Conjugate electrospinning of continuous nanofiber yarn of poly(L‐lactide)/nanotricalcium phosphate nanocomposite

The continuous nanofiber yarns of poly(L ‐lactide) (PLLA)/nano‐β‐tricalcium phosphate (n‐TCP) composite are prepared from oppositely charged electrospun nanofibers by conjugate electrospinning with coupled spinnerets. The morphology and mechanical properties of PLLA/n‐TCP nanofiber yarns are characterized by scanning electron microscope, transmission electron microscope, and electronic fiber strength tester. The results show that PLLA/n‐TCP nanofibers are aligned well along the longitudinal axis of the yarn, and the concentration of PLLA plays a significant role on the diameter of the nanofibers. The thicker yarn of PLLA/n‐TCP composite with the weight ratio of 10/1 has been produced by multiple conjugate electrospinning using three pairs of spinnerets, and the yarn has tensile strength of 0.31cN/dtex. A preliminary study of cell biocompatibility suggests that PLLA/n‐TCP nanofiber yarns may be useable scaffold materials. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Mechanical and electrical properties of the PA6/SWNTs nanofiber yarn by electrospinning

In this article, continuous PA6/single‐wall nanotubes (SWNTs) nanofiber yarns were obtained by a special electrospinning method; the mechanical and electrical properties and the electric resistance‐tensile strain sensitivity of the as‐spun yarns were specially studied. The main parameters in the spinning process were systematically studied. Scanning electron microscope images and mechanical tests indicated that the optimum parameters for the electrospinning process were operation voltage = 20 kV, spinning flow rate = 0.09 ml/h, and winding speed = 150 rpm. Transmission electron microscopy images showed that the SWNTs have aligned along the axis of the nanofibers and thus formed a continuous conductive network which greatly improved the electrical conductivity of the PA6 nanofiber yarn and the percolation threshold was about 0.8 wt%. The electric conductivities of the yarns at different stretching ratios were also measured with a custom‐made fixture attached to the high‐resistance meter, and for a given carbon nanotube concentration, the conductivity changes almost linearly with the tensile strain applied on the yarns. POLYM. ENG. SCI., 54:1618–1624, 2014. © 2013 Society of Plastics Engineers     

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     

Preparation and characterization of zein and zein/poly‐L‐lactide nanofiber yarns

Zein and zein/poly‐L ‐lactide (PLLA) nanofiber yarns were prepared by conjugate electrospinning using coupled spinnerets applied with two high electrical voltages of opposite polarities in this article. Structure and morphology of zein yarns were investigated by SEM and X‐ray diffraction. The results showed that zein yarn consisted of large quantity of fibers with diameters ranging from several hundreds nanometers to a few microns, and zein concentration played a significant role on the diameter of nanofibers in yarns. To improve mechanical property of nanofiber yarns, PLLA was then incorporated with zein. Zein/PLLA composite nanofiber yarns conjugate electrospun from solution with concentration of 7.5% (zein, w/v)/7.5% (PLLA, w/v) exhibited tensile strength of 0.305 ± 0.014 cN/dtex. The composite yarns showed better nanofiber alignment along the longitudinal axis. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Continuous polymer nanofiber yarns prepared by self-bundling electrospinning method

Continuous polymer nanofiber yarns were manufactured by self-bundling electrospinning method. Compared with typical electrospinning setup, the special difference in this method was that a grounded needle tip was used to induce the self-bundling of polymer nanofibers at the beginning of electrospinning process. Four kinds of polymer self-bundling yarns, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), polyacrylonitrile (PAN), poly(l-lactic acid) (PLLA) and poly(m-phenylene isophthalamide) (PMIA), were prepared successfully by using this self-bundling electrospinning method. Good alignment of polymer nanofibers in self-bundled yarns was confirmed by SEM observation. It was found out that the conductivity of the polymer solution was crucial to achieve stably continuous self-bundled fiber yarns. A possible mechanism for the self-bundling formation of align nanofiber yarn was proposed.     

A multispectral imaging approach to colour measurement and colour matching of single yarns without winding

This paper investigates a multispectral imaging approach to colour measurement and colour matching of single yarns. The small size of a single yarn makes it impossible for spectrophotometers directly to acquire its spectral reflectance. Multispectral imaging systems, on the other hand, have the potential to measure the reflectance of single yarns as they can record both the spectral and the spatial information of a sample. A multispectral imaging system, namely imaging colour measurement, has been developed to conduct colour measurement of single yarns. A single yarn is first detected from backgrounds by a modified K‐means clustering method. The reflectance of the single yarn is then specified by an averaging method. Comparative experiments based on 100 pairs of single yarns and corresponding yarn windings show that the reflectance magnitude of a single yarn acquired by imaging colour measurement is smaller than that of corresponding yarn winding measured by a Datacolor 650 spectrophotometer. Experiments on 16 single yarns show that the repeatability and spatial reproducibility of the imaging colour measurement system in measuring a single yarn colour are 0.1185 and 0.2827 CMC(2:1) units. A colour matching comparison experiment (pass or fail), using 24 pairs of single yarns and corresponding pairs of solid‐colour yarn dyed fabrics, shows that single yarns measured by imaging colour measurement can achieve similar colour matching results to solid‐colour yarn dyed fabrics measured by the Datacolor 650 spectrophotometer, with degrees of similarity of 87.5 and 83.3% when the CMC(2:1) and CIE2000(2:1:1) colour difference formulas are employed.     

Mechanical properties and morphology of hot drawn polyacrylonitrile nanofibrous yarn

In this study PAN nanofibrous yarn was produced by two‐nozzle conjugated electrospinning method. The nanofibrous yarns were drawn continuously in boiling water with drawing ratios of 1, 2, 3, and 4. The morphology of drawn yarns was investigated by scanning electron microscopy and tested for tensile properties as well as untreated yarn. The results showed that the nanofiber alignment in the yarn axis direction, the tensile strength, and tensile modulus of yarn increases as a result of drawing while the tensile strain and work of rapture decrease. X‐ray diffraction patterns of the produced yarns were analyzed as well. It was found that crystallinity index increases as the draw ratio increases. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Tensile fatigue behavior of polyamide 66 nanofiber yarns

Nanofiber yarns with twisted and continuous structures have potential applications in fabrication of complicated structures such as surgical suture yarns, artificial blood vessels, and tissue scaffolds. The objective of this article is to characterize the tensile fatigue behavior of continuous Polyamide 66 (PA66) nanofiber yarns produced by electrospinning with three different twist levels. Morphology and tensile properties of yarns were obtained under static tensile loading and after fatigue loading. Results showed that tensile properties and yarn diameter were dependent on the twist level. Yarns had nonlinear time‐independent stress–strain behavior under the monotonic loading rates between 10 and 50 mm/min. Applying cyclic loading also positively affected the tensile properties of nanofiber yarns and changed their stress–strain behavior. Fatigue loading increased the crystallinity and alignment of nanofibers within the yarn structure, which could be interpreted as improved tensile strength and elastic modulus. POLYM. ENG. SCI., 55:1805–1811, 2015. © 2014 Society of Plastics Engineers     

Composite yarns fabricated from continuous needleless electrospun nanofibers

In this work, a spinning metal wire collector was employed to continuously collect polyacrylonitrile (PAN) nanofibers produced by a disc fiber generator and coil them around a polyethylene terephthalate (PET) yarn. The obtained composite yarns exhibited a core/shell structure (PET yarn/PAN nanofibers) with nanofibers orderly arranged on the surface of the PET yarn. The electric field analysis showed that the position of metal wire had insignificant effect on the formed electric field and high intensity electric field was formed at the disc circumferential area, which provided a constant electric field for the production of uniform nanofibers. The spinning solution, spinning speed of metal wire, and winding speed were found to play an important role in producing good quality nanofiber yarns, in terms of morphology, strength, and productivity. Pure nanofiber yarns were obtained after dissolving the core yarns in a proper solvent. This method has shown potential for the mass production of nanofiber yarns for industrial applications. POLYM. ENG. SCI., 54:1495–1502, 2014. © 2013 Society of Plastics Engineers     

Continuous yarns from electrospun fibers

A technique for making continuous uniaxial fiber bundle yarns from electrospun fibers is described. The technique consists of spinning onto a water reservoir collector and drawing the resulting non-woven web of fibers across the water before collecting the resulting yarn. Yarns from electrospun fibers of poly(vinyl acetate), poly(vinylidene difluoride) and polyacrylonitrile are used to illustrate the process of yarn formation and fiber alignment within the yarn. A theoretical production rate of 180 m of yarn per hour for a single needle electrospinning setup makes the process suitable for lab-scale production of electrospun yarns.     

Effect of single yarn twist and ply to single yarn twist ratio on strength and elongation of ply yarns

The amount of ply twist required to bring the surface fibers of the strand parallel to ply yarn axis is half the single yarn twist and, is experimentally verified by viewing the multifilament yarns longitudinally under Scanning Electron Microscope. The effect of single yarn twist and ply to single yarn twist ratio on strength and elongation of two‐ply cotton yarn have been studied. As the single yarn twist increases the tensile strength of the ply yarns with different levels of ply to single yarn twist ratio increases and at 130–140% of normal single yarn twist level, the ply yarns attain almost the same strength. Rate of improvement in tensile strength of cotton two‐ply yarn with respect to single yarn twist is more than that with respect to ply twist. The effect of ply to single yarn and cable to ply yarn twist ratio on strength and elongation of ply and cable multifilament yarns have been studied. Tensile strength of ply and cable multifilament yarns do not vary with the change in ratio of ply to single yarn twist and cable to ply twist respectively, particularly when the resultant yarn is finer. The cosine of average filament inclination to the ply yarn axis and that to the cable yarn axis do not vary much with different levels of ply to single yarn twist ratio and cable to ply yarn twist ratio respectively. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2245–2252, 2005     

Effect of fatigue loading on wicking properties of polyamide 66 nanofiber yarns

The wicking phenomenon is of prime importance with regards to biomedical applications of nanofiber yarns such as suture yarns and tissue scaffolds. In such applications, the yarns are usually subjected to cyclic tensile forces and biological tensile stresses. There is a lack of science behind the effect of fatigue on wicking properties of nanofiber yarns and this work aims at exploring this venue. Wicking properties of polyamide 66 nanofiber yarns are investigated by tracing the color change in the yarn structure resulting from pH changes during the capillary rise of distilled water. Results show that applying cyclic loading increases equilibrium wicking height in the Lucus–Washburn equation, which is attributed to changes in the overall pore structure in the cyclic loaded yarn. The likely causes of these changes are studied by scanning electron microscope, which reveals disentangled, more or less aligned and parallel nanofibers with a smaller radius in the nanofibrous structure. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47206.     

The influence of solvent type and polymer concentration on the physical properties of solid state polymerized PA66 nanofiber yarn

We investigated the effects of two different solvent types and three solution concentrations on the electrospinning of solid state polymerized polyamide 66 (SSP PA66) nanofiber yarns. Nanofiber yarns were electrospun from SSP PA66 solutions in formic acid and formic acid/chloroform (3/1), using two oppositely metallic spinnerets system. Scanning electron microscopy (SEM) and X‐ray diffraction (XRD) were employed to characterize the morphology and properties of the nanofibrous yarns. Experimental results show that adding chloroform to formic acid as a binary solvent increases viscosity of polymer solution and the nanofibers diameter significantly. XRD patterns reveal that the presence of chloroform affects the crystallinity and the mechanical properties of the produced nanofibrous yarns. PA66 nanofiber yarn from 10 wt % formic acid/chloroform (3/1) solution was successfully electrospun with strength and modulus of 120.16 MPa and 1216.27 MPa respectively. It is also shown that the solution concentration has a significant effect on the modulus of the nanofibers yarns. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Automatic detection of layout of color yarns of yarn‐dyed fabric. Part 1: Single‐system‐mélange color fabrics

To recognize the layout of color yarns of single‐system‐mélange color fabric automatically, a novel FCM‐based stepwise classification method is proposed in this article. This method consists of three main steps: (1) warp yarn segmentation, (2) weft color recognition, and (3) the layout of color warps recognition. In the first step, the yarn segmentation method based on mathematical statistics of subimages is adopted to localize warp yarns preliminarily; and then the segmentation results of warp yarn are corrected by misrecognized‐boundary remove and missing‐boundary interpolation. In the second step, the weft color is extracted based on RGB color histograms of whole fabric image. In the third step, the pixels in each warp yarn are classified into two clusters by fuzzy C‐means clustering (FCM) algorithm in CIELAB color model separately, and the preliminary recognized layout of color warps is obtained. All warp colors are clustered by FCM algorithm in CIELAB color model again and the precise layout of color warps is output. The experimental and theoretical analysis proved that the proposed method can recognize the layout of color yarns of single‐system‐ mélange color fabrics with satisfactory accuracy and good robustness. © 2015 Wiley Periodicals, Inc. Col Res Appl, 40, 626–636, 2015     

Imparting strength into nanofiberous yarn by adhesive bonding

Low strength is one of the main disadvantages of nanofibrous structures in some applications such as suture yarns. To overcome this matter, in the present research, a novel method was applied to improve the tensile properties of nanofiber yarns. For this purpose, nanofibers and particles of polyvinyl acetate (PVAc) were added as a hot melt adhesive to nanofiber yarns in order to initiate adhesive bonding between nanofibers by two approaches. In the first one, Nylon 66/ PVAc hybrid nanofiber yarn was produced in opposite charged nozzles set up. In another approach, PVAc particles were electrosprayed through one of the nozzles while nylon 66 nanofibers were producing through another one. Afterward, thermal treatment was carried out for 78 seconds on samples in different temperatures. The results indicate that tensile strength was improved up to 1.97 and 1.7 times in comparison to nylon 66 nanofiberous yarn by adding PVAc nanofibers and particles, respectively. FTIR analysis was also carried out to assess the hybrid sample composition after heat treatment.     

Multiple conjugate electrospinning method for the preparation of continuous polyacrylonitrile nanofiber yarn

Continuous polyacrylonitrile nanofiber yarns were fabricated by the homemade multiple conjugate electrospinning apparatus, and the principle of yarn spinning was studied. The effects of the applied voltage, flow rate, spinning distance, and funnel rotary speed on the diameter and mechanical properties of nanofiber yarn were analyzed. The diameter of the nanofibers decreased with increasing applied voltage and the flow rate ratio of the positive and negative needles (F_P/F_N), whereas the diameter of nanofibers increased with increasing overall flow rate and needle distance between the positive and negative. Subsequently, the diameter of the yarns increased first and then decreased with increasing applied voltage, F_P/F_N, and needle distance. However, the diameters of the yarns increased dramatically and then remained stable with increasing overall flow rate. The nanofibers were stably aggregated and continuously bundled and then uniformly twisted into nanofiber yarns at an applied voltage of 20 kV, an overall flow rate of 6.4 mL/h, a needle distance of 18.5 cm, and an F_P/F_N value of 5:3. With increasing funnel rotary speed, the diameters of the nanofibers and yarns decreased, whereas the twist angle of the nanofiber yarns gradually enlarged. Meanwhile, an increase in the twist angle brought about an improvement in the yarn mechanical properties. Nanofiber yarns that prepared showed diameters between 70 and 216 μm. Nanofiber yarns with a twist angle of 65° showed a tensile strength of 50.71 MPa and an elongation of 43.56% at break, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40137.     

Color specification of a single strand of yarn from a multispectral image

Many applications in textile require color measurement of single strands of yarns due to unavailability of a mass of consecutive yarns. While multispectral imaging systems can capture images of single strands of yarns, an unavoidable problem accompanied is how to specify their colors from images, in which pixel values vary with positions owing to three‐dimensional shape of yarn. Based on the response of multispectral imaging systems to single strands of yarns, this article formulates the color specification problem as an optimization question and four methods are proposed: average of all pixels (AA), average of pixels in central area (AC), maxima of all pixels (MA), and lightness weighting method (LW). The first experiment analyzed color distribution of pixels on a single strand of yarn. Experimental results show pixels in central area have smallest color variation and largest intensity. The second experiment compared the proposed methods. Results show that CIEXYZ, L*, and C* values specified by the AA and MA methods are lowest and highest. Finally, colors of single strands of yarns specified by the proposed methods were compared with spectrophotometric colors of yarn windings using 12 pairs of single strands of yarns and yarn windings. Experimental results show the MA method yields the smallest lightness and chroma difference compared with spectrophotometric colors of yarn windings. The average color difference between spectrophotometric colors of yarn windings and multispectral imaging colors of single strands of yarns specified by the AA, AC, MA, and LW methods is 3.45, 2.72, 2.37, and 3.33 CMC(2:1) units. © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 500–512, 2016     

Failure mechanism of polyamide 66 nanofiber yarns under fatigue and static tensile loading

This work aims at fractography of polyamide 66 nanofiber yarns. The yarns are produced with three twist levels via electrospinning. In order to study the fracture modes of nanofiber yarns, fatigue, and static tensile tests including monotonic, low cycle fatigue, and postcyclic monotonic tensile tests are performed. It is observed that the catastrophic failure of yarns is associated with axial splitting in the three categories. The nanofibers within the yarn structure show a ductile fracture and buckle after tensile stress release. In comparison of postcyclic monotonic tensile tests with other categories, nanofibers show severe plastic buckling in response to release of the same applied force. Fractography studies reveal that twisting causes construction of a layered structure in the yarns which is similar to the ideal yarn structure as well. Applying cyclic loading causes the separation of these structural layers which is more considerable under higher number of cycles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41925.     

Crosslinking of poly(N‐vinyl‐2‐pyrrolidone) in the coating of cotton yarn

Coating of cotton yarn is employed in the textile industry to increase the mechanical resistance of the yarns and resistance to vibration, friction, impact, and elongation, which are some of the forces to which the yarn is subjected during the weaving process. The main objective of this study is to investigate the usage of a synthetic hydrophilic polymer, poly(N‐vinyl‐2‐pyrrolidone) (PVP), to coat 100% cotton textile yarn, aiming to give the yarn a temporary mechanical resistance. For the improvement of the mechanical resistance of the yarn, the following crosslinking processes of PVP were investigated: UV‐C (ultraviolet) radiation, the Fenton and photo‐Fenton reactions, and sensitized UV‐C radiation. The influence of each crosslinking process was determined through tensile testing of the coated yarns. The results indicated that the best crosslinking process employed was UV‐C radiation; increasing the mechanical resistance of the yarn up to 44% if compared with the pure cotton yarn, that is, without polymeric coating and crosslinking. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.     

Controllable Aligned Nanofiber Hybrid Yarns with Enhanced Bioproperties for Tissue Engineering

Electrospun nanofibers have large surface area, high porosity, and controllable orientation while conventional microfibers have appropriate mechanical properties such as stiffness, strength, and elasticity. Therefore, the combination of nanofibers and microfibers can provide building elements to engineer biomimetic scaffolds for tissue engineering. In this study, a core–shell structured fibrous structure with controllable surface topography is created by electrospinning polycaprolactone (PCL) nanofibers onto polyglycolic acid (PGA) microfibers. The surface morphology, surface wettability, and mechanical properties of the resultant core–shell structure are characterized. FE‐SEM images reveal that the orientation of PCL nanofibers on the yarn surface can be tuned by a fiber collector and rotating disks. Benefiting from the introduction of a shell of aligned PCL nanofibers on the core of PGA yarn, the uniaxially aligned PCL nanofiber–covered yarns (A‐PCLs) exhibit higher hydrophilicity, porosity, and mechanical properties than the core PGA yarns. Moreover, A‐PCLs promote the adhesion and proliferation of BALB/3T3 (mouse embryonic fibroblast cell line), and guide cell growth along the biotopographic cues of the PCL nanofibers with controllable alignment. The developed core–shell yarn having both the desired surface topography of PCL nanofibers and mechanical properties of PGA microfibers demonstrates great potential in constructing various tissue scaffolds.