the target orientation. In addition, the stable operation window in the De-DR plane is predicted using linear stability analysis of the draw resonance. Our analysis suggests that a fiber with the target orientation factor can be obtained if and only if the draw ratio, DR, is higher than DR0 and is within a stable operation window. The model predictions for the stability window and the effect of DR on the properties of the fibers were confirmed by experiment.

Delicacy Management on Kiloton Dry Wet Spinning Bath Liquid

During the dry-jet wet spinning process of polyacrylonitrile carbon fiber precursor, the fluctuation of the coagulation bath liquid level affects the stability of the nozzle directly. The motion trajectory and the motion intensity in all directions of the fluid during the movement of the fiber in the coagulation bath fluid field were studied. A three-dimensional model of the cross flow and jet collision motion trajectory was established, and the impact of fluids with different strengths on the surface of the coagulation bath was analyzed. Solidification of the liquid surface in the fitting strength of the peak effect of the return wave overflow trough coupled superimposed to determine the coagulation bath surface to eliminate interfering fluctuations affecting factors. Based on the above analysis, a smart device for real-time monitoring of the coagulation bath air layer has been developed by using the damping equipment in the coagulation bath, where the impact of various fluid waves on the liquid surface can be eliminated on fixed point or position. According to the understanding of kiloton dry-jet wet spinning precursor fiber production line, in-depth exploration has been made to control the high dynamic coagulation bath level effectively from the perspective of technology and delicacy management.

Chitosan Woven Meshes: Influence of Threads Configuration on Mechanical, Morphological, and Physiological Properties

This study aimed to develop meshes from the weaving of mono- and multifilament wet-spun chitosan (CS), for possible biomedical applications. In the wet-spinning process, CS solution (4% w/v) was extruded in a coagulation bath containing 70% sodium hydroxide solution (0.5 M), and 30% methanol was used. The multifilament thread was prepared by twisted of two and three monofilaments. CS threads obtained were characterized by tensile tests and scanning electron microscopy (SEM). Moreover, it was verified from the morphological tests that threads preserve the characteristics of the individual filaments and present typical “skin-core” microstructure obtained by wet spinning. CS woven meshes obtained were evaluated by optical microscopy (OM), tensile test, swelling degree, and in vitro enzymatic biodegradation. Mechanical properties, biodegradation rate, and amount of fluid absorbed of CS woven meshes were influenced by thread configuration. Hydrated CS meshes showed a larger elastic zone than the dry state. Therefore, CS woven meshes were obtained with modular properties from thread configuration used in weaving, suggesting potential applications in the biomedical field, like dressings, controlled drug delivery systems, or mechanical support.

A novel strategy to reduce the viscosity of cellulose-ionic liquid solution assisted by transition metal ions

The high viscosity of ionic liquids, even at relatively high temperatures, can greatly affect the production of cellulose fibers through the wet-spinning process. The high viscosity mainly by due to the hydrogen bond interaction between the cations and anions of ionic liquids. It is possible to reduce the viscosity by modulating the hydrogen bond interaction. In the present work, copper chloride (CuCl2) was dissolved in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl)-cellulose solution, followed by the formation of a complex with the chloride anions by converting it to [CuCl4]2− anion. Through this strategy, the extrusion velocity of the solution improved, and the produced fibers obtained smoother surfaces and shrunken diameters.

Green Preparation of Thermochromic Starch-Based Fibers through a Wet-Spinning Process

A starch-graft-poly(butyl acrylate/styrene) (St-g-PBAS) copolymer was synthesized via grafting butyl acrylate (BA) and styrene (S) monomers onto starch by radical polymerization, and ammonium persu...

Fabrication and characterization of multi stimuli-responsive fibers via wet-spinning process

Luminescent fibers have attracted much attention due to their application in smart textiles for anti-counterfeiting, camouflage, fashion designs and so on. However, fibers with single function of luminescent is fail to meet the growing demand of smart textiles. Herein, we develop a multifunctional fiber with quick-responsive reversible photochromic and light-emitting with long afterglow. Doping with rare earth material SrAl2O4:Eu2+, Dy3+ phosphors and photochromic pigments into polyacrylonitrile (PAN) fibers enable by facile wet-spinning process, the properties of photochromic luminescent fibers were experimentally investigated in details. The results make clear that resulting fibers exhibit quick-responsive reversible photochromic properties and can be excited by a wide range of ray from 300 to 450 nm, displaying a wide band with a maximum peak at 525 nm. The photochromic pigments and SrAl2O4:Eu2+, Dy3+ phosphors distributed in fibers evenly and the fibers are stable below 258.76 °C. Persistent luminescent properties of fibers are excellent and the afterglow can last for more than 1 h. The ultimate strength of fibers are more than 1.39 MPa. Comparing with a lot of investigated luminescent fibers, our work to photochromic luminescent fibers show huge potential in anti-counterfeiting, aesthetics fashion designs and so on for smart textiles.

The fiber‐matrix interface in Ioncell cellulose fiber composites and its implications for the mechanical performance

AbstractFiber‐reinforced composites based on natural fibers are promising alternatives for materials made of metal or synthetic polymers. However, the inherent inhomogeneity of natural fibers limits the quality of the respective composites. Man‐made cellulose fibers (MMCFs) prepared from cellulose solutions via wet or dry‐jet wet spinning processes can overcome these limitations. Herein, MMCFs are used to prepare single fiber epoxy composites and UD composites with 20, 30, 40, and 60 wt% fiber loads. The mechanical properties increase gradually with fiber loading. Young's modulus is improved three times while tensile strength doubles at a loading of 60 wt%. Raman spectroscopy is employed to follow conformational changes of the cellulose chains within the fibers upon mechanical deformation of the composites. The shift of the characteristic Raman band under strain indicates the deformation mechanisms in the fiber. Provided stress transfer occurs through the interface, it is a direct measure of the fiber‐matrix interaction, which is investigated herein. The shift rate of the 1095 cm−1 band decreases in single fiber composites compared to the neat fibers and continues to decrease as the fiber loading increased.