Fabrication Of Yarns Research Articles

Fabrication and characterization of PET nanofiber hollow yarn

In this study, various concentrations of polyethylene terephthalate (PET) polymeric solution were investigated to produce hollow nanofiber yarn. First, the electrospining apparatus was designed in a way that to put PVA multifilament in the core and to twist PET nanofibers onto multifilament yarn as a sheath simultaneously, followed by dissolving PVA yarn in hot water, PET hollow nanofiber yarn was produced. In this survey, it has been observed that the average thickness of sheath increased by increasing concentrations of PET polymeric solution. Results showed that maximum efficiency of extracting the PVA multifilament from the hollow yarn under certain conditions (concentration of 18 % (w/v) of PET, applied voltage of 10 kV, and flow rate of 0.0526 ml/h) was more than 85 %. The mechanical and physical properties of PET hollow yarns were investigated and indicated that the hollow nanofiber yarns at concentration of 30 % and 18 % polymeric solution had the lowest strength and the highest regain moisture, respectively.

Fabrication of continuous nanofiber yarn using novel multi‐nozzle bubble electrospinning

A novel multi‐nozzle bubble electrospinning apparatus, including spinning unit, metering pump, constant flow pump, metal funnel and yarn winder, was designed for the preparation of continuous twisted polyacrylonitrile nanofiber yarns, and the principle of nanofiber yarn spinning was studied. An innovative spinning unit consisting of nozzle and air chamber was used to improve the production of nanofibers. Double conjugate electrospinning was developed using two pairs of oppositely charged spinning units to neutralize the charges. The effects of applied voltage, air flow rate, overall solution flow rate and funnel rotary speed on the fiber diameter, production rate and mechanical properties of the nanofiber yarns were analyzed. Nanofibers could be aggregated stably and bundled continuously, then twisted into nanofiber yarns uniformly at an applied voltage of 34 kV, air flow rate of 1200 mL min−1 and overall solution flow rate of 32 mL h−1. With an increase in the funnel rotary speed, the twist angle of the nanofiber yarns gradually increased when the take‐up speed was constant. The yarn tensile strength and elongation at break showed an increasing trend with increasing twist angle. Nanofiber yarns obtained using this novel method could be produced at a rate from 2.189 to 3.227 g h−1 with yarn diameters ranging from 200 to 386 µm. Nanofiber yarns with a twist angle of 49.7° showed a tensile strength of 0.592 cN dtex−1 and an elongation at break of 65.7%. © 2013 Society of Chemical Industry

Fabrication of Micro Yarn Composed of Nanofibers by Blown Bubble Spinning

Recent years, much attention has been paid to approaches for directly producing nanofibers along with a rising trend for their exploration and application in wide fields. Considering the melt blowing and bubble-electrospinning, a novel method called blown bubble-spinning was introduced by forcing airflow onto the polymer bubble. In this paper, a special hierarchical structure has demonstrated the ability to form micro yarn composed of nanofibers in this way. The resulting yarn is about 23 micrometers while the nanofibers 376 nanometers.

Chitosan/gelatin micro/nanofiber 3D composite scaffolds for regenerative medicine

The present study reports on the fabrication of new composite chitosan-based knitted three-dimensional textile scaffolds for regenerative medicine. A critical research objective remained the fabrication of pure chitosan microfiber yarn with defined size and directional alignment, which could lead to textile structure, for example, woven and/or knitted fabrics. The construction of such textile structure with pure chitosan fibers possessing adequate tensile strength was recently realized in our laboratory. In the combination of micro/nanofiber composites, one can benefit from both the strength provided by the woven/knitted structure of the microfiber and the cell-seeding ability of the spun nanofiber mesh. Therefore, chitosan knitted fabrics were functionalized with gelatin nanofibers producing new interfaces for cell seeding. Both, pure chitosan and chitosan/gelatin scaffolds were proved non-cytotoxic to fibroblasts. Moreover, in vitro test with osteoblasts culture was carried out in order to analyze the influence of the surfaces and interfaces of the functionalized textile scaffold on cell ingrowth and proliferation.

Influence of the solvent type on the morphology and mechanical properties of electrospun PLLA yarns

An electrospinning technique based on the use of two oppositely charged nozzles was applied to fabricate continuous twisted yarns of poly(L-lactide) (PLLA) nano/micro fibers. In this study, the effect of solvent on the electrospinning of PLLA fibrous yarns was investigated. For this purpose, yarns were electrospun using chloroform, dichloromethane or 2,2,2-trifluoroethanol as solvents at a PLLA concentration of 7 wt%. The analysis of the morphology, diameter, crystallinity and mechanical properties of electrospun yarns revealed that the vapor pressure of the solvent plays an important role. Whereas the fiber diameter decreased, the crystallinity of the fibers increased using a solvent with lower vapor pressure. In addition, mechanical properties (e.g., tensile strength and modulus) revealed that the yarns composed of fibers with smaller diameters showed higher tensile strength and modulus. In summary, fine-tuning solvent properties resulted in a modulation of fiber diameter, crystallinity, and thereby yarn mechanical properties, and are important factors to consider in the fabrication and application of electrospun yarns.

Effect of twist and porosity on the electrical conductivity of carbon nanofiber yarns

This study focuses on the effect of twist and porosity on the electrical conductivity of carbon nanofiber (CNF) yarns. The process of fabrication of CNF yarns included the synthesis of aligned ribbons of polyacrylonitrile (PAN) nanofibers via electrospinning. The PAN ribbons were twisted into yarns with twist levels ranging from zero twist to high twists of 1300 turn per meter (tpm). The twist imposed on the ribbons substantially improved the interactions between nanofibers and reduced the porosity. The PAN yarns were subsequently stabilized in air, and then carbonized in nitrogen at 1100 ° C for 1 h. Compressive stresses developed between the PAN nanofibers as a result of twist promoted interfusion between neighboring nanofibers, which was accelerated by heating the yarns during stabilization to temperatures above the glass transition of PAN. The electrical conductivity of the yarns was measured with a four point probe measurement technique. Although increasing the twist promotes electrical conductivity between nanofibers by forming junctions between them, our results indicate that the electrical conductivity does not continuously increase with increasing twist, but reaches a threshold value after which it starts to decrease. The causes for this behavior were studied through experimental techniques and further explored using a yarn-equivalent electrical circuit model.

Fabrication and mechanical properties of carbon nanotube yarns spun from ultra-long multi-walled carbon nanotube arrays

Carbon nanotube (CNT) yarns have been fabricated by dry spinning from vertically aligned millimeter-long multi-walled carbon nanotube (MWCNT) arrays and their mechanical properties have been studied. By using 2-mm long CNTs and densely packing of CNT yarns we achieved a tensile strength of 1068MPa and Young’s modulus of 55GPa. Our CNT yarns have diameters of tens of micrometers being easy to handle and possessing high effective load capacity up to 0.81N. We discuss mechanical properties of CNT yarns spun from relatively thick MWCNT along with a detailed analysis of various post-spin processes and their effect on CNT yarns characteristics. Also, we point out the difference between mechanical properties of dry spun CNT yarns and conventional spun textile yarns.

Manufacturing and Process-based Property Analysis of Textile-Reinforced Thermoplastic Spacer Composites

Novel woven spacer fabrics based on hybrid yarns are suitable for an efficient fabrication of three-dimensional composite structures in high volume production. In this paper, an innovative manufacturing process with short cycle times and high automatisation is introduced for textile-reinforced thermoplastic spacer structures suited for bending load cases. The different process steps hybrid yarn fabrication, weaving technology for three-dimensional textile preforms and consolidation with unique kinematics and hot pressing technology are described in detail. The bending properties of the manufactured spacer structures are evaluated by means of experiments as well as finite element simulations. Numerical parametric studies are performed in order to validate the influence of manufacturing tolerances on the bending stiffness of the spacer structures.

Spinnable carbon nanotube forests grown on thin, flexible metallic substrates

Towards the goal of providing a continuous process for the solid-state fabrication of carbon nanotube sheets and yarns from carbon nanotube forests, we report the growth of yarn-spinnable and sheet-drawable carbon nanotube forests on highly flexible stainless steel sheets, instead of the conventionally used silicon wafers. Sheets and yarns were fabricated from the 16 cm maximum demonstrated forest width, from both sides of a stainless steel sheet, and the catalyst layer was shown to be reusable, thereby decreasing the need for catalyst renewal during a proposed continuous or semi-continuous process where the stainless steel sheet serves as a moving belt to enable forest growth at one belt end and carbon nanotube yarn or sheet fabrication at an opposite belt end.

Electrospinning of Polymers, Their Modeling and Applications

Although there are several methods for obtaining sub-micro or nanofibers, electrospinning is perhaps the most versatile process. Nanotechnology has been widely accepted as dealing with the science and technology where at least one dimension is of roughly 1 to 100 nm. Electrospinning has been recognized as a feasible technique for the fabrication of polymeric nanofiber yarns. Various materials including polymers, composites, ceramics and metals have been electrospun into nanofibers. The nanofibers thus produced exhibit novel and significantly improved physical, chemical and biological properties due to their nanolevel size. In this article, the electrospinning process, along with its modeling equations and applications have been discussed. Some typical case studies regarding electrospinning under various categories have also been discussed.

In situ fabrication of HfC-decorated carbon nanotube yarns and their field-emission properties

HfC-decorated carbon nanotube (CNT) yarns have been fabricated by pre-coating pure CNT yarns with Hf and in situ current heating in vacuum. HfC nanocrystals were formed at about 1600 K through reaction of the CNTs with Hf. The fabricated HfC-CNT yarns had a work function of 3.9 eV, lower than that of pure CNT yarns. For field-emission applications, HfC-CNT sharp tips made up of HfC nanorods were obtained by Joule-heating-induced electrical breakdown above 2100 K. Their emission current could reach 320 μA with a calculated density of 800 A/cm 2 at an extraction voltage of 400 V. The emitters could operate under a rough vacuum of 10 −2 Pa without obvious degradation. These excellent field-emission properties are attributed to the HfC nanorods, which have a low work function and are resistant to ion bombardment.

Fabrication and application of long silicon nanowire yarns

Long silicon nanowire yarns with length up to 12 mm were fabricated from aligned silicon nanowires with crystal silicon cores of bifurcation structures as well as entangled amorphous hairy silicon oxide, which played vital roles in the formation of the yarns, and the silicon nanowire yarns were used as a pH sensor with the sensitivity of 1,080 ± 31 nS/pH in the pH range of 2–12.

Manufacturing technologies of polymeric nanofibres and nanofibre yarns

AbstractIn the textile industry, although there are several methods for obtaining sub‐micro‐ or nanofibres, electrospinning perhaps is the most versatile process. Electrospinning has been recognized as a feasible technique for the fabrication of continuous polymeric nanofibre yarns desired in the textile industry. Various materials including polymers, composites, ceramics and metals have been successfully electrospun into nanofibres in recent years mostly in solution and some in the melt. Potential applications based on electrospun nanofibres as a new‐generation material in the textile industry will be realized if suitable nanofibre yarns become available to textile processes like weaving, knitting and embroidery. In this review, we present, from a textile viewpoint, a comprehensive overview of processing technologies of polymeric nanofibres in the textile industry; however, the emphasis here is focused on electrospinning. In particular, we choose to concentrate on a detailed account of research activities on the yarns and fabrics composed of electrospun nanofibres. Our discussion is concluded with some personal perspectives on the future challenges for the development and optimization of yarns based on electrospun nanofibres. Copyright © 2007 Society of Chemical Industry

A dynamic liquid support system for continuous electrospun yarn fabrication

Electrospinning is known to be a highly versatile process which is able to produce fibers made out of different compositions with diameter of a few microns down to several nanometers. Current electrospinning technology generally involves the deposition of fibers onto a solid substrate although in some cases, a liquid coagulation bath is used to collect the fibers. However, a liquid collector may offer several advantages over a solid substrate. A novel electrospun fiber manipulation process through the use of a water vortex is described in this communication where continuous yarn was made from electrospun fibers. Preliminary studies on some parameters such as solution feed rate and solution concentration and their impact on fabrication of the yarn and the fiber morphology were carried out.

Rusar microfilament yarn for ballistic protection

Technology was developed for fabrication of Rusar microfilament yarn with a linear density of 29.4 (300 filaments) and 58.8 tex (600 filaments) and textile armor with better strength properties than foreign analogs. The small diameter of the filaments combined with the chemical structure of the polymer allows the yarn to withstand important flexural stresses without fracturing.

Static and Dynamic Properties of Optical Microcavities in Photonic Bandgap Yarns

The design, fabrication, and characterization of polymeric yarns (see Figure and cover) with large photonic bandgaps and omnidirectional reflectivity combined with a micro‐cavity designed for near‐infrared applications are reported. The reversible shift of the resonant wavelength of this single‐mode optical cavity under applied strain is also demonstrated. Passive and active applications include narrow band‐pass filters and low‐threshold lasers.

Some possibilities for expanding the assortment of chemical fibres and filaments of new structures

New technological processes are described: fabrication of Lavsan-Nitron yarn from twist; fabrication of air-textured combined fibres of different raw-material composition and different linear density; fabrication of yarn using Nitron-M fibre and combined figured fibres. The technologies examined allow significantly expanding the assortment of woven and knit cloth and decreasing the specific consumption of materials and costs.

New spinnerets for fabrication of viscose fibres and yarns

New spinnerets for fabrication of viscose fibres and yarns