Dry Spinning Process Research Articles

Strengthening and toughing design of graphene oxide based artificial nacre composites regulated by dimensional hierarchy of ternary structure

The strength and toughness of materials are predominantly attributed to the structure-related stress distribution and energy dissipation in the deformation and damage process. Inspired by the hierarchical structure of nacre, the ternary structure artificial nacre composite films composed of homophonous dimensional hierarchy graphene oxide (GO) sheets and polyvinyl alcohol (PVA) were designed and prepared via the dry-spinning process. It demonstrates that there is a mechanical synergistic effect of the dimensional hierarchy GO sheets that can improve the stress distribution (suppress and disperse the local stress concentration regions) and increase the energy dissipation (trigger more crack deflection), thus improving the toughness on the premise of ensuring excellent strength of the films. Based on the dry-spinning and lamination assembly process, large-size bulk composites with excellent mechanical properties constructed by these films can be obtained and are expected to achieve mass production, which has great potential applications in aerospace, automobile, biomedical, and energyindustries.

Transparent core-sheath composite fibers as flexible temperature sensor based on liquid crystal color change for smart sportswear

The characteristic of color changes in response to external temperature stimuli has made thermochromic fibers a subject of widespread research interest. However, for practical applications, improvements are still needed in terms of color rendering and the prevention of temperature-sensitive material leakage. This study utilized an optimized thermally induced coaxial dry spinning process to prepare a transparent temperature sensing fiber (PCCF) with a core-sheath structure. The sheath layer and the core layer of the PCCF were polydimethylsiloxane (PDMS) and cholesteric liquid crystal (CLC), respectively. The high transmittance exhibited by PCCF was attributed to the pellucid PDMS, which quickly cured in oil bath to form a complete core-sheath structure. The research results indicated that PCCF displayed uniform morphology (average diameter ∼539 μm), excellent tensile properties (elongation at break up to 183 %), as well as good mechanical, thermal, and sweat resistance stability. In addition, the PCCF showed a colorful variation of hues including yellow, green, blue and purple at a very narrow temperature change from 34 °C to 38 °C, attributing to that the molecular pitch was altered to selectively reflect visible light when the CLC was stimulated by temperature. Meanwhile, high sensitivity and short response time were obtained. When the PCCF was directly integrated into sportswear, the remarkable color changes could be observed as the wearer's body temperature increases. PCCF demonstrates a great potential application in smart sportswear and healthcare area.

Novel Dry Spinning Process of Natural Macromolecules for Sustainable Fiber Material -1- Proof of the Concept Using Silk Fibroin.

Researchers around the world are developing technologies to minimize carbon dioxide emissions or carbon neutrality in various fields. In this study, the dry spinning of regenerated silk fibroin (RSF) was achieved as a proof of concept for a process using ionic liquids as dissolution aids and plasticizers in developing natural polymeric materials. A dry spinning equipment system combining a stainless-steel syringe and a brushless motor was built to generate fiber compacts from a dope of silk fibroin obtained by degumming silkworm silk cocoons and ionic liquid 1-hexyl-3-methyl-imidazolium chloride ([HMIM][Cl]) according to a general method. The maximum stress and maximum elongation of the RSF fibers were 159.9 MPa and 31.5%, respectively. RSF fibers containing ionic liquids have a homogeneous internal structure according to morphological investigations. Elemental analysis of fiber cross sections revealed the homogeneous distribution of nonvolatile ionic liquid [HMIM][Cl] in RSF fibers. Furthermore, the removal of ionic liquids from RSF fibers through impregnation washing with organic solvents was verified to enhance industrial applications. Tensile testing showed that the fiber strength could be maintained even after removing the ionic liquid. Thermogravimetric analysis results show that the organic solvent 1,1,1,3,3,3-hexafluoro-2-propanol is chemically coordinated to silk fibroin and, as a natural polymer, can withstand heat up to 250 °C.

Tailoring of advanced poly(lactic acid)‐based materials: A review

AbstractPoly(lactic acid) (PLA) stands out as the most promising biodegradable alternative to conventional petrochemical‐based polymers for manufacturing of high‐performance materials applied in medicine, pharmacy, food, textile, and electronic industry. This review was aimed to present the conventional and up‐to‐date technologies for PLA processing including melt blending and molding, hot melt extrusion, 3D printing, foaming, impregnation, thermally induced phase separation, nano‐ and microparticles preparation, wet and dry spinning processes. In addition, the effect of the processing parameters and polymer characteristics on the properties of the final material was elaborated. Diverse possibilities to tailor properties of PLA‐based materials by variation in polymer characteristics and concentration, solvent selection, drying method, processing pressure and temperature, incorporation of bioactive components, and so on were highlighted. The examples of the relations between processing methods, parameters, and end‐product properties are given for a better understanding of all aspects that need to be perceived for fabrication of PLA‐based materials with required performances.

Melt spinning of poly(acrylonitrile)-co-styrene copolymer

The search for alternative processes and high performance materials precursors for carbon fibers, has been continuously the aim for use in the aerospace, automotive, energy and sports goods market. The reduction in the precursor production cost is then essential to allow the installation of an industrial plant to produce a general purpose carbon fiber. Polyacrylonitrile has been the main precursor for carbon fiber production. It has been produced by the wet and dry spinning process since it has been discovered in the beginning of the forties. Nowadays, the extrusion process of PAN fibers shows potential of cost reduction in relation to the wet spinning method. This innovative technology enables spinning by melting PAN polymer by using glycerin as the primary plasticizer, avoiding the use of highly toxic solvents. In the present work, PAN copolymer was copolymerized by conventional aqueous suspension. Its characterization was performed by FT-IR, GPC and DSC analysis. The fibers obtained by extrusion process were characterized by SEM, DSC/TGA analysis and kinetics of the thermal stabilization process was studied by Kissinger method. The results showed that styrene monomer was suitable for polymerization with PAN leading to a molecular weight Mn= 46,000 g/mol and Mw = 138,000 g/mol. The PAN-co-Styrene copolymer was suitable for obtaining extruded PAN fibers continuously with morphological and thermal properties having properties similar to commercial PAN fibers.

Dry Spinning of Continuous Graphene Oxide/TPU Composite Fibers with Excellent Strength and Toughness

Graphene fiber has broad application prospects in aerospace, biomedical and other fields because of its excellent mechanical properties. In this paper, graphene oxide (GO) and thermoplastic polyurethane (TPU) composite fibers have been prepared by two comparable methods including wet spinning and dry spinning. The fibers obtained by dry spinning show better strength and toughness compared with wet spinning. Further research results show that the dry spinning process can effectively control the internal microstructure of the fiber, improve the internal stress distribution and load transfer efficiency, then realize the optimization of its macro mechanical properties. This study will provide useful guidance for the optimization strategy of internal microstructure and the improvement of preparation process of graphene fiber.

Films of directionally oriented carbon nanotubes as counter electrodes for electrochromic devices

Connected displays are the salient nature of our e-connected society requiring high-quality electronic conductive materials integrated in smart devices. Herein, we highlight the use of carbon nanotubes (CNTs) not only as substitutes for ITO (In2O3:Sn) but mainly as a counter electrode for electrochromic devices (ECDs). Using a dry spinning process, conductive CNT films with directionally oriented tubes were successfully laid on polyethylene terephthalate (PET) flexible substrates. The CNTs were synthesized as vertically aligned spinnable arrays by chemical vapor deposition. The transparency and optical absorption properties were tuned by adjusting the number of CNT layers (L) within the film from light gray for 1L to dark black above 10L. The CNT films, showing pseudo-capacitive to capacitive behavior in lithium-based electrolytes, were further integrated in ECDs based on poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) active layers. The fabricated PET/ITO/PEDOT:PSS/electrolyte/CNT/PET device exhibited reproducible and clear color switching from light to dark blue with a coloration efficiency of 88 cm2 C−1. This study highlights novel architecture of ECDs using CNT-based films as conductive counter electrode.

Oxide ceramic fibers via dry spinning process—From lab to fab

AbstractOxide fibers preparation and manufacturing capabilities at Fraunhofer‐Center HTL are introduced, showing the development and preparation of oxide ceramic fibers from lab scale to pilot scale up to near production scale. As a specific example, the development of an aluminosilicate fiber with mullite composition is discussed in more detail. Fiber development started from nonaqueous sol‐gel precursors in the early lab scale. With increasing fiber spinning volume, precursors were switched to water‐soluble systems. Transformation from green fiber to ceramic fiber was monitored by thermogravimetric and differential thermal analysis, X‐ray diffraction, and scanning electron microscopy. The evolution of ceramic phases, microstructure formation, and the effects on tensile strength and Young's modulus were investigated. Weibull statistics and fracture analysis helped to understand the results. Next step will be the transition from large lab scale to pilot scale, demonstrating manufacturing capability.

Gene reconstruction spandex with intrinsic antimicrobial activity

Polyhexamethylene guanidine hydrochloride (PHMG) was used as a functional “gene” to replace the diamine in ordinary spandex, and a “gene reconstruction” spandex (GRS) spinning solution was synthesized. Mixing a small amount of GRS spinning solution with ordinary spandex spinning solution, composite spandex (CS) with intrinsic antimicrobial activity was obtained by a dry-spinning process under a normal spinning condition. The TEM results indicated that PHMG in the GRS molecular chain was uniformly distributed in CS in a granular shape with 10–100 nm diameter and was aligned along the fiber axial direction with a chain-like structure. The inhibition rates of CS (containing 0.5 wt% PHMG) against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) exceeded 99.99%. CS maintained excellent antibacterial properties after soaking in acetic acid solution at pH 3 for 45 min at 95 °C and showed strong intrinsic antimicrobial characteristics. Confocal laser scanning microscopy demonstrated that bacteria was quickly adsorbed on the surface of CS fiber, the cell membrane was damaged, and gradually bacteria died. The molecular simulation indicated that the positive charges accumulated on the PHMG surface, providing the driving force to attract bacteria with negative charge on the cell membrane phospholipid layer. TGA, DSC, XRD and mechanical property analysis confirmed that the corresponding performances of CS were better than those of ordinary spandex without GRS. In summary, the as-prepared CS by “gene reconstruction” eliminated the exudation problem of antibacterial agents in the traditional antimicrobial materials.

Industrial dry spinning processes: algorithmic for a two-phase fiber model in airflows

The dry spinning of fibers can be described by three-dimensional multi-phase flow models that contain key effects like solvent evaporation and fiber-air interaction. Since the direct numerical simulation of the three-dimensional models is in general not possible, dimensionally reduced models are deduced. We recently developed a one-two-dimensional fiber model and presented a problem-tailored numerical solution strategy in Wieland et al. (J Comput Phys 384:326–348, 2019). However, in view of industrial setups with multiple fibers spun simultaneously the numerical schemes must be accelerated to achieve feasible simulation times. The bottleneck builds the computation of the radial concentration and temperature profiles as well as their cross-sectionally averaged values. In this paper we address this issue and develop efficient numerical algorithms.

Modeling and simulation of curved fibers in dry spinning scenarios

Dry spinning is characterized by the simultaneous production of multiple thin polymeric fibers in airflows and the evaporation of the solvent contained in these fibers. This involves fiber-air interactions as well as radial diffusion effects over the fiber cross-sections. Recent models for fibers in such production processes assume the fiber curves to be strictly uni-axial. But there are industrial setups showing airflow induced lateral movements of the fibers which creates the need for curved fiber models. In this paper we present a special Cosserat rod model that describes curved fibers in such dry spinning processes. Adapting the efficient simulation framework from the uni-axial fiber setting makes the simulation of industrial setups for multiple curved fibers with two-way coupled airflows possible, for which we present results for the first time in literature.

On the cross-section of shaped fibers in the dry spinning process: Physical explanation by the geometric potential theory

Abstract Shaped fibers with irregular cross-section has large specific surface area, high air permeability and low pressure drop, and are widely used in cigarette filters. Cellulose acetate shaped fibers are produced by the dry spinning, and fibers’ cross-section is controlled by the nozzle shape. In this paper, the mechanism for forming a shaped fiber is elucidated by the geometrical potential theory.

Vibration of an axially moving jet in a dry spinning process

During the dry spinning process for fabrication of cellulose acetate fibers, the moving jet is approximated as a string, and its vibration equation is established. The vibration frequency affects g...

Product integration method for simulation of radial effects in dry spinning processes

AbstractIndustrial dry spinning processes are crucially determined by the interaction of the spun fibers with the surrounding airflow as well as the radial effects of the fiber quantities due to solvent evaporation. To achieve computability for a large number of fibers the numerical simulation of the latter has to be very efficient. We present a suitable solution algorithm based on the product integration method. Thereby, accuracy and stability of the underlying quadrature formulas are discussed.

A Moss‐Inspired Electroless Gold‐Coating Strategy Toward Stretchable Fiber Conductors by Dry Spinning

AbstractStretchable fiber conductors are appealing in the field of soft electronics due to their potential to be woven into fabrics leading to smart textile electronics. Coating highly conductive metal films onto elastic polymer fibers can be a potential strategy, however, it is nontrivial to achieve strong metal/polymer adhesion to avoid interfacial failure under large mechanical strains. Here, a novel moss‐inspired gold‐coating strategy by using an ultrathin gold nanowires (AuNWs)‐seeded electroless deposition strategy to fabricate stretchable fiber conductors in a dry spinning process is reported. By optimizing Hildebrand's and Hansen's solubility parameter, the AuNWs are dispersed well in an elastomer matrix leading to the efficient scalable production of AuNWs‐impregnated elastomeric fibers. Remarkably, these AuNWs can serve as “seeds” to promote conformal electroless deposition of gold films to substantially enhance the fiber conductivity. Such gold films resemble moss exhibiting strong adhesion to elastomeric polymer fibers because they have AuNWs roots embedded in the polymer matrix. With prestrained fibers, directional cracks along the axis are found, but they can be repaired reversibly when strains are reapplied. This leads to substantial conductivity enhancement. The fiber conductors can be woven into an everyday glove to exhibit superior strain‐insensitivity without changing the intensity of the light‐emitting diode under severe deformations.

Cellulose acetate fibers with improved mechanical strength prepared with aqueous NMMO as solvent

Cellulose diacetate (CA) was successfully dissolved in N-methylmorpholine N-oxide aqueous solution (NMMO·H2O). The CA degraded little during the dissolving process and the homogenous CA/NMMO·H2O solutions were obtained even when the concentration was up to 18%. From the rheological behavior of the CA/NMMO·H2O solution, it was found that the viscosity of the solution was lower than that of lyocell solution, which is due to the lower degree of polymerization and the substitute of acetyl group. Then CA fibers were prepared by dry-jet wet spinning process. The tenacity and the E-modulus of the regenerated CA fibers were up to 3.0 cN/dtex and 75 cN/dtex respectively, and the former was larger than that of industrial CA fibers prepared by dry spinning process. This is related to the structure of the CA fibers, because the crystallinity, crystal orientation of the fibers can be improved by high draw ratio during dry-jet wet spinning process. Otherwise, the CA fibers showed no fibrillation tendency, which showed improved wearing comfort compared to lyocell fibers. This work provided an effective way to produce new CA fibers with higher tensile strength.

Improved dry spinning process at elevated temperatures for making uniform and high strength CNT fibers

Issues associated with the dry spinning process were explored and addressed in this paper. Post-treatment of dry-spun Carbon Nanotube (CNT) fibers frequently includes solvent densification. This procedure was modified in our work to enhance mechanical strength of the fiber. The effect of n–Methyl-2-Pyrrolidone (NMP) as a densifying solvent was studied at different temperatures within the range of 23 °C–153 °C. High temperature densified fibers revealed better load bearing (40% increase) and higher density compared to room temperature values, which translated to higher tensile strengths (1.2–1.3 GPa). A maximum tensile strength of 1.5 GPa was achieved with resistance assisted heating combined with NMP heating. However, all these properties, including the fiber diameter, varied depending on the position within the array from where the fibers were drawn. This was attributed to a gradation in the length of the CNT’s along the location of the drawing area within the array. Improved fiber uniformity was achieved by drawing from opposite ends of CNT arrays simultaneously. This study enabled to improve the densification process and addressed a major fiber uniformity problem accompanying the dry spinning method.

Functionalized Innovative Carbon Fibers Developed from Novel Precursors with Cost Efficiency and Tailored Properties

Lignin has attracted significant attention as an alternative carbon source for conversion to carbon fibers due to material’s abundance, high carbon content, low cost as byproduct of paper industry and renewable nature. The quality of polymer fibers spun by lignin depends on the spinning method and chemical modification of raw material. The purpose of this study is to improve the lignin fiber spinning by optimization of dry and melt spinning processes. Lignin is chemically modified through esterification and coupling reactions with other compounds and blended with polymer solutions. Various polymer-lignin fibers with diameters in the range of μm are successfully produced and characterized.

Synthesis of organosoluble copolyimide and preparation of fibers by dry-spinning process on a large scale

An organosoluble copolyimide (co-PI) was synthesized from 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), 1,4-bis-(4-aimino-2-triflupromethyl-phenoxy)-benzene ( p-6FAPB), and 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) via the one-step polymerization using N-methyl-2-pyrrolidone (NMP) as the solvent, and high-performance co-PI fibers were directly prepared by the dry-spinning process on a large scale. Scanning electron microscopic images show that all formulations of as-spun fibers exhibit elliptical cross sections as well as dense morphologies. The structural evolution of the co-PI fiber induced by the high rolling speed and post-heat-drawing treatment was studied by means of thermogravimetric analysis, dynamic thermomechanical analysis, and two-dimensional wide-angle X-ray diffraction (2D WAXD). With increasing rolling speeds, glass transition temperatures ( Tgs) and thermal stabilities of as-spun fibers slightly decrease, which may be resulted from the disentanglement of entangled molecular chains under the large deformation and high-temperature heating atmosphere in the spinning column. 2D WAXD data indicate that both increasing rolling speeds and post-heat-drawing treatment are beneficial for getting a highly ordered structure along the meridian direction of the fibers. The fibers treated at 430°C exhibit outstanding mechanical properties, and the tensile strength and modulus reach 1.44 GPa and 48.69 GPa, respectively, at a drawing ratio of 2.8.

Electrically Stable Carbon Nanotube Yarn Under Tensile Strain

We report a highly stable electrical conductance of a compact and well-oriented carbon nanotube yarn under tensile strain. The gauge factor of the yarn was found to be extremely small of approximately 0.15 thanks to the improvements in the dry spinning process, including multi-web spinning and heat treatment. The threshold strain $\varepsilon _{s}$ , below which the yarn retains its electrical conductance stability, has also been determined to be approximately $15\times 10^{3}$ ppm. Owing to its highly stable resistance under mechanical strain, the yarn has a good potential as a wiring material for niche applications, where light weight and resistance stability are required.