Xinjin Liu

Purpose: Yarns that offer desirable softness and low residual torque, while maintaining adequate strength, are highly sought after for enhancing comfort and meeting processing requirements in textiles. By structure design and modified spinning processes, we aimed to develop a novel countertwist ring-spun method to produce all-staple, sheath-core structural yarns with both optimized softness and adequate strength. Design/methodology/approach: A two-step twisting approach was used to apply counter twisted sheath-core structure to the designed ring-spun yarns. The morphological analysis reveals the twist transition between the core yarn and the outer sheath fibers during the spinning process. The effect of the applied twist factor on the softness, strength, residual torque, hairiness and abrasion resistance performance of the sheath-core countertwist yarn was systematically investigated. A comprehensive comparison between the developed countertwist yarns with conventional ring-spun yarns was also conducted. Findings: Results show that the sheath-core countertwist yarn possesses minimal loss in breaking strength (<9.2%) and a slight increase in hairiness (18.9%, p < 0.001) and maintaining desirable softness. Moreover, the overall performance of the sheath-core countertwist yarn outperforms certain ring-spun yarns produced by new spinning technologies. Practical implications: The developed sheath-core countertwist yarn offers a promising alternative for producing soft and comfortable textiles with low skew and robust mechanical properties, showing great potential for commercial applications, such as baby undergarments. Originality/value: Currently, achieving a balanced performance in both the softness and strength of ring-spun yarns remains challenging. Moreover, soft yarns spun by low-twist methods generally suffer from low abrasion resistance and high hairiness. There is no research reporting on the structure design of sheath-core countertwist yarns and systematic studies on the effects of twisting evolution of sheath and core yarns have yet to be conducted.

Purpose: Through the tracer fiber method, we strive to more accurately obtain the hook degree, straightening degree, percentage and other characteristic indexes. In order to intuitively represent the hook state from sliver to yarn, and feed back production information in combination with quality test.Design/methodology/approach: Taking the cotton fiber as an example, the hooked fibers were studied by using the tracer fiber method. Tracer fibers were made from cotton-type viscose fibers. Tracer fibers and combed cotton fibers were uniformly mixed for many times and used to produce the card sliver, semi-drawn sliver, drawn sliver, roving and yarn. With the help of ZF-20D ultraviolet analyzer, geometric parameters of hooked fibers were measured, and characterization indexes were calculated. And hook indexes and quality indexes were compared.Findings: By redefining and reclassifying hooked fibers, the change of hooked fibers in the process was tracked and characterized carefully. Some hooks in card sliver are straightened but not eliminated, and will form longer zero-angled hooks in the subsequent process. The straightening degree and number of zero-angled hooks affect the evenness CV mainly.Originality/value: The characterization of hooked fibers is important for reducing hooked fibers and spinning high quality yarns. There is no uniform standard for the characterization of hooked fibers at present. Most studies are about relationship between process and hook in carding and drawing. There is no research on hooked fibers in the whole spinning process. In the paper, hooked fibers were redefined and reclassified, the change of hooked fibers in the process was tracked and characterized carefully.

Tensile property is one basic mechanics performance of the fabric. In general, not only the tensile values of the fabric are needed, but also the dynamic changing process under the tension is also needed. However, the dynamic tensile process cannot be included in the common testing methods by using the instruments after fabric weaving. By choosing the weft yarn and warp yarn in the fabric as the minimum modeling unit, 1:1 finite element model of the whole woven fabrics was built by using AutoCAD software according to the measured geometric parameters of the fabrics and mechanical parameters of yarns. Then, the fabric dynamic tensile process was simulated by using the ANSYS software. The stress–strain curve along the warp direction and shrinkage rate curve along the weft direction of the fabrics were simulated. Meanwhile, simulation results were verified by comparing to the testing results. It is shown that there are four stages during the fabric tensile fracture process along the warp direction under the tension. The first stage is fabric elastic deformation. The second stage is fabric yield deformation, and the change rate of stress begins to slow down. The third stage is fiber breaking, and the change of stress fluctuates since the breaking time of the fibers is different. The fourth stage is fabric breaking. In this paper, the dynamic tensile process of blended woven fabrics was studied by using finite element method. Although there are differences between the simulation results and experimental testing results, the overall tendency of simulation results is the same as the experimental testing results.

In the ring-spinning process, the area between the front roller nip and twisting point is spinning triangle, and its geometry influences the fiber tension distribution in the spinning triangle directly and determines the properties of spun yarns. Therefore, in the paper, one kind of mechanical false-twisting device was introduced on the ring spinning, which can affect the twist propagation and change the spinning triangle geometry actively. First, the modification of the false-twisting device on the DTM129 ring-spinning frame was introduced. Taking the medium cotton yarn spinning as an example, corresponding ring yarn, Sirospun yarn, compact yarn were spun on the modified spinning frame under different designed twist factors, and the applicability of the false-twisting device on different spinning method was discussed. It is shown that comparing with the common yarn, the Hairiness and Strength of the modified yarns are all improved, and the effect of false-twisting device on yarn qualities is more effective for the low-twist yarn. Comparing with the ring spinning, the improvement degree of the modified compact spinning is a little smaller. Then, the long-staple cotton ring yarn, polyester and medium cotton blend ring yarn, polyester ring yarn were spun on the modified spinning frame under different designed twist factors, and the applicability of the false-twisting device on different fibers was discussed. It is shown that the influence of the false-twisting device on the long-staple cotton yarn and polyester yarn is little. That is, the false-twisting device given in the paper would be more applicable on the short fiber spinning under the low designed twist factor.

Purpose: As a natural fiber, yakwool has attracted much attention in textile processing due to its excellent properties and wearabilities. However, the main colors of yakwool are black and brown. Therefore, for extending the application scopes of the fiber, the decolorization of the yakwool fiber is usually needed, especially for the black fiber. The paper aims to discuss this issue.Design/methodology/approach: In the paper, the properties of the yakwool fiber were tested first, especially the melanin granules in the fiber. Then, the decolorization of the yakwool fiber was studied using the oxidation–reduction decolorization method, and corresponding optimal process of the decolorization was given. Then, the properties of the decolorized yakwool fiber were tested and compared with those of the original fiber.Findings: It is shown that, after decolorization, the physical and mechanical properties of the fiber were deteriorated, especially in terms of the strength and elongation. Therefore, the fiber became shorter and thinner, and the scales were damaged. When compared with the yarn spun from the original yakwool fiber, it was observed that the properties of the yarn spun from the decolorized yakwool fiber deteriorated because of the deterioration in the properties of the original fiber.Originality/value: In the paper, for extending the application scopes of the yakwool fiber, the decolorization of the yakwool fiber was studied.

Purpose: Pneumatic compact spinning is the most widely used compact spinning method at present, in which the negative pressure airflow is used to condense the fiber in order to decrease the spinning triangle and improve the yarn qualities. Therefore, the research on flow field in the condensing zone is always the emphasis for pneumatic compact spinning. The paper aims to discuss these issues. Design/methodology/approach: By using finite element method (FEM), the flow field in two kinds of pneumatic compact spinning was studied. Taking three kinds of cotton yarns as examples, with the help of high-speed camera system OLYMPUS i-SPEED3, the motion trajectory of fiber strand in the condensing zone was obtained. Three-dimensional physical models of the condensing zone of the two compact spinning systems were obtained according to the measured parameters of practical spinning systems. Findings: It is shown that on the both left edge of B1 line and right edge of B2 line, the airflow inflows to the center line of suction slot, and the condensed effects are produced, correspondingly. In the condensing zone, there are three condensing processes acting on the fiber strand, including the rapid condensing effects in the front condensing zone, the adequately condensing effects in the middle condensing zone, and stable output effects in the back condensing zone. Originality/value: By using FEM, numerical simulations of three-dimensional flow field in condensing zone for two kinds of pneumatic compact spinning with lattice apron were presented, and corresponding spun yarn qualities were analyzed.

Purpose: Spun silk is one of the top grade textile materials, and its products have high added value and meet the needs of the market. However, the technology level and process design of silk spinning are still much lower than cotton spinning; especially singeing is applied on spun silk yarn, and generates waste materials. The purpose of this paper is to introduce a kind of pneumatic compact spinning, four-line compact spinning (FLCS), into silk spinning and study the corresponding spun yarn qualities. Design/methodology/approach: First, taking the silk spinning frame FK501 as an example, the process of modification of FLCS is presented. Then, three kinds of spun silk yarns, 80 Nm (12.5tex), 100 Nm (10tex) and 120 Nm (8.3tex), are spun on the common silk spinning frame FK501 and the spinning frame modified with FLCS. The evenness, breaking strength and hairiness of spun yarns are tested and comparatively analyzed. After the ply yarn production, three singeing procedures should be applied on the ring ply yarns, while only two singeing procedures should be applied on the compact ply yarns, which is beneficial for material saving. Findings: The results show that compared with ring spun silk yarns, the comprehensive quality of compact spun silk yarns is improved, especially the harmful long hairiness (=3 mm) of yarn. Compared with the single spun silk yarn, the comprehensive qualities of the ply yarn are improved; especially, the breaking strength of the ply yarns is two times larger than the single yarn. After singeing, the hairiness of the ply yarn is decreased greatly, and the evenness is also improved, while the strength is decreased. Compared with ring spun silk yarn, the singeing times of compact spun silk yarn can be decreased, and the gas consumption in each singeing is also decreased, which is beneficial for material saving. Originality/value: In this paper, a kind of pneumatic compact spinning, FLCS, is introduced into the silk spinning. It is shown that compared with ring spun silk yarns, the comprehensive quality of compact spun silk yarns is improved, especially the harmful long hairiness (=3 mm) of yarn. After the ply yarn production, three singeing procedures should be applied on the ring ply yarns, while only two singeing procedures should be applied on the compact ply yarns, which is beneficial for material saving.

Purpose: – Pneumatic compact spinning is the most widely used compact spinning method at present, in which the negative pressure airflow is used to condense the fiber bundle and decrease the spinning triangle. Compact spinning with perforated drum and lattice apron are mainly two kinds of pneumatic compact spinning now. The purpose of this paper is to study the comparative analysis on four kinds of pneumatic compact spinning systems, including two kinds of compact spinning with perforated drum: Rieter’s COM4 and complete condensing spinning (CCS), two kinds of compact spinning with lattice apron: Sussen’s three-line compact spinning (TLCS) and Toyota’s four-line compact spinning (FLCS). Design/methodology/approach: – First, the basic properties of four systems were introduced and comparatively analyzed. Then, the 29.2 tex (20S), 14.6 tex (40S), 9.7 tex (60S) and 7.3 tex (80S) combed cotton yarns were spun in the four pneumatic compact spinning systems and ring spinning system, respectively. The evenness, breaking strength and hairiness of spun yarns were tested. Finally, the properties of corresponding woven fabric were tested. Findings: – It is shown that comparing to compact spinning with lattice apron, the disposable input cost of compact spinning with perforated drum is higher, but the maintenance cost is lower. Comparing to compact spinning with lattice apron, the evenness of yarn spun by compact spinning with perforated drum is improved whereas the breaking strength is decreased. Furthermore, although harmful long hairiness (=3 mm) of yarn spun by CCS is a little more, the beneficial short hairiness (1-2 mm) is also more, which can make the fabric fullness and have better comfortable feeling. Originality/value: – In the paper, comparative analysis on four kinds of pneumatic compact spinning systems, compact spinning with perforated drum: Rieter’s COM4 and CCS, and compact spinning with lattice apron: Sussen’s TLCS and Toyota’s FLCS, were studied. The basic properties, spun yarn qualities and properties of corresponding woven fabric of four systems were analyzed comparatively.