Table of Content

15 September 2024, Volume 45 Issue 09

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Fiber Materials

Fabrication of high molecular weight chitosan core-shell nanofibers

FANG Lei, LIU Xiuming, JIA Jiaojiao, LIN Zhihao, REN Yanfei, HOU Kaiwen, GONG Jixian, HU Yanling

Journal of Textile Research. 2024, 45(09):  1-9.  doi:10.13475/j.fzxb.20230701601

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Objective High molecular weight chitosan (HMCS) has many advantages when used in the field of wound management because of its antibacterial properties as well as the cell and tissue growth capabilities. However, fabricating HMCS nanofiber is challenging since the spinning solution's viscosity is extremely high. In order to solve this problem, solution blow spinning was studied and adjusted to fabricate HMCS nanofibers, and the spinning parameters were identified to fabricate polyethylene oxide (PEO) as shell and HMCS as core nanofibers, which were transformable to physical hydrogel when contacting the wound exudate for wound healing.

Method The spinning solutions containing 1.6% mass fraction HMCS and 2.5%-5.0% mass fraction PEO were prepared by dissolving and mixing these two species in 50% mass fraction aqueous acetic acid solutions, with 200 r/min mixer rotation rate and 10 h mixing time. The well-mixed solutions were degassed for 12 h before solution blow spinning. In the spinning process, PEO-HMCS nanofibers were spun with the parameters ranging from 0.04 MPa to 0.10 MPa air pressures and 21 cm to 33 cm collecting distances. The area of the resulting PEO-HMCS nanofibers was 2 010 cm² and the spinning duration was 45 min for each of the four spinning solutions. The temperature was kept at 24 ℃ with the relative humidity of approximately 20% during the solution blow spinning process.

Results The morphologies of the PEO-HMCS nanofibers were observed by scanning electron microscopy and field emission-scanning electron microscopy. The shapes of the nanofibers were straight lines and the fiber surfaces were not smooth, with some ripple shapes. When the PEO mass fractions in solutions increased from 2.5% to 5.0%, the mean diameters of the nanofibers increased from 133 nm to 210 nm, with the nanofibers porosities anchanged and remaining at 0.69. This study also investigated the influences of changing collecting distances on the resulting nanofibers mean diameters, as well as the influences of changing air pressures on the resulting nanofibers mean diameters. When the collecting distances increased from 21 cm to 27 cm, the PEO-HMCS nanofibers mean diameters decreased first and then increased. As the air pressures increased from 0.04 MPa to 0.05 MPa, the mean diameters increased from 637 nm to 790 nm. After further increasing air pressures to 0.07 MPa, the mean diameters dropped to 375 nm. Continuing increasing the air pressures to 0.10 MPa led to the mean diameters decreasing from 359 nm to 397 nm. The detailed nanofiber core shell structures were observed by the transmission electron microscopy. Before immersed in water, the thickness of the fiber shell was 340 nm and the thickness of the fiber core was 35 nm approximately. After immersed in water, the thickness of the fiber shell significantly decreased. When the PEO mass fraction increased from 2.5% to 5.0%, the mean diameters of the PEO-HMCS nanofibers increased from 161 nm to 211 nm, with conductivities decreasing from 1 760 μS/cm to 1 640 μS/cm and viscosities increasing from 42 082 mPa·s to 91 055 mPa·s. The dynamic viscosities of PEO 2.5% mass fraction solution dropped quickly to 0.11 Pa·s before shear rate reached 1 s^-1, and remained unchanged afterwards. The dynamic viscosities of 1.6% HMCS solution decreased slowly during shear rate sweeping from 0.1-1 000 s^-1, and the values were all higher than those of 2.5% PEO solution. For the dynamic surface tensions, higher PEO mass fractions led to lower dynamic surface tensions. Furthermore, no nitrogen element was detected on the nanofiber surfaces by the X-ray photoelectron spectroscopy. The in vivo animal experiment results showed that the PEO-HMCS nanofibers significantly promoted wound healing.

Conclusion The types as well as the mass fractions of HMCS and PEO were studied for fabricating HMCS nanofibers. The nanofibers showed unique morphological structures, mean diameters, and pore distributions. Several specialized solution blow spinning parameters, including air pressures and collecting distances, could influence the fabrication process. The solution viscosities, conductivities, and surface tensions also had an impact on the HMCS nanofibers formation. No HMCS was found on the nanofibers surfaces and only PEO existed. The resulting PEO-HMCS solution blow spinning nanofibers had core shell structures, with PEO mainly locating at the shell region and HMCS at the core region. The shell of the nanofiber was semi-flexible and the core was stiff with no flexibility. The in vivo animal experiment results showed that the PEO-HMCS core shell nanofibers could be used as the physical hydrogels to promote wound healing.

Preparation and sensing performance of flexible pressure sensor based on natural flat silk cocoon structure

WANG Yujia, WANG Yi, WANG Yasi, DAI Fangyin, LI Zhi

Journal of Textile Research. 2024, 45(09):  10-17.  doi:10.13475/j.fzxb.20230602601

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Objective Silk fabric is an ideal substrate for fabricating flexible and wearable pressure sensors because of its excellent comfort and skin-friendly properties. However, it requires complex and time-consuming process to prepare the silk fabrics from the silkworm cocoon. Flat silk cocoon (FSC) formed by the free movement of silkworm is a natural non-woven structure with high porosity and favorable flexibility. In this paper, FSC without post-treatment was used as a flexible substrate to develop flexible pressure sensor together with conductive materials MXene and AgNWs.

Method During silkworm spinning, MXene and AgNWs dispersions were repeatedly sprayed on the surface of silk fibers at a fixed time interval. MXene and AgNWs were coated on the surface of silk fibers by natural adhesion of sericin during this biospinning process, and then MA-FSC with multil-layered structure were prepared. The MA-FSC pressure sensor was assembled face-to-face with the interdigitated electrode, and its sensing performance and real-time monitoring application were studied.

Results The sprayed MXene and AgNWs alternatively distributed on the surface of flat silk cocoon, and the prepared MA-FSC exhibited a hierarchical structure with five layers. The optimizing experiment showed that the pressure detection range of the sensor gradually was increased with the increase in the number of sensing layers. However, too many or too few sensing layers led to the low sensitivity of sensor. When the number of sensing layers was too small (such as 1 layer), the conductive layer active material content inside the sensor was insufficient, resulting in a small number of conductive paths formed during the compression process, and the sensor showed low sensitivity. When too many sensing layers (such as 3 layers) was fabricated, more conductive paths existed inside the sensor even when no pressure, and the signal change of the sensor was not obvious when pressure was applied. Therefore, the 3-layer MA-FSC pressure sensor demonstrated little difference between the no-pressure state and the saturated pressure state. The 2-layer MA-FSC pressure sensor was proved to have the best sensitivity (0.20 kPa^-1). The response/recovery time was shorter than 1 s, and it could react quickly to changes in external pressure. In addition, the 2-layer MA-FSC pressure sensor maintained a stable signal output under the gradient increasing compression rate and gradient increasing pressure, with the cycle durability over 1 500 times. Owing to the excellent sensing performance, MA-FSC pressure sensor would be expected to to monitor human body movement status (such as finger pressing, finger bending, elbow bending and knee bending). The 2-layer MA-FSC pressure sensor could also be combined with Morse code to output some signals similar to ″SOS″, ″SWU″ and ″WYJ″, which were used in the field of encrypted transmission of information. 16 pressure sensor units were fitted into a 4×4 sensing array for pressure distribution visualization.

Conclusion Using natural flat silk cocoon as a flexible substrate, the MA-FSC pressure sensor was prepared. The optimization indicates that the prepared sensor with two sensing layers has the best sensing performance, which can be applied in the fields of human body movement status monitoring, information encrypted transmission, and real-time pressure trajectory tracking. This research broadens the application field of silk and provides new ideas and inspiration for the development of sensors based on natural material substrates.

Preparation and biocompatibility of temperature-sensitive composite membrane of tussah silk fibroin nanofiber

WANG Boxiang, XU Hangdan, LI Jia, LIN Jie, CHENG Dehong, LU Yanhua

Journal of Textile Research. 2024, 45(09):  18-25.  doi:10.13475/j.fzxb.20230701901

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Objective Antheraea pernyi silk fibroin (ASF)-based nanofibers have wide potential for biomaterial applications because it contains tripeptide sequences (Arg-Gly-Asp) known as RGD, whereby the integrin binding motif promotes the cell attachment. At present, electrospinning of regenerated ASF nanofibers is usually performed with volatile organic solvents, which may cause potential toxicity to the encapsulated cells, and residual organic solvents will cause safety hazards to cells and human bodies. Therefore, it is necessary to find a method for electrospinning of ASF in aqueous solutions to prepare nanofibers.

Method Novel ASF-based thermo-responsive hydrogel nanofibers were developed using aqueous electrospinning without any harsh organic solvent, and the employability of such nanofibers as an in-vitro platform for cell culture was explored. In order to study the spinning process and biocompatibility of temperature-sensitive nanofiber membrane of tussah silk fibroin, p (ASF-AGE-PNIPAAm) nanofiber membrane was prepared by in-situ solution polymerization and electrospinning, allyl glycidyl ether(AGE) modified tussah silk fibroin was used as base material (ASF-AGE) and N-isopropylacrylamide was used as monomer. The influence of monomer ratio on the formation of nanofiber membrane was investigated, and the temperature response, hydrophilicity, in-vitro degradation and cell compatibility of nanofiber membrane were analyzed.

Results ASF-based thermoresponsive nanofibers (p(ASF-AGE-NIPAAm)) were successfully manufactured by aqueous electrospinning with the polymerization of ASF and N-isopropylacrylamide (NIPAAm). The results showed that when ASF-AGE and NIPAAm were polymerized at a mass ratio of 1∶1.5, uniform and continuous nanofiber membrane with an average diameter of (452±120) nm were successfully prepared by electrospinning. The nanofibers exhibited good thermoresponsive characteristics that the lower critical solution temperature(L_CST) was similar with PNIPAAm at about 32 ℃. The nanofiber membrane showed obvious temperature responsiveness at 32.7-33.4 ℃, and significant hydrophobicity at 45 ℃. The nanofiber membrane was prone to degrade in protease XIV, and the weight loss rate reached 39.6% after 28 d of degradation. Excellent cell proliferation, viability and morphology were demonstrated for b End.3 cells on the nanofibers by the characteristic methylthiazolyldiphenyl-tetrazolium bromide assay and confocal laser scanning microscope. It was not cytotoxic in co-culture of nanofiber membrane with mouse brain microvascular endothelial cells b End.3, and good cytocompatibility was found in co-culture of 5 d and 7 d. It was demonstrated that b End.3 cells grown on nanofibers showed improved cell adhesion, proliferation, and viability. The result indicated that the nanofiber membrane was beneficial to b End.3 cells adhesion and proliferation.

Conclusion Novel ASF-based thermoresponsive nanofibers were successfully fabricated by aqueous electrospinning for b End.3 cells culture. These nanofiber membranes have obvious thermoresponsive and the L_CST is close to human body temperature. The utilization of a thermoresponsive polymer in the development of cell culture platforms allowed the dynamic control of cell adhesion and detachment in a desired manner by changing the temperature for targeted purposes. Furthermore, the nanofibers can be degraded in protease XIV solution, the degradation products of silk based materials are soluble peptides and free amino acids, which are easily metabolized and absorbed by the human body. By culturing brain microvascular endothelial cells in vitro, the nanofibers support cell adhesion and growth well. These degradable and thermoresponsive hydrogels will have potential applications for cells delivery device and tissue scaffold. This is a convenient and feasible approach to fabricate ASF-based functional nanofibers in the application of cell culture, presenting a valuable route for developing an ASF-based cell culture platform.

Preparation and functional application of polyethyleneimine/polyacrylonitrile composite fiber membrane

WANG Haoran, YU Ying, ZUO Yuxin, GU Zhiqing, LU Hailong, CHEN Hongli, KE Jun

Journal of Textile Research. 2024, 45(09):  26-32.  doi:10.13475/j.fzxb.20230600801

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Objective The CO₂ corrosion of metal-air batteries is extremely serious, which greatly limits the service life of the metal-air batteries. Existing researches generally add CO₂ absorbers or O₂ selective membranes to the cathodes, which indeed inhibit the CO₂ corrosion to a certain extent, but have a negative impact on the electrochemical performance of the batteries. Therefore, there is an urgent need to explore a new method to inhibit cathode corrosion in metal-air batteries, which would not sacrifice the electrochemical performance of the battery and can effectively inhibit CO₂ corrosion.

Method Polyethyleneimine/polyacrylonitrile (PEI/PAN) precursor solutions with different PEI contents were prepared, and PEI/PAN composite fiber membranes were fabricated by electrospinning. The microstructure of the composite fiber membrane was characterized by scanning electron microscope and infrared spectrometer. The influences of different PEI contents on the CO₂ adsorption performance of PEI/PAN composite fiber membranes were studied combining computer simulation and CO₂ adsorption-desorption experiments. An aluminum-air battery with a PEI/PAN composite fiber membrane was prepared to verify the optimization effect of the composite fiber membrane on the discharge performance of the battery.

Results PEI was successfully embedded into PAN fibers through electrospinning, and the surface was smooth and the layered fiber structure was evenly distributed. The computer simulation results showed that the PEI/PAN composite fiber membrane of system II (50% PEI) illustrated excellent adsorption performance, and the CO₂ adsorption-desorption experiment further confirmed the simulation results. When the pressure was 100 kPa, the adsorption capacity of PEI/PAN composite fiber membrane was 1.86 mmol/g. The experimental and simulation results agreed well to each other. Taking aluminum-air batteries as an example, aluminum-air batteries with PEI/PAN composite fiber membranes were assembled. Electrochemical test results showed that compared with conventional aluminum-air batteries, the cathode corrosion of aluminum-air batteries with PEI/PAN composite fiber membrane was significantly inhibited. The discharge time of the aluminum battery with PEI/PAN composite fiber membrane was 548 min, while the conventional aluminum-air battery was only 455 min. The discharge time of the battery with the composite fiber film was prolonged by 20.4%, and the specific capacity was increased by 19.5%, proving that the PEI/PAN composite fiber film could effectively inhibit the corrosion of the positive electrode and improve the electrochemical performance of the battery.

Conclusion The PEI/PAN composite fiber membrane prepared has excellent adsorption properties, and its application in metal-air batteries can effectively inhibit the corrosion of CO₂ on the air cathode. Adding PEI/PAN composite fiber membrane to the cathode of aluminum-air battery can significantly increase the specific capacity and prolong the discharge time of the battery.

Preparation and properties of polyethylene oxide/Al₂O₃ passive radiative cooling membrane

WANG Qingpeng, ZHANG Haiyan, WANG Yuting, ZHANG Tao, ZHAO Yan

Journal of Textile Research. 2024, 45(09):  33-41.  doi:10.13475/j.fzxb.20230605701

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Objective Rapid population growth and industrialization cause global warming. Improving the cooling efficiency of materials and slowing down global warming become a top priority. With the development of micro/nano technology, through the design and preparation of new materials, high solar reflectivity and high infrared emissivity in the atmospheric window band infrared emissivity can be achieved to improve the daytime radiative cooling effect.

Method Using polyethylene oxide (PEO) as the raw material, PEO fibrous membranes were prepared through electrospinning technology. PEO/Al₂O₃ fibrous membranes were fabricated by combining different contents of nano-Al₂O₃ into PEO micro-nanofibers through a blending method. The morphology, reflectance of sunlight, mid-infrared transmittance and emissivity in the atmospheric window, and daytime radiative cooling performance of fibrous membranes were studied and analyzed.

Results Through SEM analysis, it was confirmed that the nano-Al₂O₃ particles were combined into the fibers, and the diameters of the fibers obtained by electrospinning were mainly distributed in the range of 0.2-1.6 μm, while the solar spectrum was in the range of 0.25-2.5 μm, demonstrating that the fibrous membrane has a strong scattering effect on sunlight. The increase in the content of nano-Al₂O₃ particles in fibrous membrane was confirmed by EDS analysis. The crystallization properties of the fibrous membranes were analyzed, and the results confirmed the existence of nano-Al₂O₃ particles in the FPRC-4 membrane. The chemical structure analysis suggested that the FPRC-4 membrane had no obvious characteristic peak in the mid-infrared band of 8-13 μm, and that it can achieve selective emission in the wavelength range of 8-13 μm. The effects of Al₂O₃ content and membrane thickness on solar light reflectance and mid-infrared transmittance were studied. The results indicated that owing to the effective scattering of micro-nanofiber structure and nano-Al₂O₃, the average solar light reflectance of the membrane was 90.2%, and the average transmittance in the atmospheric window was 93.5%. When the Al₂O₃ mass fraction was 4%, the PEO/Al₂O₃ fibrous membrane has the best optical properties. The solar light reflectance would increase with the increase of thickness, while the change in the mid-infrared transmittance with the increase of thickness was not obvious. The influence of added Al₂O₃ nanoparticles on the emissivity of the fibrous membrane was studied. The results showed that the introduction of nano-Al₂O₃ particles increased the overall infrared emissivity of FPRC-4 membrane to 80.3%, compared to the relatively low infrared emissivity of the pure PEO membrane (56.5%), and the average emissivity of FPRC-4 membrane in the atmospheric window was as high as 90.0%. Radiative cooling experiments were conducted using a self-designed testing setup to investigate the cooling performance of the samples. With an Al₂O₃ mass fraction of 4%, a temperature decrease of 6.1 ℃ was achieved during daytime under an average solar irradiance of 712.3 W/m² and an average ambient humidity of 14.2%. The actual cooling effectiveness of the membrane was tested. Infrared camera observed that the surface temperature of the FPRC-4 sample was significantly lower than that of the control sample, indicating good radiative cooling performance of the FPRC-4 sample.

Conclusion The radiative cooling performance is closely associated with multiple factors. The Al₂O₃ content and membrane thickness have an impact on the solar light reflectance, mid-infrared transmittance in the atmospheric window region, emissivity, and radiative cooling performance of the fibrous membrane. Analysis of solar light reflectance spectra and mid-infrared transmittance spectra demonstrated that with an Al₂O₃ mass fraction of 4% and a thickness of 0.2 mm, the fibrous membrane achieved a daytime temperature reduction of 6.1 ℃. Radiative cooling technology holds promise for assisting China in achieving peak carbon emissions and carbon neutrality. The use of such fibrous membranes for energy-efficient radiative thermal regulation provides new avenues and approaches for mitigating global warming and advancing the development of renewable energy-saving refrigeration technologies.

Simulation of dry spinning process and cross-section analysis of profiled diacetate fibers

DENG Gang, ZHANG Tao, WU Chaoping, WANG Jun, ZHANG Lei

Journal of Textile Research. 2024, 45(09):  42-49.  doi:10.13475/j.fzxb.20230605301

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Objective The forming mechanism of profiled fibers of dry spinning involves heat transfer, mass transfer, phase change, deformation, and so on. The cross-sectional shape changing process, in particular, is affected by surface tension, solvent diffusion and evaporation, and it is difficult to develop quantitative research on this process. The previous studies on dry spinning process dynamics were mainly focused on circular cross-section fibers, and research on dry spinning of profiled diacetate fibers is yet to be carried out. The purpose of this research is to establish a dry spinning dynamics model of profiled diacetate fibers, and compare and validate the simulation results of fibers cross-section against the experimental data.

Method A profile degree calculation equation was derivated from the triangle spinneret hole to describe the variation of fibers cross-section, and combined with a typical one-dimensional dry spinning model to establish a hybrid dynamic model which has advantage in efficient computing. Based on this model, the variations of filament solvent mass fraction, temperature, velocity, tension and cross-sectional area during the spinning process could be obtained, so could the variation in cross-section profile degree. Profiled fibers were prepared by industrial spinning device. Stereomicroscopy was adopted to observe the cross-section of fibers, and the experimental results were compared with the simulation calculation values.

Results Spinning solution quickly evaporated after being extruded from the spinneret since its temperature is higher than the atmospheric boiling point of acetone. Besides, the small diameter of spinneret hole contributed to solvent diffusion and evaporation, and the curing point of filament was only about 50 cm away from spinneret. The glass transition temperature showed an opposite trend to the solvent content, reaching the maximum value after the filament was cured. Filament temperature was rapidly decreased by flash evaporation, with the minimum temperature dropping to -12 ℃. Because of the high specific surface area and fast heat transfer rate of profiled diacetate fibers, the constant temperature evaporation zone of spinning process was only about 20 cm. As the rapid reduction of solvent content during flash evaporation, the filament tension quickly increased under the and accelerated stretching. After that, the tension increased along with the spinline, and the friction force between filament and air was the main influence factor. The filament instantaneously accelerated to take-up velocity after being extruded from spinneret and keeps a plateau value throughout the spinning process. The variation trend of the cross-sectional area was similar to that of the solvent content. The profile degree of diacetate fibers was controlled by solvent evaporation and surface tension with solvent evaporation was found the main control factor. Length of the major and minor axes of the filament cross-section were affected by flash evaporation and significantly shortened in a few centimeters from the spinneret hole, then slowly decreased along the spinline to a plateau value at z=50 cm. However, the decrease ratio of minor axes was larger than major axes so that the profile degree could be increased. The experimental profile degree was 74.4%, and the simulation value was 72.8%. While the experimental fibers cross-sectional area is 642.0 μm², and the simulation value is 614.8 μm².

Conclusion A dry spinning dynamic model was established to simulate the spinning process of profiled diacetate fiber. The results show that solvent evaporation and temperature changes dramatically, and the constant temperature evaporation section is not obvious. Filament approaches the take-up velocity at z=1 cm and cures rapidly near the spinneret while the cross-sectional area reaches a constant value. The simulation results of the dry spinning model of fibers cross-section are consistent with the experimental values. As shown in the experiment, the cross-section of diacetate fibers exhibits as a regular "Y" shape with a high consistency of profile degree, and while there are a little differences in the cross-sectional area among single fibers. It is found that the coefficient of variation of profile degree(CV=1.12%) is smaller than the cross-sectional area(CV=4.17%).

Influence of solid-state polymerization on structure and properties of naphthalene ring structure aromatic liquid crystal copolyester

WEI Peng, LI Zhiqiang, LI Jiaojiao, LI Junhui, LIU Dong, GENG Jiajun

Journal of Textile Research. 2024, 45(09):  50-55.  doi:10.13475/j.fzxb.20230702401

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Objective Degradation, cross-link side reaction and poor processing ability are caused by high reaction temperature and melt viscosity of liquid crystal copolyesters in the final stage of melt polycondensation. In order to solve such problems, low molecular weight of liquid crystal copolyesters was prepared by one-pot melting transesterification method. The influences of solid-state polymerization time and temperature on thermal properties, crystallization properties and melt index of liquid crystal copolyesters were investigated.

Method In this study, the low molecular weight liquid crystal copolyester derived from 6-hydroxy-2-naphthalene carboxylic acid (HNA), 2, 6-naphthalene dicarboxylic acid (NDA), terephthalic acid, 4,4'-dihydroxy biphenyl (BP) were prepared by in-situ one-pot melt polymerization method. After solid-state polymerization, the structure and properties of liquid crystal polyesters were analyzed by Differential scanning calorimeter, Thermogravimetric analyzer, polarized microscope, X-ray diffraction and melt index.

Results The melting temperature of liquid crystal copolyester (T_m) and the glass transition temperature (T_g) were found to increased and then decreased with the increase of polymerization time. Crystallization enthalpy ΔH_c and melting enthalpy ΔH_m reached the maximum after 12 h of polymerization, and were decreased gradually with the increase of solid-state polymerization time ΔH_c and ΔH_m. Clear marble and textured liquid crystal texture were still observed 8 h after solid-state polymerization, showing nematic liquid crystal behavior, but with the increase of polymerization time, birefringence and texture gradually got blurred. When the polymerization time was increased to 36 h, the crystal structure did not change, remaining in the state of orthogonality. The results showed that the phase transition temperature and crystallization rate of liquid crystal copolyesters were greatly affected by polymerization time and temperature. The crystallization performance of liquid crystal copolyesters was better when the polymerization temperature was 305 ℃ and the polymerization time was about 12 h. The initial degradation temperature of liquid crystal copolyesters after solid state polymerization was generally higher than that of the initial sample, and the temperature corresponding to the maximum mass loss was somewhat lower than that of the sample. The carbon residue of liquid crystal copolyesters at 700 ℃ remained between 42% and 44.5%, indicating that the molecular weight and thermal stability of liquid crystal copolyesters were improved during the polymerization process but the possibility of thermal degradation was increased by long-term high temperature polymerization. With the increase of polymerization time, the melt index at different polymerization temperatures began to decrease rapidly. When the polymerization temperature was 315 ℃, the melt index of copolyesters was decreased the fastest. After 24 h solid-state polymerization, the melt index of copolyesters did not change significantly. Considering that high molecular weight products were obtained under low energy consumption, 8-24 h solid-state polymerization time was appropriate.

Conclusion The structure and properties of liquid crystal copolyester are influenced by the operation parameters of solid-state polymerization, such as temperature, time, nitrogen flow rate and particle size. This research was focused on the influence of temperature and time on the thermal and crystallization properties of liquid crystal copolyester. Owing to the continued reaction of the terminal group, the molecular chain of liquid crystal copolyester after solid-state polymerization increases, the molecular weight increases, and the melting temperature, glass transition temperature and thermal stability are improved. However, after solid-state polymerization for more than 12 h and the temperature is higher than 305 ℃, the concentration of the reactive terminal group inside the particles decreases. When the molecular weight reaches the equilibrium limit, the melting point of the copolyester decreases gradually, and the degradation reaction of the molecular chain gradually dominates, and the thermal stability and crystallinity decrease. The results show that the thermal and crystalline properties of liquid crystal copolyesters are improved significantly after solid state polymerization at 305 ℃ for 12 h, which is conducive to its processing and application.

Characterization of internal fiber distribution and structural morphology of Mexican red acid branch based on three-dimensional microscope imaging

ZHOU Linghui, ZHU Chengyan, JIN Xiaoke, MA Leilei, CHEN Haixiang, TIAN Wei

Journal of Textile Research. 2024, 45(09):  56-62.  doi:10.13475/j.fzxb.20230700801

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Objective Under the evolution of billions of years, all things in nature have gradually formed the structure that is most suitable for the environment and has excellent performance. Therefore, studying the microstructure of such biomaterials and applying them to the bionic design of composite structures is one of the effective ways to develop high-performance composite materials.Wood is one of the materials with good mechanical properties in nature,and its density is small.At present,most of the imitation wood materials on the market are bionic from the function and appearance.Among them,the most is wood-plastic composite material, which is used for producing products with similar appearance and good mechanical properties at a lower cost,but it can not replace wood in terms of lightweight and elastic modulus.The superior performance of wood is closely related to the composition and distribution of its internal structure.Starting from the internal structure of wood,structural imitation wood is expected to have the advantages of mechanical properties,lightweight and elastic modulus of wood.

Method In order to study the structural characteristics and distribution of Mexican red acid branch(MRAB),the structures of pores in MRAB were studied by X-ray three-dimensional microscope.The size and area of pores were measured, and the morphology and distribution of pores in each component structure were analyzed. The porosity is calculated according to the pore area of each structure, and the pore distribution was analyzed.At the same time,the structure of wood fiber was observed by scanning electron microscope,and the microfibril angle was measured by X-ray powder diffractometer to characterize the orientation degree of wood fiber.

Results The results showed that: 1) the pores of MRAB are mainly distributed in vessels, wood rays, axial parenchyma and micropores, and the pores are mainly linear and round-like on the transverse section. On the radial section, it is mainly linear and spindle-shaped ; on the string section, it is mainly round and spindle-shaped. The diameter of the catheter hole was 109.53 μm, and the density was 2.83 /mm²; the average pore diameter of wood ray was 13.01 μm and the pores of the axial parenchyma are usually composed of two spindle-shaped cell cavities with an average pore diameter of 20.19 μm; 2) the porosity of MRAB is 31.27%, and the pore distribution increases slowly from inside to outside; and 3) wood fibers are closely arranged in parallel along the axial direction, and the microfibril angle is 3.27°, which is smaller than the microfibril angle of most wood, giving wood superior mechanical properties. The transverse mechanical properties are mainly provided by wood rays, and lignin acts as a stress buffer between wood fibers.

Conclusion Since the Mexican red sour branch is a natural cellulose composite material with excellent performance, it can be used as an object for the design of composite imitation wood. Through the analysis of its internal structure, it can be cut from three aspects: pore, wood fiber, wood ray (fiber reinforcement) and lignin (resin matrix) related to fiber reinforced composites. The structural design of high-performance wood-like fiber reinforced composites was realized by unidirectional fabric, resin, pore generation method and ply direction,and then prepare lightweight and high-strength fiber-reinforced composites.

Textile Engineering

Simulation and analysis of dynamic deformation of densely woven filter fabrics based on ANSYS Workbench

TIAN Shaomeng, ZHANG Li, SHI Haoxuan, XU Yang

Journal of Textile Research. 2024, 45(09):  63-69.  doi:10.13475/j.fzxb.20230503401

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Objective Woven filter materials are privileged amongst solids-liquid filtration materials by virtue of their superior strength, durability, superior filtration precision, ease of residue disposal, and soon. The efficacy of woven fabric filtration hinges upon the weave aperture, with both the fiber inner aperture and yarn interlace aperture influencing the filtration efficiency and resistance. In addition, yarns are typically elastomeric materials, and their weave behaviors under varying pressure contribute to further alterations in the fabric structure hence impacting the filtration efficiency and resistance. Consequently, the comprehension of deformation mechanisms of textiles under high pressure holds pivotal implications for enhancing the design and optimization of filter cloth.

Method This paper presents a comprehensive study on an archietypal plain woven filtration fabrics using VHX-500 super high-depth digital microscope for imaging the cross section of the fabric, and Image J software for collecting data regarding yarn curvature wave height and yarn spacing. Experiments were conducted to validate the model's accuracy under diverse pressure conditions. The fabric models were established via Solid Works software and a finite element analysis method was employed to simulate deformation of high density woven filter under varying pressures utilizing ANSYS Workbench's Mechanical module, which was adopted to analyze factors such as maximal deformation quantity, form contour curve progression, and hole diameter changing trends.

Results The simulation results indicated that maximum deformation of the fabric took place at the original form, with a gradual decline in deformation along the diameter. The fabric underwent an escalating deformation as pressure was increased. Within a certain threshold, a non-linear increase in maximum deformation of filter fabrics residing centrally was proportional to the applied pressure. Initially, lesser pressure induced substantial deformations in the fabric, but further increments in pressure resulted in a diminished incremental deformation. The longitudinal and latitudinal profile of the fabric showed congruent deformation, with the center contour curve conforming to the sine function pattern.

The strain demonstrated a maximum at the outermost regions of the fabric, where it diminished progressively from the center to the edge, with excrescent strain along the warp yarns towards both sides from the core. For individual thread, it was observed that the interlacing region illustrated lesser strain than the noninterlacing region. The strain distribution across various positions within the same circumference of the fabric varied with the strain on the warp yarns augmenting steadily and the weft yarns decreasing gradually. The mismatch between warp and weft strain not only amplified the size difference but also alters the shape. With similar warp and weft exerted strain, there occurred an equivalent increase in the post-deformation pore dimension compared to the unvaried pore. On the other hand, the significant disparity in the strain of the warp and weft underwent greater deformation in one direction relative to the other, thereby inducing a change in the pore's shape and dimension. In accordance with the fabric's strain pattern, the compressibility manifested different pore dimensions throughout the fabric, with the pore being larger in the central position rather than in the outer regions. Moreover, the size and shape of the pore across the same direction would also vary post compressing.

Through the deployment of a textile surface deformation experiment, it was established that the maximum strain measured for plain weave fabric under diverse pressure conditions paralleled with the simulation's prediction, with an error rate less than 10%. This substantiated the accuracy of the simulation. Additionally, the fabric curve deformations were fitted to follow a sine function, corroborating with the the simulation result.

Conclusion This study employs finite element software ANSYS Workbench to simulate the deformation of high-density filter fabrics under various pressures, scrutinizing the fabric's maximum deformation quantity, distortional profile, and pore size distribution post-deformation. A validating experiment for this simulation was conducted through an actual fabric deformation test, demonstrating accurate predictive capability. The outcomes suggest that 1) the maximum deformation quantity is located at the circle center, decreasing in a gradient manner as per diameter; 2) within a particular range, the maximum deformation at the center of the filter fabric increases non-linearly with pressure augmentation; 3) further, the contoured curve of polyamide 66 woven fabric resembles a sine wave pattern significantly; and 4) as pressure acts on the fabric, the pore size expands, with larger pore size at the central region compared to apices away from the center, simultaneously modifying the dimensions and shape of periodic pores. This research aids in comprehending the dynamic deformation and pore size variation of woven fabrics under compressive conditions, thus offering a valuable reference for the custom design and analysis of filtration fabrics.

Design and performance analysis of embroidered electrocardiogram electrode

LU Tong, TANG Hong, ZHAO Min

Journal of Textile Research. 2024, 45(09):  70-77.  doi:10.13475/j.fzxb.20231008001

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Objective Embroidery electrode is known to have numerous merits including personalized customization function, good reproducibility, fast and flexible production and reliable electrical performance, and much research attention has been attracted to the development of smart electrocardiograms (ECG). In order to improve the sensitivity and stability of embroidered ECG electrodes and standardize the design and application of electrodes, this paper carries out the design of electrode size, pattern and embroidery type, and analyzes its influence on the physical characteristics and electrical properties of the electrodes.

Method Embroidery electrodes were fabricated by embroidering conductive yarns on textile substrates. The upper and lower surfaces were both covered by the conductive yarn. The embroidery parameters were shown to affect its physical characteristics and appearance, which in turn affected its electrical properties. In this paper,electrode thickness, flatness, skin-electrode interface impedance, signal-to-noise ratio, baseline stability time, and baseline offset amplitude were taken as performance indicators, performances of individual electrodes were tested and analyzed so as to identify and understand the influencing factors.

Results The area, pattern and stitch of the embroidered electrode were found to affect its performance in every aspects. Too large or too small an area would negatively affect its sensing sensitivity and the quality of the captured signal. The diameter of the electrode has a significant impact on the arrangement of machine-embroidered stitches, influencing whether they overlap or are placed side by side; consequently, the electrode's size directly affects its thickness. When the electrode diameter was smaller than 23 mm, the signal-to-noise ratio was found negatively correlated with the thickness of the embroidery electrode. When the diameter increased to 26 mm, the signal-to-noise ratio was increased significantly, and the baseline stabilization time appeared smaller. However, when the diameter was more than 26 mm, the surface deformation of the embroidery electrode became larger when it touched the skin This resulted in decreased signal-to-noise ratio, and increased baseline stabilization time. However, the sensing stability of the embroidered electrode was shown to decrease with the increase of the signal capture pathway, indicating that the larger the area, the greater the amplitude of the ECG baseline shift. For embroidery electrodes with the same surface area, when the pattern of the electrode is closer to a circular pattern, the current in the electrode is distributed more uniformly, so the skin-electrode interface impedance of the electrode is smaller, the signal-to-noise ratio is larger, the baseline stabilization time is shorter, and the magnitude of the baseline shift is smaller. When the electrode area and pattern are the same, embroidery electrodes prepared using embroidery stitches with uniform thickness and flat surface of the finished product have smaller skin-electrode interface impedance, larger signal-to-noise ratio, and smaller baseline shift, in which the baseline stabilization time of the softer samples is shorter. In summary, the final optimized solution was derived as 5.3 cm² area, circular pattern and satin stitch for embroidery. The preferred embroidered electrode reduced the skin-electrode interface impedance value by 1.064 MΩ, improved the signal-to-noise ratio by 3.161 dB, shortened the baseline stabilization time by 3 s, and reduced the baseline offset amplitude by 0.07 mV when compared with the commercial 3M gel electrode.

Conclusion As a new type of electrode material, the design and performance study of the embroidery electrode area, pattern and embroidery type was studied, the factors influencing the electrode performance were analyzed in detail. By establishing the performance evaluation system of embroidery electrodes, different embroidery electrodes were compared and evaluated. Compared with the commercial 3M gel electrodes, the embroidery electrode prepared by adopting the optimized design demonstrated better electrical properties, with better sensitivity and stability. In addition, the embroidery electrode itself showed improved comfort and better fit to the skin when used. This work provides a useful information for the subsequent research of embroidery electrodes.

Numerical simulation of air permeability of warp-knitted jacquard shoe upper materials

ZHANG Qi, ZUO Lujiao, TU Jiani, NIE Meiting

Journal of Textile Research. 2024, 45(09):  78-83.  doi:10.13475/j.fzxb.20230504201

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Objective Air permeability affects the comfort of shue upper materials. Before making footwear products, it is necessary to test the air permeability of the sample upper materials. In order to study the influence of organizational structure on the air permeability of warp-knitted jacquard upper materials, it is necessary to explore a method for predicting the air permeability of warp-knitted jacquard upper materials. It is also necessary to verify the feasibility of data simulation research methods to improve the efficiency of shoe upper materials from design to production and then to final application, and reduce unnecessary waste of resources and time.

Method The experimental samples were selected from different functional areas of the jacquard upper material. The front and back sides of the wear resistance zone were with dense surface and solid bottom (sample A), and the front and back sides of the breathable zone were with mesh surface and solid bottom (sample B1). sample B2 was obtained by adjusting the positive and negative orientation of sample B1. The fabric structure of each sample was observed by Nikon E100 microscope, and then the geometric model of the fabric sample structure was established by Solidworks three-dimensional modeling software. The geometric model of the sample was imported into Workbench finite element analysis software for model preprocessing and meshing, combined with geometric model and computational fluid dynamics. Fluent, a fluid analysis software, was adopted to calculate the permeability behavior of the fabric. In order to verify the feasibility of the simulation data, the permeability of the sample was tested by YG46IE-III automatic permeability meter, and the simulation results were compared with the experimental results.

Results Speed cloud chart showed that the closer to the yarn model, the more blocked the airflow and the smaller the air flow rate. The pores in the coil were smaller than the gap at each longitudinal interval of the fabric, so the air flow rate between the pores in the coil was found much smaller than the air flow rate at the longitudinal interval. In addition, the flow velocity of model A is more uniform, while the air velocity at the grid of model B1 is much larger than that at the surrounding meshless due to the existence of the grid. In summary, under the same conditions, the air permeability of the mesh fabric B1 was larger than that of the mesh fabric A, that is, the air permeability B1 > A. When the air flows from the mesh surface, much air was accumulated at the mesh due to the large pores, and the flow rate of the air at the mesh is much larger than that of the same surface layer without mesh, resulting in uneven distribution of air flow rate in the spacer layer. When the air contacted the bottom layer of the fabric through the spacer layer, which was subjected to resistance, thus reducing the air flow rate. When the air flowed from the non-grid surface of the fabric, the air had to flow uniformly from the inlet boundary. After passing through the spacer layer to the grid, the flow rate became larger, so the overall flow rate became larger. In summary, the air permeability B2 > B1.

Conclusion Due to the complicated preparation process of warp-knitted jacquard upper material, in order to better study its air permeability and save the time consumed by sample preparation and test performance, this research attempts to use numerical simulation method to predict the air permeability of warp-knitted jacquard upper materials. The results show that the simulation results are similar to the experimental results, and the error is less than 20%. Therefore, this method is feasible. However, there are still some shortcomings. For example, the model establishment process ignores its actual friction factors, so the simulation results are greater than the actual results. Secondly, the upper material structure of warp-knitted jacquard is very complex, and the modeling process is cumbersome. It is necessary to develop better procedures for jacquard fabric modeling to save time and cost.

Three-dimensional simulation of warp knitted pile fabrics with double needle bar based on loop structure

GUAN Songsong, JIANG Gaoming, YANG Meiling, LI Bingxian

Journal of Textile Research. 2024, 45(09):  84-90.  doi:10.13475/j.fzxb.20230902101

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Objective Owing to the procedural intricacies in the production of double needle bar pile fabrics, the pace of product innovation is sluggish, and the design cycle is protracted. Presently, simulations of pile fabrics are conducted at a holistic level, lacking in-depth investigation pertaining to loop-based structures. Consequently, this paper aims to achieve simulations of double needle bar pile fabrics grounded in loop-based structures, thereby enhancing simulation efficiency.

Method This paper establishes a digital and threading mathematical model of yarn, By adding a control nodes at the pile stretching lines, the broken stretching lines is controlled to simulate the effect of pile fibers, and a random.Next() function is used controls the rotation angle of the pile, adjusts the position of the control nodes using a calculation formula to make the pile appear in a random bending state, and establishes a loop and weft insertion pile model.

Results Through the process design of loop and weft insertion pile fabrics, the knitting technique was studied, and the mathematical model of the guide needle movement and yarn threading was established. The plush formed by both needle front padding and needle back padding is called looped pile. The plush fabric that is only used for needle back padding and not for needle front padding is called weft insertion pile. The structural characteristics of the loop and weft insertion pile were analyzed, and the design process and knitting characteristics were combined to establish loop and weft insertion pile model. The pile loop model was divided into a fundamental loop model segment and a pile segment. The fundamental loop segment was mainly used for displaying the piercing of the back pile organization and the ground organization, while the pile segment was exposed on the fabric surface post-finishing. The loop for loop pile consists of ten control nodes, with two additional nodes added at two stretching lines. Similarly, the weft insertion pile loop comprises six control nodes, with one additional node at each of the two stretching lines. The control nodes are connected using Bezier curves to form the loop model. The rotational height of the pile segment remained constant, while the length of pile fibers changes with the rotation angle of the pile fibers. The rotational angle was generated using random functions in the C# programming language. This determines the bending direction, simulating the pile's bending effect. With each pile fiber's rotational angle being random, increasing the number of pile fibers at the stretching lines resulted in their dispersion, and a higher fiber count would lead to a denser and more pronounced pile pattern, enhancing the realism of the pile fabric's three-dimensional simulation.

Conclusion The establishment of loop and weft insertion pile structural models has facilitated the three-dimensional simulation of double needle bar warp knitted pile fabrics, addressing the issue of extended design cycles and enhancing production efficiency. This advancement has propelled the widespread adoption of double needle bar warp knitted pile fabrics in various markets, including home textiles, automotive seat cushions, sofa coverings, curtains, and other related fields.

Impact properties of three-dimensional woven composites with variable thickness

LÜ Lihua, PANG Xianke, LIU Ao

Journal of Textile Research. 2024, 45(09):  91-96.  doi:10.13475/j.fzxb.20230404901

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Objective The production costs of most metal variable thickness plates are high and some composite plates with variable thickness are generally based on laminated composites, which are prone to interfacial delamination and property degradation. This study was designed to solve the problem of delamination of laminated composites, aiming to improve the overall performance against impact.

Method Basalt yarn is a green and environmentally friendly materials. And, it has high strength and excellent durability. Three-dimensional(3-D)variable-thickness fabrics with 3-layered angle interlocking structure change from 9 to 3 layers were designed and woven on a conventional loom using basalt yarns as warp and weft yarns. Resin-impregnated variable-thickness 3-D woven composites were prepared using a vacuum-assisted resin transfer molding (VARTM) process. The variable thickness laminated composites were subjected to low velocity impact tests at 25, 50, 75 and 100 J according to American Society of Testing Materials (ASTM) standards. The damage mechanism of the material was analysed by the damage area at 100 J impact.

Results The 3-D woven variable thickness composites exhibited high consistency in stiffness and stiffness degradation under impact energy of 25, 50 and 75 J compared to the same weft lay-up structure. This was based on the fact that the layers of yarn are interconnected in the 3-D woven variable thickness composites, whereas there was little adhesive action between the the same weft lay-up structure. At the same time, the damage load of the composite with the 3-D woven variable thickness structure was greater than that of the two lay-up composites. This indicated that the composite with the 3-D woven variable thickness structure had a higher damage tolerance and carries more load before damage occurs. At an impact energy of 100 J compared to 25-75 J, the damage load was reduced in a 3-D woven variable thickness structure with co-layered layers. This was due to the large amount of kinetic energy that was instantaneously released by the impact head when a high energy impact occurs. These kinetic energies caused the surface bearing yarns in the material to quickly break and lost their load-bearing capacity. The damage load on the material was reduced because the yarn on the bottom layer of the material had not yet reached a responsive state. When the material was impacted in the forward direction, the damage showed a cross-shaped or rectangular distribution with a greater extension along the weft direction than the material along the warp direction. As the thickness variation of the composite was determined by the number of yarn layers, the energy consumed decreased with the thickness, so that the stress could propagate through the material for a longer period of time. Along the warp direction of the material, the number of layers of material within the same thickness layer remained the same as the thickness, and the stress waves were consumed rapidly, creating a short damage extension range. Damage to the material in the dorsal direction also showed a cross-shaped or rectangular distribution with greater extension along the weft direction than the material along the warp direction. But the damage of the composite material with the same warp-layered structure had slightly less damage along the weft direction than the warp direction. This was because the material encountered a strong impact under the action of 100 J impact energy, the energy of the impact was enough to quickly break through the fabric of all layers of the same layered structure. It completely destroyed the integrity of the material and made the damage to the material more concentrated.

Conclusion Compared with laminar composites, 3-D woven composites of variable thickness have higher damage tolerance and better impact resistance because of the internal warp connection. Compared with the metal variable thickness plate, the variable thickness 3-D woven composite material has the characteristics of low production costs, low manufacturing and maintenance cost of production equipment and low energy consumption. It has reference significance for future application research of variable thickness plate.

Modeling of carbon footprints for producing wool blended fabrics and model applications

WU Tao, LI Jie, BAO Jinsong, WANG Xinhou, CUI Peng

Journal of Textile Research. 2024, 45(09):  97-105.  doi:10.13475/j.fzxb.20230600301

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Objective In the context of the 2030 carbon peak target, the green transformation of the textile industry is the only way to achieve the carbon neutrality. However, the flow and distribution of carbon footprints are extremely complex, making green carbon tracing and management for the whole life cycle very difficult. This study aims to address the complex issue of tracing and managing the lifecycle carbon footprint of wool blended fabrics in the green transformation of the textile industry. The specific goal is to develop a carbon emission knowledge graph (simplified ″carbon knowledge graph″) model for the production process of wool blended fabrics, quantify carbon emissions, and apply this model to provide guidance and decision-making support for the industry's carbon reduction efforts.

Method The study employs industrial intelligent technologies such as process mining and knowledge graph. Initially, a carbon emission quantification model is developed considering four dimensions: energy flow, material flow, personnel flow, and carbon flow throughout the various stages of wool blended fabric production, facilitating the modeling of local-level carbon emission management. Subsequently, a carbon emission knowledge graph modeling approach is introduced on the foundation of the quantification model, which allows for the calculation of carbon emissions in fabric production processes. In the end, directly-follows graphs are produced to model the global-level carbon emission distribution throughout the fabric production process, accomplishing bidirectional modeling of both global-level and local-level carbon emissions.

Results Using real data as an example, this paper constructs a carbon knowledge graph model for the production process of wool blended fabrics. The model comprises 8 045 nodes, 15 717 edges, 264 order nodes, and 779 process steps. The results show that the total carbon emissions for weaving in the current 264 orders amount to 385 010.707 kg CO₂, and the total carbon emissions for dyeing amount to 2 385 362.262 kg CO₂. Therefore, analyzing the energy consumption, material usage, and personnel carbon emissions of the dyeing process in the production of wool blended fabrics is crucial for understanding its carbon footprint. Furthermore, a specific order case involving the dyeing process of a fabric blend of 80% wool, 12% nylon, and 8% other fibers was selected for analysis. The experiment shows that the operation of production equipment is the main source of electrical energy carbon emissions in the actual production process, accounting for 93.92% of the total, or 1 634.263 kg CO₂. Moreover, the carbon emissions from the air compressor and lighting equipment were found to be 31.720 kg CO₂ and 24.494 kg CO₂, respectively. The results indicate that optimizing the carbon emissions of operating production equipment is key to reducing overall carbon emissions in the production process. In brief, the method proposed in this study has shown high effectiveness and feasibility in managing carbon emissions throughout the product lifecycle, providing an important reference for the field of low-carbon industrial manufacturing.

Conclusion This study successfully proposes a method for carbon knowledge graph modeling, carbon emission quantification, and application for the production process of wool blended fabrics. The effectiveness of the model has been verified through real-world cases, and it provides guidance and decision-making support for its application in industry carbon emission reduction. The research approach is expected to be applied to other textile production processes, aiding in the green transformation of China's textile industry.

Dyeing and Finishing Engineering

Degumming process and properties of spinnable natural bamboo fibers

YIN Xiang, ZHU Enqing, YANG Jing, YANG Haiyan, WANG Dawei, SHI Chun, SHI Zhengjun

Journal of Textile Research. 2024, 45(09):  106-112.  doi:10.13475/j.fzxb.20231105101

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Objective Bamboo is a promising alternative source of textile fibers by virtue of its rapid growth, ease of cultivation, wide availability and renewable nature. The preparation of traditional natural bamboo fibers has drawbacks such as high energy consumption, environmental pollution and long processing time, resulting in rough fibers with low length. Hence, it is of great practical value to explore for a cost-effective, eco-friendly, and efficient method for preparing natural bamboo fibers.

Method Three green degumming methods were developed to address these issues, which are choline chloride-lactic acid deep eutectic solvent (DES) degumming, peracetic acid (PAA) degumming, and DES synergistic PAA degumming. Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy, and X-ray diffraction were adopted to test and characterize the physicochemical properties of fibers obtained using conventional methods and the three different green degumming methods.

Results FT-IR results show that the lignin benzene ring characteristic absorption peaks were near 1 610 cm^-1and 1 500 cm^-1. The lignin benzene ring characteristic peaks were weakened by PAA and DES synergistic PAA treatment, indicating that PAA has good delignification effect. Besides, all four methods of preparing natural bamboo fibers can remove the gum part. DES consisting of choline chloride-lactic acid could effectively remove the hemicellulose of the bamboo chips, reducing from 12.85% to 8.67%. However, the residual lignin content remained high at 27.10%, close to 28.77% of bamboo chips. PAA had the highest efficiency in removing lignin, with only 2.05% remaining. The highest cellulose content was obtained by DES synergistic PAA degumming, at 86.72%. The surface of fibers prepared by DES synergistic PAA degumming was significantly less rough, its fibers surface was smoother. Furthermore, with the removal of the amorphous area of the glue part of natural bamboo fibers, it was shown that none of the four degumming methods changed the crystal structure of the fibers and all four deacetylation methods can increase the relative crystallinity of the fibers, among them, DES synergistic PAA degumming obtained the largest crystallinity of 69.22%. But the crystallinity of fibers prepared by conventional degumming changes the least, at 62.42%. Fibers prepared by DES, DES synergistic PAA degumming and conventional degumming all had high lengths of 6.97 cm, 6.19 cm and 6.72 cm, respectively, with DES having the highest line density of 123.98 tex and DES synergistic PAA degumming having the lowest line density of 50.07 tex. Fibers prepared by conventional degumming had the highest moisture regain of 9.39% and DES had the lowest moisture regain of 6.55%. Fibers prepared by DES synergistic PAA degumming had the highest stress, strain and breaking strengths of 236.35 MPa, 1.8% and 2.98 cN/dtex, respectively.

Conclusion DES synergistic PAA degumming can more effectively extract natural bamboo fibers. Compared to conventional delignification processes, this method has advantages of lower chemical usage, reduced pollution and shorter processing time. It provides positive guidance for the preparation and development of spinnable natural bamboo fibers.

Preparation and characterization of waterborne flame retardant polyurethane for microfiber synthetic leather

XIAO Ningning, CHEN Zhijie, OUYANG Yufu, MENG Jingui, SUN Yangyi, QI Dongming

Journal of Textile Research. 2024, 45(09):  113-120.  doi:10.13475/j.fzxb.20231001501

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Objective In order to solve the problems of non-flame retardancy, low strength and lack of toughness of polyurethane coating on microfiber synthetic leather, type of phosphate-containing bialcohols as reactive flame retardants were prepared. It was copolymerized with methylene diphenyl diisocyanate (MDI), polytetramethylene ether glycol (PTMEG) and 2,2-dimethylol butyric acid (DMBA) to prepare water borne flame retardant polyurethane (WPU) with good dispersion, stability and performance, which is used for coating microfiber synthetic leather.

Method A reactive flame retardant containing phosphorus was synthesized. It was characterized by Fourier transform infrared spectrometer (FT-IR) and nuclear magnetic resonance spectroscopy (¹H NMR). Then, DHIMP was copolymerized with MDI, PTMEG and DMBA to obtain waterborne flame retardant polyurethane (P-WPU). P-WPU was prepared into coating slurry, and the soft and strong polyurethane coating was constructed on the surface of microfiber synthetic leather by double-side scraping, exchange curing and drying.

Results The water dispersion of P-WPU was good. The particle size of the dispersion increased with the increase of DHIMP mass fraction. With the introduction of DHIMP, the Young's modulus of P-WPU film was gradually increased. When the mass fraction of DHIMP was 13.9%, the mechanical properties of P-WPU reached the best. The LOI of microfiber leather was continuously increasing with the gradual increase of DHIMP mass fraction. The results of vertical combustion test illustrated that the microfiber leather coated by P-WPU with different DHIMP mass fractions had a certain degree of flame retardancy. When the mass fraction of DHIMP was 16.1%, the vertical damage length was 2.3 cm, the continuous burning time was 0.6 s, the smoldering time was 0.3 s, the number of droplets was reduced to 0-1, and the absorbent cotton was not ignited, demonstrating a good flame-retardant effect.

Conclusion 1) DHIMP was successfully prepared from p-hydroxybenzaldehyde, 3-amino-propanol and DOPO. 2) By introducing DHIMP as chain extender into waterborne polyurethane macromolecules, waterborne polyurethane with flame retardancy was successfully prepared. 3) The flexible and flame-retardant microfiber synthetic leather was prepared with P-WPU coating. The maximum limiting oxygen index was 28.6%, the vertical damage length was 2.3 cm, the follow-fire time was 0.6 s, and the smoldering time was 0.3 s.

Functionality of cotton fabrics finished by montmorillonite combined with TiO₂

ZHAO Qiang, LIU Zhengjiang, GAO Xiaoping, ZHANG Yunting, ZHANG Hong

Journal of Textile Research. 2024, 45(09):  121-128.  doi:10.13475/j.fzxb.20230904801

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Objective In order to enable multifunctions of cotton fabrics and reduce agglomeration of TiO₂ on cotton fabric surface, TiO₂/montmorillonite finishing agent was prepared by sol-gel method at lower temperature using tetrabutyl titanate and montmorillonite as the precursor, aiming to reduce agglomeration of TiO₂. At the same time, the reduction of TiO₂ consumption was fargetted to increase the added value of montmorillonite products.

Method TiO₂/montmorillonite was firstly synthesized using ultrasound-sol-gel method and then deposited onto the surface of cotton fabrics by two-dipping and two-rolling processes. The properties of the cotton fabric before and after treatment were analyzed using Fourier transform infrared (FT-IR) spectrometer and energy dispersive spectrometer, while the surface morphologies of the cotton fabrics were analyzed by scanning electron microscopy. The whiteness, air permeability, breaking strength and elongation of TiO₂/montmorillonite-finished cotton fabrics were measured, respectively. In addition, the performance such as hand feel attributes, softness, smoothness and stiffness were measured. Rhodamine B was used as a test contaminant to qualitatively assess the self-cleaning performance of the TiO₂/montmorillonite finished cotton fabric.

Results The SEM and EDS results indicated that TiO₂/montmorillonite was uniformly distributed on cotton fibers surface. UV-visible diffuse reflectance spectrum result showed that TiO₂/montmorillonite finished cotton fabric demonstrated excellent absorption capability to UV light, while the FT-IR result showed that the bonding mode between TiO₂/montmorillonite and cotton fiber was formed through covalent bonding. The anti-aging performance test showed that after 96 h UV irradiation, the strength loss of TiO₂ finished cotton fabric was 22.9%, while the strength loss of TiO₂/montmorillonite finished cotton fabric was 15.4%, indicating that the montmorillonite compound could improve the anti-aging performance of TiO₂. The self-cleaning performance test showed that TiO₂/montmorillonite finished cotton fabric had satisfactory self-cleaning capability. Nevertheless, compared with raw cotton fabric, the whiteness of TiO₂/montmorillonite finished cotton fabric was decreased by 25.8%, the breaking strength decreased by 10.2%, and the air permeability decreased by 5.7%, respectively.

Conclusion A cotton fabric with UV protection, anti-aging, and self-cleaning performances was prepared by applying TiO₂ and montmorillonite onto the fabric surface using the rolling-baking-baking process. The result indicated that the UVA transmittance, UVB transmittance, and UPF value of TiO₂/montmorillonite finished cotton fabric were 1.81%, 0.87%, and 100+, respectively. Moreover, the UPF value of the treated cotton fabric was still maintained at 50+ after 50 cycles of soap washing, and the fabric's anti-aging performances were increased by 16.7% after post-treatment. Also, the Ti—O—Si bond was formed between TiO₂ and montmorillonite, which reduces recombination of electron-hole pairs of TiO₂, and effectively controls the TiO₂ particle size, thus improving the properties of TiO₂ finished cotton fabrics.

Eco-friendly mercerization of wool carpet using protease method based on substrate activation

WANG Le, DUAN Zhixin, YAO Jinbo, LIU Jianyong, LU Jianjun

Journal of Textile Research. 2024, 45(09):  129-136.  doi:10.13475/j.fzxb.20231100101

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Objective In order to fundamentally solve the severe environmental pollution problem caused by the existing chlorinated wool carpet mercerizing finishing, much research has been focused on ecological mercerizing. The protease method is a mild and green finishing process. However, the low hydrolysis efficiency of protease on wool keratin remains to be a technical bottleneck, and it is necessary to develop the protease method for the wool carpet mercerizing process with ecological characteristics. It is conducive to promoting green and sustainable development of the textile industry.

Method A protease-catalyzed system consisting of substrate activator LKZ-630 and protease Savinase 16L was constructed and used for mercerizing wool carpets by combining mechanical scraping and brushing. The role of LKZ-630 in the enzymatic degradation of wool was studied by measuring the sulfhydryl content on the wool surface, protease activity, protease adsorption, and degree of hydrolysis of wool. The structure of wool carpets before and after treatment was examined by scanning electron microscopy, Fourier infrared spectroscopy, and X-ray diffraction energy spectroscopy.

Results The results showed that LKZ-630 could open disulfide bonds in wool fibers and convert them to sulfhydryl groups. It facilitated the rapid degradation of high-sulfur wool tissues by proteases. By adding LKZ-630, the protease activity (substrate of wool fibers) increased by 1 575 times when the concentration of LKZ-630 was 2 g/L. Under the treatment conditions of LKZ-630 2 g/L, Savinase 16L 1 g/L, and 50 ℃, LKZ-630 increased the equilibrium adsorption of protease on wool fibers by 12.7 times and increased the hydrolysis rate by 36.3 times. Wool carpet mercerizing equipment with brushing and scraping functions was developed. A protease-catalyzed system (LKZ-630 2 g/L and Savinase 16L 1 g/L) combined with brushing and scraping was used for mercerizing pure wool carpets at 50℃ for 40 min. Brushing and scraping cause the mechanical force on the carpet fiber to gradually increase from the tail to the tip during treatment. As a result, the fineness of the treated wool fibers gradually became finer from the tail to the tip. The fiber tip fineness after treatment even reached 1 μm, giving the treated carpet a layered feeling and a soft touch. In addition, the surface of the upper and middle fibers of the treated carpet was exceptionally smooth compared to the untreated carpet. As a result, the treated carpet had a better gloss, with CIE brightness and whiteness values increased by 6.99 and 50.12, respectively, and the yellowness value reduced by 14.84. The surface group structure of the treated carpet was similar to that of the untreated. However, the crystallinity was reduced due to the destruction of the disulfide bond cross-linking in the scale proteins.

Conclusion The protease-catalyzed system consisting of the substrate activator LKZ-630 and Savinase 16L was constructed to degrade wool high-sulfur hard keratin. LKZ-630 could efficiently open the disulfide bond in the wool fiber and significantly increase the adsorption rate of the enzyme on wool fiber and the hydrolysis efficiency of the enzyme on wool high-sulfur keratin. The higher the concentration of LKZ-630, the higher the adsorption of wool to the protease, and the higher the reactivity of the protease to the wool. The protease-catalyzed system was combined with brushing and scraping to mercerize the wool carpet. Compared with the untreated carpet, the degree of exfoliation of keratin tissue of the treated carpet fibers was gradually strengthened from the tail to the tip, and the fineness was also gradually thinned. The treated carpet was soft to the touch and had a sense of hierarchy and a silk-like luster, realizing the ecological chlorine-free mercerization of wool carpet. Further studies on the dyeing and finishing properties of carpets treated with the protease-catalyzed system are necessary.

Construction of MXene-based conductive fabrics and their multifunctional applications

LU Daokun, WANG Shifei, DONG Qian, SHI Naman, LI Siqi, GAN Lulu, ZHOU Shuang, SHA Sha, ZHANG Ruquan, LUO Lei

Journal of Textile Research. 2024, 45(09):  137-145.  doi:10.13475/j.fzxb.20230603801

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Objective The two-dimensional material MXene can be easily integrated with textiles because of its excellent dispersion, good mechanical properties, and high conductivity, and has shown potential applications in many areas. In order to expand the application of two-dimensional titanium carbide materials into smart textiles, Ti₃C₂T_x and carbon nanotubes (CNTs) were sprayed on pure nonwovens as the substrate to prepare a multifunctional electronic textile which integrates sensing, energy storage, and thermal energy conversion.

Method Ti₃C₂T_x MXene sheets were synthesized through the typical chemical etching method by selectively etching Al layer from Ti₃AlC₂ phase. Ti₃C₂T_x (2 mg/mL) and CNTs dispersion (2 mg/mL) were then ultrasonically mixed (at a volume ratio of 1∶1) and repeatedly sprayed on nonwoven fabric substrate until the surface resistance of the fabric was lower than 150 Ω. The Ti₃C₂T_x/CNTs/nonwoven (MCF) composite was finally prepared and characterized by scanning electron microscope and X-ray diffraction. In addition, the photothermal and electrothermal conversion performance, electrochemical properties and sensing performance were also explored.

Results The thread-like CNTs on the fabric surface were wrapped around the entangled Ti₃C₂T_x flake, connecting Ti₃C₂T_x from different regions and forming a stable conductive network. The Ti₃C₂T_x was successfully synthesized and uniformly attached on the surface of nonwoven substrate. When MCF was used for photothermal conversion, it was quickly heated up to 65 ℃ in 60 min and maintained stable. In terms of the electrical heating performance, the thermal response time of MCF was shorter than 2 s, and the aperture on the infrared thermal image was uniformly distributed. The reason is that the addition of CNTs further improved the overall conductivity of the material, and exploited the large volume and contact area of the CNTs to bond with more Ti₃C₂T_x, and created more conductive pathways on the surface of the fabric. When the MCF electrode was used in a flexible semi-solid supercapacitor, the specific capacitance remained at 70 mF/cm² even at a high current density of 2 A/cm². After 10 000 cycles, the MCF still maintained a capacitance retention of 74%, indicating that the MCF electrode had a good cycling durability. In addition, the MCF was also used as sensors and fixed on the neck, wrist, fingertips, knee, and elbow of the human body to monitor human motions. With each bending of the human body, the resistances of MCF underwent regular changes, which were captured and recorded clearly and stably.

Conclusion MCF was successfully prepared by modified mixed solution of CNTs/Ti₃C₂T_x on the nonwoven substrate using a simple spraying method. Owing to the synergistic effect of CNTs and MXene films, MCF was rapidly heated up to 65 ℃ at room temperature of 32 ℃ after being exposed to sunlight and 115 ℃ under a voltage of 15 V, demonstrating good photothermal conversion and joule thermal performance. When used as a flexible semi-solid supercapacitor electrode, MCF exhibited a high specific capacitance of 125 mF/cm². Additionally, MCF could be applied as a flexible strain sensor to detect human motions, exhibiting significant negative resistance changes and high sensitivity. In summary, MCF presents great potential applications in wearable electronic products and multifunctional garments.

Apparel Engineering

Personal pattern generating method for speed skating suits

XIAO Boxiang, ZHANG Yue, HU Zhiyuan, ZHAO Yuxiao, LIU Li

Journal of Textile Research. 2024, 45(09):  146-153.  doi:10.13475/j.fzxb.20230203101

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Objective Speed skating suits are an important sport equipment, where the generation of efficient and good-fit patterns are a primary challenge in customization. In order to achieve the personalized pattern, a pattern generating method for speed skating suits is proposed based on the mass-spring system. The aim of the research is to determine precise pattern shapes according to individual body build. It is helpful and significant to improve fitness of the suits and to promote the pattern-making efficiency.

Method 3-D model of athlete's body shape was obtained by scanning, and 3-D mesh models of each part of the suit were extracted based on the body shape features of athlete and the structural line distribution of suits., and the mass-spring system models were then constructed based on 3-D meshing of suit parts. Multi-angle tensile tests were carried out on the elastic fabric used in the suits to obtain the mechanical and physical properties of the fabric, and the parameters of the mass-spring model were determined by fabric properties. 3-D models of suit parts were flattened into the 2-D plane, and the mass-spring models were repeatedly used in the 2-D plane under the given model parameters and constraints. After the garment CAD pattern adjustment, accessories supplement, cutting and sewing and other processing steps, the sample suits were manufactured.

Results In experiments, 3-D body models of one male athlete and one female athlete were acquired through scanning, and their main body shape parameters were obtained. Instron 3343 material testing machine was adopted to test the mechanical properties of the elastic fabrics and the data were analyzed aiming at the making of speed skating suits. The measured properties were employed to calculate the elastic modulus of the virtual springs in the mass-spring models, which were constructed by 3-D meshes of pattern pieces extracted from scanned human models. They were used in 3-D flattening to obtain the 2-D pattern pieces' shape. The models converged under the objective constraint of internal energy minimization, and the boundary shapes obtained were considered to be the 2-D pattern of the suit components. In a typical suit, 5 pieces including front, back, arm, upper leg and lower leg were extracted and flattened. Owing to symmetry, only the left parts were selected. The mean errors of 3-D flattening algorithm were limited in a low level from 3-D to 2-D flattening. The basic shapes of pieces were obtained, and then made a series of adjustments were performed to achieve the final pattern. Flattened pattern shapes from body poses of standing and skating action were compared and the results showed obvious shape differences, indicating that the material properties constrained 3-D flattening pattern-making method. Personal body shape as well as that in designated pose could be used directly to determine the optimal pattern shapes. Furthermore, comparisons have been conducted between sample suits of our algorithm-based pattern-making and conventional manual pattern-making. After the athletes' try-on and evaluate, the final sample suits were formed to enable the personalized pattern making. The experimental results showed that the measurement errors of the generated pattern were within the acceptable range, and the athletes' subjective try-on feedback suggested that the sample suits were fitting well.

Conclusion The method can effectively facilitate the personalized pattern generation of speed skating suits, so as to provide effective technical support and practical tools for personal customized pattern making of speed skating suits. The achieved twofold advantages of proposed method are. One is that the flattening-based algorithm is helpful to determine optimal pattern shapes directly and quickly according to personal human body. Another is that the method is semi-automatically implemented by programs to promote pattern-making efficiency. The main limitations are that the method relies on the accuracy of scanned human models and the pattern structure needs to be given beforehand. The future meaningful work includes parametric pattern-making and intelligent models based on a large number of pattern-body shape practices.

Structural creation of striped skirt and its three-dimensional virtual restoration

HUANG Ziwei, YANG Lang

Journal of Textile Research. 2024, 45(09):  154-163.  doi:10.13475/j.fzxb.20231200501

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Objective Soft cultural relics such as clothing are easy to decay, and most of them are fragmentary when unearthed. In order to provide better repair and protection, digital technology are used for non-contact virtual restoration in the early stage. From the perspective of ″costume-personage-environment″, through the dress collocation of inner and outer layers, dynamic display of the characters' clothing, and wearing scene construction of ancient clothes, a three-dimensional dynamic digital model is established to inject more background information, so as to effectively retrieve the singularity of two-dimensional display. This paper proposes a digital restoration method based on the combination of 2-D and 3-D methods to build the digital intelligence platform construction of clothing relics and the creative design for new Chinese style clothing.

Method Three striped skirts in the museum collection of BIFT were taken as research objects. Firstly, the structural data of these skirts was inferred through image analysis, process inference and geometric scaling methods. Their structures were restored, and the structure of side panel was conceived and practised by the universal engineering drawing software AutoCAD. The pattern and texture were then restored with PhotoShop and AI. At last, the virtual fitting of inner and outer textile relics was carried out in CLO3D software, and the restoration effect was evaluated by dressing pressure analysis and questionnaire method.

Results Through image analysis, process inference, geometric scaling methods, the structural measured data of the three striped skirts were obtained. Through comparing the inferred data with the measured data of the three striped skirts, the error of waist girth was found less than 2.5%, and the error of sweep girth less than 3.3%, demonstrating a high accuracy of the the inferred structural data. The waistline adjustment proportion based on the width difference between inside and outside horse-face was 10%. Based on the inferred data, their structural diagrams were obtained using the AutoCAD software. The structural design theory of A-shape skirt was introduced into the design of striped skirts' side panel, therefore, the conventional trapezoidal side panel was improved into a fan-shaped structure by arc fitting, which not only fulfilled its flat pattern geometry model, but also improved the balance of the skirt sweep. In the flat pattern of side panel, the relationship between the center angle and the warping angle of the waist line was summarized, that is, the center angle was twice that the up warping angle of the waistline. Not only does this make the stereoscopic effect of striped skirt materialize into a three-dimensional model of the circular truncated cone, but its spatial form is more intuitive and controllable. The structural design and practice for striped skirts in line with modern women's body shape and aesthetic value was conducted. In the wearing state of spreading out, the space between striped skirt and avatar was discussed, which proves that the structural creation is correct. In the virtual fitting experiment by CLO3D, the custom of wearing striped skirt together with the pants inside was complied and the three-dimensional dressing effects were obtained. Objective evaluation of appearance comparison and pressure analysis together with subjective evaluation of questionnaire survey indicated that the comprehensive evaluation of the recovery effect is good.

Conclusion The result shows that the method can achieve precise virtual restoration of clothing cultural relics, and their digital models for static and dynamic displays are obtained. On one hand, it offers structural data reference for physical restoration, and on the other hand, it also provides strong technical support for the construction of virtual display platforms in digital intelligence museums. With the development of three-dimensional virtual technology, ancient clothing relics and culture will be communicated and promoted in more vivid forms.

Lightweight parser-free virtual try-on based on mixed knowledge distillation and feature enhancement techniques

HOU Jue, DING Huan, YANG Yang, LU Yinwen, YU Lingjie, LIU Zheng

Journal of Textile Research. 2024, 45(09):  164-174.  doi:10.13475/j.fzxb.20230904501

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Objective In order to address the issues of low accuracy in clothing deformation, texture distortion, and high computational costs in image-based virtual try-on systems, this paper proposes a lightweight parser-free virtual try-on based on mixed knowledge distillation and feature enhancement techniques.

Method Firstly, by integrating global features and calibrating the results of flow computation at different scales, an improved appearance flow estimation method was proposed to enhance the accuracy of appearance flow estimation. Moreover, a lightweight try-on network based on depth separable convolution was constructed by decoupling image segmentation results and virtual try-on processes using knowledge distillation. Finally, a garment complexity index GTC (garment texture complexity) based on the pixel-wise average gradient was proposed to quantitatively analyze the texture complexity of clothing. Based on this, the VITON dataset is divided into a simple texture set, a moderately complex texture set, and a highly complex texture set.

Results This paper used the VITON dataset to verify and analyze the proposed model. Compared with the SOTA (state-of-art) model, the number of parameters and computational complexity (flops) was decreased by 70.12% and 42.38%, respectively, suggesting a faster and better model to meet the deployment requirements of the mobile Internet. Moreover, the experimental results showed that the scores of the proposed model in image quality evaluation indicators (FID, LPIPS, PSNR, KID) were increased by 5.06%, 28.57%, 3.71%, and 33.33%, respectively, compared with the SOTA model. In the segmentation analysis of clothing complexity, the score of KID and LPIPS in this model was 48.08%, 30.45%, 1.03%, 35.54%, 30.41%, and 12.94% higher than that of the SOTA model, respectively, proving that the method proposed is superior to other methods in restoring and preserving original clothing details when warping clothing images with complex textures.

Conclusion A lightweight parser-free virtual try-on based on mixed knowledge distillation and feature enhancement techniques is proposed, which uses an efficient appearance flow estimation method to reduce registration errors, complex texture loss, and distortion during the clothing distortion process. In addition, the method proposed is shown to reduce the size and computational complexity of the final model by mixing distillation and using depth-separable convolution effectively and speeding up the running of the model. Finally, a quantitative index used for characterizing the complexity of clothing texture is proposed and the VITON test set is divided into samples. Compared with other virtual try-on methods, the experimental results show that on the VITON test set, the evaluation index results obtained from the proposed method are better than the current virtual try-on method with the best performance, and the ability of the proposed method to deal with clothing with complex patterns is also better than other methods. In addition, the ablation experiment proves that the proposed method has an obvious improvement on the final virtual try-on result.

Design of heated bedding for localized differential thermal needs of the elderly

GU Shuting, CHEN Chenyi, XU Jingxian

Journal of Textile Research. 2024, 45(09):  175-182.  doi:10.13475/j.fzxb.20231006901

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Objective Studies on winter bedding systems have been carried out to improve the thermal comfort and sleep quality of the elderly. Previous studies mainly focused on the overall thermal needs of the human body during sleep, such as temperature-control mattresses and electric blankets, while ignoring the specificity of the thermo-physiology in the elderly and the variability of localized thermal needs of the body. In order to make the temperature control more targeted, localized heating was proposed instead of whole-body heating to meet the local thermal needs of the human body, which would help save energy at the same time.

Method An artificial climate chamber, along with a lying thermal manikin, was adopted to simulate the real sleep scene of the elderly in winter. Three groups of sleeping tests were conducted. The first scenario involved no heating elements in the bedding system, and the body parts which need additional heating were figured out by comparing the measured skin temperatures with neutral skin temperatures. In the other two groups of tests, electrical heating pads and hot water bags were attached to the quilt and mattress separately to heat the body parts which need heating. By comparing the skin temperatures under the two heating methods, the design of a localized heating bedding system was proposed.

Results It was found that the skin temperature at chest, back, hands and feet were significantly (p<0.05) lower than the corresponding neutral skin temperature. This indicates that these four body parts would need additional heating to satisfy the thermal comfort needs of the elderly. After applying the electric heating pads, the skin temperature of back increased rapidly at a rate of 0.224 ℃/min. The lowest and highest comfortable skin temperature of 32.8 ℃ and 35 ℃ were reached in 10 min and 22 min, respectively. The skin temperature of the back continued rising for another 2 min before starting to decrease after turning off the heater, and after 20 min it stays within the comfortable temperature range of around 33.7 ℃ for sleeping. After applying the heating pad for 15min, the skin temperature of the foot reached the lowest comfortable temperature of 32.2 ℃, and the maximum comfortable temperature of 35.8 ℃ was reached after 43 min. The skin temperature of the feet continued rising for another 2 min before it started to decrease after turning off the heater, and after 16 min it stably stayed within the comfortable temperature range of around 35.3 ℃ for sleeping. The data suggests that electrical heating of the chest and hands improves their localized thermal comfort. However, considering the really sleep scenario, heating at chest is somewhat unsafe due to its proximity to the heart. The human hand moves a lot during sleep and is difficult to be fixed. The lowest (32.8 ℃) and highest (35 ℃) comfortable skin temperature of the feet were reached in 10 min and 22 min, respectively under the hot water bag heating. After 10 min, the temperature of the foot rose to 38.02 ℃ and then began to gradually decrease to a cooler temperature. In the heated futon design scheme, when the back and feet were heated with electric heating pads, there was no significant difference between the human local skin temperature and the comfortable skin temperature range (P>0.05).

Conclusion Local body parts of chest, back, hands and feet of the elderly need additional heating during sleep in winter. Taking both the safety and practicality into consideration, auxiliary heating system is suggested to be applied to back and feet. The heating method of hot water bag leads to a fast increase of skin temperature, while the water temperature would drop and cause cold contract feeling for the elderly. Thus, the heating method of electric heating pad, which brings a slow increase of skin temperature but can maintain the skin temperature in the comfortable rang of 34.5-35 ℃, overwhelms the heating method of hot water bag. Bedding system with localized electric heating pads are proposed and verified to effectively improve overall and local sleep thermal comfort for the elderly. These research findings can provide evidence for the design of high-performance localized heated futons to achieve thermal comfort during sleeping.

Research on newtype shared wardrobe virtual construction and practice

LI Xinhua, LI Jiakun, ZHENG Fangying, ZHANG Jie

Journal of Textile Research. 2024, 45(09):  183-193.  doi:10.13475/j.fzxb.20230802901

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Objective Clothing waste is a severe problem in textile industry. Terminal incineration disposal not only brings a huge waste of resources, but also cruel threat to the environment. Sharing economy and circularity concept of the textile industry provide the necessary conditions for cooperative consumption, which can integrate and reallocate the existing resources in the market. Renting and sharing are the cores of collaborative consumption. However, the conventional form of renting has many obstacles in the global shared wardrobe market, which results in most consumers do not know enough about this consumption mode and have little trust in sharing platform, its commercial value is not be proven. Therefore, fundamentally change about concept of consumption is of great significance for enhancing consumer trust, realizing the green consumption, and promoting the progress of the circularity system of the textile industry.

Method By literature reviewing, it was found that the generally' key factors that restrict the development of shared wardrobe and collaborative consumption mainly are consumer's cognitive limitations, attitude variances, personality traits, and values. Positively, circularity concept, new digital technologies, and collaborative consumption can provide a beneficial economic environment, retail model, and spatial consumption for the newtype shared wardrobe's establishment in the future. From the perspective of quality and trust guarantee system, Blockchain technology, with its distinct functions of decentralization, immutable information, independence, and anonymity can supervise clothing quality and build up consumer's trust system. From the perspective of marketing strategy, Curetail (Curated + Retail ) can integrate Exhibition-style rental system and experiential consumption together and thus bring consumer into a circularity world and enlighten them to take part in the newtype shared wardrobe consumption. Moreover, new digital technology, such as VR, AR, metaverse, can make the virtual space construction and operation of newtype wardrobe be realized.

Result Based on the knowledge of literature theory and technical support for the establishment of newtype shared wardrobe in the future, the research virtually constructed and operated the newtype shared wardrobe, and made profit estimation respectively of commercial lease, consumer and society. The result is newtype shared wardrobe can enhance people’s cognition of green consumption, thereby contributing to reduce clothing waste and lead to an effective utilization of circularity system of textile industry.

Conclusion The market and management of China's shared wardrobe is still in a primary stage. Though the related department has not yet issued a relatively complete and final standard system for the circular using of waste clothes, it gives related enterprises and technical practitioners a great potential chance and autonomy to carry on the research. This research applies the new concept and technologies for constructing newtype shared wardrobe and offers pathways and methods for its practice in the textile industry's circular practices in the future. The core content includes the application of blockchain technology within circular systems and the virtual construction of consumer spaces. The research also estimates the social benefits arising from its virtual operation. Hopefully, the finding serves as an initial outcome for the futural establishment and practice of newtype shared wardrobe. The research also reveals that not all garments are suitable for the shared wardrobe circular system, only meeting the circular number for bring profit can enter the circular system. Therefore, the core basis of its operation, namely the value evaluation of clothes before entering the recycling and the establishment of inspection standards at various stages, will be the crucial content for further in-depth research.

Machinery & Equipment

Influence of transport channel structure for foreign fiber sorting machine on airflow stability

HU Sheng, WANG Ziyue, ZHANG Shoujing

Journal of Textile Research. 2024, 45(09):  194-203.  doi:10.13475/j.fzxb.20230601201

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Objective The stability of the airflow inside the channel affects the flow of cotton in the pipe, which in turn affects the subse quent detection and rejection of foreign fibers. The purpose of this paper is to reduce the fluctuation of airflow inside the transport channel and minimize the wall attachment phenomenon on the upper and lower walls of the channel by improving the structure of the transport channel, so that the cotton flow can be transported smoothly inside the channel and improve the efficiency and rejection accuracy of foreign fiber detection.

Method ANSYS software Fluent module is adopted to model the CS808 foreign fiber machine channel structure in equal scale, set the simulation parameters according to the actual working conditions of the foreign fiber machine, use computerized fluid dynamics simulation calculation, analyze the flow field characteristics of the original channel structure, and then propose two improvement options such as changing the curvature combined with the length of the inlet section and adding diffusers and simulate them, and draw velocity profiles to compare the effect before and after the improvement.

Results The simulation results show that: 1) due to the original cotton transport channel structure of the elbow, the pressure difference between the upper and lower walls of the place reached 23 Pa, the velocity field is disordered and the air velocity fluctuation is large, which is not conducive to the smooth transportation of the cotton flow. Therefore, it is proposed to improve the internal airflow stability of the channel by improving its own structural parameters and adding an external diffuser, respectively. 2) Reducing the angle of the bend and increasing the length of the inlet section of the cotton transport channel is conducive to reducing the coverage of the high and low pressure imbalance region at the bend of the channel, which can effectively reduce the velocity difference between the upper and lower walls at the bend, so that the airflow can restore smoothness more quickly. And the quantitative analysis of the channel shows that reducing the angle of the bend is better than changing the length of the channel inlet section to improve the stability of the airflow. 3) In the second optimization scheme, first, three different types of nozzles were screened as the diffuser in this paper; and then the design of the structural parameters of the diffuser into the cotton channel entrance section and simulation analysis, it was found that the addition of the diffuser of the cotton channel can effectively reduce the pipeline wall effect, and will control the flow of cotton in the pipe. It is found that the additional diffuser can effectively reduce the wall effect of the pipe, control the cotton flow in the middle of the pipe, and the pressure and velocity imbalance phenomenon at the bends is significantly improved; in order to reduce the diffuser caused by the resistance caused by the wall transition is not smooth, the section optimization is carried out for the shrinking and expanding diffuser surface, and the double arc tangent section with the smallest coefficient of resistance is screened as the optimal diffuser from the three section improvement schemes; finally, it can be seen that the added diffuser can be used as the optimal diffuser through the simulation experiments. Finally, through simulation experiments, it can be seen that the airflow in the cotton transport channel with the addition of the double arc tangent section diffuser can be stabilized 0.3 m earlier than that in the original cotton transport channel.

Conclusion The unreasonable structure of the original cotton transport channel is the main reason for the fluctuation of cotton flow velocity. By changing the angle of the bend combined with the length of the inlet section and adding a taped and expanded diffuser can effectively reduce the degree of velocity fluctuations inside the pipe and significantly shorten the distance to restore smooth airflow, to a certain extent, to ensure the efficiency of the subsequent detection and rejection of cotton foreign fibers. The degree of improvement of the efficiency of foreign fiber detection and rejection in the practical application of the improvement scheme proposed in this paper needs to be further verified in theory and practical application.

Non-contact yarn tension measurement based on singular value decomposition algorithm

JIANG Jing, PENG Laihu, SHI Weimin, YUAN Haowei

Journal of Textile Research. 2024, 45(09):  204-211.  doi:10.13475/j.fzxb.20230400701

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Objective Yarn tension is closely related to product quality and production efficiency. The size and stability of tension run through each process from spinning to manufacturing. The excessive tension of yarn will lead to irreversible deformation of yarn, which will not only increase the yarn breaking rate, but also affect the mechanical strength, surface performance, dyeing performance and process structure of the fabric. The excessive tension of yarn will lead to poor formation of fabric organization, poor structure and poor elasticity. Modern technology requires the size and stability of yarn tension is increasingly high, so it is extremely important to realize the real-time measurement of yarn tension in operation.

Method The singular value decomposition (SVD) algorithm is adopted to obtain the amplitude frequency information by reducing the dimension of video image data, recombining vibration displacement extraction, and iterative denoising. With the help of fast Fourier transform, the yarn vibration time domain characteristics are converted into frequency domain characteristics and draw the frequency domain map, and finally, the yarn vibration monitoring experiment platform is built to test the feasibility and reliability of the algorithm.

Results An experimental set-up was built and experimentally verified to test the feasibility and reliability of the provided scheme. Different yarn running speeds were set and the experimentally derived tensions were compared with the measured tension magnitudes during yarn movement. The results indicated that when the speed of yarn movement was increased, the vibration amplitude of the yarn became smaller, the vibration frequency of the yarn larger, and the tension of the yarn larger. The tension of the yarn and the vibration frequency of the yarn were positively correlated, which is consistent with the theoretical equation of yarn vibration. Statistical results of yarn tension calculated by conventional image processing showed that when the yarn motion speed was 50-70 mm/s, the experimental value of yarn tension was close to the measured value of yarn tension with an absolute error of no more than 4%. However, when the yarn speed exceeded 75 mm/s. the yarn was irreversibly deformed due to the excessive tension and friction between the yarn and mechanical structure such as yarn guide wheels, and the yarn demonstrated a sudden change in the linear density, resulting in an absolute error of more than 10% occurs between the experimental and test values. The algorithm was computationally fast and accurate, and the yarn tension could be measured in real time with good performance.

Conclusion The results of experiments show that the non-contact yarn tension measurement based on machine vision successfully solves the problem of inaccurate tension values caused by the contact between the yarn and the measuring element during the contact yarn tension measurement, and the measurement accuracy can meet the performance requirements of most textile processes for yarn tension.

Tie-positioning method based on improved convex hull defect algorithm

ZHOU Qihong, CHEN Chang, REN Jiawei, HONG Wei, CEN Junhao

Journal of Textile Research. 2024, 45(09):  212-219.  doi:10.13475/j.fzxb.20230603701

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Objective Aiming at difficult detection, missed detection, difficulty in locating the position of ties and slow speed in conventional algorithms when detecting ties due to the color similarity between ties and woven bags, as well as the small area occupied by ties, the conventional vision is difficult to detect the position of ties, and deep learning algorithms are difficult to create datasets. Therefore, a strap positioning method based on improved convex hull defect algorithm is proposed.

Method An adaptive histogram equalization image enhancement algorithm was adopted to increase the contrast between the woven bag contour area and the background, and to improve the extraction accuracy of the woven bag contour. A fast convex hull algorithm was then adopted to obtain the convex hull of the woven bag contour, aiming at reducing the time required to obtain the convex hull of the woven bag contour. Consequently, an improved convex hull defect algorithm was established and used for defect detection of woven bags. Based on the location and depth of the convex hull defect points in the detection results, defect points were screened to obtain the final required defect point, which is the tie positioning point.

Results In order to verify the accuracy and robustness of the algorithm, experiments were conducted in an environment with complex background interference, based on the fact that the number of ties commonly used for bundling woven bags is 2 or 3 in practice. In order to fit the actual situation, three types of woven bag images were captured using a ZED camera with a number of 2-4 ties. Due to the small pixel difference between the woven bag and the surrounding environment, direct image pre-processing may result in low accuracy of the subsequently extracted woven bag contour. In order to retain more details of the woven bag contour, the image was first processed using adaptive histogram equalization, and then the woven bag contour was obtained by image pre-processing, morphological processing, contour rendering and filtering. Afterwards, a fast convex hull algorithm was adopted to solve the convex hull of the woven bag contour, reducing the time required to solve the convex hull of the woven bag contour. Three algorithms were adopted to solve the convex hull of woven bags. The Andrew algorithm took 0.07 s, the Graham algorithm took 0.04 s, and the fast convex hull algorithm took 0.02 s, which is 0.05 s faster than the Andrew algorithm and 0.02 s faster than the Graham algorithm, verifying the feasibility of the fast convex hull algorithm. Next, the conventional convex hull defect algorithm and the improved convex hull defect algorithm were adopted, respectively to detect the convex hull of the woven bag contour. The conventional convex hull defect algorithm only detects the deepest defect point between the defect starting point and the defect ending point. In the case of multiple defects between the defect starting point and the defect ending point, some defects may not be detected leading to the increased number of missed detection. Where the positioning points of the ties cannot be fully detected with conventional methods, the improved algorithm demonstrated that all defects cpuld be detected with a missed detection rate of 0. The positioning error was less than 4 mm, and could accurately locate the positions of all ties. The feasibility and robustness of the algorithm were verified.

Conclusion The experimental results show that the improved convex hull defect algorithm can solve the problem of missed detection in conventional convex hull defect methods, detect all defects in woven bags, accurately locate the position of ties, and the algorithm can be applied to the positioning of various colored ties, indicating the effectiveness and applicability of the algorithm.

Modeling of rotary variable motion and shedding driving mechanism based on motion synthesis

YUAN Ruwang, LI Wenhao

Journal of Textile Research. 2024, 45(09):  220-227.  doi:10.13475/j.fzxb.20230504801

Abstract ( 36 )   HTML ( 2 )   PDF (3975KB) ( 10 )   Save

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Objective In order to achieve and optimize the stop-rise-stop motion characteristics of heald frames to meet the shedding requirements, a variable speed motion model was established and different driving mechanisms adopted to achieve variable speed motion was analyzed. A systematic design method was proposed for the rotating variable speed mechanism with different configurations.

Method Based on the principle of motion synthesis, a method of constructing the rules of movement of the heald frames was proposed. The model of rotating motion was accordingly established to analyze the characteristics of the shedding mechanism under different parameters. From the perspective of mechanism of combination, the rotating-variable-speed motion driving mechanism and its improvement were put forward. The relative motion transfer function models of different heald frame driving mechanisms were established, and the scale optimization was carried out using objective optimization.

Results By comparing and analyzing the motion characteristics of the cycloidal function under different offset coefficients, changing the offset coefficients of the cycloidal function can meet the technological requirements of the loom at different rest times. The cycloidal rest time, relative displacement and velocity extremes decrease with the increase of the offset coefficient, and the acceleration is the least when the offset coefficient (b) is 0.199 1. When the offset coefficient is 0.414 7 and radius of roller (r_c) is 31 mm, the kinematic characteristics of the fixed cam-gear rotating transmission mechanism with different gear ratios are analyzed. With the reduction of the transmission ratio, the rotor arm displacement, cam pressure angle and cam curvature also decrease. The dimensional design of the evolved mechanism is carried out by means of objective optimization method, and its motion characteristics are analyzed. When the offset coefficient is 0.414 7 and the transmission ratio is lower than 0.9, the size of the hinged four-bar mechanism satisfying the constraint conditions can be obtained. The transmission ratio of the hinged four-bar mechanism and the guide slider mechanism both fluctuate uniformly above and below the transmission ratio. The transmission ratio range of the guide bar slider mechanism increases with the increase of the transmission ratio, while the transmission ratio range of the hinged four-bar mechanism is small. With the increase of transmission ratio, the error fluctuation of guide bar slider mechanism increases, and the error fluctuation of hinged four-bar mechanism is the smallest when the transmission ratio is 0.90. Under the same transmission ratio, the transmission performance of the guide bar slider mechanism is better than that of the hinged four-bar mechanism. By reducing the center distance of the hinged four-bar mechanism, the transmission performance of the mechanism is improved, the CAM pressure angle is reduced by 2.95%, and the transmission angle of the connecting rod is increased by 2.93%. The maximum diameter of the CAM rod is reduced by 2.90%.

Conclusion In the motion period, the relative angular displacement, angular velocity and angular acceleration curves of the corrected cycloid motion law are continuous without sudden change, and the offset coefficient is the only control parameter, which can meet the different process requirements of loom. When a four-bar mechanism is used instead of a gear mechanism to realize the transmission of relative motion, the transmission of relative motion can only be approximately realized, and the transmission ratio fluctuates within a certain range. By reducing the distance from the center, the size of the rotary gear can be reduced, the transmission performance of the return gear can be improved, and the speed of the loom can be increased.

Tension analysis and modeling of ribbon drive process in thermal transfer printing systems

WU Jianzhong, XU Yang, SHENG Xiaowei

Journal of Textile Research. 2024, 45(09):  228-234.  doi:10.13475/j.fzxb.20230902201

Abstract ( 37 )   HTML ( 5 )   PDF (4895KB) ( 17 )   Save

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Objective In the thermal transfer printing process, the thermal transfer film ribbon causes drive tension changes in the the film ribbon when winding through various structures of the drive system, which often results in the phenomena of ribbon relaxation, unclear transfer quality and even ribbon breakage. In order to ensure the stability of the film ribbon drive during the thermal transfer printing process and to achieve high quality transfer printing, this paper analyzes and establishes a tension model of the thermal transfer printing ribbon drive system.

Method Based on studying the composition of the thermal transfer printing ribbon drive system and the transfer printing principle, the drive path of the ribbon was divided. Combined with the viscoelasticity of the thermal transfer printing ribbon web, a film ribbon tension model was established for the inter-roll section. The intluence of friction on the tension of the film ribbon drive was analyzed, a tension drop coefficient was proposed to evaluate the tension loss in the unwinding area, and a stepper motor load model was constructed to solve the ribbon tension in the winding area.

Results The composition and transfer printing principle of the thermal transfer printing ribbon drive system were studied, and the drive path of the ribbon was delineated. The Voigt model was adopted to describe the viscoelasticity of film ribbons under small deformation, and combined with Hooke's law and Amontons-Coulomb's law, the tension formation mechanism of the inter-roll section was analyzed, and the classical tension equation of the winding system was improved to establish an equivalent tension model of film ribbons in the complex domain. By studying the composition of the drive system and drive principle, it was found that the ribbon tension in the unwinding section was mainly affected by three types of friction, i.e., rolling friction of the traction roller, relative sliding friction of the ribbon and the traction roller, and contact friction of the print head downward pressure and movement. However, in the actual operation of the system, the weakening effect of the tension was only considered by the rolling friction of the traction roller, and therefore, a tension drop coefficient was put forward to evaluate the loss of tension and to solve for the unwinding. Therefore, a tension drop coefficient was proposed to evaluate the tension loss and solved the unwinding section tension. Through the kinetic analysis of the winding section, it was found that the ribbon tension was nonlinear time-varying and was affected by the change in speed and the diameter of the ribbon roll. A stepper motor load model was constructed, and the transfer printing function of the tension in the winding section was deduced from the relevant parameters of the stepper motor. Taking the thermal transfer printing mixed-base ribbon as an example, the experimental platform of the ribbon drive system was built for tension test, and the simulation and experimental data are compared, it was found that the simulation was the same as the experimental data in intermittent mode, and the rebound phenomenon occurred in continuous mode, which was about 4 s periodicity.

Conclusion The thickness and width of thermal transfer printing ribbons affect their tension properties, and the classical tension model is improved by combining their viscoelasticity. Friction and changes in the stepper motor input pulse cause fluctuations in the ribbon drive tension. The simulation results in the intermittent mode are basically consistent with the experimental results, and the ribbon tension model is accurate, which can be used as a reference for the subsequent research on the design of the tension control scheme.

Comprehensive Review

Research progress in microcapsules of phase change materials

LIU Wenjing, ZHANG Xinrui, ZHAO Xiaoman, HONG Jianhan, WANG Hongbo, HAN Xiao

Journal of Textile Research. 2024, 45(09):  235-243.  doi:10.13475/j.fzxb.20230800502

Abstract ( 113 )   HTML ( 15 )   PDF (3647KB) ( 51 )   Save

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Significance Influenced by global energy crisis in the 1970s, improvement of energy efficiency and identification of alternative sustainable energy have become an urgent need of the moprden society. Along with this, the research and application of microcapsules of phase change materials (PCMs) have attracted much attention. Microcapsules of PCMs are a type of core-shell structured micro/nano smart materials. The core materials are the phase change materials and the shell materials are organic or inorganic substances. Encapsulation technology for phase change materials can facilitate the maintenance of shape in solid-liquid PCMs and can overcome phase segregation and low thermal conductivity. It effectively overcomes defects such as volume changes, leakage, and supercooling that occur during solid-liquid phase transitions of phase change materials. As a result, it significantly reduces the "phase separation" phenomenon and improves the stability of phase change materials. Owing to their unique advantages in energy storage and temperature regulation, microcapsules of PCMs have been widely applied in various fields such as textiles, medical care, architecture and solar energy. Therefore, the exploration of their preparation techniques and applications presents important scientific significance and research value.

Progress The clarification of the commonly used core and shell materials, the preparation technologies of microcapsules of PCMs and their applications were comprehensively reviewed. The microcapsules of PCMs consist of a core material, which is the phase change material itself, encapsulated within the microcapsule, a shell material used to protect the core material from leakage. The shell material should possess certain mechanical strength, compactness, and should not react chemically with the core materials. The preparation techniques for PCM microcapsules mainly include physical methods, chemical methods, and physicochemical methods. Physical methods are those in which the encapsulation of PCMs uses only physical processes such as drying and bonding, where the materials forming the shell do not undergo any chemical reactions with the core materials. The obtained microcapsules of PCMs exhibit good stability and controllability, and are suitable for micro-scale systems. For the chemical methods, the shell of microcapsules is synthesized through polymerization or condensation reactions between monomers, oligomers, or pre-polymers at the oil-water interface. Microcapsules of PCMs prepared by chemical methods have excellent performance and small particle sizes and simple operation. Physicochemical methods are a technique that combines physical methods such as heating and cooling with chemical methods such as hydrolysis, crosslinking and polycondensation. Microcapsules of PCMs with different characteristics and functions such as enhanced stability, small particle size and improved controllability can be prepared by adopting different preparation methods. Therefore, PCMs are widely used in textiles, medical care, architecture, solar energy, and other fields.

Conclusion and Prospect PCM Microcapsules have broad applications. There are still some challenges and problems in practical production. Firstly, the high cost of phase change materials limits their widespread applications due to the expensive production process. Secondly, the material loss is quite high in the preparation of PCM microcapsules. In order to the above problems, the preparation process of microcapsules of PCMs can be improved or replaced by a more economical and efficient production mode. Meanwhile, how to improve the coating rate of microcapsules and increase the response speed are also the current research and development directions of PCM microcapsules. Finally, it is conducive to the promotion of development of the microcapsules of PCMs to green and multi-functional directions by combining the properties of heat storage and temperature regulation with the environmentally friendly multi-functional materials. It can also contribute to the reduction of energy consumption and the enhancement of energy utilization efficiency, which would benefit human beings and the environment.

Progress in peparation and application of micro-nanofiber wound dressings loaded with growth factors

LIN Zhihao, FANG Lei, JIA Jiaojiao, HU Yanling, FANG Kuanjun

Journal of Textile Research. 2024, 45(09):  244-251.  doi:10.13475/j.fzxb.20230401702

Abstract ( 60 )   HTML ( 11 )   PDF (2810KB) ( 24 )   Save

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Significance Wound healing is a dynamic, complex and multicellular process. The healing process of skin involves four distinct stages: hemostasis, inflammation, proliferation, and tissue remodeling. Although the skin has the ability to regenerate itself, certain types of wounds such as extensive injuries or chronic wounds are difficult to self-heal, so it is very important to develop wound dressings that promote self-healing. Micro-nanofibers have a high surface area-to-volume ratio area and high porosity, and have a similar structure to extracellular matrix, which is conducive to cell adhesion and proliferation, thus promoting wound healing. Growth factor is a signaling protein that regulates cell growth, differentiation, proliferation, migration and metabolism during different wound healing processes. The use of growth factors and their combination on the basis of the dressing is considered to be a promising treatment method to promote active healing.

Progress Firstly, the three growth factors and their functions are summarized. At present, the most studied growth factors are basic fibroblast growth factor, epidermal growth factor and platelet-derived growth factor. Growth factors are involved in the four stages of skin wound healing. Growth factors play a key role in granulation tissue formation, regulating inflammatory response, and promoting angiogenesis. In addition, growth factors can also promote the proliferation and migration of wound cells to accelerate or improve the wound healing process. Secondly, growth factor delivery strategies are explored. In order to avoid degradation or inactivation of growth factors at the wound site and to maintain their continuous release at the wound site, a large number of studies have explored the effective loading mode of growth factors and developed excellent growth factor delivery systems. These methods include micro-nanofiber scaffolds, microspheres combined with nanoparticles and heparin, which avoid the burst release of growth factors and are conducive to its long-term effect. Finally, the micro/nanofiber dressings loaded with basic fibroblast factor, epidermal growth factor, platelet-derived growth factor, and multiple growth factors were described. The textile materials, preparation process and experimental results of micro-nanofiber dressings were summarized.

Conclusion and Prospect Micro/nanofiber dressings are one of the ideal wound repair materials, and the introduction of growth factors and their combinations can better promote active wound healing. It was found that the role of growth factors has been widely proved, and the use of a single growth factor can no longer meet people's needs for wound healing. Because different growth factors participate in different stages of wound healing, the use of multiple growth factors to promote wound healing has become the future trend. Secondly, in order to match the release of multiple growth factors in different wound healing stages, the delivery methods of growth factors are no longer single, but are developing towards the direction of combination of multiple delivery methods. At present, the burst release in the initial stage and the sustained release in the subsequent stage are the main delivery methods. Finally, with the increasing availability of textile materials for the preparation of micro/nanofibers, the co-application of natural and synthetic polymer materials is being extensively investigated so as to meet the needs of appropriate delivery of growth factors. At present, although most of the related research is still in the stage of animal experiments, micro/nanofiber dressings loaded with growth factors have a wide application prospect in the field of skin healing and repair materials, and it is believed that this repair material will be widely used in clinical practice.