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15 December 2023, Volume 44 Issue 12

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Fiber Materials

Fabrication and properties of metallocene polyethylene spunbond filament based on Polyflow simulation

LIU Ya, ZHAO Chen, ZHUANG Xupin, ZHAO Yixia, CHENG Bowen

Journal of Textile Research. 2023, 44(12):  1-9.  doi:10.13475/j.fzxb.20220705301

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Objective Spunbond products are widely used in the fields of sanitary materials, packaging, and agriculture. Currently, spunbond products on the market are mainly made from polypropylene (PP) and polyester (PET). Although these materials have high strength, their softness is not good enough to meet the requirements of high softness applications. The metallocene polyethylene (mPE) is used to form membrane for its excellent softness. Because of its poor spinnability, mPE is rarely used in spunbond technology. As such, it is important to study the spinning properties of mPE to modify the performance of traditional spunbond products.
Method The thermal and rheological properties of mPE were analyzed first. According to data available, the flow velocity distribution and extrusion state of mPE melt were simulated by Polyflow numerical simulation method during the preparation of mPE spunbond filament. The velocity distribution and extrusion expansion trend of mPE melt were analyzed under different extrusion temperature. According to the simulation results, the parameters of spinning experiment were guided, and the spunbond filaments of mPE with different mechanical drafting multiples were achieved. In order to characterize the mechanical properties of mPE fiber, numbers of common fibers were used for comparison.
Results The thermos-gravimetric analysis result showed that the thermal decomposition temperature of mPE was 405 ℃ (Fig. 1 (a)), and the differential scanning calorimetry result showed the melting range of mPE was 93.9-130.1 ℃ (Fig. 1(b)). According to the thermal properties, the simulation temperature of rheological test was preliminarily set in the range of 220-280 ℃. The melt flow velocity of mPE increased with the increase of melting temperature (Fig. 5) but decreased rapidly after extruding from the spinneret orifice (Fig. 6) in the simulation experiments. The extrusion swell phenomenon of mPE was quite evident after melt extrusion, the lower the extrusion temperature was, the higher the die swell ratio was, and the maximum was 1.52 at the temperature of 230 ℃. The results of Polyflow simulation were used to guide and optimize the parameters of the spunbond process. Finally, the mPE spunbond filaments with different mechanical drafting multiples were successfully prepared at the spinning temperature of 240 ℃. The performance of series mPE filaments were characterized. The results showed that the diameter of mPE filament decreased with the increase of drafting multiple, and the minimum diameter of mPE filament was 64.2 μm with the drafting multiple of 6 times, the variation reached 61.5% compared with the drafting multiple of 1 time (Fig. 8). Because of the rapid cooling of the trickle flow, the amorphous part disentangled and carried out preferred orientation along with mechanical drafting, more molecular chains in the polymer participated in crystallization, the crystallinity of mPE filament increased with the increase of drawing multiple (Fig. 9). The maximum of the crystallinity was 50.1% with the drafting multiple of 6 times. As the trickle flow further oriented and crystallized with the increase of the drafting multiple, the breaking strength of mPE filament increased and the fracture elongation decreased with the increase of the drawing multiple (Fig. 10). Compared with the common fibers appeared on the market, the mPE filament drawn to 6 times exhibited the best mechanical performance, the breaking strength was 3.44 cN/dtex, and the fracture elongation was 85.69%.
Conclusion Polyflow simulation is used to simulate the flow velocity distribution and extrusion state of the mPE melt in the spunbond process. It proves that the Polyflow simulation results can be used to guide and optimize the process parameters for mPE spinning experiment. The performance test of mPE spunbond filament proves the reliability of the simulation method and the feasibility of mPE application in spunbond technology. The testing results also reveal that mPE filament has excellent mechanical properties, which can be used to form the bi-component spunbond with PP, PET and other raw materials, so as to modify the performance of traditional mono-component spunbond material with softer feeling, which can meet the requirements of high softness for certain applications.

Preparation and photocatalytic properties of g-C₃N₄/MXene/Ag₃PO₄/polyacrylonitrile composite nanofiber membranes

WANG Peng, SHEN Jiakun, LU Yinhui, SHENG Hongmei, WANG Zongqian, LI Changlong

Journal of Textile Research. 2023, 44(12):  10-16.  doi:10.13475/j.fzxb.20220901601

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Objective Aiming at problems in the field of photodegradation, such as low mass transfer efficiency of a single catalyst, easy recombination of photogenerated carriers, limited light absorption performance and reaction active site, and poor reusability, a self-assembly method was used to construct a g-C₃N₄/MXene/Ag₃PO₄ S-type heterojunction catalyst structure, attempting to dope catalyst into polyacrylonitrile (PAN) spinning solution. The g-C₃N₄/MXene/Ag₃PO₄/PAN composite nanofiber membranes were successfully prepared using electrospinning technology.
Method In order to further characterize the morphology and structure of the composite nanofiber membrane, we used scanning electron microscopy, transmission electron microscope, infrared spectroscopy, and X-ray diffraction to characterize the size and morphology of the nanofiber membrane and its photocatalytic degradation performance for specific dyes. We also investigated its photocatalytic degradation performance for dye wastewater such as Reactive Red 195 in order to further explore its practical application potential. SEM and TEM characterization analysis showed that when photocatalysts were added, the nanofibers changed from a uniform long straight fibrous structure to a curved network structure.
Results The morphology of the nanofibers in the PAN composite nanofiber membrane was better, and g-C₃N₄/MXene/Ag₃PO₄ could be loaded onto the PAN through electrospinning technology. The g-C₃N₄/MXene/Ag₃PO₄ could be uniformly distributed on the surface of the composite nanofiber membrane. The diameter before and after loading g-C₃N₄/MXene/Ag₃PO₄ on the fibers showed a uniform state, with a size of approximately 200-400 nm. To investigate the specific impact effects, a composite nanofiber membrane was used for photocatalytic degradation of 50 mL of Reactive Red 195 (0.05 mmol/L) solution. The experimental results showed that the degradation rate of g-C₃N₄/MXene/Ag₃PO₄ gradually increased with time, and the dye was almost completely degraded after 60 min. This fully demonstrated the very important role of g-C₃N₄/MXene/Ag₃PO₄ in the degradation of Reactive Red 195 dye. In addition, although the degradation rate of dyes by g-C₃N₄/MXene/Ag₃PO₄/PAN was slow in the early stage of the reaction, the dyes were almost completely degraded at 180 min, indicating that the composite nanofiber membrane showed the same degradation effect as g-C₃N₄/MXene/Ag₃PO₄ and still had good photocatalytic degradation performance for dyes. After 180 min, the photocatalytic activity of g-C₃N₄/MXene/Ag₃PO₄/PAN composite nanofiber membrane was still high, with a degradation rate of 91.23%, exhibiting good recyclability. The g-C₃N₄/MXene/Ag₃PO₄/PAN still had a high decolorization rate for Reactive Red 195 after 5 cycles of used. The degradation rates of Reactive Red 195 were 91.23%, 82.54%, 81.40%, 79.30%, and 77.11% after 5 cycles of reaction for 180 min, respectively, indicating that g-C₃N₄/MXene/Ag₃PO₄/PAN had good reusability and stability. Exploring the photocatalytic mechanism of g-C₃N₄/MXene/Ag₃PO₄ catalyst, it was found through radical quenching experiments that superoxide radicals ·$\mathrm{O}_{2}^{-}$ and hole h⁺ were the main active species in the oxidative degradation reaction of dyes. After adding tert-butanol, disodium ethylenediaminetetraacetic acid, and p-benzoquinone to the reaction system, the degradation rates of Reactive Red 195 were 86.15%, 42.31%, and 10.82% at 180 min, respectively. This indicated that in the g-C₃N₄/MXene/Ag₃PO₄/PAN system, the contributions of ·OH, h⁺ and ·$\mathrm{O}_{2}^{-}$ to the decolorization and degradation reactions of dyes were 5.05%, 48.89%, and 80.38%, respectively. The ·$\mathrm{O}_{2}^{-}$ and h⁺ were the main active species in the oxidative degradation reactions of dyes.
Conclusion It was proposed that the mechanism of photocatalytic oxidation degradation of dyes may be the formation of a reasonable S-type heterojunction in g-C₃N₄/MXene/Ag₃PO₄. The introduction of MXene with high conductivity as a solid-state electron mediator leads to faster electron transfer from Ag₃PO₄ to the surface of g-C₃N₄, resulting in higher catalytic performance of the catalyst. This S-type heterostructure provides stronger reduction/oxidation ability to generate more active free radicals and higher catalytic activity to degrade pollutants, thereby decomposing Reactive Red 195 into small molecules under the synergistic effect of ·$\mathrm{O}_{2}^{-}$ and h⁺.

Fabrication and properties of biocompatible nanocellulose self-healing hydrogels

WANG Hanchen, WU Jiayin, HUANG Biao, LU Qilin

Journal of Textile Research. 2023, 44(12):  17-25.  doi:10.13475/j.fzxb.20220704301

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Objective Hydrogel materials have a wide range of promising applications in various fields such as drug delivery, tissue healing, and wearable electronic devices because of their soft texture and 3-D porous structure. However, the low durability and poor biocompatibility of traditional hydrogels have limited their practical applications. Therefore, a self-healing hydrogel with good biocompatibility and injectable capacity should be designed to provide novel perspectives to break the current technological bottleneck.
Method The self-healing property of hydrogels depends mainly on dynamic chemical bonding, which restores damaged chemical bonds and resumes the hydrogel to its original properties. Biocompatible nanocellulose self-healing hydrogels (Gel/DNCC/Borax/Ta) with triple crosslinking networks were prepared by reversible crosslinking the amino group in gelatin (Gel) and the aldehyde group in dual formaldehyde nanocellulose (DNCC) to form imine bonds as the first crosslinking network. Then tannin (Ta) and borax(Borax) were introduced into the hydrogels to form multiple hydrogen bonding network and dynamic borate ester bonding network.
Results The thermal stability of Gel/DNCC/Borax/Ta hydrogels was enhanced compared to gelatin, with the thermal decomposition temperature increasing from 277.3 ℃ to 301.0 ℃, and the maximum mass loss rate temperature increasing from 312.9 ℃ to 320.9 ℃. Compared with Gel/DNCC hydrogel, the mechanical properties and colloidal viscoelasticity of Gel/DNCC/Borax/Ta hydrogel were significantly enhanced, with the fracture strength increasing from 0.138 MPa to 0.353 MPa, representing an increase of 155.7%, and the compressive strength increasing from 0.686 MPa to 1.422 MPa, and the energy storage modulus increasing from 960 Pa to 1 550 Pa with an increase of 61.4%. The beneficial thermal and mechanical properties of Gel/DNCC/Borax/Ta hydrogels was due to the synergistic effect of multiple hydrogen bonds and dynamic covalent bonds in the hydrogels, forming a compact triple cross-linked network, thus enhancing their structural stability and improving their thermal stability. The human prosthetic hand model fitting experiments showed that Gel/DNCC/Borax/Ta hydrogel could follow body movement with good flexibility. Syringe injection experiments showed that Gel/DNCC/Borax/Ta hydrogels had good flowability and gelation ability. The cut hydrogel could heal itself and keep its original shape within 1 h at room temperature. The compressive strain of Gel/DNCC/Borax/Ta hydrogel before after healing was 0.519 and 0.509 mm/mm with a self-healing efficiency of 98%, respectively. This indicats the outstanding healing ability of Gel/DNCC/Borax/Ta hydrogel. The self-healing property of the hydrogel is derived from the dynamic borate ester and imine bonds that are re-formed and healed rapidly by their dynamic reversibility after being disrupted during the self-healing process. Detection of the proliferation of fibroblasts treated with various concentrations of gelatin cellulose complex extracts by the CCK8 method. The results showed that 0.5% of gelatin cellulose complex extracts had a well promotion effect on cell proliferation. Flow cytometry was used to measure fibroblast survival, and fibroblasts treated with an infusion containing 0.5% gelatin cellulose complex still had less than 5% apoptosis after 72 h. Cell staining assay showed that fibroblasts were able to survive normally in 0.5% of gelatin cellulose complex extracts.
Conclusion A self-healing hydrogel with good biocompatibility and injectability is developed to solve the problems of low durability and poor biocompatibility that existed in hydrogel materials, which obstructed their applications in wearable electronic devices, tissue healing, and drug delivery. The three-dimensional interpenetrating network structure endows the Gel/DNCC/Borax/Ta hydrogel with strong mechanical properties, thermal stability and good elasticity. The dynamic borate ester bonds and imine bonds give Gel/DNCC/Borax/Ta hydrogels a strong self-healing ability, enabling them to self-heal within 1 h after damage, with a self-healing efficiency of 98%. Since gelatin, a high molecular mass water-soluble protein mixture, can act as a cell culture substrate to promote cell proliferation, DNCC also possesses excellent biocompatibility, giving the Gel/DNCC/Borax/Ta hydrogel a high degree of biocompatibility. Favorable thermal stability, mechanical properties including injectability and flexibility, and biocompatibility give the hydrogel promising potential for use in biomedical and tissue engineering.

Preparation of polylactic acid/magnetic metal organic frame material composite melt-blown fabrics and air filtration performance

SUN Hui, CUI Xiaogang, PENG Siwei, FENG Jiangli, YU Bin

Journal of Textile Research. 2023, 44(12):  26-34.  doi:10.13475/j.fzxb.20220702201

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Objective The rapid development of modern industry and agriculture has promoted the progress of society and improved the quality of people's life. However, the air pollution problem accompanied by the development also poses a serious threat to public health. Melt-blown filter materials with the advantages of high protection, simple preparation process and low price can provide strong defense for human health. In order to prepare the magnetic biodegradable melt-blown air filter material with high filtration efficiency, a magnetic metal organic frame mate-rial (MMOF) was synthesized and mixed with polylactic acid (PLA) to prepare PLA/MMOF composite melt-blown fabrics.
Method MMOF was first synthesized via the hydrothermal method and mixed with PLA resin in different mass ratios by the melt blending in a twin-screw extruder. Then these blends were granulated to obtain PLA/MMOF composite master batches. After that, PLA/MMOF composite master batches were fabricated into the composite melt-blown fabrics with different mass ratios by use of a micro melt-blown testing machine. The morphology, structure, thermal behavior, magnetism, air filtration and mechanical properties of PLA/MMOF composite melt-blown fabrics were characterized and studied.
Results It could be seen that the fiber surface of pure PLA melt-blown fabrics was smooth and had a few small grooves. For PLA/MMOF composite melt-blown fabrics, some MMOF particles appeared on the fiber surface. The fiber surface of the composite melt-blown fabrics became more and more rough with the increasing of the mass of MMOF (Fig. 1). Moreover, the average fiber diameter and pore size of PLA/MMOF composite melt-blown fabrics also increased when the mass of MMOF increased (Fig. 2 and Fig. 3). The addition of MMOF did not change the crystalline structure of PLA, but the higher mass of MMOF inhibited the PLA crystallization (Fig. 4). When the mass ratio of PLA to MMOF was 1:0.03 and 1:0.05, the glass transition temperature of the composite melt-blown fabrics slightly enhanced compared to the pure PLA melt-blown fabric. The crystalline and melting temperatures of the composite melt-blown fabrics increased with the increasing of the mass of MMOF. The moderate input of MMOF had a heterogeneous nucleation effect on PLA crystallization (Fig. 5 and Tab. 2). When the mass of MMOF increased, the saturation magnetic strength of PLA/MMOF composite melt-blown fabrics was also continuously enhanced (Fig. 6). In comparison to the pure PLA melt-blown fabric, the air permeability of the composite melt-blown fabrics was increased, while the filtration resistance reduced. The filtration efficiency of PLA/MMOF composite melt-blown fabric reached the maximum of 65.03% when the mass ratio of PLA to MMOF was 1:0.03 (Fig. 7). The tensile strength of pure PLA melt-blown fabric was about 0.16 MPa, and the elongation at break was about 76.80%. When MMOF was incorporated, the tensile strength of the composite melt-blown materials first enhanced and then reduced. The tensile strength reached the maximum of 0.21 MPa when the mass ratio of PLA to MMOF was 1:0.03. On the other hand, the elongation at break of the composite melt-blown fabrics enhanced with the increasing of MMOF mass (Fig. 8 and Tab. 3).
Conclusion The incorporation of MMOF endows the PLA/MMOF composite melt-blown fabrics with magnetism and improves the air filtration performances. When the mass ratio of PLA to MMOF is 1:0.03, the filtration efficiency and tensile strength of the composite melt-blown fabric reach the maximum. It is believed that PLA/MMOF composite melt-blown fabric with a mass ratio of PLA to MMOF is 1:0.03 has the optimal overall performances. The finding of this research provides some theoretical references for the development of magnetic PLA-based melt-blown filter materials.

Textile Engineering

Cotton foreign fibers detection algorithm based on residual structure

SHI Hongyu, WEI Yingjie, GUAN Shengqi, LI Yi

Journal of Textile Research. 2023, 44(12):  35-42.  doi:10.13475/j.fzxb.20220702801

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Objective Aiming at the low detection accuracy of foreign fibers in cotton, and the poor detection effect caused by the hidden or corner position of foreign fibers, the author propose cotton foreign fibers detection algorithm based on residual structure. Its design is based on the characteristics of the different colors and shapes of foreign fibers in cotton, as well as the different shades and light layers of foreign fibers.
Method For the detection target, an online detection scheme for cotton foreign fibers was proposed. A mixed dataset of deep and shallow layers was constructed based on the color, texture, position, and other characteristics of foreign fibers. Building upon this, a foreign fiber detection network model algorithm with a residual structure was designed, addressing issues such as low accuracy in existing detection algorithms and the presence of hidden or corner-positioned foreign fibers.
Results Ultimately, the dataset constructed in this paper includes five common types of foreign fibers, which are plastic film, plastic rope, polypropylene thread, polyester thread, and hair strand. In order to enrich the dataset and increase the validity of the experiment, the dataset also contains samples with no foreign fibers. Comparative experiments are carried out by using the newly developed detection algorithm and other classical algorithms. In the constructed dataset, the experimental results show that the detection accuracy of foreign fibers and plastic film are as high as 92.81% and 95.76%, respectively, while the identification accuracy of hair, polypropylene thread and polyester wire is low (Tab. 1). Plastic film and plastic rope, which are larger than hair strand, are easier to detect. In industry, there are foreign fibers such as hair, polypropylene thread, polyester thread, etc. in the deep and shallow layers of cotton, and the characteristics of these deep foreign fibers are not obvious. Especially the targets of smaller hair strands, After a series of convolutional extraction features. The deep information is more abstracted, so there is less semantic information of such small target objects. In this paper, the attention mechanism is introduced into the residual structure, and different weights are given to the feature map to enhance the representation ability of the key feature of foreign fibers. Experimental results showed that the algorithm reported in this paper achieved remarkable success on deep and shallow datasets. The average detection accuracy of the deep and shallow dataset was 88.48% (Tab. 3). In addition, the algorithm performed well when processing a single image, with an average detection speed of only 0.019 s per image. In comparison to classical algorithms such as GoogleNet, MobileNetV1, MobileNetV2 and EfficientNet, the algorithm improved accuracy by 10.85%, 3.32%, 26.47% and 26.96%, respectively. Compared to MobileNetV2 and EfficientNet, the algorithm tested a single image with shorter running times and higher accuracy. Hence, the algorithm offered a balance between high accuracy and moderate detection speed in foreign fiber detection, catering to the real-time requirements of the industry. It addressed the issues of low accuracy in existing detection algorithms and the presence of hidden or corner-positioned foreign fibers. Furthermore, it introduced a novel approach to foreign fiber detection in cotton.
Conclusion In this paper, the algorithm not only achieves a high detection effect on shallow cotton foreign fibers dataset, but also achieves a good results on the mixed dataset of deep and shallow layers cotton foreign fiber. However, for the small objects in the deep depth of the actual industry, the method in this paper will also have false detection and missed detection. In the future, the network structure and network parameters will be optimized to improve the real-time detection of foreign fibers in cotton while maintaining a high detection accuracy.

Model construction and analysis based on rotor spinning merging effect

LI Ling, DING Qian, WANG Jun

Journal of Textile Research. 2023, 44(12):  43-49.  doi:10.13475/j.fzxb.20220806301

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Objective Rotor spinning is one of the most mature and widely used spinning technologies among various new types of spinning practically used mass production. The research on the merging effect of rotor spinning is relatively less involved. Therefore, exploring the fiber agglomeration process in the rotor groove and the merging effect will contribute to clarify the spinning mechanism of rotor spinning, study the yarn structure of rotor spinning, and guide the development of new-type rotor spinning.
Method According to the advanced motion characteristics of rotor spinning, it is assumed that the peeling point, rotor reference point and sliver feeding point coincide in the initial state, and the original fiber-layer exists. Without considering the factors of twisting, the ideal distribution shape of fiber-layer in the rotor groove caused by the relative movement between the peeling point, the reference point and the fiber feeding point at each stage, as well as the shape of the output yarn in the process, are derived in combination with the way (Fig. 2). Based on the agglomeration process of whiskers, combined with the fiber supplement amount equal to the output of whiskers peeling, the number of layers of original fiber-layers can be obtained. By combining the original fiber-layer distribution characteristics with the merging effect model, the fiber-layer distribution characteristics of the output yarn can be obtained.
Results The ideal distribution state of condensation whiskers in each representative stage was shown (Fig. 2). The merging situation at any stage was obtained through inductive method. Among rotating cup reference point A, fiber filling point C and peeling point P, coincidence of any two of these three points was taken as a representative stage. The number of original fiber layers for each representative stage of the output yarn was calculated based on the input of the fiber equal to the output of the yarn, and the distribution pattern of the fiber layer of the output yarn was outlined. The distribution characteristics of the number of original fiber-layers in a peeling cycle were derived (Tab. 1 and Fig. 3). It was found that the morphological characteristics of the original fiber-layers not only changed from coarse to fine, but also showed the characteristics of steps. The width of each ″step″ was the length of the output yarn bar. The fiber layer of the output yarn was not simply a layer-by-layer superposition and collection, but the same circle of fiber-layer along the output direction of the yarn, taking the length of the output yarn bar as the unit, was scattered in the lower layer of the composite layer in the yarn body until this circle of fiber layer is completely peeled (Fig. 5). By analyzing the merging effect model, the merging number was obtained, which was equal to the ratio of the number of fibers in the yarn section to the number of fibers in the average section of the fiber flow. The simulated results were validated against practical merging effect from experiments to verify the correctness of the model.
Conclusion Based on the characteristics of advanced peeling of rotor spinning and the analysis of the law of fiber flow collecting and peeling in the rotor groove, a theoretical model of the merging effect of rotor spinning is constructed. The model deduces that the morphological characteristics of the original fiber-layer not only change from coarse to fine, but also show the characteristics of steps. The fiber-layer of the output yarn is not simply a layer-by-layer superposition and collection, but the same circle of fiber-layer taking the length of the output yarn bar as the unit, and it distributes in the lower layer in the yarn body until this circle of fiber-layer completely peeled. By using this model, the calculation formula of the merging number is derived, and the merging number has a positive correlation with the diameter of the rotor and the twist of the yarn.

Influence of core filament type and delivery speed on performance of air-jet vortex spun core-spun yarns

MIAO Lulu, DONG Zhengmei, ZHU Fanqiang, RONG Hui, HE Linwei, ZHENG Guoquan, ZOU Zhuanyong

Journal of Textile Research. 2023, 44(12):  50-57.  doi:10.13475/j

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Objective In order to optimize the structure and performance of core-spun yarns made by air-jet vortex spinning, the paper reports on the effects of core filament types and delivery speed on yarn properties, so as to better predict yarn properties and guide the product development of core-spun yarns based on air-jet vortex spinning.
Method The core-spun yarns were prepared using viscose staple fiber as the sheath and different polyester filaments, including polyester draw textured yarn (DTY), polyester full draw yarn (FDY), and polybutylene terephthalate filament yarn (PBT), as the core filament. Through studying the yarn performance test and scanning electron microscope (SEM) images, the differences between different types of core-spun yarns and pure viscose yarns made by Murata vortex spinning were compared and analyzed, and the effects of core filament types and delivery speed on the core-spun yarn tenacity and elongation, evenness CV value and hairiness H value were investigated using two-factor ANOVA.
Results Due to the existence of core filaments, the mechanical properties of the air-jet vortex spun core-spun yarns are significantly improved than that of staple yarns (Tab. 3). The ANOVA results showed that the type of core filaments were the main factor affecting the performance of core-spun yarns and had a significant effect on breaking strength, elongation and hairiness H value; In the considered range, the delivery speed only had a significant effect on the yarn hairiness H value, but had no significant effect on the yarn strength, elongation and evenness. The interaction of filament types and delivery speed had a significant effect on the breaking strength of core-spun yarns (Tab. 4-7). At any delivery speed, the core-spun yarns containing DTY filaments had the highest breaking strength. Although the strength of PBT filament was second only to DTY filament (Tab. 1), the breaking strength of PBT core-spun yarn was the lowest among the three core-spun yarns. The reason is that the excessive difference in elongation at break between filaments and staple fibers. And the breaking strength of PBT core-spun yarn increased with the increase of delivery speed (Fig. 2). At lower spinning speeds, the increased twist of the staple fibers leads to a decrease in their stretchable distance along the yarn axis, which further exacerbates the different simultaneity of filament and staple fiber breakage, with multiple breakage peaks appearing on the stretch curve (Fig. 3).The elongation at break of PBT core-spun yarn was the largest, followed by DTY and FDY core-spun yarn (Fig. 4). Core-spun yarns with elastic filaments are more easier to adapt to the change in the core-sheath structure and adjust in time during stretching, resulting in higher elongation at break. The evenness CV value of the PBT core-spun yarns were most affected by the delivery speed, while the FDY core-spun yarns were less affected by the delivery speed. This because elastic filaments are more easily deformed in the spinning process. The low delivery speeds contribute to short fiber twisting and improve the yarn evenness. However, for PBT or DTY core-spun yarns, low delivery speeds also increase the probability of deformation of elastic filaments, and bring the risk of yarn evenness deterioration. In order to obtain a better yarn evenness, PBT or DTY core-spun yarns should processed at 380 m/min (Fig. 5). The three types of core-spun yarns were not very different in terms of hairiness H value, and hairiness H value increased with increasing delivery speed (Fig. 6). Because the twisting and wrapping effect of the airflow on the free end of the fiber is weakened during high-speed spinning, the amount of fluffy hairiness of the yarn increases.
Conclusion The tenacity and elongation of air-jet vortex core-spun yarns are obviously affected by the mechanical properties of the core filament. In order to obtain high strength yarns, DTY filament with good strength can be selected as the core, and PBT filament with good elasticity can be selected to improve the elongation at break. However, due to the large difference in the elongation at break between PBT filament and viscose staple fiber, the yarn breaking strength is low when there is a difference in breakage between the sheath and core fibers. Therefore, the breaking strength of PBT core-spun yarn can be enhanced by increasing the delivery speed to improve the simultaneity of fibers breakage. The effect of delivery speed on yarn evenness is also related to the elasticity of the core filament, the lower the speed, the more intense the filament is affected by the high-speed rotating airflow, and the greater the deformation of the elastic filament, resulting in a more negative impact on the core-spun yarn evenness. But for FDY core-spun yarn, the effect of high-speed rotating airflow on staple fiber wrapping is more prominent, so low speed helps to reduce the yarn's evenness CV value. In addition, the lower delivery speed allows the staple fibers to be fully twisted, constraining the yarn body to become tighter, and also helps to improve yarn hairiness.

Processing of wool yarn/polyamide filament covered yarns and their properties and applications

JIA Bingfan, AO Limin, TANG Wen, ZHENG Yuansheng, SHANG Shanshan

Journal of Textile Research. 2023, 44(12):  58-66.  doi:10.13475/j.fzxb.20220504601

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Objective There are some performance defects in wool yarn itself, such as low breaking strength and excessive yarn hairiness, which affect its processability and fabric wearability, for example, low strength makes it unable to withstand larger weaving tension, and excessive hairiness leads to yarn entanglement during weaving and fabric pilling. This article explores the feasibility of using filament yarn to wrap wool yarn by hollow spindle covering to improve its processability and fabric wearability, as well as the impact of the main wrapping process on the technical effect, aiming at providing reference for the development of covered wool yarn and its fabric products.
Method Four twist levels of single-covered and cross-wrapped double-covered composite yarns were applied to the yarns using the hollow spindle covering machine, where 26.3 tex black wool worsted yarn was used as the core yarn, and 44.4 dtex(34 f) polyamide white Fully-Drawn-Yarn(FDY)filament yarn was used as the outer wrapping yarn. The structure of the two types of composite yarns were observed by magnification, the tensile properties, hairiness, evenness and yarn defects were tested according to corresponding standards and comparatively analyzed, and the application of wool yarn covering processing was discussed.
Results The spinning principle of single-covered and double-covered yarn were shown (Fig. 1), and the structure models of the two types of covered yarn were given correspondingly (Fig. 2), as well as the partial enlarged views of the two types of composite yarns(Fig. 3), so as to observe and compare their composite structures. The package appearance (Fig. 4) and the photos of the yarn card (Fig. 5) of the two types of composite yarns were presented respectively to show the appearance characteristics. A partial enlarged picture of 750 twists/m single covered yarn was provided (Fig. 6) for presenting the obvious twist irregularity of single covered composite yarn. In order to compare and analyze the influence of covering processing and its parameters on the tensile performance of the wool yarns, the total tensile fracture curves of 50 times of polyamide wrapped yarn(Fig. 7(a)), wool core yarn (Fig. 7(b)), four twist levels were applied to the single-wrapped composite yarn (Fig. 8) and the typical double-wrapped composite yarn (Fig. 9), and the tensile strength of all raw yarns, single-covered yarns and double-covered yarns were listed (Tab. 1), including breaking strengths/tenacities and their CV value, break elongations and their CV value, and the failure of the core and cover yarns. The hairiness test results of the wool yarn and two type of composite yarn were exhibited (Tab. 2), and the test results for evenness and yarn defects were provided (Tab. 3). The performance changes of composite yarn compared with the wool yarn and the influence of different twist configurations were compared and analyzed, and based on this, the industrial application and requirements of wool yarn covering processing were discussed.
Conclusion The composite yarn has a mixed color appearance of the color of core yarn and outer wrapping yarn. The single-covered composite yarn has the characteristics of uneven distribution of twist, the twist on the thick place is smaller, and the twist on the thin place is larger. The breaking strength of the composite yarn is greater than that of the wool yarn, and the double-covered yarn is greater than the single-covered yarn. The elongation at break of the composite yarn is significantly higher than that of the wool yarn, and the double-covered yarn is greater than that of the single-covered yarn. The covering composite yarns can significantly reduce the hairiness of wool yarn and improve wool yarn evenness and reduce yarn defects. Taking wool yarn as the core yarn, reasonably selecting the type and specification of wrapping yarn and the covering process can improve the processability of wool yarn and change the style and performance of fabric products.

A method for sizing hairiness reduction during drying and effect analysis

GAO Bo, WU Juming, ZHU Bo, WANG Jing'an, GAO Weidong

Journal of Textile Research. 2023, 44(12):  67-72.  doi:10.13475/j.fzxb.20220702101

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Objective In modern textile industry, the reduction of yarn hairiness has become more critical than improving yarn strength and abrasion resistance in the sizing process. In order to further reduce warp hairiness, this paper reports a method for enhancing the hairiness reduction during the drying process in warp sizing based on the analysis of hairiness attaching mechanism.
Method A laboratory scale XSY617-700 sizing machine was used for research. The sizing guide roller between the pre-drying drum and the combined drying drum was transformed into an actively rotating hairiness attaching roller to build a hairiness attaching device. According to the rule that the adhesion force of the size liquid carried by the yarn changes with the drying process, the effect of scraping action on the surface of the yarn by the hairiness attaching roller was studied. The values for two system parameters, the liquid content of the yarn when it is scraped by the roller and the friction length applied by the roller were optimized to achieve the beset hairiness reduction effect.
Results Based on the above device and method and under the same scraping action, the moisture regain of the yarn was controlled from 40% to 10% and the hairiness performance index was measured when adjusting the temperature of the pre-drying drum. The number of unwanted hairiness showed a trend of increasing first and decreasing afterwards (Fig. 3). The possible reason for this phenomenon was that after pre-drying, the moisture regain of sized yarn was reduced and the concentration of liquor in the yarn was increased, which improved the adhesion of the hairs to the yarn body. While after the moisture regain of sized yarn was reduced to a certain level, the yarn and the hairs was drying out thus the adhesion of them was reduced, more hairs could not be adhered to the yarn surface. It showed that 20% moisture regain of sized yarn was more beneficial in reducing harmful hairiness in the proposed system. The friction length was a comprehensive representation of the operating parameters of the hairiness attaching device, and it was used as a control variable influencing the hairiness reduction effect. When the moisture regain of sized yarn was set as 20% as optimized above, and the friction length was controlled to vary the extent of the applied scraping action. As the friction length increased the scraping action increases and the number of harmful hairiness showed a decrease followed by an increase (Fig. 4). The possible reasons were considered as follows. Firstly, a higher friction length indicated a longer actuation duration of the adhesion effect leading to more hairs being adhered, which would approach a maximum as the friction length increases, while a higher friction length also indicated a higher possibility of adhered hairs to be scraped from the yarn surface. Under the combined effect of them, the unwanted hairiness decreased as the friction length increased at first and increases after the friction length reached a certain point. Finally, under the experimental conditions of this research, when the proposed hairiness attaching device was established and applied, a friction length controlled around 81.6 mm would be more beneficial to the harmful hairiness reduction.
Conclusion With the optimal combination of the parameters and under the experimental conditions in this research, the proposed hairiness attaching device has been proved to be able to reduce the unwanted hairiness by 36.3%. The best reduction of hairiness is achieved when the system parameters are set to 20% moisture regain and 81.6 mm of friction length of the roller attachment effect. The hairiness attaching method and the parameter optimization method proposed in this research can be applied to the production process, considering analysis of the variation of moisture regain of yarn on the target sizing machine, selection of appropriate device forms, device installation position, and the adoption of process parameters for achieve convenient, efficient and stable hairiness attaching.

Influence of stitching method on color rendering of double-face full-color jacquard fabric

ZHANG Meng, BAI Linlin, LI Xiaxin, ZHOU Jiu

Journal of Textile Research. 2023, 44(12):  73-80.  doi:10.13475/j.fzxb.20221106901

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Objective In double-face jacquard fabric design under layered-combination design mode, the weave used in two-layer structure with self-stitching is compound full-color weave, and the one used in two-layer structure with central weft stitching is covered full-color weave. Grayscale difference exists between the two full-color weaves, and the color expression of double-face jacquard fabric is determined by the grayscale of full-color weave. Whether the color expression of double-face jacquard fabric will be influenced by stitching methods is the main problem in this paper. The purpose is to provide fabric designers with a better choice of stitching methods.
Method 3 sets of double-face jacquard fabric samples with self-stitching, central weft stitching, and central weft non-stitching were produced under the same technical specification, including yarn thickness, color, and yarn density on both sides of the fabric. The compound full-color weave and the covered full-color weave were designed with the same weave repeat (R) and enhancement of weave points (E) to ensure the test comparability. The fabrics were then tested for color influence by the color range, color transition uniformity and color differences.
Results There were 2R/E gray level differences between the compound full-color weave and covered full-color weave. On the fabrics, taking the 6 landmark lines with monochromatic gradient and two-color gradient as an example (Fig.4), the color ranges of the 2 sets of double-face jacquard fabrics with self-stitching and central weft stitching were slightly different. The color range differences between the 2 sets of fabric samples are shown in Tab.4 and Tab.5. All of the differences were in either acceptable or similar range. In terms of color transition, 24 landmark lines were among the 2 sets of double-face jacquard fabric samples, and the R2 values of the fitted lines of relevant color values were all greater than 0.7(Tab 6), with 18 of them greater than 0.9. That indicates that the face and back the 2 sets of double-face jacquard fabrics have a uniform transition, namely, the stitching methods have almost no influence on the color transition of double-face jacquard fabrics. In terms of the color difference on the fabric surface, the color difference values of corresponding color blocks were calculated between the fabric samples with self-stitching and central weft stitching(Tab.7 and Tab.8). The average color difference value of the face side was 3.10, and the average color difference value of the back side was 4.11, both of which were within the acceptable range. The color difference values of corresponding color blocks were calculated between the 2 sets of double-face jacquard fabric samples with central weft stitching and central weft non-stitching(Tab.9 and Tab.10). The average color difference values of the face and back sides were 1.48 and 0.77 respectively, which represent slight influences. It suggests that the central weft stitching method itself has slight influence on color rendering on the face and back sides of the double-face full-color jacquard fabric.
Conclusion To sum up, there is an acceptable or slight color range difference on the double-face jacquard fabric surface with different stitching methods. It has no significant influence on the uniformity of color transition, and the central weft stitching method does not have significant color influence on double-face jacquard fabrics. This indicates that designers have the freedom to choose the stitching method according to the product needs.

Three-dimensional simulation and realization of sweater cabled fabrics

ZHAO Junjie, JIANG Gaoming, CHENG Bilian, LI Bingxian

Journal of Textile Research. 2023, 44(12):  81-87.  doi:10.13475/j.fzxb.20220700901

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Objective The loop-transfer cable stitch is the main structure that forms the surface texture effect of the flat knitted sweater product, and its application is very extensive. Achieving the rapid design and three-dimensional structure simulation of the cable fabrics to facilitate quick prediction of the fabric effect of the cabled fabrics is of great significance to reduce the design and development cost of cable-knitted sweater fabrics.
Method Based on the knitting principle and knitting method of the cable stitch, the knitting action was parameterized, and the mathematical models for the pattern and for the knitting structure diagram were proposed. Combined with the structural characteristics of each loop of the cable fabrics, an ideal loop model was established, and the trajectory of the value point for the transfer loop was analyzed. Finally, C# and WebGL were used to program the three-dimensional structure simulation of the flat knitted cable fabric.
Results The pattern matrix model and the minimum structure unit matrix were established by the minimum pattern cycle of the cable fabric, and the block matrix F_A of the expanded pattern was established according to the color value of the pattern matrix. Then the relationship between the block matrix F_A and the structure diagram matrix in the pattern diagram matrix was obtained in combination with Equation 4, and the process knitting diagram matrix model of cable fabric was obtained by replacing the matrix elements, see Equation 5. The loop of transferred was based on the normal flat needle loop knitting, and the needle was transferred through the needle bed traversing to transfer the needle arc to form the loop tilt effect. A loop geometry model based on the normal flat needle loop geometry model showed that transfers one needle to the right, based on the establishment of the loop type value point and the loop root junction point (Fig. 4). The coordinates of the 4 type value points near the root junction point of the transfer loop remain basically unchanged, and the coordinates of the 4 type value points near the needle arc were related to the ratio between the number of needles transferred by the loop and the loop distance (g_w) and loop height (g_h). For the transfer loop with different needle transfer directions, needle transfer rows and needle transfer needle numbers showed the change law of the type value point of the transfer loop (Fig. 5). It can be seen that the coordinate values of the four type value points near the root junction point of the transfer loop are determined by the loop root junction point O₀ before the transfer loop, and the coordinate values of the four type value points near the needle arc of the transfer loop are determined by the loop root junction point O₁ at the next position of the transfer loop. Such change was reflected in Equations 7 and 8. Based on the above theory and model, the three-dimensional structure simulation diagram of the cable fabric was finally obtained, and the loop structure of the cable fabric in several weaving states was clearly presented (Fig. 6).
Conclusion Through the conversion between the pattern model and the knitting structure diagram model of the cable fabric, and based on the establishment of the fabric loop geometry model under the ideal state, the rapid design and three-dimensional simulation of the sweater cable fabric can be realized. Although the three-dimensional simulation of the fabric based on the geometric models can clearly represent the string relationship of the fabric, the realization of the cable fabric simulation requires the next step of research on the physical and mechanical model.

Finite element simulation of torsion behavior of braided composite tube based on multi-scale model

GU Yuanhui, WANG Shudong, ZHANG Diantang

Journal of Textile Research. 2023, 44(12):  88-95.  doi:10.13475/j.fzxb.20220505501

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Objective The mechanical properties of braided composites affect the scope of their applications. However, due to the complexity of the meso-structure of braided composites, the experimental research alone can no longer meet the further exploration of the mechanical properties of braided composites. To further investigate the mechanical response of braided composite tube under torsion loading, it is necessary to establish a finite element model of braided composite tube, which can well reflect the mechanical response state and has low calculation cost.
Method On the basis of previous research, a carbon fiber/resin braided composite tube with a 45° braiding angle was selected as a representative research object. Taking into account the meso-structure and full-scale simulation calculation cost, a finite element model of the braided composite tube based on real size was constructed using a micro-meso-macro multi-scale method, and its torsional loading process was systematically simulated. The torsion loading process of the braided composite tube was systematically simulated, and the shear progressive damage of the unit cell and the torsion progressive damage of the tube were discussed separately. The effectiveness of the established model was verified by comparing simulation results with experimental results.
Results The simulation results indicated that under XY shear loading, the damage of a braided composite tube unit cell generated first at the weak point where the braided fiber bundles interweave around the unit cell before the damage failure of the unit cell. The damage area was symmetrically distributed (Fig. 4). When shear failure generated in the unit cell, the fiber bundle showed significant delamination, which was consistent with the observed phenomenon of fiber separation towards both sides in the fractured fiber bundle in the experimental SEM image (Fig. 5). The torsion loading with an angular velocity of 30(°)/min was applied to the finite element model. The torque-twist angle curves and macroscopic failure morphologies obtained from experiments and simulations showed high consistency. These two cases showed that the model was accurate and effective (Fig. 7). The braided composite tube exhibited brittle fracture characteristics under torsion loading. The overall bearing capacity was stronger in the early stage, and damage elements only generated in the middle of the tube at the end of loading. The tube took only about 3.2 s from the appearance of damage to its structural failure. At the beginning, the composite tube was subjected to torsional force. At this point, the composite tube structure undergone load distribution again as a whole. Until 36.202 s, the middle area of the braided tube reaches the bearing limit due to a small amount of fibers and matrix, forming a damage unit. As the loading progressed, the damage diffused around the tube wall towards both ends of the tube at approximately 45° to the axial direction, which was basically consistent with the fiber bundle space braiding path. At 39.418 s, the braided composite material tube reached its load-bearing limit and the braided tube structure failed. At the same time, finally formed a clear space spiral shear band damage morphology on the surface of the tube (Fig. 8).
Conclusion The finite element model of braided composite tubes constructed based on multi-scale methods can effectively reflect the torsional mechanical response state of the tubes. The spatial braiding path of fiber bundles with impact on the torsional damage propagation of braided composite tubes, which means that the mechanical properties of braided composite tubes can be further optimized by adjusting the braiding path.

Dyeing and Finishing & Chemicals

Anti-fibrillation pretreatment technology for Lyocell woven fabrics

SHI Lujian, SONG Yawei, XIE Ruyi, GAO Zhichao, FANG Kuanjun

Journal of Textile Research. 2023, 44(12):  96-105.  doi:10.13475/j.fzxb.20221002001

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Objective Lyocell fibers are prone to high fibrillation owing to the friction under alkaline condition. In order to reduce the fibrillation behavior, herein, the effects of pretreatment process, like cold pad-batch desizing, hot-alkali desizing, enzyme desizing, bleaching, and mercerizing on the fibrillation phenomenon were investigated. The relationship between chemicals such as NaOH, H₂O₂, as well as treatment conditions like time and temperature, and fibrillation generation process was analyzed. Then, the pretreatment conditions and process of Lyocell woven fabric were optimized.
Method In this paper, in order to investigate the effect of desizing process on fibrillation phenomenon, cold pad-batch desizing, hot-alkali desizing, and enzyme desizing were conducted, respectively. Then, the desized Lyocell woven fabric was bleached and mercerized. The treatment conditions like time, pH value, temperature and the chemical concentration were determined. The capillary effect and whiteness were measured. The fibrillation behavior was determined using Martindale abrasion machine and observed with scanning electron microscope. From the comparison of the fabrics after the treatment of deszing, bleaching and mercerizing, the pretreatment process and conditions were optimized.
Results The effects of desizing processes on the properties of capillary effect, whiteness, and fibrillation behavior were investigated. In the cold pad-batch desizing of Lyocell fabrics, capillary effect and whiteness increased as the NaOH concentration increased from 10 to 30 g/L (Fig. 1 and Fig. 2). However, when the concentration of NaOH was above 25 g/L, the pilling grade decreased and fibrillation appeared. Comparatively, the pilling grade of the Lyocell fabric decreased from significantly when the concentration of NaOH is above 20 g/L using hot-alkali desizing (Fig. 5). It means that low temperature desizing could avoid the generation of fibrillation phenomenon to a certain extent. In enzyme desizing, the fabric obtained satisfactory capillary effect and whiteness at the enzyme concentration of 8 g/L with a batching time of 12 h. Moreover, the pilling grade maintained at 4 and no obvious fibrillation phenomenon appeared when the enzyme desizing condition varied. It was indicated that enzyme desizing was a good choice for good capillary effect and whiteness with lower fibrillation behavior. The influence of bleaching treatment on fibrillation behavior was presented (Fig. 13 and Tab. 3). In can be seen that, increasing the H₂O₂ concentration could significantly increase the whiteness, but fibrillation appeared when the H₂O₂ concentration was above 3 g/L and the treatment time was above 30 min. The effect of mercerizing on fibrillation was also investigated (Fig. 15 and Fig. 16). The result shows that, when the concentration of NaOH was above 125 g/L and the treatment time was above 1 min, serious fibrillation appeared on Lyocell fabric surface. The reason is that alkali treatment could cause obvious fiber swelling, then Na⁺ carried a large number of water molecules into the amorphous region of the fiber, resulting in the decrease of fiber lateral force.
Conclusion In the pretreatment process of Lyocell fabrics, obvious swelling and fibrillation could be caused by NaOH. From the comparison of cold pad-batch desizing, hot-alkali desizing and enzyme desizing, the last method could effectively reduce the fibrillation behavior of the Lyocell fabrics because there is no alkali consumed. H₂O₂ bleaching can further improve the whiteness of the fabric, but when the concentration is higher, the fabric of Lyocell will be slightly fibrillated. In addition, because Lyocell fabrics have less impurities than cotton, light bleaching process can be used to obtain higher whiteness. In addition, alkali mercerization can cause serious fibrillation, so mercerization was not suggested to be conducted in the pretreatment process. Therefore, in order to reduce the fibrillation tendency in Lyocell woven fabric pretreatment, low temperature, low alkali consumption or enzyme treatment was suggested.

Preparation of gelatin-based carbon dots by pyrolysis and its applications in flame retardant and anti-counterfeiting

WEI Jianfei, MA Guocong, ZHANG Anying, WU Yuhang, CUI Xiaoqing, WANG Rui

Journal of Textile Research. 2023, 44(12):  106-114.  doi:10.13475/j.fzxb.20220705901

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Objective Carbon dots (CDs), as a type of carbon nanomaterial, possess inherent fluorescence as a characteristic property. They also hold significant potential as flame retardants in polymer materials. However, the current cost of preparing carbon dots is high. The objective of this study is to explore new precursor materials, potentially with lower cost, for carbon dot synthesis, enhance the carbon dot synthesis process, reduce production costs, improve production efficiency, and investigate the application of modified carbon dots in PET flame retardancy and fluorescence anti-counterfeiting.
Method This research employs low-cost and non-toxic gelatin and urea as precursors and utilizes a high-efficiency pyrolysis method to synthesize gelatin-based nitrogen-doped carbon dots (NCDs). The study also optimizes the synthesis conditions, including precursor-to-feed ratio, reaction temperature, and reaction time. Following the purification of NCDs synthesized under the optimal conditions, their morphology, structure, and fluorescence properties are characterized and tested. Furthermore, NCDs are blended with PET to produce PET-NCDs flame-retardant modified composite materials, and the thermal stability, flame-retardant performance, and combustion behavior of PET-NCDs are examined. NCDs are also employed as fluorescent agents to prepare fluorescent ink, and their anti-counterfeiting effectiveness is assessed.
Results The test results show that the optimal preparation conditions for synthesizing NCDs using gelatin and urea as precursors are as follows: a mass ratio of gelatin to urea of 5:1.1, a reaction temperature of 260 ℃, and a reaction time of 12 hours (Fig. 1). TEM characterization reveals that NCDs have a quasi-spherical structure, with particle sizes ranging from 2.03 to 4.62 nm and an interplanar spacing of 0.21 nm (Fig. 2). Characterization using XPS, FT-IR, and NMR H indicates the presence of functional groups such as hydroxyl and amino groups on the surface of NCDs (Figs. 3 - 5). The UV-vis spectrum of NCDs in ethanol solution exhibits an absorption peak at 241 nm, attributed to the π-π* transition of sp² bonds, and the solution displays prominent blue fluorescence under a 365 nm UV lamp (Fig. 6(a)). Fluorescence emission spectra of NCDs under different excitation wavelengths demonstrate significant changes in fluorescence intensity, indicating typical excitation wavelength dependency (Fig. 6(b)). Using an integrating sphere, the fluorescence quantum yield of NCDs is determined to be 47.12% under optimal conditions (Fig. 6(c)). The fluorescence lifetime of NCDs is measured using a fluorescence spectrometer, excited with 360 nm light, and the decay curve at 430 nm is fitted using an exponential function (exponential). Analysis reveals two fluorescence emission centers with lifetimes of 2.37 ns and 6.70 ns, resulting in an average lifetime of 4.92 ns (Fig. 6(d)). In the characterization of NCDs-PET with a 5% NCDs doping level, the thermal stability of PET-NCDs is significantly improved compared to pure PET, as evidenced by TG and DTG curves, with a notable reduction in the maximum mass loss rate and increased residual char content at 700 ℃ (Tab. 1). Flame-retardant performance has an elevated limiting oxygen index (LOI) of 26% and its vertical combustion test (UL-94) is rated V-2 (Tab. 2). Cone calorimetry testing demonstrates a 42% reduction in the peak heat release rate for PET-NCDs compared to PET, with lower overall heat release rates and the formation of an evident expanded char layer after combustion (Fig. 8 and Fig. 9). Additionally, the fluorescent ink containing NCDs produces patterns that are invisible under natural light but visible under UV light, thus demonstrating its anti-counterfeiting effect (Fig. 10).
Conclusion NCDs synthesized through the pyrolysis method using gelatin and urea as precursors exhibit excellent fluorescence properties and a high fluorescence quantum yield. When incorporated into PET through blending, they demonstrate effective flame-retardant properties, making them suitable for the production of fluorescent ink with potential applications in fluorescence-based anti-counterfeiting.

Preparation and properties of flame retardant hydrophobic cotton fabric with eugenol-based composite coating

CHEN Shun, QIAN Kun, LIANG Fuwei, GUO Wenwen

Journal of Textile Research. 2023, 44(12):  115-122.  doi:10.13475/j.fzxb.20221200401

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Objective As the most commonly used natural fiber textile, cotton fabrics are widely applied for various end uses because of their biodegradability, moisture absorption and breathability, softness and wide range of sources. However, cotton fabrics also display extremely flammable, hydrophilic and easily contaminated. In order to solve these problems and further improve the applicability of cotton fabrics in daily life, a simple two-step impregnation method is proposed in this paper to add flame retardancy and hydrophobicity to cotton fabrics.
Method Firstly, eugenol and phenyl dichlorophosphate were used to synthesize the bio-based flame retardant (DEP) by substitution reaction to prepare flame-retardant cotton fabrics. The phosphorus-containing substances in flame retardant can be decomposed in advance, catalyzing the dehydration of cotton fabrics into carbon and improve the thermal stability of cotton fabrics. Subsequently, zirconium based organometallic framework UiO-66 particles were modified with methyltrimethoxysilane to prepare the hydrophobic agent by simple surface modification, used for hydrophobic finishing of flame-retardant cotton fabrics. Low surface energy substances and micro-nano materials are combined on the surface of the fabrics to construct a micro-nano hydrophobic coating.
Results The structure, thermal stability, flame retardancy, hydrophobic capacity and antifouling property of the obtained flame retardant and hydrophobic cotton fabrics were characterized by scanning electron micro-scope (SEM), thermogravimetric analysis (TGA), vertical burning test, water contact angle (WCA) and droplet diagram, respectively. Furthermore, the flame retardant mechanism and hydrophobic mechanism were further investigated. The chemical structure of the product in the FT-IR spectra (Fig. 2) and ¹H NMR spectra (Fig. 3) both conform to the chemical structure of the flame retardant, demonstrating the successful synthesis of the flame retardant. The surface morphology of the treated cotton fabric and hydrophobic particles was observed by SEM, and the results showed that the flame retardant and hydrophobic agent were successfully and uniformly attached to the cotton fabric without destroying the original structure of the fabric and not affecting the normal morphology of the cotton fabric (Fig. 4). That the residual char content at 800 ℃ ranges from 1.7% of the raw cotton fabric to 8.6% of DEP3-UiO-66/MTM with an obvious char layer (Fig. 5), indicating that the thermal stability of the treated cotton fabric has been improved, which also reflect the enhancement of flame retardancy of the treated cotton fabric. This is mainly attributed to the flame retardant role played by phosphorus-containing flame retardants in the condensed phase. The LOI of pure cotton and DEP3 were 18.5% and and 26.5% (Tab. 2), respectively. The treated cotton fabric presented good char-forming ability after combustion (Fig. 6), and the introduction of DEP flame retardant coating effectively improves the flame retardancy of cotton fabric. In addition, the treated fabrics show good hydrophobicity. Among them, the WCA of DEP3-UiO-66/MTM is as high as 139° and the slide angle is 28° (Fig. 7). As can be seen from the droplet diagram of the treated cotton fabrics (Fig. 8), DEP3-UiO-66/MTM can withstand a variety of common stains in life such as ink, mud, coffee, milk, tea, acid (hydrochloric acid dyed with methyl red), alkali (sodium hydroxide solution dyed with thymolphthalein) and water droplets, and remain rounded on the surface of the treated cotton fabrics, showing excellent anti-fouling performance. The whiteness and bending length of the flame retardant hydrophobic fabrics were 83.89% and 21.0 cm (Tab. 3), respectively, which were not much different from those of pure cotton fabrics.
Conclusion The results confirm that the modified cotton fabric has good flame-retardant, hydrophobic and antifouling properties. The flame retardant hydrophobic composite coating is constructed via a simple, efficient, eco-friendly way using biomass as the raw material, which is green, environment-friendly and easy to operate. The prepared flame retardant hydrophobic multifunctional fabrics have broad application prospects in protective clothing, medical equipment, clothing, decoration and industrial buildings.

Preparation and pH-detection properties of Tb-metal-organic frameworks modified cotton fabric

CHEN Bei, REN Lipei, XIAO Xingfang

Journal of Textile Research. 2023, 44(12):  123-129.  doi:10.13475/j.fzxb.20220900801

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Objective Luminescent metal-organic frameworks (MOFs) are a new type of inorganic-organic hybrid materials made from an assembly of metal ions with organic linkers. They have excellent applications in the fields of fluorescence detection, radiometric nanothermometers, luminescent thin films, and so on. However, the inherent characteristics of particle materials restrict their further application in practice. Therefore, it is of great importance to deposit MOFs onto suitable substrates to reduce aggregation and improve utilization.
Method Flexible fluorescent pH sensing materials were prepared using cotton fabric as the substrate. Terbium nitrate hexahydrate, fumaric acid, and oxalic acid were used to prepare micro-nano Terbium-metal-organic frameworks (Tb-MOFs) particles by adding the sodium acetate as a blocking agent with the same group of the ligands. Then, the Tb-MOFs particles were coated on the surface of the cotton fabric by hot pressing method to obtain Tb-MOFs-cotton fabric (Tb-MOFs-CF). The morphology, crystallization, fluorescence, and pH sensing properties of the Tb-MOFs-CF were characterized and analyzed.
Results The Tb-MOFs particles with uniform particle size were synthesized by hydrothermal method, and the particle size in the range of 4-6 μm (Fig. 2). The dense and uniform micro-nano Tb-MOFs were formed on the surface of the cotton fabric, and the Tb-MOFs-CF has the same white appearance and crisscross textures with the pristine cotton fabric (Fig. 3). The Tb-MOFs-CF exhibited the characteristic peaks of the pristine cotton fabric and Tb-MOFs, indicating the hot press process has no significant influence on the crystal structure of Tb-MOFs (Fig. 4). The water contact angel test of the pristine cotton fabric and Tb-MOFs-CF are 0°, indicating that both have the good hydrophilicity (Fig. 5). The optical images of the Tb-MOFs-CF is blue-green under UV light, as the cotton fabric is blue and Tb-MOFs is green (Fig. 6), which revealed the good fluorescent properties of Tb-MOFs-CF. The fluorescence spectra of the Tb-MOFs-CF in the solution of different pH (from 1-13) using 510 nm as the excitation wavelength showed that there are mainly two peaks from 375-650 nm (Fig. 7). The broad peak about 415 nm is the emission of the cotton fabric, and the peaks at about 510 nm is the typical peak of the Tb ions. The position, shape, and range of the peaks remain unchanged, but the intensity changes obviously with different pH. With the increase of the pH from 1-5, the fluorescence intensity decreased obviously. Then, with the increase of the pH from 8-13, the fluorescence intensity showed no significant change. However, there were obviously changes in fluorescence intensity in the pH 1, 7, and 13. The curve of fluorescence intensity vs. pH showed that at acidic conditions, the fluorescence intensity decreased obviously, while at alkaline conditions, the fluorescence intensity leveled out (Fig. 8). Especially in the range of pH from 1-5, the fluorescence intensity was in linear relation with pH. Therefore, the pH dependence of the Tb ions could be used as the fluorescent sensor. The brightness of fluorescence color for Tb-MOFs-CF was different under UV light, in the pH 1, 7, and 13, demonstrating the Tb-MOFs-CF could be applied for detecting acid-base (Fig. 9). Besides, the color of the Tb-MOFs-CF under UV light had no difference with different wash times, indicating the Tb-MOFs is firmly adhered on the Tb-MOFs-CF (Fig. 10).
Conclusion The micro-nano Tb-MOFs are uniformly coated on cotton fabric and retain their crystal morphology with good adhesion. Tb-MOFs-CF demonstrates excellent fluorescence properties and exhibits rapid response in the detection of pH. Especially at acidic conditions, the characteristic emission peak of Tb ions shows a linear relationship with pH.

Apparel Engineering

Structural design and realization of warp-knitted fully formed hollow maillot

DONG Zhijia, GUO Yanyuqiu, LIU Haisang, YAO Sihong

Journal of Textile Research. 2023, 44(12):  130-137.  doi:10.13475/j.fzxb.20221100201

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Objective Hollow-meshes are widely used in fabrics and clothing, but there is little research on warp-knitted hollow-mesh clothing to enable the design of hollow maillot with different sizes and styles. Warp-knitted hollow garments are greatly deformed after wearing, and many efforts are needed during the design process, leading to prolonged working procedures and waste of raw materials. This research aims to investigation the tensile deformation of hollow mesh to improve production efficiency.
Method When knitting, the jacquard makes chain knitting movement on the bottom fabric and does not form a connection in the adjacent wales, resulting in cracks in the fabric. This is the principle of forming hollow meshes in warp-knitted full-formed fabrics. Based on this principle, the hollow maillot was designed, which was made on RDPJ6/2 jacquard warp-knitting machine with nylon (44.4 dtex) and nylon/spandex covered yarn (22.2 dtex/55.6 dtex). Twelve woven fabrics with different hollow-meshes were designed with the same raw materials and process parameters, and eight observation points were added at the edge of the hollow-meshes to study the influence of the crosswise elongation of woven fabrics on the mesh morphology.
Result Tight maillot was designed the style of tights according to the characteristics and specific dimensions of women's upper body. The hollow-meshes were added and distributed longitudinally at equal intervals on the front, back and sleeves (Fig. 2). Jacquard stitches were formed according to the structural design drawing of a hollow maillot, with thin organization and thick organization as the bottom fabric respectively (Fig. 5). When the crosswise elongation of the samples increased, the crosswise diameter CC' tended to increase (Fig. 7), and vice versa. The correlation coefficients between the crosswise diameter CC' and the woven fabric elongation were all greater than 0.95, which shows a significant correlation. Besides, the three observation points on the same side fitted well with the top and bottom observation points on the parabola. The ratio of crosswise diameter CC' to vertical diameter AE (crosswise-vertical ratio) was linearly related to the fabric elongation (Fig. 8), in which the linear relationship between the crosswise-lengthways ratio y_g of thin tissue hollow-mesh and fabric elongation x was found to be y_g=0.012 9x+0.185. The linear relationship between the crosswise-vertical ratio y_h of thick tissue hollow-mesh and fabric elongation x was y_h=0.011 5x+0.15. The hollow-mesh and the surrounding bottom fabric were divided into several zones, and the calculation model of the length of the hollow-mesh crosswise diameter CC'was deduced and the calculation model of the width of pattern and width of area e was designed (Fig. 9). The actual mesh shape was calculated based on the model data, and it was simulated using WKCAD of Jiangnan University and Lingdi Style3D full-forming clothing module (Fig. 11).
Conclusion According to the tensile experiment of the hollow-mesh, there is a linear relationship between the shape change of the hollow-mesh and the elongation of the fabric. The deformation law of the tissues around the hollow-mesh is summarized, and the deformation prediction model of the hollow-mesh under tensile conditions is established. Through the prediction model, the deformation of the hollow-mesh is calculated, and the hollow maillot is modeled and simulated by WKCAD software of Jiangnan University and Style3D software of Lingdi Company, and the 3-D model of the deformed hollow maillot is obtained. By comparing the model with the shape of the deformed hollow-mesh, it is found that the error is controlled within the allowable range.

Digital design method of clothing reverse modeling

ZHOU Li, FAN Peihong, JIN Yuting, ZHANG Longlin, LI Xinrong

Journal of Textile Research. 2023, 44(12):  138-144.  doi:10.13475/j.fzxb.20221001901

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Objective Aiming to obtain doubled amount of design through data reconstruction during generating the digital model from the physical object of the design work, a digital design method of clothing reverse modeling is built up. It mainly addresses two problems: one is to restore and save the data of irreproducible clothing, the other is to carry out reverse modeling and extension design of excellent clothing works.
Methods The point cloud data obtained through 3-D scanning were simplify, and the topology into a quadrilateral grid was optimized. Then, surface reconstruction design was carried out on the special-shaped grids caused by singular points, with position adjusting, quantity increasing and decreasing, and shape changing. As the last step, the digital simulation design of clothing modeling was set up following reverse engineering through mapping and restoration.
Results The clothing design ideas and methods were submitted based on the reverse modeling process (Fig. 1), which could restore quickly the virtual experimental objects and provide designers with new design methods and skills for secondary expansion modeling. The rationality of the pattern structure was verified by the three-dimensional effect of the clothing and the actual object with distinctive features. First, it collects, restores and stores data of irreproducible clothing by clothing models acquiring model topological surface reduction, modeling structure splitting, and texture mapping (Fig. 2). Second, it calibrates the position of the singularity to provide a reference method to quickly carry out reverse modeling and extension design on excellent clothing works (Fig. 3). Third, it carries out extension modeling by adjusting the position of the singularity, increasing or decreasing the number, changing the shape of the surface reconstruction design, and making a real entity for objective verification (Fig. 4). The shape and structure of improved extension design work could be transformed into planes, and the pattern drawing of the reverse topology clothing provides a basis for pattern adjustment, and also lays the foundation for clothing shape design and same type clothing structure optimization (Fig. 5). Fourth, it can be converted into an editable structural pattern based on the expansion of the pattern drawing, so as to further carry out the simulation operation and experiment of the clothing model (Fig. 6). At the same time, dynamic simulation of a series of transformations such as on clothing material, texture and new shape can be carried out (Fig. 7).
Conclusion Taking a drape-cut garment with complex shape as an example, the rationality and feasibility of the garment reverse shape design method are verified. At the same time, it is possible to reversely draw out the clothing version or digital model, to carry out version extension and try-on corrections with 3-D digital software, and to verify the final shape obtained by the reverse modeling method. This method aims to reduce the waste of resources and pollution caused by forward fashion design, to address the long production cycle, and to use digital modeling to improve the high-quality development of design innovation.

Determination of sweating locations and sweating rate of young female breasts

WANG Zhaofang, DING Bo, ZHANG Hui, CHEN Silin

Journal of Textile Research. 2023, 44(12):  145-152.  doi:10.13475/j.fzxb.20221001001

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Objective Current studies on human sweating have not involved the investigation of the distribution and sweating rate of women's breast, resulting in lack of systematic and scientific guidance on women's bra design. To fill this knowledge gap, this research aims to investigate the distribution of breast sweating locations, sweating rates in different parts of breast and the average sweating rate, taking young women as research objects.
Method Fifteen young female participants were selected to proceed a series of sedentary sitting with a metabolic rate of 50-60 W/m² and medium-high intensity exercise with a metabolic rate of 200-250 W/m² at 26 ℃ and 50% RH environment condition. A new ″sandwich″ structured sweat absorptive patch proposed in this research was used to measure the overall distribution of breast sweating, dominant and recessive sweating rate and sweating rate variation under different exercise conditions (Fig. 1). A 1 cm × 1 cm medical sweat absorptive patch was used to measure the sweating rate in seven regions of A-G of breast (Fig. 6). Mean filtering, threshold segmentation and Sobel operator digital image processing were carried out on the obtained images of breast sweating distribution, and paired T test was performed on the obtained sweating rates in different areas to analyze their differences.
Results No significant difference in the sweating rate of left and right breasts was found after independent samples test. The distribution of dominant breast sweating was identified. The annular region around BP (breast point) with a radius of about 1 cm was the first to sweat, then the rim ring area near the front chest and armpit with a radius of about 0.5 cm began to sweat soon afterwards. The above two annular regions continued to expand until the entire cup was soaked through (Fig. 4). Thermal imaging of female upper-body was taken before and after the 30 min medium-high intensity exercise, which showed that the temperature of front chest and mammary gland region were the highest resulting in early sweating. The results showed significant differences in sweating rates of breast areas A to G according to the Kruskal-Wallis H-test, the median test, and the Yorkhale-Tapastra test (P<0.05). The front chest region and annular region of BP were the two centers of high sweating. The maximum sweating rate near the front chest was 1.844 mg/(min·cm²), followed by sweating rate at 0.664 mg/(min·cm²) around the BP, and then the upper and lower edges of the breast (Tab. 5). It was found that breast average recessive sweating rate was (0.004 7±0.003 7) mg/(min·cm²) in sedentary state for six h, and the average dominant sweating rate was (0.405 5±0.178 4) mg/(min·cm²) in medium-high intensity exercise state for 30 min. During six 10-min intervals of medium-high intensity exercise, average breast sweating rate increased with the progress of exercise, reaching a peak at 0.409 mg/(min·cm²) at the 40th min, and finally slowly decreased to 0.356 mg/(min·cm²) due to the physical limitations and increase of fatigue.
Conclusion It is concluded that the annular region around the BP point and the annular region at the edge of the breast (especially near the front chest area) have relatively high sweating rate and thus perspired earlier. Therefore, it is suggested that in the moisture permeability design of the bra fabric, such as certain ventilation holes can be set in the above areas to accelerate the evaporation of sweat, which can improve the overall thermal and wet comfort of the bra. For daily wearing bras, it is suggested that the innovation of fabric fiber and the three-dimensional structure design of cup padding materials can refer to the recessive sweat rate. For sports bras, it is recommended that the optimal design of fabrics and cup padding materials should refer to the above mean and maximum sweat rate. The results from this research may be used to guide the optimal design ventilation hole distribution and to provide theoretical reference for the selection of moisture permeability index of bra cup material and the development of new materials for commercial purposes.

Effect of virtual influencer entertainment value on fashion brand purchase intention

WU Yanfei, ZHANG Ying, XUE Zhebin

Journal of Textile Research. 2023, 44(12):  153-161.  doi:10.13475/j.fzxb.20221103301

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Objective There has been a surging interest in the realm of virtual influencer marketing in the recent years. The virtual influencer can be defined as a digital character created by using computer graphics software, which is then given a personality defined by a first-person view of the world, and made accessible on various media platforms to exert their influence. AYAYI, for instance, stands as a prominent example in this domain. With over 124 thousand followers on Red, AYAYI has emerged as one of the most influential figures in the fashion industry. Therefore, a lucid theoretical explication of this new phenomenon between virtual influencers and consumers' purchase intention that is based on empirical investigation, from the perspective of consumers, is greatly needed.
Method In order to analyze the influence of the entertainment value of virtual influencers on fashion brands' purchase intention, a theoretical model with three variables was established, including entertainment value, flow experience, and purchase intention. Through literature review and theoretical research, this research delved into exploring the mediating role of the flow experience in shaping the path toward purchase intentions. Moreover, the study took into account the moderating effects of two critical factors: the type of digital persona (ultra-realistic virtual avatar versus secondary anime character) and the gender of the consumers (male versus female). This led to the construction of a model that encompasses mediation and moderation effects. A total of 282 questionnaires were collected from the respondents and were usable for further analysis. The statistical software SPSS 24.0 was employed to rigorously test not only the mediating and moderating effects but also the overall influence of these variables on the research framework.
Results The results of our quantitative experiments have yielded valuable insights. Firstly, they demonstrate that the entertainment value provided by virtual influencers exerts a significant and positive influence on consumers' purchase intentions. This influence operates along two distinct paths: an indirect route through the mediating factor of the flow experience, and a direct one. Moreover, within the mediation model, it's noteworthy that consumers' gender differences play a significant moderating role. However, it's interesting to observe that the differences between virtual characters do not exert a significant moderating effect on the mediation process. Further analysis through a bootstrap test reveal that the moderating impacts of entertainment value and flow experience were more pronounced when the user identified as male and opted for a secondary anime character. Conversely, these moderating effects were less pronounced when the user identified as female and chose an ultra-realistic virtual avatar. These findings shed light on the intricate interplay of these variables and offer valuable insights into consumer behavior in the context of virtual influencer marketing.
Conclusion The study provides several key insights. Firstly, it underscores the importance of tailoring marketing strategies for virtual influencers based on audience gender characteristics and the selection of different character types. By doing so, companies can enhance the entertainment value delivered to consumers, thereby stimulating their purchasing behavior. This highlights that consumers' perception and acceptance of products or services are not solely based on their intrinsic qualities but also on the emotional and experiential values they provide. These values include feelings of enjoyment, emotional comfort, and the excitement generated through interactions with preferred avatar types. The ability of companies to offer these entertainment values during the consumer experience directly influences their purchasing decisions. Secondly, the study reveals that the relationship between the entertainment value of avatars and consumer purchase intentions is partially mediated by the flow experience. In other words, the virtual image crafted by a company can impact a consumer's purchase intention directly. Simultaneously, part of this influence is channeled through the immersive and engaging experience that consumers themselves create while interacting with the avatar.

Machinery & Accessories

Research on filament collection and discharge technology with an automated shoveling system under non-stop-spinning condition

DING Caihong, ZUO Jinzhao

Journal of Textile Research. 2023, 44(12):  162-169.  doi:10.13475/j.fzxb.20220703001

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Objective Regular shoveling on the spinneret surface is necessary to ensure spinning quality. Automated shoveling under non-stop-spinning conditions can ensure stable spinning quality without stopping the pump. However, the technical solution of rotating the filament collecting bobbin and the shovel assembly together requires high rotation speeds to ensure successful collection of the waste filament, which to some extent negatively affects the shoveling results. In order to eliminate the negative effects of waste filament collecting operation on the shoveling effect when non-stop-spinning automated shoveling, a method was proposed for the design of a non-stop automated shoveling system with the filament collecting device stationary at the center and the offset shovel assembly for continuous rotation, so that board shoveling and filament collection could operate simultaneously without any mutual influence on the operating effect.
Method By applying mechanical design and gearing technology, the inverted collecting funnel was located directly below the spinneret to collect filament and the shovel assembly was driven by a motor to rotate around the spinneret axis to do shove movement. Based on hydrodynamics, the airflow field was designed by combining upper positive pressure blowing with lower negative pressure pumping to form a spiral downward flow of air. In such a way, the waste filament was blown away from the funnel wall and gathered inwards to wind down and discharge. The structural and airflow parameters of the filament collecting assembly were designed in detail by applying fluid simulation analysis methods, and an experimental equipment was developed for test verification.
Results Firstly, the layout and inclination of the air guide holes were designed to form a spiral cohesive airflow field inside the funnel. A spiral-blowing pipeline with multiple spaced through holes was arranged on the outer wall of the collection funnel to guide the external air with positive pressure into a spiral airflow inside the funnel (Fig. 2). The simulated flow field domain model of the filament collection system was built (Fig. 4). After setting the relevant flow parameters, the flow field simulation was carried out for the cases with different number of air guide holes 5, 6 and 7, whose inclination angle was between 25° and 55°, and through the simulation analysis the number of holes was determined to be 6 and the inclination angle to be 40° (Fig. 5). Then, setting the design targets as the peak temperature fluctuation of the spinneret surface at no more than 3 ℃ and the temperature drop of the surface at no more than 18 ℃, simulation of the internal flow field of the collection system was carried out for working conditions with blowing flow rates of 20, 35, 40 and 45 m/s. By observing the temperature cloud of the spinneret surface and measuring the flow velocity in the shielding zone, the relationship between the relevant temperature and flow parameters and the blowing rate was obtained (Tab. 1), and it was found that the design specifications could be satisfied when the blowing rate was valued less than 25 m/s. Finally, the negative pressure parameter at the end of the filament discharge pipeline was adjusted to achieve effective contact between negative pressure pumping and positive pressure blowing at the lower end of the funnel, and thus the flow distribution of the filament collection system was further optimized to form a spiral cohesive downward airflow field. Setting the blowing rate at 15 and 20 m/s, a steady-state analysis of the flow field of the filament collection system was carried out (Fig. 6), and it was found that the trend of uneven flow distribution in the circumferential direction inside the funnel increased as the end vacuum increased. Further combined with transient analysis of the flow field, it was found that at a blowing rate of 15 m/s and an end pressure of -85 Pa, the filament collection system was able to quickly generate a spiral downward flow field within 2.5 s (Fig. 7). As a result, the flow parameters of the blowing rate and end negative pressure were determined.
Conclusion After completing the design of the main parameters of the non-stop automated shoveling system, the design correctness was further tested through fluid simulation and actual experiments. It was found that the traces presented a curved and oblique inward shape, and closer to the center of the pipeline, the pitch of the trace decreased until it became straight, so the airflow field of the collecting system could achieve spiral cohesive downward flow. The simulated filaments converged inwards and intertwined within the positive and negative pressure flow field, thus also verifying the correctness of the system design above. The research reported in this paper has achieved the independence of the board shoveling and wire collection in terms of design parameters, and effectively solved the adverse effects of waste filament collecting operation on the shoveling effect, and thus provided a new technical solution for automated board shoveling under non-stop-spinning condition.

Mobile robot positioning method in textile production environments

LI Xun, LI Zhewen, ZHANG Tingwen, JING Junfeng, LI Pengfei

Journal of Textile Research. 2023, 44(12):  170-180.  doi:10.13475/j.fzxb.20220606701

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Objective The intellectualization and green production of textile industry are the contents that must be upgraded following the "double carbon" strategy, and the large number of applications of mobile robots will be a fact in the future. However, robot has not been widely used in the textile workshop, and most of the robot positioning method are based on the traditional magnetic signals such as conductor. With the expanding of the scale of production, scalability is not strong. The ground environment, textile machinery and textile workshop electromagnetic interference problem will have to be solved. Therefore, a multi-sensor hybrid filtering method is proposed.
Method In order to solve the impact of physical environment in textile workshop, the Inertial Measurement Unit (IMU) sensor data carried by the robot was compared with other sensor data, and a data preprocessing model was established to reduce the impact of ground and electromagnetic on sensor data. According to the characteristics of each sensor, the data processed by LiDAR, IMU and wheel odometer were fused by UKF(Unscented Kalman Filter) filter, and the global pose estimated by AMCL (Adaptive Mentcarto Localization)meter was added to UKF to solve the problem of positioning failure caused by the initial value and abnormal data.
Results The simulation environment of textile workshop with and without electromagnetic interference was constructed based on ROS operating system, and the algorithm proposed in this paper was compared with other algorithms. Under the condition of no electromagnetic interference, the positioning accuracy of single sensor was found to decrease significantly and even fail due to the influence of complex ground and similar environment in textile workshop (Fig. 6). Compared with UKF and EKF multi-sensor fusion algorithms, AMCL-UKF algorithm demonstrated better fitness and stronger robustness in the face of complex environment in textile workshop. AMCL-UKF algorithm reduced the positioning error by 85.9% and 34.8% and the maximum positioning error was reduced by 8.1% and 7.6%, indicating that multi-sensor fusion could effectively improve the positioning accuracy (Tab. 3). It showed that the multi-sensor algorithm could effectively reduce the error caused by EKF and UKF linearization process. In the environment with electromagnetic interference, as shown in Tab.4, the maximum error of the data preprocessing model was reduced by 32.5%, the average value reduced by 37.6%, the root means square error reduced by 36.7%, and the standard deviation reduced by 12.7%, proving the effectiveness of the method. The AMCL-UKF algorithm provided relatively accurate positioning accuracy and stability in the face of strong magnetic field interference in the textile workshop (Fig. 11).
Conclusion The experimental results show that the data preprocessing model can effectively reduce the influence of physical environment of textile workshop on sensor data. Through the AMCL algorithm, the global pose is calculated and input into the UKF filter, which can improve the positioning failure of the Kalman filter caused by the interference in the working process of the textile robot and improve the working stability. Problems such as electromagnetic interference, ground, and error introduction during collaborative work in textile workshop have limited influence on positioning accuracy. However, the proposed algorithm does not use data information interaction between multiple robots for collaborative positioning. The latest research method of robot positioning is graph-based optimization algorithm, which has higher positioning accuracy. Therefore, the future research direction is to improve the positioning accuracy through graph optimization algorithm by using mutual measurement between multiple robots and reduce the computational complexity of graph optimization algorithm to further improve the positioning accuracy of robots. In conclusion, the improved AMCL-UKF method in this paper can provide accurate positioning information for mobile robots and provide theoretical and experimental data support for mobile robot application schemes required for intelligent upgrading of textile workshops in the future.

Characteristics of weft insertion synthetic airflow from main nozzle and high-speed special-shaped auxiliary nozzles

XIAO Shichao, SHEN Min, FANG Jingbing, WANG Zhen, YU Lianqing

Journal of Textile Research. 2023, 44(12):  181-188.  doi:10.13475/j.fzxb.20211000401

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Objective The auxiliary nozzles are key components in air jet looms. While the single circular auxiliary nozzles have problems of low speed, poor air concentration and high air consumption, this research aims to design a new type of auxiliary nozzle with special-shaped hole and to study the influence of the structural parameters of auxiliary nozzles on the synthetic airflow in the profiled reed. A three-dimensional(3-D) synthetic airflow field consisting of a main jet and auxiliary nozzle jets was numerically simulated based on the Reynolds time-averaged equations (RANS) and eddy viscosity turbulent model.
Method 3-D model of synthetic airflow field of different Y1, Y2 and Y3 type of auxiliary nozzles were established with Solidworks before the 3-D synthetic airflow model was meshed with professional ICEM software and the boundary conditions were set in the CFD software Fluent. The numerical simulation on the synthetic airflow model was accomplished based on the RANS equations. The numerical simulation results were validated by the experimental results. Thereafter, the comprehensive comparison of synthetic airflow characteristics and air consumption were investigated for single round-hole and Y1, Y2 and Y3 type auxiliary nozzle with different structure parameters under same gas pressure.
Results The simulation results were in agreements with the experimental test results regarding the synthetic airflow velocity trend. When the airflow from an auxiliary nozzle jet was injected into the profiled reed and merged with the main jet, the synthetic airflow experienced attenuation. The Y2 type relay nozzle has the minimal attenuation, and the airflow speed was 8 m/s higher than that of the auxiliary nozzle with a single circular hole structure. The inject angle of auxiliary nozzle was found to have a significant impact on the velocity of the synthetic airflow. The inject angle of the Y2 type auxiliary nozzle varied between 4°and 7°, while the speed deviation of the Y2 relay nozzle was 13 m/s. The outlet shape of auxiliary nozzle was also found to have influence on the turbulence distribution of the synthetic airflow in the profiled reed. The outlet shape of auxiliary nozzle demonstrated effects on the velocity and direction of the synthetic airflow. The jet core speed of the Y2 auxiliary nozzle jet was 320 m/s and the jet core velocity area is the longest, better than single circular hole auxiliary nozzle. On the other hand, the single round-hole jet core area is the smallest and spreads quickly. The weft thread was pulled forward by the high-velocity airflow in the profile reed. The outlet shape had an influence on the weft insertion stability. The radial velocity of synthetic airflow was measured at three cross sections of 5 mm, 10 mm and 15 mm from the first auxiliary nozzle outlet, respectively. The radial velocity amplitude and the equivalent circle radius are largest for the Y2 type auxiliary nozzle. Statistics on the mass flow rate at the outlet related to the gas consumption of three types of auxiliary nozzles.
Conclusion Based on the above simulation analysis, some useful results are obtained. Compared the single round hole auxiliary nozzle with the Y2 type auxiliary nozzle, the average velocity increased by 6% and the maximum velocity increased by 12%. The injection angle of auxiliary nozzle is a sensitive factor that affects the axial velocity of synthetic airflow in the profiled reed. A small change in the injection angle will have a significant impact on the velocity of synthetic air flow in the profiled reed. Among them, the best injection angle of Y2 auxiliary injection is 4°. The maximum speed of the potential core of the Y2 type auxiliary jet flow reaches 324 m/s, and the potential core area is the longest. The Y2 auxiliary jet can converge with the main jet at a higher speed. At the section 10 mm away from the auxiliary jet outlet, the radial velocity of Y2 type auxiliary jet flow exceeds 80 m/s, and the equivalent circle radius is significantly greater than that of single circular-hole auxiliary nozzle. It can be seen that the radial velocity attenuation is the slowest and the stability of weft insertion is the best with the Y2 type auxiliary nozzle.

Task scheduling technology for automatic bobbin replacement in intelligent knitting workshop

SUN Lei, TU Jiajia, MAO Huimin, WANG Junru, SHI Weimin

Journal of Textile Research. 2023, 44(12):  189-196.  doi:10.13475/j.fzxb.20220801001

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Objective Aiming at the automatic production of the whole process of the circular knitting machine in an intelligent workshop, this research concentrates on the reasonable scheduling of the automatic bobbin replacement of the knitting robot with acceptable efficiency.
Method In the knitting production shops, the effectiveness of bobbin replacement plays a critical role in ensuring uninterrupted production on circular knitting machines. In order to satisfy production demands for bobbin replacement, a comprehensive consideration of various factors is required, such as the amount of yarn remaining in the bobbin, the response time of the bobbin replacement task, and the path followed by the robot during bobbin replacement. This paper presents a multi-objective optimization model for the bobbin replacement task in intelligent knitting workshops and prioritizes the bobbin replacement tasks based on optimizing the heuristic rules for the replacement process. An improved genetic algorithm that takes into account the amount of remaining yarn is introduced for minimizing the overall path length of the bobbin replacement process and decreasing emergency coefficients for bobbin replacement. Emphasis is placed on replacing yarn bobbin with high emergency coefficients to optimize the production sequencing and bobbin replacement path planning, leading to improved bobbin replacement efficiency.
Results To further verify the effectiveness of the algorithm proposed in this paper, comparative experiments were conducted with ant colony algorithm, genetic algorithm, and the improved algorithm presented in this paper. The results showed that compared with the other two algorithms, the proposed algorithm exhibited outstanding performance in both algorithm convergence and solution stability. Compared to the traditional genetic algorithm, the proposed algorithm demonstrated a 50% improvement in early convergence speed and a theoretical 40% increase in efficiency for bobbin replacement. An effective solution is proposed for the bobbin replacement task in the knitting intelligent workshop.
Conclusion This paper proposes an improved genetic algorithm that takes into account the remaining yarn amount. By optimizing the sequence of bobbin replacement from both the total path of the replacement task and the urgency level of the replacement, it has been demonstrated that the constraint of remaining yarn amount can improve the quality of the initial solution of the algorithm. This algorithm can both eliminate inferior solutions with high urgency coefficients of remaining yarn amount and enhance the convergence speed. As a result, the efficiency of bobbin replacement has been improved by 40%, making it a viable solution for scheduling massive bobbin replacement tasks in the intelligent knitting workshop.

Motion control and experimental analysis of linear maglev knitting needle actuator

SHENG Xiaochao, LIU Zexu, XU Guangshen, SHI Yingnan

Journal of Textile Research. 2023, 44(12):  197-204.  doi:10.13475/j.fzxb.20220604001

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Objective Aiming at the poor performance of the traditional knitting needle drive system and the electromagnetic force nonlinearity of the reluctance force actuated maglev knitting needle drive system, a linear Lorentz force actuated maglev knitting needle drive system is proposed, and the adaptive robust sliding mode control is used to improve the system response speed, disturbance suppression ability, and robustness, realize the stable control of magnetic levitation knitting needles.
Method An electromagnetic force testing system was built to measure the linear characteristics of the driving force through a single-DOF force sensor. The robust and adaptive aspects were taking into account in the differential equation of the system, and an adaptive robust sliding mode controller was designed to improve the system response speed, disturbance suppression ability and adaptability to system uncertainty. A prototype of the Lorentz force actuated maglev knitting needle drive system was built, and the performance of the maglev knitting needle drive system was verified through experiments.
Results Twelve test points were evenly distributed within the effective stroke of the knitting needle to test the output characteristics of the electromagnetic force. Experiments showed that under the same current excitation condition, the output of electromagnetic force at each test point was consistent (Fig. 4). At different test positions, the electromagnetic force varied linearly with the continuously changing excitation current (Fig. 5). It showed that the driving force of the Lorentz force actuated knitting needle drive system had a linear relationship with the input current and had nothing to do with the output position. Under the action of adaptive robust sliding mode control, the step response of the system demonstrated that the knitting needle reached a steady state in 0.6 s without overshoot (Fig. 7(a)), and the steady-state error remained within ±15 μm (Fig. 7(b)). Compared with proportional, integral, and derivative (PID) control, adaptive robust sliding mode control had a faster response speed (Fig. 9), but its steady-state noise was about 1.5 times that of PID control (Fig. 10). It was found that the adaptive robust sliding mode control had a large static error due to the influence of chattering, while the PID control had a smaller static error of the knitting needle and better steady-state control performance. When the system was disturbed, the two control methods could restore the needle displacement to a steady state (Fig. 11), but the system would have a displacement deviation of about 0.7% under the PID control, causing 20 μm in a short time, while the displacement of the knitting needle did not change significantly under the adaptive robust sliding mode control. Compared with PID control, the disturbance suppression ability and robustness of the system was stronger under adaptive robust sliding mode control. The response of the 'three-position knitting' excitation trajectory showed that the system could reach the height of looping, tucking, and floating line and make a stable stop, and the actual displacement was consistent with the expected displacement. Under the action of the adaptive robust sliding mode controller, the designed system was able to drive the knitting needle to complete the 'three-position knitting' action.
Conclusion The experimental results show that the Lorentz force actuated maglev knitting needle drive system is a linear system with high linearity. The designed adaptive robust sliding mode control system has a good control effect, and compared with PID control it has obvious advantages in improving response speed, reducing overshoot and disturbance rejection ability. The designed knitting needle drive system can complete the 'three-position knitting' action.

Comprehensive Review

Research progress in graphene fiber-based flexible supercapacitors prepared by microfluidic spinning

GUAN Tuxiang, WU Jian, BAO Ningzhong

Journal of Textile Research. 2023, 44(12):  205-215.  doi:10.13475/j.fzxb.20220903902

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Significance Corresponding to the increasing demand for the electronics with higher portability, intelligence, and conformability, wearable devices present a fast-growing market and application prospect. The application scenarios of these wearable devices normally present features of high flexibility, deformability and complexity that restrict the service of traditional rigid energy storage systems. In this context, fiber shaped flexible supercapacitors have aroused vast interests for their distinctive advances in flexibility, power density, operation safety and cycling life. Thereinto, graphene fiber-based supercapacitors show the characteristics of high energy density, good flexibility and high safety, presenting great potential to power wearable devices. To date, remarkable progress has been achieved in designing and fabricating graphene-based fiber via different spinning methods such as wet spinning, dry spinning and hydrothermal spinning. However, to accommodate simultaneously the requirements of high electrochemical property and mechanical robustness of electrode materials that originate from the complex application scenarios, it is still highly demanded to develop new spinning approaches to further control the chemical component and structure of graphene-based fiber.
Progress Microfluidic spinning method, as a new generation of spinning approach evolving from microfluidic chip technology, has aroused wide attention for its advantages in preparing refined hetero-structured fibers, and a number of studies have been reported. Precise control of primitive structure and chemical component can be facilitated on graphene fiber through simulating fluid flow of graphene oxide (GO) dispersion, through designing spinneret with different structures and adjusting spinning solution composition and fluid flow state. Typically, for fiber structure adjustment, converging, expanding and coaxial spinning channels have been developed to prepare graphene fibers with high axial order degree, vertical sheet alignment and core-shell structure, respectively. Correspondingly, the as-prepared graphene fibers present high mechanical strength, short ion transport pathway and multi-scenario application capability. For chemical component adjustment, coagulation methods including chemical crosslinking, ionic crosslinking, solvent exchange and solvent vaporing are selected to fabricate graphene based composite fiber with capacitance reinforcement phase. On this basis, heteroatom doping, porous structure and core-shell structured graphene-based composite fibers have been subsequently developed. Through structure and component adjustments, graphene-based fibers exhibit large ion accessible surface, improved ion/electron transport ability, high electrochemical activity and great mechanical stability. Accordingly, the graphene fiber-based supercapacitor prepared by microfluidic spinning technology present high energy density and desirable dynamic output, which can steadily drive multi-color display.
Conclusion and Prospect Predominant progresses have been acquired in preparing hetero-structured graphene based composite fibers that show ideal mechanical-electrochemical performance via microfluidic spinning technology. Basing on the computational fluid dynamics simulation, structure design of spinneret, and spinning solution compound regulation, microfluidic spinning technology can effectively control the flow behavior and composition. The resultant programmable chemical component adjustments combined with accurate regulation in fiber structure endow graphene-based fiber one of the best candidates in flexible energy storage application. In this regard, with the persistent growth of wearable device, microfluidic spinning technology will become an indispensable method for preparing high performance graphene fiber-based supercapacitor. In this process, it would be helpful to consider the following issues. Exploration of appropriate methods and materials for microfluidic channel fabrication. To date, numerous materials and fabrication methods have been developed to prepare spinning channel. Nevertheless, with the consideration that structure design of the spinning channel is the primary approach to control the fluid flow, and it is still necessary to further explore relevant preparation methods and materials to realize the refined channel structure. Simulation of the flow behavior of GO dispersion in microchannels. The complex rheological behaviors of GO dispersion led to difficulty in formulating flow equations to describe solution process, and thus numerical simulation remains the fundamental method for investigation, where, unfortunately, the research in this regard appears to be limited. It is hence highly necessary to simulate and predict the flow behavior of GO dispersion in microchannels based on the experiences of computational fluid dynamics in other fields. Development of graphene fiber-based electrode with novel structure and chemical composition. Although graphene presents the advantages of high conductivity, high strength, and large specific surface area, its assemblies suffer from the severe restacking structure and inferior electrochemical activity. To this end, exploration of graphene fiber-based electrode with novel structure and electrochemical active composition is of profound significance to narrow the Laboratory-Factory gap in the area of flexible energy storage.

Research progress of hydrothermal degradation of waste cellulose textiles

ZHANG Yongfang, FEI Pengfei, YAN Zhifeng, WANG Shuhua, GUO Hong

Journal of Textile Research. 2023, 44(12):  216-224.  doi:10.13475/j.fzxb.20230402602

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Significance Large amount of waste textiles are heaped up, landfilled or incinerated as solid waste year by year, leading to heavy pollution of the environment and waste of the resources. In the face of the worsening energy crisis and environment troubles, the recycling of waste textiles has become a pressing social problem to be tackled. Various ways have been used physically or chemically in the study of the recycling of waste textiles. Among others, hydrothermal degradation is a highly noticeable thermochemical conversion technology featuring environmental friendliness, productive richness, and economy, which can effectively degrade and recycle cellulose textiles, and obtain high value-added hydrothermal products. The green and high-valued recycling of waste textiles are of great economic and social importance for the development of circular economy and reduction of pollution and carbon emission.
Progress New technologies are introduced for hydrothermal degradation of waste cellulose textiles in subcritical (supercritical) environments. With the special properties of subcritical (supercritical) water, cellulose fibers can be degraded hydrothermally into high value-added chemical products such as water-soluble sugar, hydrothermal carbon, and bio-oil. After step-by-step separation, the hydrothermal products can be effectively recovered without pollutant emission. The strong hydrogen bond and stable structure of high crystallinity of cellulose makes it hard to degrade at room temperature, which is the biggest problem in natural cellulose utilization. This paper analyzed the mechanism and reaction process of cellulose fiber hydrothermal degradation, summarized different processes of the hydrothermal degradation and corresponding target products, and concluded the influencing factors of the process and products. In the subcritical (supercritical) water system, acting as a reactant, a catalyst and an organic solvent concurrently, water can effectively break the hydrogen bond and crystal structure, and promote the break of glycosidic bond of cellulose. Under certain hydrothermal conditions, cellulose materials are degraded into substances such as glucose, fructose, 5-HMF (5-hydroxymethylfurfural), and organic acids. The soluble oligomers obtained through hydrolysis will form various carbon containing materials, bio-oils, and a small amount of gases after dehydration, polymerization, condensation, and aromatization. The hydrothermal degradation can be divided into processes of hydrolytic saccharification, hydrothermal carbonization, hydrothermal liquefaction and hydrothermal gasification, with respective products of water-soluble sugar, hydrothermal carbon, bio-oil and gas products. Temperature, time, catalyst, and cellulose structure are important factors affecting the hydrothermal degradation process and degradation products of cellulose. Different reaction conditions result in different degradation rates, products, yields, and properties of the hydrothermal degradation. By adjusting the temperature, catalyst and other parameters, the hydrolysis process can be regulated and the selectivity of target products can be adjusted to achieve different target products.
Conclusion and Prospect Hydrothermal treatment of cellulose fibers can yield high value-added chemical products such as glucose, 5-HMF, lactic acid, and carbon microspheres, while selective degradation of cellulose fibers can achieve effective separation and recycling of cellulose based blended fabrics, demonstrating that hydrothermal degradation technology of cellulose fibers is an effective way for high-valued recycling of waste textiles. However, researches in the area are still in the phase of laboratory exploration, at certain distance from large-scale production, due to the complex process relating to cellulose hydrothermal degradation. Still, the complexity of the hydrothermal degradation process and uncertainty of the decomposition mechanism and pathway of intermediate products, and the catalytic mechanism and regulatory mechanism of catalysts led to low yield of target products. Consequently, additional research should be conducted on the existing issues. With the evolution of the research, the industrial application of hydrothermal degradation technology in waste textiles treatment in the future will achieve significant social and economic benefits.

Research progress in electret technology for melt-blown nonwovens

MENG Na, WANG Xianfeng, LI Zhaoling, YU Jianyong, DING Bin

Journal of Textile Research. 2023, 44(12):  225-232.  doi:10.13475/j.fzxb.20220701302

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Significance Industrial development caused air pollution. Parallel to the effort of control air pollution, it has become necessary and important to have materials which is capable of filtering the polluted air for people to breathe clean air. The most direct and effective way to achieve this goal is to use air purifiers, masks, and other related filtering equipment. The outbreak and spread of COVID-19 pandemic in recent years have brought great challenges to global public health protection, and various countries took various protective measures. Filtering materials with low air resistance, high filtration efficiency, and high charge storage stability have attracted much attention, and the market demand has been growing. Safety protection articles such as masks, protective clothing, and respirators have become indispensable pandemic prevention materials and for normal epidemic prevention. Melt-blown nonwovens, as the key materials of protective articles, have attracted much attention in the research of melt-blown nonwovens with high efficiency, low resistance, and stable charge storage.
Progress In order to deeply understand the research status of the electret technology of melt-blown nonwovens, this paper systematically reviewed the electret technology for making melt-blown nonwovens, the electret effect of melt-blown nonwovens and the prospect of electret melt-blown nonwovens. The paper summarized the characteristics and mechanisms of six electret technologies, including corona charging, friction electrification, electrospinning, and water electret. The technology and application status of corona electret and water electret treatment were analyzed in the main. Additionally, the mechanism of electrostatic storage and its stability were introduced. Then the influence of electret material, electret process, and polymer crystal structure on the electrostatic storage performance of melt-blown nonwovens was also analyzed. Furthermore, in view of the challenges to electret technology, this paper summarized the development of new electret materials with multi-function and high-added value and the combination of multiple electret technologies as the main development direction of electret melt-blown nonwovens in the future.
Conclusion and Prospect With the continuous outbreak of global infectious diseases, awareness of health, safety, and protection is gradually enhanced, and the quality requirements for protective articles are constantly improved. The research and development of electret melt blown nonwovens with stable charge storage has become a scientific problem that needs to be solved urgently, which is of great significance to promoting the construction of emergency public health safety in the world. At present, electret melt blown nonwovens are made using mainly two processes, i.e., electrostatic electret and water electret. Researchers of electrostatic electret preparation methods have made some positive achievements, but the technical development and research of water electret need to be further explored. In general, with the development of new materials and the improvement of new technologies, electret melt-blown nonwovens with stable charge storage, longer service life, diverse functions, and good comfort will be more widely used in the fields of filter materials, barrier materials, medical and health materials, and so on. With the progress of information and digital technology, as well as the acceleration of industrialization and manufacturing power, intelligent, information-based, and digital electret melt blown nonwovens will also become a new trend of development. Improving the electrostatic storage and stability of electret melt blown nonwovens has also become an important and necessary work for industrial textile workers.

Research status and development trend in individual cooling garment

LIU Yuting, SONG Zetao, ZHAO Shengnan, WANG Xinglan, CHANG Suqin

Journal of Textile Research. 2023, 44(12):  233-241.  doi:10.13475/j.fzxb.20221003402

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Significance In high-temperature environments during the summer and high heat scene, workers' body core temperature keeps rising, leading to heat stress issues such as heat exhaustion, heat stroke, and heat cramp. Individual cooling garment are capable of mitigating heat stress issues that workers may experience in high-temperature environments. By regulating the temperature inside the clothing, they enhance the comfort of the wearer and improve their work efficiency. These suits serve as effective protective equipment with notable cooling effect. Traditional individual cooling garment face key issues such as short cooling duration, hot and humid when worn, and coolant leakage. The emergence of new cooling systems has provided research directions for improving cooling garment. Based on the latest research findings, the classification of cooling garment from a cooling system perspective has been introduced. The latest cooling system designs have been summarized, and the main factors influencing cooling garment performance have been analyzed. Additionally, the future development trends have been outlined with the aim of providing reference for the research and development of cooling garment.
Progress It is crucial to develop new cooling systems and find solutions to enhance the comfort of cooling garment. Researchers have conducted extensive studies to improve cooling systems, aiming to enhance cooling effectiveness and refrigeration efficiency. In the field of gas cooling garment, researchers have compared the impact of garment size and ventilation rate on thermal resistance and cooling effectiveness. The results indicate that loose-fitting gas cooling garment exhibit superior ventilation efficiency and cooling effectiveness compared to form-fitting suits. To address practical applications, researchers have developed gas cooling garment with adjustable fan speeds. The results demonstrate that incorporating fans both in the front and back of the garment not only improves comfort but also reduces energy waste while maintaining longer cooling effects. In the field of liquid cooling garment, the latest approach for pipe preparation involves using PU fabric and heat pressing techniques to create cooling pipes. Liquid cooling garment designed with semiconductor refrigeration devices have effectively addressed coolant leakage issues and improved thermal comfort for wearers. Regarding pipe layout, research indicates that transverse arrangement of cooling pipes yields higher cooling efficiency compared to longitudinal arrangement. In the field of phase-change cooling garment, multiple studies have shown that increasing the temperature difference between the cooling pack and the environment improves cooling efficiency. Therefore, scholars have developed hybrid cooling jackets using dry ice and fans, resulting in improved refrigeration efficiency, extended cooling duration, and easier cleaning of the cooling garment. In the development of new cooling garment, thermoelectric refrigeration systems are gaining attention. These systems do not require compressors and allow for quick and accurate adjustment of cooling efficiency by regulating electric current. The temperature range that can be controlled is wide (-130 ℃ to 90 ℃), and there is no risk of refrigerant leakage with semiconductor cooling plates. Radiative cooling is another research direction of interest. Nanofabricated silk cooling garment based on radiative cooling principles can lower skin temperature by 8 ℃ in high-temperature environments, meeting comfort requirements. Furthermore, it is essential to develop new materials that offer excellent wearer comfort, high cooling efficiency, and enhanced environmental sustainability for new cooling systems. Examples include temperature-sensitive shape-memory bacteria and nanoporous polyethylene materials. Addressing the portability issues of convection-based gas cooling garment and insufficient power supply for cooling devices, a vacuum desiccant cooling (VDC) system has been developed. VDC pads are prepared and initialized by a high-performance vacuum pump, with the vacuum layer facilitating evaporation for cooling effects.
Conclusion and Prospect The development of cooling clothing in the future is mainly reflected in the research and development of green functional fabrics with good cooling effect, and in optimizing the packaging of the cooling medium to reduce energy waste. The future development of cooling clothing is mainly reflected in the development of green functional fabrics with good cooling effects and new lightweight and durable materials. The following are believed to represent the research directions: optimization of the packaging of cooling medium to reduce energy wastel; further research and development of automatic adjustment heat exchange network to improve wearing comfort; more comprehensive ergonomic evaluation of cooling garment, taking into account the thermal perceptual response and ergonomics and other factors to improve the performance of cooling garment, and development of more intelligent, simple, miniaturized intelligent temperature control system.

Research progress in ergonomic performance of caps based on pressure measurement

WANG Zhongyu, WANG Yunyi, WANG Shitan

Journal of Textile Research. 2023, 44(12):  242-250.  doi:10.13475/j.fzxb.20220808502

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Significance Caps are common head accessories in people's daily life. In practical use, ergonomic function of caps relies on its stable attachment to the head causing the pressure from the cap to the head. The pressure at 'head-cap' interface are the key factors affecting the comfort of caps while wearing. Through analysis of 'head-cap' interface pressure mechanism, this article reviews the current research of cap pressure measurement methods and characterization indicators, as well as the research progress based on these evaluation technologies. In order to summarize characteristics and applicability of different measurement methods and provide effective suggestions for 'head-cap' interface pressure study, this paper offers a theoretical basis for the optimization design of cap products aiming at improving fit, pressure comfort, wearing stability as well as thermal and moisture comfort.
Progress In current studies, pressure measurement of specific test points on the head is the most commonly used method, performing by human subjects or head mannequins, with different data collection methods. Head pressure distribution under caps could also be measured by subjects' trial experiments and head mannequins, characterized by pressure maps, and researchers have developed corresponding testing devices, such as pressure sensing pads, silicone pressure sensing caps and pressure testing head manikins. The gap between the ″head-cap″ interface could provide the morphology relationship between them, indirectly evaluating the cap pressure by measuring the difference of size or spatial morphology of the interface. Researchers also monitored physiological signals' change under the degree of compression, however, the skin blood flow, surface electromyogram, electroencephalogram signals tend to be interfered the hair or electrode, meanwhile, whether characterizing ″head-cap″ pressure by infrared camera is feasible remains to be verified. In the study of pressure related ergonomic performance of caps, pressure and comfort sensations were frequently used as characterization indexes in the study of pressure comfort, with perceptions of pressure varying among people and head regions. The wearing stability of caps was often evaluated by holding power, as researchers used critical load and critical wind speed to characterize the holding power of the caps under external forces. The fitness of caps directly affects the pressure on the ″head-cap″ interface, which is based on morphology of human head. At present, normalized head and face sizes have been specified in certain standards, and head statistical databases and interaction design platforms were set up for product development for the head.
Conclusion and Prospect Based on existing research, it is pointed out that the research on ergonomics of caps has not yet been systematically established. In order to improve the ergonomics and wearing experience of caps, further research orientations are put forward. Firstly, head mannequins with hard material and statistical middle sizes are used in pressure measurement, and the evaluation indexes are single and unrepresentativeness. Following research could focus on developing a series of biomimetic head manikins while considering the influence of hair. The evaluation index should be built characteristic of interface pressure, from the perspective of multi-index comprehensive evaluation. Secondly, for dynamic situations, the accuracy and repeatability of the existing measurement devices and indicators need to be improved. In the future, dynamic pressure measurement methods should be expanded, so as to explore the influence law of the objective pressure distribution on the dynamic stability. Thirdly, formation mechanism of cap pressure and its influence on head perception has yet to be systematically studied, which remains necessary to be further investigated combined with anatomy and physiological knowledge, with the relationship between pressure distribution and subjective comfort be explored, and the potential correlation between subjective evaluation indicators deeply analyzed. Furthermore, as fitness is the key to the study of the caps' ergonomic properties, it is not enough to characterize only through the ″head-cap″ interface. Further research could adapt virtual technologies and numerical simulation to study the interaction impact of caps' structure and materials based on parametric structure design and mechanical properties of materials. Last, the ″head-cap″ interface pressure may affect the head thermal and moisture comfort, but the exploration of mechanism research is still in its infancy. The relationship between head pressure and thermal comfort will be a complex but worthy topic.