Wet Spinning Research Articles

Effect of heat treatment on the radial structure of coaxial polyacrylonitrile/mesophase pitch composite fiber

AbstractCoaxial composite fibers with a cortex of polyacrylonitrile (PAN) and a core layer of mesophase pitch (MP) and PAN were prepared by wet spinning, then heat‐treated in air. The effects of heat treatment on the thermal reaction characteristics, pre‐oxidation degree, radial structure, and thermal stability of coaxial composite fibers were studied by differential scanning calorometry, Raman, and thermogravimetric analysis. As the heat treatment temperature increases, the coaxial composite fibers only undergo cyclization without oxidation, the peak temperature of the thermal reaction increases from 258 to 270°C, and the enthalpy increases from 19.66 to 237.82 J g−1, the heat mainly arises from the PAN component. The Dr value of the coaxial fiber skin layer increases from 0.193 to 0.255 (330°C) and then decreases to 0.236; the core layer Dr value increases from 0.353 to 0.392 (310°C) and then decreases to 0.368. The pre‐oxidation reaction leads to an increase in sp2‐hybridized carbons and an increase in pre‐oxidation degree. When the heat treatment temperature <310°C, the pre‐oxidation degree of the composite fibers increases, leading to formation of a more stable structure compared with that at lower temperatures and an increase in the carbon residue rate.

Nanoparticle-filled oriented nanofiber membrane for effective emulsion separation via spin coating

Patterned membranes, particularly those modified with nanoparticles, are commonly used in the effective filtration separation of emulsions. However, the conventional fabrication methods are based on wet spinning that require large quantities of organic solvents, necessitating treatment and recycling. This increases the economic and environmental cost, damages the environment, and lowers the production efficiency. In this study, we develop a novel spin-coating method to directly fabricate oriented and patterned nanofiber membranes from powders without harsh solution treatment. The patterned nanofiber membrane exhibits a higher flux than a traditional porous membrane with disordered nanofibers and the same retention rate. The use of oriented nanofiber membranes filled with multi-walled carbon nanotubes and graphene enhances the emulsion-breaking effect during emulsion separation. The effect of the type and diameter of the nanofibers on the orientation degradation of the oriented nanofiber membrane is analyzed. The combination of nanofiber membranes with nanoparticles enables the design and synthesis of composite nanofiber membranes with precisely tailored pore structures for various applications.

Woven Agarose-Cellulose Composite Aerogel Fibers with Outstanding Radial Elasticity for Personal Thermal Management.

Aerogel fibers are good thermal insulators, suitable for weaving, and show potential as the next generation of intelligent textiles that can effectively reduce heat consumption for personal thermal management. However, the production of continuous aerogel fibers from biomass with sufficient strength and radial elasticity remains a significant challenge. Herein, continuous gel fibers were produced via wet spinning using agarose (AG) as the matrix, 2,2,2,6,6-tetramethylpiperidine-1-oxyl radical-oxidized cellulose nanofibers (TOCNs) as the reinforcing agent, and no other chemical additives by utilizing the gelling properties of AG. Supercritical drying and chemical vapor deposition (CVD) were then used to produce hydrophobic AG-TOCN aerogel fibers (HATAFs). During CVD, the HATAF gel skeleton was covered with an isostructural silica coating. Consequently, the HATAFs can recover from radial compression under 60% strain. Moreover, the HATAFs have low densities (≤0.14 g cm-3), high porosities (≥91.8%), high specific surface areas (≥188 m2 g-1), moderate tensile strengths (≤1.75 MPa), excellent hydrophobicity (water contact angles of >130°), and good thermal insulating properties at different temperatures. Thus, HATAFs are expected to become a new generation of materials for efficient personal thermal management.

Advanced Fabrication and Characterization of Hydrothermal Responsive Fabric from Microcrystalline Cellulose-Reinforced Shape Memory Polyurethane Filament

Demands for smart textiles have recently increased quickly in terms of functionality and responsiveness to wearers and environmental changes. This paper explores the development of hydrothermal responsive shape memory woven fabric from Microcrystalline Cellulose Reinforced Shape Memory Polyurethane Microcomposite Filament. The concentration of microcrystalline cellulose and drawing ratio of the filaments were first optimized according to the tensile strength and shape recovery ratio and taken as 15 wt% and 2.0 respectively. Hydrothermal responsive shape memory micro-composite filaments were then produced from shape memory polyurethane (SMPU) and microcrystalline cellulose (MCC) with optimized concentration and draw ratio by wet spinning process. The physical, mechanical, thermal and shape memory performances of the filaments were studied. The optimized filament was found to have a tensile strength of 0.91 cN/dtex and elongation of 385.2% in which the strength is much more improved when compared to a pure SMPU filament of strength 0.72 cN/dtex. The shape fixity and shape recovery results of the micro-composite filament were found to be 71.2% and 93.6% respectively. A woven fabric was manufactured from pure polyester, cotton as warp and SMPU-MCC filaments as weft and its breathability and shape memory properties were investigated. The air permeability of SMPU-PE fabrics was found to be 172.9 mm/s and 155.1 mm/s in its fixed temporary shape and recovered shape respectively. The water vapour permeability of SMPU-CT fabric was found to be 612.01 g/m2.h and 540.28 g/m2.h in its fixed temporary and recovered shape respectively which shows smart breathable fabrics can be made and adopted with enhanced properties.

Wet Spun Composite Fiber with an Ordered Arrangement of PEDOT:PSS‐Coated Te Nanowires for High‐Performance Wearable Thermoelectric Generator

AbstractThermoelectric (TE) fibers are more suitable than films for portable or wearable devices. Herein, 2–3 nm thick poly (3,4‐ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS) layer‐coated tellurium nanowires (PC‐Te NWs) are in situ prepared by a hydrothermal method. Then a series of PEDOT: PSS/PC‐Te NWs composite fibers are prepared by wet spinning and post‐treatment. The nanolayer prevents the agglomeration of the Te NWs and makes the NWs and PEDOT:PSS matrix have good compatibility, which results in the PC‐Te NWs content to a high value of 70 wt% and the fibers still with flexibility. The high aspect ratio of the PC‐Te NWs and the stress from the inner wall of the needle during spinning make the NWs ordered align along the composite fiber. Due to the large content and orientational arrangement of the PC‐Te NWs, as well as effective post‐treatment, an optimized composite fiber shows a power factor of 385.4 µW m−1 K−2 at 300 K, which is ≈4.9 times as high as the highest value of previously reported PEDOT:PSS/Te NWs‐based composite fibers. In addition, the composite fiber has good flexibility. The flexible TE generators assembled have excellent output performance. This work provides an effective strategy for the preparation of high‐performance flexible TE composite fibers.

Ultra-strong and conductive graphene fiber via sacrificial layer technology

Microfluidic spinning technology (MST) is an emerging method specialized in the construction of multi-component and multi-structure fibers. In this study, we designed an ultra-strong coaxial graphene oxide (GO) fiber by employing sodium alginate (SA) as sheath flow via MST. The diameter of the fiber and the arrangement of GO molecules could be controlled by adjusting process parameters. More importantly, the outer SA layer could be removed during a subsequent reduction process of GO, which served as a sacrificial layer to GO fiber formation and enhanced the fiber strength. Ultimately, this could achieve a conductive graphene fiber with a maximum strength of 365.2 MPa and electrical conductivity of 52 Ω/cm via a common wet spinning mechanism.

Heat-Insulated Regenerated Fibers with UV Resistance: Silk Fibroin/Al2O3 Nanoparticles.

The various wastes generated by silkworm silk textiles that are no longer in use are increasing, which is causing considerable waste and contamination. This issue has attracted widespread attention in countries that use a lot of silk. Therefore, enhancing the mechanical properties of regenerated silk fibroin (RSF) and enriching the function of silk are important directions to expand the comprehensive utilization of silk products. In this paper, the preparation of RSF/Al2O3 nanoparticles (NPs) hybrid fiber with different Al2O3 NPs contents by wet spinning and its novel performance are reported. It was found that the RSF/Al2O3 NPs hybrid fiber was a multifunctional fiber material with thermal insulation and UV resistance. Natural light tests showed that the temperature rise rate of RSF/Al2O3 NPs hybrid fibers was slower than that of RSF fibers, and the average temperature rose from 29.1 °C to about 35.4 °C in 15 min, while RSF fibers could rise to about 40.1 °C. UV absorption tests showed that the hybrid fiber was resistant to UV radiation. Furthermore, the addition of Al2O3 NPs may improve the mechanical properties of the hybrid fibers. This was because the blending of Al2O3 NPs promoted the self-assembly of β-sheets in the RSF reaction mixture in a dose-dependent manner, which was manifested as the RSF/Al2O3 NPs hybrid fibers had more β-sheets, crystallinity, and a smaller crystal size. In addition, RSF/Al2O3 NPs hybrid fibers had good biocompatibility and durability in micro-alkaline sweat environments. The above performance makes the RSF/Al2O3 NPs hybrid fibers promising candidates for application in heat-insulating and UV-resistant fabrics as well as military clothing.

Coagulation engineering of surfactant-based wet spinning of carbon nanotube fibers

Coagulation engineering of surfactant-based wet spinning of carbon nanotube fibers

Scalable Fabrication of Ionic-Conductive Covalent Organic Framework Fibers for Capturing of Sustainable Osmotic Energy.

High-performance covalent organic framework (COF) fibers are demanded for an efficient capturing of blue osmotic power because of their excellent durability, simple integration, and large scalability. However, the scalable production of COF fibers is still very challenging due to the poor solubility and fragile structure of COFs. Herein, for the first time, it is reported that COF dispersions can be continuously processed into macroscopic, meter-long, and pure COF fibers using a wet spinning approach. The two presented COF fibers can be directly used for capturing of osmotic energy, avoiding the production of composite materials that require other additives and face challenges such as phase separation and environmental issues induced by the additives. A COF fiber exhibits power densities of 70.2 and 185.3 W m-2 at 50-fold and 500-fold salt gradients, respectively. These values outperform those of most reported systems, which indicate the high potential of COF fibers for capturing of blue osmotic energy.

Durable and Wearable Self-powered Temperature Sensor Based on Self-healing Thermoelectric Fiber by Coaxial Wet Spinning Strategy for Fire Safety of Firefighting Clothing

Durable and Wearable Self-powered Temperature Sensor Based on Self-healing Thermoelectric Fiber by Coaxial Wet Spinning Strategy for Fire Safety of Firefighting Clothing

Coaxially spinning stretchable zin-ion battery fiber with waterproof and scissorability

Wearable energy storage with super mechanic flexibility, stretchability and safety has been in pursuit for smart flexible textiles. Fiber batteries, though having their superiority in spinnability, knittability and adaptability for breathable textiles with comparison to planar batteries, were normally produced with complicated procedures. To simplify the production process, in this study we showed that stretchable and scissorable Zinc-ion battery fibers could be spun through a dual-core spinning head with double concentric sheathes, by combining a one-step coaxial wet-spinning process and an in-situ photo-polymerization process. The resultant fibers showed super stretchability up to 500 % strain. The presence of outer protection layer also offered super abrasion resistance and endurability to water and stress. Besides the spinnability and knittability into fabric, the battery fibers also maintained their functionality even after being cut into short segments. Thus, this study may not only offer a platform of one-step coaxial wet spinning process to produce battery fibers, but also offer an endurable energy-storage solution applicable in various wearable devices.

Ordered mesoporous hairbrush-like nanocarbon assembled microfibers for solid-phase microextraction of benzene series in oilfield sewage.

The development of advanced functional nanomaterials for solid-phase microextraction (SPME) remains an imperative aspect of sample pretreatment. Herein, we introduce a novel SPME fiber consisting of graphene fibers modified with ordered mesoporous carbon nanotubes arrays (CNTAs) tailored for the determination of benzene series in oilfield wastewater, which is synthesized by an ionic liquid-assisted wet spinning process of graphene nanosheets, followed by a precisely controlled growth of metal-organic framework and subsequent pyrolysis treatment. The resulting robust microfiber structure resembles a "hairbrush" configuration, with a crumpled graphene fiber "stem" and high-order mesoporous CNTAs "hairs". This unique architecture significantly enhances the SPME capacity, as validated by gas chromatography-mass spectrometry. The hairbrush-like nanocarbon assembled microfibers possess structural characteristics, a high specific surface area, and numerous binding sites, offering efficient enrichment of benzene series compounds in oilfield wastewater, including benzene, ethylbenzene, m-xylene, p-xylene, and toluene. Our analysis demonstrates that these microfibers exhibit broad linear ranges (0.2-600μg L-1), low detection limits (0.005-0.03mg L-1), and excellent repeatability (3.2-5.5% for one fiber, 2.1-6.7% for fiber-to-fiber)for detection. When compared to commercial alternatives, these hairbrush-like nanocarbon-assembled microfibers exhibit significantly enhanced extraction efficiency for benzene series compounds.

Core-sheath smart polymer fiber composites with high elasticity and thermal conductivity

Thermal conductive polymer fibers have broad development prospects because of its excellent thermal and mechanical properties. However, currently reported polymer fibers cannot simultaneously possess high thermal conductivity and high resilience, which greatly limits the application of thermal conductive polymer fibers. Therefore, preparing fibers with high thermal conductivity and high resilience is extremely challenging. The thermoplastic polyurethane/boron nitride liquid metal (TPU/BN-LMs) fiber with core sheath structure is prepared by coaxial wet spinning technology, the boron nitride (BN) doped in thermoplastic polyurethane elastomer (TPU) as sheath and the liquid metal (LMs) as core. The maximum tensile strength of the fiber is 3.9 MPa, and the elongation can reach 400 %. After multiple cycles of stretching, it can return to its original state. In addition, the thermal conductivity of the fiber in the horizontal direction and the vertical direction are 10.0 W m−1 K−1 and 4.6 W m−1 K−1, respectively. This work solves the current problem of high thermal conductivity and high resilience of thermally conductive polymer fibers that are difficult to be compatible. And it provides a new research idea for the design and preparation of new high thermal conductivity and high resilience polymer fiber materials.

Multifunctional fiber-shaped flexible wearable strain sensor with high sensitivity and wide sensing range for detecting autonomous driving technology in automobiles

Flexible strain sensors have developed rapidly and shown enormous application prospects in human motion detection, intelligent robots, and other fields in recent years. However, developing satisfactory strain sensors that meet the requirements of high sensitivity, wide detection range and prominent durability remains a significant challenge. Herein, we developed a flexible and wearable multifunctional fiber-shaped carbon black (CB) and thermoplastic polyurethane (TPU) strain sensor (defined as CTSS) by combining wet spinning and ultrasound. The CTSS possesses characteristics of lightweight, wide sensing range (>390 %), high sensitivity (up to 1414), short response and recovery time (200 ms), ultralow detection limit (0.005 % strain) and good durability. These advantages endow the CTSS with good capability to monitor complicated human activities efficiently (e.g., joint bending, facial expression and breathing). CTSS can also clearly distinguish different bending states. It was then used to monitor the steering of a car in real-time, proving its tremendous potential as high performance flexible electronics device. CTSS is then encapsulated with Ecoflex (E-CTSS) as a single packaged fiber, exhibiting good triboelectric nanogenerator (TENG) performance, with a maximum output voltage beyond 12V for a single packaged fiber, and can maintain stable output. Indicating that E-CTSS has self powered sensing capability.

Hydrophobic Silk Fibroin-Agarose Composite Aerogel Fibers with Elasticity for Thermal Insulation Applications.

Aerogel fibers, characterized by their ultra-low density and ultra-low thermal conductivity, are an ideal candidate for personal thermal management as they hold the potential to effectively reduce the energy consumption of room heating and significantly contribute to energy conservation. However, most aerogel fibers have weak mechanical properties or require complex manufacturing processes. In this study, simple continuous silk fibroin-agarose composite aerogel fibers (SCAFs) were prepared by mixing agarose with silk fibroin through wet spinning and rapid gelation, followed by solvent replacement and supercritical carbon dioxide treatment. Among them, the rapid gelation of the SCAFs was achieved using agarose physical methods with heat-reversible gel properties, simplifying the preparation process. Hydrophobic silk fibroin-agarose composite aerogel fibers (HSCAFs) were prepared using a simple chemical vapor deposition (CVD) method. After CVD, the HSCAFs' gel skeletons were uniformly coated with a silica layer containing methyl groups, endowing them with outstanding radial elasticity. Moreover, the HSCAFs exhibited low density (≤0.153 g/cm3), a large specific surface area (≥254.0 m2/g), high porosity (91.1-94.7%), and excellent hydrophobicity (a water contact angle of 136.8°). More importantly, they showed excellent thermal insulation performance in low-temperature (-60 °C) or high-temperature (140 °C) environments. The designed HSCAFs may provide a new approach for the preparation of high-performance aerogel fibers for personal thermal management.

Cover Image, Volume 141, Issue 20

Wet spinning of chitin nanowhiskers: Effects of electrolyte composition in coagulation baths on mechanical properties and nanowhisker orientation by Jun Araki and Minami Nakajima. DOI: 10.1002/app.55335 image

Construction of thermally conductive and insulating fibers of BN nanosheet/aramid nanofiber composites with high-temperature resistance via sol-gel wet spinning

With the intensification of global warming and the occurrence of extremely hot weather, there is an urgent need for textiles that can effectively regulate temperature. Using amino-functionalized boron nitride nanosheets (K-BNNSs) and aramid nanofibers (ANFs) as materials, the well-oriented thermally conductive insulating textile fibers with “lotus root” structure were directly prepared by sol–gel wet spinning process. The axial thermal conductivity of a single fiber can be as high as 22.4 W/(m·K), and has an excellent tensile fracture strength (176.6 MPa). Thermal infrared imaging revealed that the fibers woven into textiles had a more significant heat dissipation capacity than commercial cotton fabrics. The fiber obtained by this low-cost preparation method provides a cooling textile with excellent heat-dissipation ability and has wide application prospects in emerging textiles.

RGO/ANFs composite fibers with dual functions of thermal conductivity and electromagnetic shielding of lotus root structure based on sol-gel wet spinning

Textiles that exhibit electromagnetic shielding and high thermal conductivities are valuable materials. Graphene is considered the best candidate material because of its excellent thermal and electrical conductivities. However, there is a challenge that the strong interaction between the layers is easy to aggregate and affect the mechanical properties. At present, the graft modification of graphene can effectively improve its dispersion in solvents. Herein, we fabricate highly oriented composite fibers with “lotus root” structures via sol-gel wet spinning using graphene and aramid nanofiber (ANF) raw materials. The reduced graphene oxide (RGO)/ANFs composite fibers (50RGO/ANF-Ca2+-0.5) exhibit an excellent tensile fracture strength (304.05 MPa). The axial thermal conductivity of a single fiber is 30.42 W/(m·K) due to its highly oriented structure along the axis and dense three-dimensional network structure inside. Thermal infrared imaging shows that the 50RGO/ANF-Ca2+-0.5 textile has a higher surface temperature of 1.1 °C than commercial cotton fabric on human skin, and has a more significant heat dissipation capacity. The 50RGO/ANF-Ca2+-0.5 textiles exhibit electromagnetic shielding efficiencies of up to 49.8 dB. The composite fiber obtained via this low-cost preparation method endows textile with dual functions of thermal conductivity and electromagnetic shielding and has wide application prospects in emerging textiles.

Gas-Blows-Liquid Spinning Strategy Toward Mechanically Strong, Thermally Protective, Efficiently Hemostatic Aerogel Fibers/Fabrics.

Nanoporous aerogel fibers enjoy the luxury of being one of the most attractive nanomaterials. However, the representative fabrication pathways have faced up with low production rates due to significant speed mismatch between slow sol-gel transition and as fast as possible spinning in the same period. Herein, a novel gas-blows-liquid spinning (GS) strategy with a spinning speed of 300-700ms-1 is developed to get the high-speed and high-efficiency production of aerogel fibers/fabrics. The spinning speed of the GS strategy is 900 times higher than various techniques reported for aerogel fibers. The resulting aerogel fibers exhibit a high specific surface area (180m2g-1). In comparison, the aerogel fiber possesses the highest tensile strength (58.7±3.9MPa) among its counterparts and aerogel fabric with surprising water-absorption and microparticle-blocking performances exhibits the application prospect for better hemostasis than that of commercial gauze and cotton ball. Besides, the GS aerogel fabrics with hierarchical aligned structures show better thermal insulation (≈0.035Wm-1K-1) than wet spinning aerogel fabric and commercial insulation felts. This work has provided inspiration for fast fabricating more aerogel fibers/fabrics with this GS strategy, and the resulting aerogel fibers/fabrics may find significant application in the fields of 5G smart phones, wound hemostasis, etc.

Wet Spinning Fabrication of Robust and Uniform Intrinsically Conductive Cellulose Nanofibril/Silk Conductive Fibers as Bifunctional Strain/Humidity Sensor in Potential Smart Dressing

Wet Spinning Fabrication of Robust and Uniform Intrinsically Conductive Cellulose Nanofibril/Silk Conductive Fibers as Bifunctional Strain/Humidity Sensor in Potential Smart Dressing