Untwisted Filaments Research Articles

Assessing the contribution of sewing threads to microfiber release during domestic laundering

Environmental science studies from the past decade have emphasized that microplastics in aquatic environments are mostly caused by domestic laundering of synthetic textiles. Although many studies have explored the microfiber release behavior of fabrics washed in laundry, attempts to witness microfiber release from sewing threads, which are an inevitable part of any finished garment, are meager. With this research gap, this study attempted to analyze the potential of sewing threads to release microfibers during washing and the extent to which they can contribute to the overall microfiber release during domestic laundering. The study's findings revealed an average release of 2.65 ± 0.70 (n = 33) microfibers/m from the sewing thread sewn on the fabric during laundering. The sewing process was noted to cause damage to the sewing thread, which led to a comparatively higher microfiber release (∼114%) compared with the sewing threads that were washed before sewing. Among the selected sewing threads, higher microfiber emissions were reported with spun threads, followed by twistless filaments, and twisted filament threads. The results showed that coarser sewing threads with higher Tex values released more microfibers than finer Tex threads. Compared to the 20 Tex spun thread, the 80 Tex spun thread showed a 22–150% increase in microfiber release. In the case of filament sewing thread, a similar impact was noted, whereas the role of twist was found to be efficient in reducing microfiber emission. Compared to the untwisted filaments, the ply twisted filaments exhibited approximately 76% lower microfiber emissions. The findings of this study showed that sewing thread contributed approximately 1.09% of the total microfiber emissions from apparel during laundry.

Untwisted α-Synuclein Filaments Formed in the Presence of Lipid Vesicles.

Accumulation of filamentous aggregates of α-synuclein is a pathological hallmark of several neurodegenerative diseases, including Parkinson's disease (PD). The interaction between α-synuclein and phospholipids has been shown to play a critical role in the aggregation of α-synuclein. Most structural studies have, however, been focused on α-synuclein filaments formed in the absence of lipids. Here, we report the structural investigation of α-synuclein filaments assembled under the quiescent condition in the presence of anionic lipid vesicles using electron microscopy (EM), including cryogenic electron microscopy (cryo-EM). Our transmission electron microscopy (TEM) analyses reveal that α-synuclein forms curly protofilaments at an early stage of aggregation. The flexible protofilaments were then converted to long filaments after a longer incubation of 30 days. More detailed structural analyses using cryo-EM reveal that the long filaments adopt untwisted structures with different diameters, which have not been observed in previous α-synuclein fibrils formed in vitro. The untwisted filaments are rather similar to straight filaments with no observable twist that are extracted from patients with dementia with Lewy bodies. Our structural studies highlight the conformational diversity of α-synuclein filaments, requiring additional structural investigation of not only more ex vivo α-synuclein filaments but also in vitro α-synuclein filaments formed in the presence of diverse cofactors to better understand the molecular basis of diverse molecular conformations of α-synuclein filaments.

Influence of yarn structure and coating on the mechanical performance of continuous viscose fiber/epoxy composites

AbstractThe present study investigated the effect of selected structural parameters on the mechanical performance of regenerated cellulose composites. The experimental setup comprised continuous viscose (rayon) yarns embedded in a matrix of epoxy resin. Mechanical and microscopic characterizations involved comparing the following: yarns consisting of untwisted filaments and twisted warp and weft yarns taken from a plain weave fabric, yarns with and without avivage (fiber finish), as well as yarns with and without an acrylic coating. During the epoxy treatment, samples were either prestressed or laid horizontally to preserve the original yarn structure. Tensile tests revealed that yarn crimp had a significant impact on the strength properties of composite specimens, a higher crimp ratio leading to a decrease in performance. Applying prestress to crimped yarns has proven to be an effective way to enable straight alignment in the loading direction, which is essential for the design of stiffness‐ and strength‐optimized yarn composites. Unlike an avivage, which did not markedly affect the mechanical properties of composite yarns, the application of an acrylic coating prior to resin impregnation was found to provide significantly increased extensibility and more ductile fracture behavior.

Study on the effects of the characteristics of a vortex on splice strength in pneumatic yarn splicing

Pneumatic yarn splicing is a complex process that involves the simultaneous movement of two strands of counter-rotating yarn. Depending on the process and structural parameters of the mingling chamber, the airflow field is more dominant in influencing the wrapped effectiveness of untwisted filaments and consequently the splice strength. This study establishes a computational domain of a mingling chamber comprising an inlet channel, accelerating channel, rotating channel, and groove channel. The renormalization-group k–ε turbulence model is adopted to simulate the vortex patterns in the rotating channel under different inlet pressure. Furthermore, a transient mass flow test bench based on the isothermal principle is used to verify the numerical simulation results by comparing the mass flow of a pneumatic splicer. A wrapped model of spliced yarn is presented to describe the effects of wrapped force determined by the characteristic of vortex patterns on the strength of spliced yarn. A strength tester is also used to acquire the strength of spliced yarn produced under different inlet pressures and interpret the reliability of theoretical analysis. Comparisons between numerical results and experimental data show that the inlet pressure of the mingling chamber clearly affects the vorticity of the vortex and the strength of spliced yarn. The vorticity of the vortex will be enhanced with increasing inlet pressure and improve splice strength to avoid insufficient twisting of the yarn end. However, excessive twisting of the yarn end, as reflected by splice strength, would occur if the inlet pressure strengthens continually.

A 3D Model on the Electromechanical Behavior of a Multifilament Twisted Nb3Sn Superconducting Strand

At present, conventional low-temperature superconductors such as Nb3Sn strands have been extensively applied in high-energy and nuclear physics, as well as in magnetic resonance imaging systems. In this paper, a 3D finite element model considering sophisticated structure of superconducting filament bundles and metal matrix elements is built to deal with the electromagnetic behaviors of a Nb3Sn strand exposed to tension and bending loads. The mechanical constitutive relations of filament bundles and metal matrix are described with elastic and elasto-plastic axial stress–strain curve, respectively. The voltage–current characteristic of the metal matrix elements is determined with the Ohmic law, and that of the superconducting filaments follows the n power relation. The stress–strain state is simulated and then implemented in the electromagnetic model, through the scaling law of ITER Nb3Sn strand. We find that the plasticity of copper and the twist filaments cause the enhanced inhomogeneous strain profile in a strand composite, compared to the strain profile in a strand with untwisted filaments. We also discuss the current/field profile, critical current degradation, and AC loss in the strand composite under the tension and bending loads.

Experimental study of magnetization AC loss in MgB2 wires and cables with non-magnetic sheath

The influence of MgB2 wires design on the magnetization AC loss was studied. AC loss in external AC magnetic field perpendicular to the wire axis was measured in the temperature range from 18K up to 40K and at the frequencies of 72Hz and 144Hz, respectively. For this purpose the experimental apparatus combining magnetization measurement system and non-magnetic vacuum vessel with two-stage crycooler for sample cooling has been used.To clarify the influence of wire architecture on the AC loss in non-magnetic GlidCop sheathed MgB2 composites experiments on a single-core, 30-filament un-twisted and also twisted samples were performed. MgB2 cables containing 7 mono-core strands and 30 filament strands were also measured. While in the cable containing single core strands the hysteresis loss was dominant, in the un-twisted wire and the cable with un-twisted filaments the coupling loss prevailed. The effect of decoupling was observed in all twisted filamentary wires. The obtained results show that in 7 strands cable the AC loss of strands is crucial to the overall AC loss of a cable.

Numerical Simulation of $\hbox{Nb}_{3}\hbox{Sn}$ Strands Performances With Bending Strain and Comparison With Experimental Measurements

In order to study the effect of bending on strands' performances, a finite differences numerical method has been implemented at ENEA, which discretizes a single strand in several elements representing bundles of twisted filaments. The code has been validated, and a satisfactory agreement has been obtained with experimental measurements carried out on an ITER-type OST strand, highlighting the critical impact of geometric modeling and the potential of the model as a predictive tool. The aim of this work is to verify the agreement between model results and critical current measurements of bent strands, and to help in clarifying some aspects of current redistribution process within the strand cross-section, in view of developing more appropriate theoretical models. Further improvements to the model system are presented: in order to simulate more representative conditions for cables in operating conditions, periodic bending is now introduced. Simulation results are compared with available experimental data on OST Dipole strand, with both twisted and untwisted filaments. Numerical values from the inter-filament resistivity measurements carried out at ENEA, are introduced as computational parameters, being the transverse resistance the main physical factor governing the analyzed mechanisms in multi-filamentary superconductors. In all those cases a satisfactory agreement among measurements and computational results has been found.

AC Losses in ${\rm MgB}_{2}$ Multifilamentary Strands With Magnetic and Non-Magnetic Sheath Materials

AC applied magnetic field loss measurements have been performed on MgB2 superconducting strands. We measured strands with six untwisted filaments made via an in-situ route with Nb chemical barriers, a Cu-inter-filamentary matrix, and with either non-magnetic (glidcop) or magnetic (monel) outer sheaths. AC losses in magnetic fields applied perpendicular to the wire axis have been measured in fields up to 140 mT (peak) in the frequency range 50-200 Hz in a liquid helium bath at 4.2 K. For samples with no ferromagnetic elements present in their matrix there is a reasonable agreement of the losses with the critical state model in low frequency region. At higher frequencies the losses are dominated by eddy currents in Cu matrix. The samples containing a weakly ferromagnetic matrix showed complex hysteresis loops and AC loss dependencies.

DC and AC self-magnetic field profiles of (6+1) filamentary BSCCO tapes with different filament arrangements measured by Hall probe magnetometry

The magnetic field distribution in the vicinity of (BiPb) 2Sr 2Ca 2Cu 3O 10+ x tapes carrying a transport current was measured with AC/DC Hall probe scanning magnetometer. Magnetic field profiles of multifilamentary BSCCO tapes supplied by DC transport current were compared with those of tapes supplied by AC transport current at frequency 90 Hz. The samples had seven untwisted filaments arranged in columns, in slanted columns or evenly distributed across the tape cross-section. Areas of filamentary regions and the aspect ratios of the samples were nearly identical. We compared calculated magnetic field profiles of each geometry in the regime of full penetration with the measured ones. It was found that in the case of evenly distributed filaments the shapes of DC and AC profiles were very similar, however the tapes with filaments stacked in columns and in slanted columns had very different shapes of DC and AC profiles at the same current amplitudes, especially in low current region. This effect can be attributed to the differences in static and dynamic penetration of flux into the interior of multifilamentary structure of the conductor.

AC losses in superconducting Ag/Bi-2223 composite tapes with interfilamentary barrier

Power dissipation in multifilamentary Ag/Bi-2223 composite tapes was measured using AC magnetization loss measurement method. In order to decrease the interfilamentary electromagnetic coupling currents in the tapes the filaments were separated by resistive ceramic barriers, made of Bi-2201 phase or Al 2O 3 powder. The tape samples used in this study were with twisted and untwisted filaments. The magnetization loss measurements were performed in a sinusoidally varying external magnetic field (parallel to the plane of a tape) and with a DC transport current flowing along a tape. The frequency range of the sinusoidal varying field was 11–115 Hz. Some anomalies in magnetic losses due to DC current flowing distributions are observed. The obtained results are compared with the critical state model predictions.

Study of important factors affecting AC losses of multifilamentary Bi-2223 tapes

We measured DC critical currents and magnetization curves on samples of Bi-2223/Ag multifilamentary tape with 55 untwisted filaments and on individual filaments extracted from the tape at frequencies from few mHz up to 150 mHz at 77 K. Hall probe technique was used for magnetization measurements on tape as well as filament samples. A calibration method based on the properties of the virgin curve is described. We also measured resistivity between a filament and Ag matrix for an individual filaments extracted from the tape. To detect filament intergrowths we measured I– V curves on tape sample with current flowing in the tape perpendicular to its axis. Consequences of the observed effects for the interpretation of AC loss behavior of multifilamentary tapes are discussed.

Power dissipation in composite Ag/Bi-2223 tapes with twisted and untwisted filaments

Power dissipation in a set of multifilamentary Bi2223 silver sheathed composite tapes (with 61 filaments) was measured using AC magnetization and transport loss measurement techniques. In order to decrease the interfilamentary bridging and thus electromagnetic coupling, the space between filaments was considerably increased. The tape samples used in this study were with twisted (twist pitch 15 mm) and untwisted filaments. Critical currents were of the order of 55 Amps, as measured by a standard four-point technique, and corresponds to a critical current density of approximately 9 kA cm/sup -2/. The AC transport current losses were measured by a standard four-point lock-in method; in the range of-the transport current frequency of 40-160 Hz. The magnetization loss measurements were performed in a sinusoidally varying external magnetic field, at the frequency range of 11 to 155 Hz. The external magnetic field was oriented parallel to the plane of a tape. The obtained results are compared with theoretical predictions of the critical state model.

Reduction of the a.c. losses in Ag sheathed PbBi2223 tapes with twisted filaments

Measurements of the total a.c. losses in an applied parallel a.c. magnetic field have been measured for Bi2223/Ag tapes with twisted and untwisted filaments. The measurements were undertaken using suitable pickup loops and a lock-in amplifier. For all frequencies (37–200 Hz) and field amplitudes used (<45 mT) the tape with untwisted filaments behaved as if its filaments were fully coupled. For this situation, the total losses were accurately described using the Bean model for a 1D slab (assuming the tape acts as a monoblock). In contrast, the losses for the tape with twisted filaments (10-mm pitch) were considerably less than for the tape with untwisted filaments over the entire frequency and field amplitude range. The loss behaviour indicated that the filaments were partially decoupled, and the total losses in this tape were best described by adding the filament hysteresis losses to the coupling current losses. The filament losses were calculated using the Bean model for a slab with dimensions of an individual filament and the coupling current losses predicted from existing theory for a tape geometry in parallel field.

Experimental study on AC losses in Ag sheathed PbBi2223 tapes with twist filaments

Experimental measurements of AC losses were carried out on Ag sheathed PbBi2223 tapes with twisted and untwisted filaments. Losses were measured at 77 K as function of frequency and magnetic field parallel and perpendicular to the tape surface, using appropriate pick-up loops. Both the first and third harmonics of the signal were measured, in order to distinguish between the hysteresis loss and other types of loss. The effect of filaments uncoupling by twisting was clearly identified. For a tape with a twist pitch of 10 mm and I c=40 A (∼20 kA cm −2) operating at 43 Hz, the filaments are uncoupled in fields less than 40 mT, which is greater than the full penetration field for both the filaments and the tape. Hence, a reduction in the hysteretic loss of the superconducting core is realised at power frequency between 10 and 40 mT. Results form the self-field loss measurement implies the uncoupling of twisted filaments at relative low transport current ( I<0.5 I c)