Table of Content

15 March 2023, Volume 44 Issue 03

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Fiber Materials

Preparation of polyamide 6-based elastic fibers and its structure and properties

YANG Hanbin, ZHANG Shengming, WU Yuhao, WANG Chaosheng, WANG Huaping, JI Peng, YANG Jianping, ZHANG Tijian

Journal of Textile Research. 2023, 44(03):  1-10.  doi:10.13475/j.fzxb.20211005610

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Objective The binary acid method can be used for preparing polyamide 6 (PA6) based elastomer easily and efficiently, but stoichiometric number balance is strictly required when feeding. Once the molecular mass of the soft and hard segments is determined, the proportion of the soft and hard segments cannot be changed, which limits the development of functional products.The paper is to propose a new polymerization method based on the binary acid method to flexibly adjust the relative molecular weight and proportion of the soft and hard segments of PA6-based elastomers and to provide the basis for the subsequent research of PA6-based elastomers.

Method On the basis of the binary acid method, ethylene glycol is introduced to participate in the esterification and ester exchange reaction between polyamide 6 and polyether segments. With the ethylene glycol component, the system can ensure the balance of stoichiometry and adjust the ratio of soft and hard segments more flexibly to obtain the PA6-based elastomer. All reactions for preparing the PA6-based elastomer were performed in a 10 L reactor with a vacuum pump, a vacuum tube, and a nitrogen cyllinder.

Results It can be seen from the infrared spectra of the polymer that there are ester bonds in the product, indicating that ethylene glycol and polyethylene glycol were introduced into the system in the form of copolymerization (Fig.3). The structure of PA6 based elastomer (Fig.4), and combined with the peak (Fig.5), six bonding structures of PA6-based elastomer were made known. The relative integral area of the peak was introduced into equations (5) and (6), and it was proved that the molecular mass and PEG segment content were consistent with the design. The contents of low molecular extractants in PA6 based elastomer (Tab.4). The low content of low molecular extractants was conducive to the subsequent melt spinning of PA6-based elastomer. When the molecular weight of the soft and hard segments was given, the crystallization enthalpy and melting enthalpy of PEG segments would increase with the increase of the content of PEG segments, and the crystallization enthalpy and melting enthalpy of PA6 segments would decrease accordingly (Fig.7). With the same content of soft and hard segments, when the molecular mass ratio of hard segment to soft segment (M_n,PA6/M_n,PEG) increases, the melting and crystallization temperatures of PA6 and PEG segments would increase (Fig.8). It can be seen that the smaller the PEG content, the greater M_n,PA6/M_n,PEG, the higher the thermal stability of the resulting elastomer (Tab.5). It can be seen that the characteristic peaks of PA6 based elastomers were consistent with those of PA6, indicating that the crystal structure of this series of PA6-based elastomers was solely determined by PA6 chain segments(Fig.9). It can be seen that the elasticity of PA6 based elastic fibers increases with the increase of the PEG segment content, while the fracture strength and fracture elongation of fibers decrease sharply (Fig.10). It is evident that with the decrease of PEG segment content and the increase of M_n,PA6/M_n,PEG, the main chain structure of PA6 based elastic fiber is similar to that of pure PA6, and the fracture strength and elongation of the fiber increase (Tab.6).

Conclusion After the introduction of ethylene glycol, a series of PA6-based elastomers were prepared by changing the molecular weight and feeding ratio of polyethylene glycol (PEG) to PA6, making PA6-based elastomers more designable. The molecular structure design of a series of PA6-based elastomers was verified to be effective through the analysis of ¹H-NMR and infrared spectra. The thermodynamic properties, the crystal structure, the fiber mechanical properties and the elastic properties of the series of PA6-based elastomer samples were tested and analyzed. The results show that the crystal structure of PA6-based elastomer is dominated by PA6 segments. With the increase of the PEG segment content, the elastic recovery of fiber increased, and the strength and elongation of fiber decreased. Compared with PA6 fibers, elastic fibers with above 20% PEG content shows higher resilience at high constant elongation (≥10%), the elastic recovery rate are increased by up to 17.5%. PA6-based elastic fiber is found to possess encouraging comprehensive properties, among which the strength is 1.57 cN/dtex, the elongation is 106.89%, and the elastic recovery at 10% constant elongation is 94.3%.

Preparation and properties of eco-friendly polycaprolactone-based composite phase change fibrous membranes

ZHANG Shaoyue, YUE Jiangyu, YANG Jiale, CHAI Xiaoshuai, FENG Zengguo, ZHANG Aiying

Journal of Textile Research. 2023, 44(03):  11-18.  doi:10.13475/j.fzxb.20220103808

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Objective Latent heat energy storage materials absorb and release the latent heat during phase change, which could provide a kind of efficient and clean energy storage method. Electrospun fibrous membranes have potential application prospects in various latent heat energy storage materials. However, challenges remain in the development of eco-friendly phase change materials (PCMs) with high thermal conductivity and no leakage. Hence, the study of efficient latent heat energy storage materials as green energy carrier has essential scientific significance and potential application prospects.

Method Polycaprolactone (PCL) has been widely used as a medical biodegradable material and drug release system because of its good biodegradability and biocompatibility. However, few studies of the PCM composite based on PCL matrix were carried out. In order to explore polycaprolactone (PCL) as a kind of eco-friendly polymer in the application of phase change energy storage fibers, this paper proposes a new type of composite phase change fibers consisting of PCL as sheaths, polyethylene glycol (PEG) and hydroxylated multiwall carbon nanotubes (MWCNTs-OH) as cores by coaxial electrospinning.

Results The obtained PCL/PEG/MWCNTs-OH phase change composite fibers have smooth surface and core-shell structure, and the introduction of MWCNTs-OH did not affect the core-sheath structure of the fiber (Fig.3), and the thermal conductivity of the fiber is greatly improved. When the mass fraction of MWCNTs-OH reaches 4%, the thermal conductivity of PCL/PEG/C4 fiber membrane increases to 0.121 8 W/(m·K) (Fig.4). Compared with PCL/PEG membrane without MWCNTs-OH, the thermal conductivity of PCL/PEG/C4 fiber membrane increases by 9.53%. Meanwhile, the thermal stability of PCL/PEG/MWCNTs-OH enhance remarkably because of the addition of MWCNTs-OH in the core layer. Moreover, the PCM composites display the desirable thermal reliability as well as the effective temperature regulation capacity. It is almost no change of latent heat for the PCL/PEG/C4 after 100 thermal cycles (Fig.7). It is clear that PCL sample presents much faster temperatare rise and decrease rates than PCL/PEG/C4 PCM composite (Fig.8). The thermal energy storage and release time of PCL/PEG /C4 are 33.3% and 48.8% longer than that of PCL, suggesting the existence of PEG in the PCM composite could realize the effective thermal energy regulation. Derived from the excellent mechanical properties of PCL and MWCNTs-OH, composite phase change fibrous membranes exhibit higher tensile strength and elongation at break, and the composite phase change fibrous membrane containing 4% MWCNTs-OH has a tensile strength of 7.43 MPa and elongation at break of 132.2%. Compared with PCL/PEG, the tensile strength and elongation at break of the composite phase change fibrous membranes with MWCNTs-OH are significantly improved, showing excellent mechanical properties that are conducive to its repeated use in practical applications.

Conclusion In summary, a series of PCL/PEG/MWCNTs-OH composite phase change fibrous membranes have been prepared by coaxial electrospun in this research, exhibiting perfect thermal conductivity and thermal stability by virtue of the addition of MWCNTs-OH. Since the components of composite phase change fiber are physically mixed, the phase change characteristics of PEG remain unchanged, and the melting temperatures of composite phase change fibrous membranes have no obvious change, ranging between 38.85 ℃ and 39.35 ℃, slightly higher than the normal temperature of human body. Therefore, the composite phase change fibrous membranes are promising for the biomedical materials with temperature regulation. The proposed method provides a new avenue for degradable phase change fibrous membrane to simultaneously achieve robust mechanical properties and leakage-free.

Preparation and properties of Ag/Zn modified polystyrene/polyvinylidene fluoride composite fibrous membranes by magnetron sputtering

CHEN Meng, HE Ruidong, CHENG Yixin, LI Jiwei, NING Xin, WANG Na

Journal of Textile Research. 2023, 44(03):  19-27.  doi:10.13475/j.fzxb.20211107609

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Objective Air filter material is the most commonly used and effective medium to deal with air pollution as well as ultraviolet radiation, especially to block the transmission of pathogens in the air. In addition, the bacteria intercepted during use are loaded on the surface of the filter material, which is easy to cause secondary pollution. In order to deal with air pollution and ultraviolet radiation and acquire antibacterial function at the same time, this paper focuses on the preparation of an air filter material with antibacterial and ultraviolet protective properties.

Method PS/PVDF nanofibrous membranes were prepared by electrospinning using polystyrene (PS) and polyvinylidene fluoride (PVDF) as the main raw materials. The optimal volume ratio of PS and PVDF spinning solutions was determined by analyzing the micromorphology, mechanical properties and air permeability of the fibrous membranes with different mixing ratios. Silver (Ag) and zinc (Zn) nanocoatings were sputtered on both sides of the selected nanofibrous membrane, respectively. The micromorphology, element composition, pore size distribution, air permeability, filtration, ultraviolet (UV) protection and antibacterial properties of the PS/PVDF/Ag/Zn composite membrane were studied.

Results When the volume ratio of PS to PVDF is 1:2, the fibrous membrane has high breaking stress (2.31 MPa) and good air permeability (177.2 mm/s), which meet the requirements of the practical application. On this basis, PS/PVDF fibrous membrane with a surface density of 2.88 g/m² and a volume ratio of 1:2 was prepared. The surface of the fibrous membrane was modified with different sputtering time periods to prepare PS/PVDF/Ag/Zn fibrous membrane. The Ag and Zn metal particles sputtered on the fibrous membrane surface achieve uniform deposition (Fig.4), and the combination stability between them and the fibrous membrane is excellent (Fig.6). After performance characterization, it was found that when the sputtering time was 8 min, compared with the PS/PVDF fibrous membrane without sputtering, the pore diameter of PS/PVDF/Ag/Zn fibrous membrane was 7.76 μm reduced to 6.36 μm, air permeability decreases slightly (Fig.7), the filtration efficiency of 300 nm NaCl aerosol particles was increased to 99.7%, the pressure drop slightly increased to 103 Pa, and the quality factor value increased to 0.056 Pa^-1 (Fig.8). Compared with the PS/PVDF fibrous membrane without sputtering, when the sputtering time was 8 min, the ultraviolet protection factor (UPF) of PS/PVDF/Ag/Zn membrane reaches 702.52±55.15, and the transmittance of long wave ultraviolet (UVA) and short wave ultraviolet (UVB) was (0.26±0.01)% and (0.20±0.02)%, respectively, showing excellent UV protection performance. The PS/PVDF fibrous membrane without sputtering did not demonstrate antibacterial effect, while the width of the inhibition zone of the PS/PVDF/Ag/Zn membrane with sputtering time period of 8 min against Escherichia coli and Staphylococcus aureus reached 3.5 mm and 6.2 mm, respectively, which can effectively reduce the growth of bacteria and prolong the service life of the filter material in practical applications.

Conclusion PS/PVDF fibrous membrane was prepared by electrospinning, and Ag and Zn nanocoatings were deposited on both sides of the fibrous membrane by magnetron sputtering. The results show that the metal coating on the fibrous membrane surface roughens the fibrous surface, reduces the pore size, and improves the filtration efficiency of the fibrous membrane. The presence of Zn and Ag also endows the fibrous membrane with UV protection and antibacterial properties. An air filter material with antibacterial and UV protective properties has been successfully prepared. This research provides a new idea for the research and development of functional air filter materials.

Preparation and property optimization of waterproof and moisture permeable membrane made from thermally induced fusion bonded polyurethane/polydimethylsiloxane

YANG Guangxin, ZHANG Qingle, LI Xiaochao, LI Siyu, CHEN Hui, CHENG Lu, XIA Xin

Journal of Textile Research. 2023, 44(03):  28-35.  doi:10.13475/j.fzxb.20211100408

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Objective This research was an effort to prepare electrospun nanomembranes having good waterproofness, mechanical properties, moisture permeability, improved wearing comfort and required mechanical properties. It also expected to expand the applications of nanomembranes into areas such as outdoor sports, protection and filtration.

Method PU/PDMS nanofiber membranes (PU/PDMS NMs) were prepared by electrospinning by adding non-fluorinated hydrophobic polydimethylsiloxane (PDMS) into PU spinning solution. The electrostatic sprayed PU/PDMS NMs were then prepared by depositing PU/PDMS microspheres on the PU/PDMS NMs substrate, and the PU/PDMS NMs and electrostatic sprayed PU/PDMS NMs were modified by using a heat thermal induction process, respectively. The influences of heating temperature and heating time on the morphology, pore size distribution, waterproof, permeability and mechanical properties of nanofiber membranes were studied, and the influencing mechanism was analyzed.

Results The waterproofness and moisture permeability of the electrostatic sprayed PU/PDMS waterproof and moisture permeable membrane before heat treatment is better than that of the electro spun PU/PDMS waterproof and moisture permeable film (Tab.3), where the waterproofness and moisture permeability of the electrostatic sprayed PU/PDMS waterproof and moisture permeable membrane is greatly improved. Heat treatment of electrostatic sprayed PU/PDMS waterproof permeable membrane achieves the waterproofness and permeability property not as good as that of the heat treatment of electrostatic spun PU/PDMS, mainly because heat treatment of electrostatic sprayed PU/PDMS waterproof permeable membrane causes more adhesion, porosity reduction, making the waterproof and moisture permeability not as good as its electrostatic spun counterpart (Tab.3 and Tab.4). The pore size of the electrospun PU/PDMS NMs after heat treatment was greatly reduced (Tab.2), and the beading structure of the electrospun PU/PDMS NMs was transformed into a spider structure (Fig.3 and Fig.4), which not only greatly improved the waterproof property of the PU/PDMS NMs but also significantly improved its mechanical properties. When the heat treatment temperatures were 80 ℃ and 100 ℃, the temperatures were not enough to allow the nanofibers and microspheres in the membrane to be fully softened, so that the heat treatment time had to be increased to form a sufficient adhesion structure. However, when the heating temperature was 120 ℃, the excessive temperature caused the polymer molecules to become relaxed and disrupted the micro-nanostructure, resulting in a reduction in the waterproof and mechanical properties of the membrane (Tab.3 and Tab.5). When the heating temperature was 100 ℃ and the heating time was 90 min, the electrospun PU/PDMS NMs showed the excellent performance with a water contact angle of 144.7°, and also exhibited good moisture permeability, air permeability and mechanical properties, the moisture permeability was up to 5 666.7 g/(m²·d), air permeability was up to 9.91 mm/s, breaking strength was up to 17.89 MPa, and the elongation at break was 210.68%.

Conclusion The heat treatment transforms the bead structure of the electrospun PU/PDMS NMs into a spider web structure, which improves the performance of the waterproof and permeable membrane. However, after heat treatment, the spider web structure of the former PU/PDMS NMs disappears and the waterproof and permeable properties of the membrane decreases. On the other hand, the spider web structure of the membrane becomes stable after heat treatment. By increasing the heat treatment temperature and time period, the adhesive structure in the waterproof permeable membrane can be increased, the pore size can be reduced, and the surface roughness can be improved, so as to improve the mechanical and waterproof properties of the waterproof permeable membrane. It was found that excessive temperature would relax the polymer molecules, while prolonging the heating time reduces the mechanical properties of the membrane, so that the adhered nanofibers almost become smooth, leading to a decrease in waterproofing properties. Although the membrane prepared by this method has good waterproof, permeable and mechanical properties, it cannot meet the demand for waterproof property under harsh conditions and still has a certain gap compared to the waterproof permeable fabric containing fluorine, which calls for further improvement.

Influence of voltage on forming process of electrospinning beaded fiber

GE Cheng, ZHENG Yuansheng, LIU Kai, XIN Binjie

Journal of Textile Research. 2023, 44(03):  36-41.  doi:10.13475/j.fzxb.20220204006

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Objective The sizes and morphologies of microbeads on beaded fibers will lead to great differences in the overall performance of electrospinning fiber membranes, and thus fiber membranes with specific functions can be prepared in a directional manner by adjusting the size and morphology of beads on beaded fibers. As an important factor affecting the electrospinning process, electric field has not been used as the main research object in the process of preparing beaded fibers up to date. Therefore, it is necessary to investigate the influence of applied voltage on the structure and morphology of microbeads during electrospinning.

Method Beaded fibers were prepared by electrospinning using polystyrene (PS). Light microscope and scanning electron microscope (SEM) were adopted to observe the morphology of fibers, and the influence of applied voltage on the morphology of microbeads was studied. By observing the beaded fibers intercepted in different areas of the electrospinning jet, the evolution of beading morphology during jet whipping was explored. At the same time, the finite element simulation software COMSOL was adopted to simulate the three-dimensional electric field, bead morphology and beaded fiber movement speed. The simulation results were compared with the experimental results for model validation.

Results Based on the simulation results of the magnitude and direction of the electric field, it is evident that the strong electric field is mainly concentrated near the spinneret. As the spinning voltage increases, greater electric field strength in the spinning area leads to stronger tensile effect of the jet. This results in a beaded shape that is approximately circular at an applied voltage of 15 kV and the beaded fibers are bent disorderedly. When the applied voltage is 25 kV, the shape of the beads is close to the spindle shape, and the fibers between the beads are more regular and orderly. As the spinning voltage increases, the speed of the beaded fibers gradually increases. When the voltage is in the range of 20 and 25 kV, the speed of the beaded fibers increases more significantly, because at larger spinning voltages, the solution in the jet is more polarized, the charge on the jet surface is higher, and the force of the electric field is stronger. Owing to the larger surface area of the bead, more charge is generated by the electric field polarization of the jet in the beaded part, which is associated to stronger the electric field drafting, resulting in a greater speed in the beaded part than the speed of the fiber part. It is clearly shown that only the Shish-Kebab (string crystal) structure exists in the linear segment of the jet. This is because the strong electric field is concentrated near the spinneret and the polymer is strongly sheared or stretched. Gradual formation of a beaded structure is observed at the end of the straight segment, because the large tensile force of the electric field causes the jet to break, the broken jet is directly drawn from the Taylor cone, and the droplet tends to contract to form beaded fibers. The result also shows that the closer is the fiber morphology intercepted in the spinning direction to the collector, the longer the electric field of the jet is subjected to and the longer the whipping disturbance action time. The shape of the beads gradually tends to spindle shape under the action of stretching.

Conclusion In this paper, PS was used as raw material to prepare beaded fiber membranes by electrospinning method, and the evolution process of solution electro spun PS beaded fibers and the influence of spinning voltage on beaded morphology and fiber speed were investigated. The experimental results provide a theoretical basis for the controllable preparation of beaded fibers. 1) In the process of electrospinning, as the applied voltage increases, the stretching effect of the jet is more obvious, the beaded shape gradually changes from an approximate sphere to a spindle shape, and the movement speed of the beaded fiber also increases with the increase of the applied voltage. 2) The beaded structure is not formed on the linear segment of the jet, and gradually forms in the whipping zone, and the jet zone is made closer to the collector, the jet is subjected to the electric field and whipping action for a longer time, and the stretching effect of the beaded fiber is more obvious.

Property characterization and comparative analysis of Lyocell fibers

HUANG Wei, ZHANG Jiayu, ZHANG Dong, CHENG Chunzu, LI Ting, WU Wei

Journal of Textile Research. 2023, 44(03):  42-48.  doi:10.13475/j.fzxb.20211006107

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Objective A varity of Lyocell fibers in the market are different in the product quality and spinnability. In order to understand the performance and quality differences of different Lyocell fibers and the analysis of the causes, this research systematically studied the differences of Lyocell fibers in terms of morphological structure, mechanical properties, wear properties, crystallinity, orientation and filament ratio, and analyzed the reasons for the differences. This paper provided suggestions for the subsequent improvement and development direction of domestic Lyocell fibers.

Method Lyocell fibers from 9 different manufacturers were selected for characterization and comparative analysis on the apparent morphology, mechanical properties, frictional properties, crystallinity, orientation and filament ratio. Due to the differences in the process route and post-treatment technology, the quality of domestic Lyocell fibers has a certain gap compared with Lyocell fibers prepared by major international manufacturers. The characterization instruments used in this research includes SEM,XRD,microscope,fiber wet tribometer and fiber strength tester.

Results Except for domestic Lyocell fibers, filament cross sections are approximately circular with certain defects and creases on the surface and uneven fiber diameter thickness (Fig.2). The 1^# and 3^# fibers have a small amount of hollow structure, and the 7^#fibers have a large amount of hollow structure. The mechanical properties of all Lyocell fibers from different manufacturers have little difference in dry breaking strength ranging from 3.6 to 4.0 cN/dtex, elongation at break ranging from 7% to 10%, and initial elastic modulus ranging from 60 to 70 cN/dtex (Tab.3). The polymerization degree of the 1^# fiber is low (Tab.3). When the capacity of the spinneret component is the same, the cellulose concentration in the spinning stock solution of the 1^# fiber is higher, which is more conducive to the increase of production line output and reduce the fiber production cost. The rotation time of friction axis of 1^# Lyocell fiber is 8.76 s. The rotation time of friction of domestic Lyocell fiber is short and the degree of fibrillation is relatively high (Tab.4). There is no significant difference in the major diffraction peaks of all Lyocell fibers, and the diffraction peaks of 1^# and 2^# fibers are significantly lower than those of other fibers (Fig.3). Most of the domestic Lyocell fibers have (040) crystal planes near 2θ of 35.5°, indicating that there are a few quasicrystals in amorphous regions in the fibers. The crystallinity of domestic Lyocell fibers is higher than that of foreign countries on the whole, and the orientation of Lyocell fibers of different enterprises has little difference (Tab.5).

Conclusion The morphological structure, degree of polymerization, mechanical properties, wear properties, crystallinity, orientation and filament ratio of Lyocell fibers from sampling suppliers were characterized and compared, and the following conclusions were obtained. The Lyocell fiber prepared by major international manufacturers seems to have regular and smooth appearance and regular round cross section, with wet wear loss of 8.76 s, crystallinity of 78.8%, low degree of fibrination, low filament ratio (2.591%), fiber breaking strength of 3.91 cN/dtex, elongation at break of 9.79%. With high yarn strength and excellent fiber quality, Lyocell fiber downstream manufacturers have a high degree of recognition. Due to the difference in processing route and post-treatment technology, the quality of domestic Lyocell fiber is better than that of foreign Lyocell fiber. Domestic manufacturers should continue to optimize the fiber microstructure, gloss, spinnability and brand promotion to further improve the market share of domestic Lyocell fiber. In the future, the domestic manufacturers should continue to optimize the micro-morphology, filament ratio, gloss, spinnability and brand promotion, so as to further improve the market share of domestic Lyocell fiber.

Textile Engineering

Influence of blending ratio on mechanical properties of bio-polyamide 56 staple fiber/cotton blended yarn

WU Jiaqing, WANG Yiting, HE Xinxin, GUO Yafei, HAO Xinmin, WANG Ying, GONG Yumei

Journal of Textile Research. 2023, 44(03):  49-54.  doi:10.13475/j.fzxb.20211100306

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Objective Bio-polyamide 56 (PA56) is a new type of bio-based fiber with insufficient basic spinning data. The content ratio (blending ratio) of each component fiber of blended yarn is an important factor that affects its mechanical properties and yarn function. By means of theoretical models, the relationship between yarn strength and blending ratio can be predicted, thereby speeding up production process design and shortening production lead time. This research aims to study the influence of fiber content on the mechanical properties of PA56 staple fiber/cotton blended yarn and establish its strength prediction model.

Method Cotton fiber and PA56 staple fiber were mixed to produce various blended yarns. Pure PA56 staple fiber yarn, pure cotton yarn and PA56 staple fiber/cotton blended yarn with various blending ratios were prepared on the ring spinning machine. In addition, the mechanical properties of the PA56 staple fiber and cotton fiber, and all pure yarns and blended yarns were evaluated. Prediction models for breaking strength of blended yarn were established by using pure yarn (model 1) and fiber (model 2), respectively.

Results By combining with the tensile breaking strength curves of the PA56 staple fiber pure yarn and cotton pure yarn (Fig.2) the pure yarn breaking strength predicted blended yarn strength curve (model 1) was drawn, and the predicted breaking strength expression of blended yarn was established as shown in equation 3. It could be seen that the predicted breaking strength of blended yarn decreased first and then increased with the increase of cotton content. Using model 1, the breaking strength of blended yarn was found to be the smallest when the cotton content was 52.8% (Fig.3). On the other hand, the breaking strength curve of the fiber predicted blended yarn (model 2) could be built by the tensile breaking strength curve of the PA56 staple fiber and cotton fiber (Fig.4 and the equation 3). The trend of model 2 resembled that of model 1, but the predicted minimum blended yarn breaking strength was associated to cotton content 47.9% (Fig.5). In order to verify the accuracy of the prediction model, the consistency between the measured value and the predicted value was obtained by testing the breaking strength of the PA56 staple fiber/cotton blended yarns with different cotton content (Tab.3, Fig.6). The results showed that model 1 was closer to the measured value, while model 2 was smaller than the latter. In order to modify model 2, it was proposed to use the utilization rate of fiber strength in pure yarn. The utilization rate of cotton fiber strength in pure cotton yarn was 45%, and the utilization rate of PA56 staple fiber strength in PA56 pure yarn was 40%. Furthermore, the modified fiber model of the prediction breaking strength of blended yarn (Fig.7) was obtained by combining model 2 and equation 4. The trend of the modified model 2 and the predicted minimum breaking strength cotton content of 50.9% were very close to model 1.

Conclusion The minimum breaking strength point and overall trend of blended yarn on the prediction curve of the pure yarn were well fitted with the trial spinning data, so that the model 1 can predict the breaking strength of the PA56 staple fiber/ cotton blended yarn. The model 2 needed to be modified by using the utilization rate of the fiber strength in pure yarn. The results of the modified model 2 were similar to those of the model 1. Therefor, the modified fiber model could quickly complete the prediction of blended yarn strength without the pure spinning processing flow, and it was very suitable for blending ratio design and product development of blended yarn, especially PA56 staple fiber blended yarn.

Analysis of structure and properties of cotton/wool siro segment colored yarns

SHI Jingjing, YANG Enlong

Journal of Textile Research. 2023, 44(03):  55-59.  doi:10.13475/j.fzxb.20210908905

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Objective Aiming at uneven of segment colored yarns made by three-roller and four-roller methods, coaxial double rear rollers were adopted to achieve the same linear density cotton/wool siro segment colored yarn by the method of two sets of roving at the same spindle position and equal coupled feeding. Two rovings are fed on the same position, and the drafting control condition of two rovings is consistent. The roller speed can be coupled to achieve equal fiber feeding. However, the spinning process, yarn structure and properties of cotton/wool siro segment colored yarn produced by coaxial roller spinning technology are rarely studied.

Method Cotton/wool siro segment colored yarn with constant linear density was spun on HFX-A4J ring spinning frame. Two rovings were fed into the coaxial double rear roller equally at the same position. The lengths of spinning segmentation time were 1, 2, 4, 8 s, and the mass ratio cotton to wool during spinning were 87.5/12.5, 80/20, 75/25, 62.5/37.5 and 55/45. The influences of the proportion of mass ratio cotton to wool and the segmentation time on the breaking strength, evenness and hairiness of the colored yarn were investigated. The longitudinal and sectional yarn morphologies were observed with the KH1300 three-dimensional video microscope made by Questar Ltd.

Results As is shown in the longitudinal and cross-sectional images of the yarn, the segment color effect of the yarn is more obvious with the increase of the difference in the mass ratio cotton to wool and the segmentation time. Owing to the different mass ratio cotton to wool in the adjacent two segments, the segment color effect appears in the longitudinal direction of the yarn. With the longitudinal observation results of the yarn, the longer the segmentation time is, the longer is the color segment length. Cross-sectional observations show that the cotton and wool fibers are compressed and wrapped in the yarn to form a structure similar to Yin and Yang fish of the Tai Chi pattern. When the mass ratio cotton to wool is constant, the breaking strength of the yarn decreases as the split time increases, and when the segmentation time is fixed, the yarn breaking strength decreases with the increase of the segment mass ratio cotton to wool difference. When the segment time is shorter than 2 s, the yarn breaking strength decreases slightly with the increase of segment mass ratio cotton to wool difference. When the segmentation time is more than 4 s, the breaking strength of yarn decreases greatly with the increase of segment mass ratio cotton to wool difference. The evenness of cotton/wool segment colored yarn suggested that when the mass ratio cotton to wool is constant, the evenness increases with the increase of segmentation time. When the segment ation time is fixed, the unevenness of the yarn increases with the increase of segment mass ratio cotton to wool difference. With the increase of segment time, the ratio of roller speed change transition time to segmentation time decreases, the difference between real mass ratio cotton to wool and the designed value decreases, and the CV value of yarn increases with the increase of segment mass ratio cotton to wool difference.

Conclusion As the diameter of wool fiber is thicker than cotton fiber, the total number of fibers in the cross section of yarn segment decreases with the increase of the mass ratio of wool, which reduces the breaking strength of the yarn segment and ultimately the breaking strength of the whole yarn. When the segmentation time is within 2 s and the difference of mass ratio cotton to wool is not more than 75/25, the cotton/wool segment colored yarn with weak segment color effect is produced, and the breaking strength and evenness of the yarn meet with the requirements of wearing performance. With such a yarn, woven fabric can be designed for colored patterns. This spinning method enriches the product types of existing fancy yarns. Meanwhile, under the condition of simple modification of the spinning frame, the strand-style wool-like segment color yarn is produced.

Preparation and UV stability of flame-retardant acrylic/aramid core-spun yarns

WU Junxiong, WEI Xia, LUO Jingxian, YAN Jiaoru, WU Lei

Journal of Textile Research. 2023, 44(03):  60-66.  doi:10.13475/j.fzxb.20220803407

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Objective Aramid fiber has become the most widely used high performance fiber for protective fabrics because of its good flame retardancy and chemical stability. But, due to the penetration of the molecular chain contains a lot of chromogenic groups, it is prone to aging degradation under high-energy rays, especially UV light, and the UV aging performance seriously affected usability of the aramid products used outdoors. Therefore, it is necessary to study how to improve the UV aging resistance of aramid fiber in fabrics.

Method Aiming at the problem of poor UV light stability and easy photodegradation and aging of aramid, the core-spun yarn structure was adopted to block the direct UV irradiation of aramid by covering the aramid core with flame-retardant acrylic fibers. Five core-spun yarns were designed, including aramid/aramid, flame-retardant acrylic/aramid, modacrylic/aramid, flame-retardant acrylic/flame-retardant viscose/aramid and flame-retardant acrylic/flame-retardant Modal/aramid. The core-spun yarns were used as weft and aramid as warp to weave fabrics, and the UV aging, comfort and flame retardant properties were tested.

Results Compared with pure aramid fabric, the UV protection coefficient of flame-retardant acrylic/aramid fabric, flame-retardant acrylic/flame-retardant viscose/aramid fabric and flame-retardant acrylic/flame-retardant Modal/aramid fabric increased by 25.8%, 18.7% and 20.8%, respectively(Fig.4), while the fracture strength decreased by 23.1%, 37.9% and 27.0%, respectively(Fig.1). The continuous combustion time was prolonged by 0.9 s, 0.2 s and 0.2 s respectively, and the smoldering time was prolonged by 0.3 s, 0.4 s and 0.7 s respectively. The fracture strengths of pure aramid yarn, flame-retardant acrylic/aramid yarn, flame-retardant acrylic/flame-retardant viscose/aramid yarn and flame-retardant acrylic/flame-retardant Modal/aramid yarn decreased by 43.6%, 5.9%, 8.3% and 9.1%, respectively(Fig.2). The comfort of flame-retardant acrylic/aramid fabric decreases, but the comfort of flame-retardant acrylic/flame-retardant viscose/aramid fabric increases.

Conclusion Before UV aging, the breaking strength of pure aramid fabric is the largest, and the breaking strength of nitrile and chloroprene fabric is the smallest. After 18 months of UV-accelerated aging, the breaking strength of the fabrics with flame-retardant acrylic fibers decreases, but that with flame-retardant acrylic fibers decreases the most, and that with flame-retardant acrylic fibers/aramid fibers decreases the least.The UV transmittance of flame-retardant acrylic/aramid fabric is the lowest, and the UV transmittance of pure aramid fabric is the highest. Flame-retardant acrylic/aramid fiber has the best UV protection performance, while pure aramid fiber has the worst. The yarn component contains flame-retardant acrylic fiber, which can effectively improve the UV resistance of the fabric, and the greater the yarn density in the same fabric, the lower the UV transmittance of the fabric. Flame-retardant acrylic/flame-retardant viscose/aramid core yarn has the best comprehensive performance, good UV stability, comfortability and flame retardant.

Weaving process design for three-dimensional changeable spacer jacquard fabrics

ZHOU Zhifang, ZHOU Jiu, PENG Xi, HUANG Jinbo

Journal of Textile Research. 2023, 44(03):  67-72.  doi:10.13475/j.fzxb.20211107206

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Objective In order to bypass the limitation of the number of heald frames on the preparation of three-dimensional woven fabric and improve the design-ability of three-dimensional woven fabrics and weaving process, a weaving method of three-dimensional spaced jacquard fabric with variable spacer core structures is proposed.

Method An electronic jacquard loom was modified for weaving spacer fabrics. The ground warp is controlled by two groups of heald frames with different heald eye positions to form double sheds and the longitudinal warp was controlled by jacquard together with the use of weaving CAD. With the aid of the support rod, the longitudinal warp was interwoven with the weft to form the ground fabrics. When the movement direction of the support rod was changed, the longitudinal warp would cross between the two ground fabrics and connect the ground fabrics into one three-dimensional structure, so as to complete the weaving of three-dimensional spacer Jacquard fabric.

Results A three-dimensional spacer fabric is composed of three groups of yarns, where the ground weave warp yarn constitutes the fabric length direction, the surface weft yarn forms the width direction of the fabric, and the longitudinal warp yarn constitutes the fabric thickness direction. The weaving structure suggested that the longitudinal warp yarns are divided into two groups, and the yarns are interlaced with the upper and lower weft yarns in turn to form a three-dimensional spacer fabric with solid core. The longitudinal warp yarn is controlled by jacquard. According to the jacquard CAD design, with the assistance of the support bar, the weft yarn can be interweaved in different ways, forming a three-dimensional spacer fabric with variable hollow core structure. The longitudinal warp can be evenly divided into two groups with the help of the supporting shaft, and the yarn can be interwoven with the upper and lower weft separately. The longitudinal warp can also move vertically with the supporting stem between the ground tissues. When the supporting rod changes the direction of movement, the longitudinal warp will also move with it, completing the exchange of longitudinal positions, connecting the upper and lower layers of ground tissues into a whole. The surface texture of the test fabric is plain weave structure, the side section is hollow core structure and solid core structure are interlaced (Fig.5(c)), and the hollow part is square structure(Fig.5(b)). Through the tensile test of solid/hollow three-dimensional spacer fabric, as shown in Tab.2, the breaking strength of hollow fabric is reduced by about 20%, and the breaking elongation is increased by about 8% compared to the solid fabric, because there are fewer longitudinal warp junction points in the hollow fabric. Moreover the hollow structure makes the fabric bear uneven force when being stretched, resulting in a decrease in strength. The hollow structure also enhances the deformability of the spacer fabric.

Conclusion This paper proposed a production process of three-dimensional spaced jacquard fabric with variable hollow core structure. In actual production, the spacing distance of three-dimensional fabric can be adjusted by the warp let off of longitudinal warp and the movement height of the supporting rod. Using this weaving method, healds of different heights can be adopted to design the weaving process of three-shed or multi-shed, so as to complete the weaving of multi-layer spacer hollow core fabric. Compared with the strength of solid core spacer fabric, the strength of hollow core spacer fabric in both warp and weft directions decreased, and the strain increased slightly. This process can produce three-dimensional fabric with variable hollow core structure under the premise of less strength damage, and increase the designability and application field of three-dimensional spacer fabrics.

Study on composite acoustic material of polyvinyl alcohol nanofiber membrane and Milano rib knit fabric

ZHOU Linghui, ZENG Pei, LU Yao, FU Shaoju

Journal of Textile Research. 2023, 44(03):  73-78.  doi:10.13475/j.fzxb.20211002406

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Objective Noise pollution is harmful to people's daily life and health. Knitted materials have the characteristics of porous structure, high machinability and softness, which have research significance for sound absorption and noise reduction. According to research, polyvinyl alcohol(PVA)nanofiber membrane has excellent sound absorption performance in the low and middle-frequency band, which may be complementary to the knitted textiles. In order to verify the effectiveness of knitted fabric-based composite sound-absorbing materials in absorbing noise, we explored the sound absorption performance and other fundamental characteristics of composite material of PVA nanofiber membrane and Milano rib knit in this paper.

Method A wool/acrylic fiber (50/50) blended yarn and a 100% wool yarn were used to produce the Milano rib knitted fabrics, whose linear density is 35 tex×2 and is 42 tex ×4 respectively. PVA nanofiber membrane is prepared by the electrospinning method. By placing the knitted fabric on the receiving plate in the electrospinning device, the PVA membrane was directly formed on the knitted fabric, creating the acoustic material. Three factors that may affect the acoustic characteristics i.e., fabric density, yarn types, and use of membrane were examined by orthogonal experiment and range analysis.

Results Eight samples are tested and the test results are summarized (Fig.3). The average sound absorption coefficients of each sample at medium and low frequency (250-1 600 Hz) and high frequency (2 000-6 300 Hz) are compared. The sound absorption coefficients of the 8 samples in the middle and low-frequency band (250-1 600 Hz) are all less than 0.1, and there is no significant change. The sound absorption effect of sample No.3 is relatively better. In the high-frequency range (2 000-6 300 Hz), sample No. 1 has the best sound absorption effect, with the average sound absorption coefficient higher than 0.3, which can be used as sound absorption material for research, and the other samples have little difference in sound absorption effect. It can be seen that the factor that has the greatest impact on the sound absorption performance of the sample is the use of membrane, and the optimal combination of all factors is "density dial scale 2, wool/acrylic fiber (50/50) blended yarn and covering membrane". Multiple groups of data are obtained by multiple measurements of each fabric, and the average value is obtained (Fig.5). The samples are arranged in the order of average permeability from high to low, which is 7 > 6 > 8 > 4 > 5 > 2 > 3 > 1. The range analysis method is used for further study of the influence level of density dial scale, yarn type, and the membrane covering or not on fabric breathability, and by comparing the value of R', yarn type demonstrates the greatest influence on air permeability(Tab.6). When the level of the three factors is "density dial scale 4, wool yarn (100%), and not covering membrane", the fabric has the best air permeability. The thickness of each sample is not very different, so the influence on the sound absorption performance is not great(Fig.7 and Fig.8). The order of the weight of square meters from high to low is 5 > 3 > 2 > 1 > 8 > 6 > 7 > 4, indicating that sample No. 5 is the heaviest and sample No. 4 is the lightest. According to the areal density of the fabric, these 8 samples belong to medium thickness fabric.

Conclusion This paper explores the application of composite material combining nanofiber membrane and knitted fabric in the field of sound absorption and noise reduction. The results show that the composite material has a certain effect on sound absorption and reaches the standard of sound absorption material. This research work also investigates the optimum parameters for sound absorption of the material. The results show that the influence factors of the sound absorption performance of the composite are membrane covering or not, density dial scale, and yarn type in descending order. The optimum combination parameters are found to be density dial scale 2, wool/acrylic fiber (50/50) blended yarn, and covering membrane. The average sound absorption coefficient of the material is over 0.3 so it can be used as acoustic material. The sound absorption performance of the fabric is greatly improved by the PVA nanofiber membrane and the sound absorption coefficient of the fabric increases from the increase in the fabric density.

Projectile penetration mechanism of ultra-high molecular weight polyethylene fabric/polyurea flexible composites

LIU Dongyan, ZHENG Chengyan, WANG Xiaoxu, QIAN Kun, ZHANG Diantang

Journal of Textile Research. 2023, 44(03):  79-87.  doi:10.13475/j.fzxb.20220303809

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Objective Fragmented pieces resulted from explosion on doors, windows and walls are hidden dangers threatening people's life and safety. At present, the explosion-proof equipment is used for high-efficiency, high-speed and large-area protection. Ultra-high molecular weight polyethylene (UHMWPE) fabric/polyurea flexible composites received much attention recently owing to their low density, high performance, flexibility, corrosion resistance, outstanding intrusion resistance and portability. Therefore, it is important to understand the damage mechanism of UHMWPE fabric/polyurea flexible composites under the high-speed impact of broken fragments for engineering applications.

Method 15 mm angle-interlocked monolithic fabrics and laminated plain fabrics (single layer thickness of 0.39 mm, 40 layers) were used in this research. Flexible composites were manufactured by surface spraying with polyurea, named 2D-C and 3D-C, respectively. A 1.1 g wedge-headed cylindrical projectile was adopted to impact on the two types of UHMWPE fabric/polyurea flexible composites to obtain the ballistic limiting velocity V₅₀, the specific energy absorption (SEA) and the backface deformation. Based on this, surface and internal damage morphology studies were carried out to reveal the intrusion damage mechanism.

Results In case of equal thickness, 3D-C panel demonstrates greater V₅₀ and SEA values and a wider overall area of deformation on the backface with greater depth of backface signature. This is related to the fact that the binding warp yarns in the angle-interlock fabrics can transmit stress waves in the thick direction. In addition, the damage to the polyurea surface is minor for both types of composites. At the same time, computed tomo-graphy (CT) scans were carried out in the warp, weft, and thick directions of the local areas of the non-penetrating bullet holes of the two types of composites to study the penetration process and damage patterns in the non-penetrating state. In the thickness direction, the annular stripes near the 3D-C bullet holes is relatively denser and more pronounced, which is related to the fact that shock waves propagate faster in angle-interlock fabrics and that more yarns are involved in the energy dissipation. Cross-sectional profiles of 2D-C and 3D-C illustrate that 2D-C damage areas are dominated by massive fiber compression shear damage in both the warp and weft cross-sections at the upper end of the bullet hole. The compression shear damage to the fibers at the upper end of the 3D-C perforations is less severe than in 2D-C, but the tensile deformation of the top layer fibers is clearly visible in almost every cut. At the same time, four main types of damage areas were obtained by observing and counting the damage morphology of the two types of composites, and they are the perforated zone of the polyurea layer (Zone 1), the zone where the broken piece is caught (Zone 2), and the zone where the left and right sides of the broken piece are subjected to shearing and stretching (Zone 3, Zone 4). it can be seen that along the weft and warp directions after chip penetration 2D-C accounted for 54.82% and 69.98% of the damage in Zone 2. Cross-sectional view of 2D-C and 3D-C. However, 3D-C accounts for relatively little of the damage in Zone 2, with the main areas of damage being Zone 3 and Zone 4.

Conclusion The study showed that the resistance of the UHMWPE/polyurea flexible composites to projectile penetration has a significant fabric structure effect. The ballistic limiting velocity of the angle-interlock fabric-reinforced polyurea flexible composite is increased by 4.9% compared to that of the laminated plain fabric-reinforced polyurea flexible composite of the same thickness. For the unpenetrated UHMWPE/polyurea flexible composites, the penetration process involves mainly polyurea wrapping around the projectile, shear punching and fiber tensile fracture damage. The main failure modes for laminated plain fabrics are shear punch plugging and delamination failure, which for angle-interlock fabrics are mainly fiber tensile deformation and tensile fracture damage.

Correlation of braiding parameters and mechanical properties of mechanically braided integrated esophageal covered stents

JIANG Bochen, WANG Yue, WANG Fujun, LIN Jing, GUO Aijun, WANG Lu, GUAN Guoping

Journal of Textile Research. 2023, 44(03):  88-95.  doi:10.13475/j.fzxb.20220702308

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Objective Minimally invasive intervention with esophageal covered stents is an important means of palliative treatment of esophageal stenosis. However, adverse events of conventional esophageal covered stents have often been reported in publications recently. A new mechanically braided integrated esophageal covered stent is designed and expected to overcome the shortcomings of the existing esophageal covered stent and become the next generation of innovative products, but its basic research is not sufficient.

Method A series of integrated esophageal covered stents were braided using integrated braiding technology by adjusting the point per inch (PPI), the diameter of nickel titanium alloy wire and the number ratio of the wire to PET yarns. Moreover, the mechanical properties and compliance of these covered stents were systematically studied, mainly discussing the structure-property relationship between the above braiding parameters and the radial compression force, elastic recovery rate, stress relaxation rate, diameter reduction rate and elastic straightening force of the covered stents.

Results The diameter of nickel titanium alloy wire is the main parameter affecting the radial compression force of the esophageal covered stent. Within the scope of this study, the larger the diameter of nickel titanium alloy wire, the better the radial support of the covered stent. Compared with 0.24 mm nickel titanium alloy wire, 0.20 mm and 0.22 mm nickel titanium alloy wires can meet the radial support force required for esophageal stent, and a larger nickel titanium alloy wire diameter reduced the flexibility of the covered stent (Fig.7), so the suitable nickel titanium alloy wire diameter should be 0.20-0.22 mm. PPI has less effect on the radial support and compliance of the covered stent (Fig.4), that when the PPI increases, the radial support of the covered stent is better. When the PPI is 40, the diameter reduction rate increases when it is bent (Fig.7), so the optimal PPI should be 35. The number ratio of the wire essentially refers to the content of nickel titanium alloy wire in the covered stent. The ratio is large, the content of nickel titanium alloy wire is high, and the radial support force of the covered stent is high (Fig.4). However, at the same time, that the diameter reduction rate and elastic straightening force of the covered stent increase, that is, the compliance decreases (Fig.7 and Fig.8). Therefore, the more suitable number ratio should be 1:3. It is comprehensively considered from the perspective of the properties of radial support, bending compliance and lumen conformation of mechanically braided integrated esophageal covered stent, that its optimal parameter combination included the diameter of nickel titanium alloy wire were 0.20 mm and 0.22 mm, PPI was 35, and the number ratio of the wire was 1:3.

Conclusion Correlations of braiding parameters and mechanical properties of mechanically braided integrated esophageal covered stents have been established by designing, braiding and characterizing a series of esophageal covered stents. Disclosure of the structure-property relationship may extremely facilitate and push the development of mechanically braided integrated esophageal covered stents, since braiding machines for producing large diameter ones are customized and high-cost. On the other hand, clinical needs for the mechanically braided integrated esophageal covered stents are versatile and personalized. Therefore, it is facilitated to design and produce customized covered stents for varying patients based on the results of the present work. If one needs a strong support covered stent, the first influencing factor considered should be the diameter of nickel titanium alloy wire. Likewise, if the permeability is firstly considered, then PPI should be selected to adjust first. The number ratio mainly affects the flexibility of the covered stents. To sum up, this study may provide an experimental basis for accelerating the commercialization of the mechanically braided integrated esophageal covered stent. It is expected that this study can provide beneficial reference for the further development of integrated esophageal covered stent products, and promote the personalized and precise treatment of esophageal covered stent in clinical practice.

Dyeing and Finishing & Chemicals

Structural changes and effects of bacterial community in bamboo retting

LI Yu, FU Jiajia, CAVACO-PAULO Artur, WANG Hongbo, GAO Weidong

Journal of Textile Research. 2023, 44(03):  96-103.  doi:10.13475/j.fzxb.20211202308

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Objective Bacteria produce enzymes, which can hydrolyze the ingredients from bamboo. Based on this understanding, the water-retting process is adopted to extract bamboo fiber bundles. Changes in the bacterial community structure of the water-retting liquid are investigated to reveal key functional bacteria in bamboo-retting process and to obtain high-quality bamboo fiber bundles within less time.

Method The images of the cross-section and longitudinal structure of bamboo fiber bundles were recorded by the optical microscope, and the main chemical components of bamboo fiber bundles, such as cellulose, hemicellulose, lignin, and pectin, were evaluated and compared with that of un-retted bamboo culms. High-throughput sequencing and culturable methodology were adopted to explore the dominant strains during bamboo retting. Furthermore, the changes in morphology and chemical components of bamboo were characterized to analyze the effect of bacterial community during the retting.

Results The obtained bamboo fiber bundles are composed of many single fibers which are as long as the un-retted bamboo culms. The cellulose content in bamboo fiber bundles increases by 6.56%, while the lignin content declines by 4.01% relative to un-retted bamboo culms(Tab.1). High-throughput sequencing results (Tab.2) provide 39636-57850 sequences, which are classified as 483-900 operational taxonomic units (OTUs) at the similarity level of 97%. Alpha diversity of retting liquid shows high microbial diversity in all the flora. From Fig.3 and Tab. 3, 14 phyla and 25 genera are detected from 6 samples collected at different retting time periods. At the phylum level, about 99% of the sequences belong to Proteobacteria and Firmicute. Also, Firmicute reaches the highest relative abundance of 29.25% on the 18th day of retting. Pseudomonas and Enterobacter with lignin-decomposing capability are founded as the dominant bacterial throughout the retting at the genus level. The abundances of other lignin-decomposing bacteria (Sphingomonas and Acinetobacter) are higher in the first six days. The bacteria related to the fermentation of bamboo culms belongs to Lactococcus, which is only detected on the 3rd day of retting. As the retting goes on, the abundances of Stenotrophomonas, Clostridium sensu stricto, and Clostridium IV appear to rise, resulting in the hydrolysis of hemicellulose and cellulose. The bacteria that can degrade pectin belongs to Ralstonia, taking a proportion of 10.97% on the 21st day of retting. When the bamboo powder is used as the only carbon source, 5 strains are able to multiply and account for 0.70%-3.21% of the total bacteria community at the genus level (Fig.4). Serratia marcescens and Bacillus subtilis subsp. Subtilis are regarded as key functional bacterial and these strains effectively degrade non-cellulose compounds with the cooperation of Citrobacter sp. and Klebsiella oxytoca. Macromolecule lignin in bamboo is broken into small molecules by Serratia marcescens and Citrobacter sp., and then decomposed by Bacillus subtilis subsp. Subtilis and Klebsiella oxytoca. With the degradation of lignin, Bacillus subtilis subsp. Subtilis can efficiently attack hemicellulose and pectin in the internal structure of bamboo. However, strains that can swell the bamboo culms are lacking among the culturable bacteria.

Conclusion Lignin degradation is crucial to bamboo retting. Bamboo fiber bundles in any required length can be obtained by retting with the purpose to meet the needs for subsequent processing. In all the flora, Pseudomonas and Enterobacter are the predominant bacteria and contribute to decomposing lignin, but they could not take advantage of bamboo powders as the only carbon source. Among the culturable bacteria, Serratia marcescens and Bacillus subtilis subsp. Subtilis are the primary bacteria, acting on the degradation of non-cellulose components. At the early stage of retting, bamboo swelling is not enough, so a combined treatment with pretreatment and complex use of dominant strains may efficiently improve the bamboo fiber extraction.

Structure of polylactide/poly(3-hydroxybutyrate-co-3-hydroxylvalerate) blend fibers and dyeing properties for their fabrics

QIAN Hongfei, KOBIR MD. Foysal, CHEN Long, LI Linxiang, FANG Shuaijun

Journal of Textile Research. 2023, 44(03):  104-110.  doi:10.13475/j.fzxb.20220202107

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Objective In order to improve the heat resistance and flexibility of polylactic acid (PLA) fibers, the polylactide (PLA)/3-hydroxybutyrate-co-3-hydroxyl valentate (PHBV) blend fibers is one of the wildly used methods which received increasing attention. The literature for their preparation process, microstructure and mechanical properties were frequently found. But the relationship between the microstructure and dyeing properties lacked systematic investigation. The aim of this work is to explore the effect of structure for PLA/PHBV blend fibers on the dyeing properties of disperse dyes for their fabrics with a comparison to that of PLA fibers.

Method By using the thermal weight, differential scanning calorimeter and X-ray diffraction methods, the crystallization and thermal properties including glass transition, melting temperature and thermal stability for the PLA/PHBV blend fibers and PLA fibers were investigated, respectively. The dyeing properties such as dyeing rate, build-up and color fastness of two fabrics were measured with three different types of disperse dyes which corresponded to the grades of low, medium and high energy, respectively.

Results The analysis of X-ray diffraction showed that the pattern of peaks (16.74°, 19.30°) for the PLA/PHBV blend fibers was similar to that for the PLA fibers (16.68°, 18.90°) except a small peak at 13.82° being found (Fig.2). The crystallinity for PLA component (83.16%) was larger than the PLA fibers (77.14%). Based on the results obtained from previous research, it was confirmed that there were microphase separation between PLA and PHBV component, the small diffraction peak was derived from the PHBV component, which formed lower crystallinity. The measurement of the differential scanning calorimeter revealed that the glass transition temperature of the PLA / PHBV blend fibers (72.21 ℃) was slightly lower than that of the PLA fibers (74.85 ℃) (Fig.3), while the melting temperature (167.46 ℃) was slightly higher than that of the PLA fibers (166.35 ℃). The analysis of thermal weight illustrated that the thermal decomposition for the PHBV component in blend fibers occurred at the temperature of 280.67 ℃, and at 358.39 ℃ for PLA component, which was higher than that for the pure PLA fibers (343.30 ℃), which may be caused by its higher degree of crystallinity (Fig.4). In addition, the results for dyeing properties showed that the blend fiber has a lower dyeing transition temperature (T_D) than the PLA fibers, and can reach the dyeing equilibrium at a lower temperature (Fig.5). In the case of high-energy grade disperse dyes, the Dyeing transition temperature (T_D) was 70 ℃ for the blend fibers and 80 ℃ for the PLA fibers, and the temperature of dyeing equilibrium was 100 ℃ for the blend fibers and 110 ℃ for the PLA fibers. Under the same dyeing conditions, the apparent color depth value of the dyed blend fabric was almost twice that of the dyed PLA fabric (Fig.6), and its soap washing fastness performance was not good enough as the PLA fibers, especially for the staining fastness on wool, nylon and acetate fibers was only 1-2 rate (Tab.1).

Conclusion It was concluded that two components in blend fibers were in the form of microphase separation,the PLA phase had a similar crystal structure and a higher crystallinity compared to that of the PLA fibers, and the PHBV phase formed a small number of crystal structures. Therefore, PLA / PHBV blend fibers had a slightly higher melting point and lower glass transition temperature than PLA fibers, while PLA components had higher decomposition temperatures than PLA fibers, but the PHBV component was lower than the PLA components. Owing to the lower glass transition temperature, the blend fibers exhibited a higher dyeing rate than the PLA fibers. Under the same dyeing conditions, the color of the fabric derived from PLA/PHBV blend fibers was deeper than that of PLA fabric, and the apparent color depth value of the former was generally about 2 times that of the latter due to higher amorphous area in blend fibers. The color fastness properties for the fabric from the blend fibers was not desirable. Further research is needed to improve its dyeing properties to promote the development and application of these biodegradable fibers.

Preparation of catechin complex dye and its dyeing properties on silk fabric

QI Di, DING Hong, WANG Xiangrong

Journal of Textile Research. 2023, 44(03):  111-118.  doi:10.13475/j.fzxb.20220303008

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Objective The application of natural dyes in textile printing and dyeing has attracted extensive attention because of their non-toxic and harmless characteristics. In order to improve the color yield and color fastness of plant dye dyeing products, mordant dyeing treatment is often needed in the dyeing process, but this will lead to long dyeing process and a large number of metal ions in wastewater. Metal ions were introduced into natural dye molecules in advance through complexation reaction to prepare metal complexed plant dyes, and their dyeing properties and influencing factors on textiles were studied in detail. These studies were deemed necessary for developing short dyeing process with natural dyes and achieving energy saving and emission reduction.

Method In this paper, catechin-iron ion complex dye C-Fe was prepared by hydrothermal method through the coordination reaction between catechin and metal ion Fe²⁺. Fourier transform infrared spectroscopy (FT-IR), ultraviolet visible spectrophotometer (UV-VIS), scanning electron microscope energy spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) were adopted to characterize and analyze the structure of the complex dyes. The dyeing of a silk fabric with iron ion complexed catechin was studied by grinding dispersion method. The influences of technological parameters such as pH value, dyeing temperature and dye dosage on the K/S value of textiles were analyzed, and the technological conditions were optimized.

Results Energy spectrum analysis of plant complex dyes showed that the C-Fe molecules contained not only C and O elements, but also Fe elements(Fig.2, Tab.1). Based on the energy spectrum scanning component element content analysis and the structure analysis of the complex dye, the complex ratio of C-Fe molecule was calculated as 1:2. UV-VIS spectrum analysis showed that the maximum absorption wavelength of catechin was red shifted after complexation with metal ions, which was consistent with the law that the UV-VIS spectrum of dye molecules moved to the long wavelength direction caused by the attraction of metal ions to electrons (Fig.3). IR spectrum analysis showed that the complex dye C-Fe produced a new absorption peak at 556 cm^-1, indicating that it was the stretching vibration peak of Fe—O bond formed after coordination (Fig.4). X-ray photoelectron analysis showed that the peak position of Fe element was found at 706.7 eV for the complex dye C-Fe (Fig.5). The coordination of metal ions had different effects on the whole molecular chemical environment. The complex dye occurred on the adjacent hydroxyl groups or the adjacent hydroxyl groups and carbonyl groups of the benzene ring (Fig.6, Fig.7, Tab.2 and Tab.3).

A complex dye suspension with an average particle size of 405.47 nm was obtained by grinding and dispersion (Fig.8). The test showed that the optimal process parameters for dyeing silk fabrics with complex dye C-Fe were pH value of 4, dyeing temperature of 90 ℃, and temperature maintaining and continuous dyeing for 60 min (Fig.9, Fig.10 and Fig.11). The color fastness to sunlight and rubbing of silk fabrics dyed with complex dye C-Fe reached grade 3, and the color fastness to perspiration and soaping were all above grade 4 (Tab.4). The UPF value of silk fabrics dyed with complex dye was 72, reflecting excellent ultraviolet protection performance (Tab.5).

Conclusion In this paper, plant complex dyes were prepared by the coordination reaction between plant dyes and metal ions, and then the silk fabric was dyed with good dyeing effect, and the fabric demonstrated good color fastness and UV resistance. The experimental results show that the preparation of plant complex dyes from plant dyes as raw materials is feasible for textile dyeing. It is expected to be developed as a short process technology for plant dye dyeing, which provides a theoretical basis for the development of metal complex natural dyes and their application in textile dyeing.

Dyeing properties and adsorption kinetics of oak leaf extract on tussah silk

JIA Yanmei, YU Xuezhi

Journal of Textile Research. 2023, 44(03):  119-125.  doi:10.13475/j.fzxb.20220102907

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Objective This study fabricates functional textiles from biological sources using waste plant resources, and the dye was extracted from waste oak leaves. Tussah silk was dyed with oak leaf extract for making ultraviolet (UV)-resistant ecological textiles, which has a significance for the green and sustainable development of the textile industry. The kinetic mechanism of dyeing tussah silk with oak leaf extract was investigated, the dyeing kinetic curve was measured, the pseudo-first-order and pseudo-second-order kinetic equations were fitted, and the thermodynamic parameters were calculated.

Method This study extracted a natural dye solution from oak leaves (Dandong) with deionized water as the extraction solvent. The dyeing properties of oak leaf extract on tussah silk fabric under different conditions were explored by dip dyeing, and the color fastness and UV resistance were measured. The dyeing kinetics curves of oak leaf extract on tussah silk were drawn (70-90 ℃), and the dyeing kinetics parameters were calculated.

Results The influence of dyeing parameters on the dyeing properties of tussah silk fabrics dyed with oak leaf extract was discussed. When the dyeing temperature increased, the K/S values of dyed tussah silk were increased, the L ^*value decreased, and the a^*and b^* values increased, with 98 ℃ identified as optimal dyeing temperature (Tab.1). When the pH were changed from 3.0 to 7.0, the K/S values of the dyed samples were gradually decreased, the L^* value progressively increased, and a^*and b^* values decreased (Tab.2). The K/S values of the dyed samples were increased with the time, and the appropriate dyeing time was found to be 60 min (Tab.3). Moreover, the building-up property of oak leaf extract displayed that K/S values of the dyed tussah silk gradually increased with the dye dosage increasing, and the K/S values tended to increase slowly when the dye dosage was 6.25% (o.w.f)(Fig.3). The results demonstrated that the pseudo-first-order kinetic model was unsuitable for describing the adsorption process (Fig.6 and Tab.1). The pseudo-second-order kinetic fitting curves and parameters calculation results (Fig.7 and Tab.5) exhibited R²>0.99 which was higher than those of the pseudo-first-order kinetic models. Therefore, the adsorption process of oak leaf extract on tussah silk could be accurately described by the pseudo-second-order kinetic equation. The color fastness of tussah silk fabric dyed with oak leaf extract revealed that all the measured color fastness were rated above 3 (Tab.6). In addition, the UV resistance property of tussah silk fabric suggested that the UV transmittance of dyed samples was significantly lower than the undyed sample (Fig.8). The UV protection coefficient (UPF) value of dyed tussah silk fabric reached more than 40 when the dye dosage was more than 7.5% (o.w.f).

Conclusion 1) The optimal dyeing conditions for oak leaf extract on tussah silk were as follows: pH value was 3.0, and dyeing at 98 ℃ for 60 min. The oak leaf extract exhibited good building-up property on tussah silk and could obtain deep color without medium treatment. The color fastness to washing, rubbing and the light was rated above 3.2) The adsorption kinetics study illustrated that the adsorption mechanism of oak extract on tussah silk was consistent with the pseudo-second-order kinetic model. Dyeing rate constant and equilibrium adsorption capacity were increased with temperatures and the half-dyeing time decreased.3) Compared with undyed tussah silk, the UV transmittance of dyed tussah silk was decreased prominently, the UPF value was increased, and the dyed samples had good UV protection performance. When the dye dosage was higher than 7.5% (o.w.f), the UPF value of tussah silk could reach above 40.

Wear performances of cotton fabrics reactive-dyed in salt-free waste cooking oil-water system

QI Haotong, ZHANG Linsen, HOU Xiuliang, XU Helan

Journal of Textile Research. 2023, 44(03):  126-131.  doi:10.13475/j.fzxb.20210504006

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Objective Conventional aqueous phase dyeing produces a large amount of wastewater containing high concentrations of dyes and salts. A new waste cooking oil-water two-phase dyeing system was investigated to prove the effectiveness in cotton dyeing, and the minimal discharge of hydrolyzed dyes, salts and alkali.

Method An oil-water two-phase dyeing system and a conventional aqueous dyeing system were adopted to dye cotton fabrics. Wear performances include capillary adsorption, combustion behavior, kubbing resistance, wrinkle-recovery behavior, water vapor permeability, moisture regain, and hand feeling of fabrics dyed in the two systems were studied and compared.

Results Wicking heights of two-phase dyed cotton fabric are about 10% and 20% lower than their water dyed counterparts in both warp and weft directions, respectively. A small amount of oil may remain in the fiber interior, causing plug of the capillaries. Continuous burning time of two-phase dyed cotton fabric are slightly shorter than that of aqueous dyed cotton fabric. Smoldering time of two-phase dyed cotton fabrics were (8.14 ± 0.58)s and (7.90±1.43) s, respectively, and that of aqueous dyed cotton fabric were (7.70 ± 0.67) s and (8.24 ± 0.61) s, respectively. The limit oxygen index (LOI) of two-phase dyed cotton fabric was (17.60±0.05)%, close to (17.85±0.06)%, the LOI value of aqueous dyed counterparts. With regard to wear resistance, two-phase dyed cotton fabric resembled aqueous dyed cotton fabric with 24±2 and 25±2 cycles, respectively. The warp and weft elastic recovery angles of two-phase dyed cotton fabric are (68.32 ± 10.98)(°) and (65.80 ± 8.31)(°), respectively, higher than the angles of aqueous dyed cotton fabric are (57.92 ± 9.97)(°) and (54.92 ± 11.78)(°), respectively. Recovery angles of two-phase dyed cotton fabric are (62.14 ± 7.23)(°) and (54.10 ± 8.80)(°), respectively, also moderately higher than that of aqueous dyed cotton fabric. Moisture regain of two-phase dyed and aqueous dyed cotton fabrics are (8.75±0.84)% and (9.59±0.23)%, respectively, while moisture transmittance of two-phase dyed and aqueous dyed cotton fabrics are (3 827±453) and (2 562 ± 136) g/(m²·24 h), respectively. Overall hand feeling indices of two-phase dyed and aqueous dyed cotton fabrics are 0.60±0.02 and 0.58±0.02, respectively, indicating similar hand feeling of the two fabrics.

Conclusion In general, although there were some slight differences in wear performances and hand feeling between cotton fabrics dyed in a two-phase system and an aqueous system, most of the properties could meet the industry standards.

Color characteristics of Qianlong palette based on chromaticity measurement

SU Miao, ZHOU Kaili, DUAN Yiting, LU Jialiang, YANG Limei

Journal of Textile Research. 2023, 44(03):  132-138.  doi:10.13475/j.fzxb.20211203107

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Objective In order to gain more accurate and scientific understanding of the color of Qing dynasty silk cultural relics, this research attempts to analyze the color data of Qianlong palette from the perspective of chromaticity, and to provide a reference for the exhibition and digitalization of Qing dynasty silk cultural relics.

Method The Qianlong palette were measured with spectrophotometer CM700D, and then the color difference caused by the change of dye concentration and the stability of Qianlong palette were discussed. The colors of Qianlong palette were analyzed in L^*a^*b^* color space. By comparing the color gamut of Qianlong palette with that of sRGB, Adobe RGB and CMYK, the possibility of color restoration in the digitalization of silk relics in the Qing dynasty was analyzed.

Results It is found that when dye concentration increased, the lightness of all Qianlong palette colors decreased, but the change of chroma was inconsistent, where the chroma of green and purple decreased and the chroma of red increased (Tab. 2). In addition, when the dye concentration is increased uniformly, the color difference does not change uniformly. When the dye concentration changes, the green system of the Qianlong palette is greatly affected by the dye concentration, while the yellow system is less affected by the dye concentration. The average color difference between yellows dyed with different dye concentrations is less than 3 (Fig.2). Three repeated measurements of Qianlong palette within five months showed that Qianlong palette was stable within half a year under the natural conditions used for this study. In 42 colors Qianlong palette, the range of a^* is from -18 to 47, and the range of b^* is from -22 to 74, while in the extended 210 colors Qianlong palette, the range of a^* is from -18 to 47, and the range of b^* is from -23 to 78 (Fig.3). Comparing 42 colors Qianlong palette with 210 colors Qianlong palette, it was found that for the same dyeing process, changing only the dye concentration cannot broaden the maximum parameter range of a^* and b^*, but it greatly enriches the number of colors within the parameter range. In addition, it was found that there is an obvious color loss in the third quadrant of a^*b^* diagram. Converting (L^*, a^*, b^*) to (L^*, C^*, h), it can be seen that the hue of missing color is in range of 170°—240°(Fig.4), revealing the comparison results between the Qianlong color gamut and sRGB, Adobe RGB and CMYK. Most of the colors of the Qianlong palette are in these three color gamut, but some high chroma and lightness yellow colors exceed the gamut (Fig.5). The number of colors beyond Adobe RGB is small, and the number of yellow colors beyond sRGB is the largest, accounting for 38% of the yellow system.

Conclusion The yellow of Qianlong palette is less affected by the dye concentration, while the green is more affected by the dye concentration, and it would be more likely to make mistakes when dyeing green in Qing dynasty. In the silk cultural relics handed down in the Qing Dynasty, if the color recorded on the two fabrics is green, but the colors look different, it is necessary to consider not only the possibility of fading, but also the possible deviation in dyeing at that time. In addition, the Qianlong palette has an approximate range of a^*, b^* values, the color beyond this range was proven to be difficult to achieve in the Qing dynasty. Through strict color management and color, most of the silk relics of the Qing dynasty can display colors correctly in sRGB, Adobe RGB and CMYK. However, part of the high lightness and high chroma yellows of Qianlong palette are out of the gamut of sRGB, Adobe RGB and CMYK. Therefore, the color of these handed down silk relics of the Qing dynasty with yellow background may be distorted when they are displayed online, so it is suggested that these relics be displayed offline.

Release curve of nicotinamide from viscose fabrics and its model fitting

ZHU Weiwei, LONG Jiajie, SHI Meiwu

Journal of Textile Research. 2023, 44(03):  139-146.  doi:10.13475/j.fzxb.20210911508

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Objective Supercritical carbon dioxide fluid (SCF-CO₂) is a new green processing and high-efficiency finishing technology, nontoxic, nonflammable and can be recycled, which have been used to impregnate the drug into polymer matrix in biomedical field widely and is superior to the traditional finishing technology. In order to fabricate bioactive textile with good bioactive drug release property through SCF-CO₂impregnation processfor increasing the added value of clothing fabrics, it is necessary to analysis the variation and influence factors of release property of drug from bioactive textile fabricated by SCF-CO₂.

Method The bioactive drug nicotinamide with skin whitening, nourishing was used as the model drug, and viscose fabric was used as the substrate. Nicotinamide-loaded bioactive viscose fabrics processed by SCF-CO₂ under different temperatures (60, 70 and 80 ℃) and different pressures(12, 16 and 20 MPa), which were placed in the same release medium and measured the drug release amount in specific time by ultraviolet spectrophotometer. Ethanol was regarded as the release medium. Finally, the release curves that the drug release amount varied with time were drawn. The drug loading capacity was also measured. Besides, the release curves were fitted by different release models.

Results A higher absolute release quantity and a higher absolute release rate are obtained respectively when the supercritical CO₂(SCCO₂)temperature is 80 ℃, compared to 60, 70 ℃ of SCCO₂ temperature. Besides, the drug loading capacity increases with increasing SCCO₂temperature and the values are 6.165 4, 6.617 2 and 8.936 7 mg/g per weight of raw viscose fabric respectively. A higher absolute release quantity and a higher absolute release rate are also obtained respectively when the pressures are above 16 MPa as illustrated, compared to 12 MPa of SCCO₂ pressure. The drug loading capacity also increases with increasing pressure and the values are 0.838 7, 4.955 3 and 6.617 2 mg/g per weight of raw viscose fabric respectively. A lower cumulative release percentage and a lower cumulative release rate are obtained respectively when the SCCO₂ temperature is 60 ℃, which have an increasing tendency with increasing SCCO₂ temperature, and the cumulative release percentage can be as low as 87.6% when it reaches the releasing equilibrium. On the contrary, a lower cumulative release percentage and a lower cumulative release rate are obtained respectively when the SCCO₂ pressure is 20 MPa, which have a decreasing tendency with increasing SCCO₂ pressure, and the cumulative release percentage can be as low as 87.3% when it reaches the releasing equilibrium. The R² of Korsmeyer-Peppas model for all the release curves of nicotinamide-loaded viscose fabric processed by different SCCO₂ temperature, pressure is much higher than Zero-order release model, Higuchi model, and the R²is above 0.935 39 as depicted in Tab.1 and 2. Moreover, the corresponding diffusion index is generally below 0.45 except that the one processed under 60 ℃ of SCCO₂ temperature.

Conclusion The absolute release quantity and release rate of nicotinamide from viscose fabric are positively related to its loading capacity on the viscose fabric that vary with different SCCO₂ temperature and pressure. A higher loading capacity results in a higher absolute release quantity and a higher release rate. A lower cumulative release percentage and a lower cumulative release rate can be obtained when nicotinamide-loaded bioactive viscose fabric is processed by a lower SCCO₂ temperature or a higher SCCO₂ pressure. It means the cumulative release property is correlated to the density of SCCO₂. The release kinetics of nicotinamide-loaded viscose fabric processed by SCCO₂ are more consistent with Korsmeyer-Peppas model. Moreover, the diffusion behavior of nicotinamide from viscose fabric is mainly belong to Fick diffusion.

Efficient removal of polyvinyl alcohol and synergistic reduction of Cr(VI) from textile wastewater

LI Fang, PAN Hang, ZHANG Yaopeng, MA Huijie, SHEN Chensi

Journal of Textile Research. 2023, 44(03):  147-157.  doi:10.13475/j.fzxb.20220904111

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Objective Polyvinyl alcohol (PVA), a major sizing agent used in textile weaving, is eluted in the pretreatment of textile wet processing and becomes the main source of organic pollutants in textile wastewater. Meanwhile, textile industries sometimes adopt chromium-containing developers for the printing screen, leading to Cr(VI) pollution in the textile wastewater. The simultaneous treatment technology of high concentration of PVA and highly toxic Cr(VI) in printing and dyeing wastewater is of great concern. Persulfates can initiate the free radical crosslinking of the polymeric chain, which is considered as one of the solutions for the crosslinking-induced precipitation of PVA. Additionally, under high temperature and acidic conditions, PVA can reduce Cr(VI) to Cr(III) which is less toxic. Thus, in the thermally activated persulfate system, with the rapid precipitation of high concentration of PVA, the effective reduction of Cr(VI) becomes possible.

Method To achieve the simultaneous removal of PVA and Cr(VI) from wastewater, persulfate (K₂S₂O₈) was chosen as free radical crossling initiator. Simulative wastewater containing the high concentrations of PVA (10 g/L) and the coexisting Cr(VI) was the object of treatment. The thermal activation was used to activate K₂S₂O₈ because desizing wastewater is often processed at high temperatures (70-80 °C) and Cr(VI) is more easily reduced under high temperature. The remoal performance of PVA and chemical oxygen demand(COD) and the reductive efficiency of Cr(VI) were studied, with specific attention paid to the performance of free radical-induced crosslinking of PVA and the production of free radicals and explored the critical factors controlling their efficacy by electron spin-resonance spectroscopy (ESR). In addition, the possible underlying mechanism was studied using X-ray photoelectron spectroscopy (XPS), gel permeation chromatography (GPC), and gas chromatography-mass spectrophotometry (GC-MS).

Results The K₂S₂O₈ dosage, reaction temperature, and pH value of the solution were the key factors affecting the removal efficiency of PVA and Cr(VI). When the concentration of K₂S₂O₈ was 8.0 g/L, the reaction temperature was 70 °C and the pH value of wastewater was less than 6, the COD value of simulated printing and dyeing wastewater were reduced from 18 000 to 1 458 mg/L with a removal rate of 91.9%, the removal rate of PVA could reach 98.0% and the reduction rate of Cr(VI) was 94.3%. As a crosslinking agent, K₂S₂O₈ can induce the generation of PVA carbon radicals and promote the effective crosslinking. Meanwhile, the oxidation of —OH groups of the PVA polymer could enhance the production of $\mathrm{O}_{2}^{.-}$ radicals. This property which is analogous to catalyst could effectively promote the crosslinking of PVA. In addition to the reduction property of PVA itself, the reactive oxygen species(ROS) such as $\mathrm{O}_{2}^{.-}$ produced from the process of inducing radical cross-linking of PVA can also reduce Cr(VI) to Cr(III).

Conclusion Based on the free radical cross-linking technologies for polymers, a synergistic treatment technique for PVA and Cr(VI) pollutants removal using thermally activated persulfate system was proposed. The radical induced cross-linking and the reducibility of PVA under high temperature is found to be the main reason for efficient precipitation of PVA and synergistic reduction of Cr(VI), which has a certain application prospect in the treatment of textile wastewater. The advantages of this technology are as follows. 1) The thermally activated K₂S₂O₈ can efficiently induce the radical based crosslinking of PVA and promoted the precipitation. 2) As a strong oxidant, K₂S₂O₈ can oxidize the hydroxyl groups in PVA to promote the crosslinking efficiency. 3) The oxidation of —OH groups of the PVA polymer can enhance the production of ROS, which facilitates the simultaneous reduction of coexisting Cr(VI). Under optimal conditions, the maximum removal efficiencies of PVA and COD reached 98.0% and 91.9%, and the reduction rate of Cr(VI) was 94.3%. This process is technically highly efficient and cost effective, and provides new insights for the simultaneous treatment technology of high concentration of PVA and highly toxic Cr(VI) in printing and dyeing wastewater.

Apparel Engineering

Parametrical modeling of sewing process for automatic stitching of garment fabrics

WEN Jiaqi, LI Xinrong, LI Xingxing, WU Liubo

Journal of Textile Research. 2023, 44(03):  158-167.  doi:10.13475/j.fzxb.20220102410

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Objective In order to improve the sewing quality of garments and to solve the current problem of matching fabric properties and sewing processing parameters by skilled workers in sewing relying only on experience, this research selects sewing processing parameters that match fabric properties by establishing a mathematical model of the multi-force field coupling of fabrics in the sewing process, which not only realizes an unmanned and automated production method in the garment industry, but also meets the future trend of multi-batch and multi-variety development in the garment industry.

Method In this research, a structural model of a weft knitted fabric is established followed by an investigation on the influence of the holding force between fabric tissue and yarn on the piercing process of the sewing needle. A novel force-field coupling model is developed based on the mechanical properties of the fabric during the sewing process. A finite element model of the fabric and a geometric model of the sewing needle are developed to verify the correctness of the multi-field coupling model, and a collaborative automatic sewing platform is built to verify the matching between the fabric and the sewing process parameters based on the multi-position coupling model.

Results Larger the needle size resulted in greater frictional resistance of the fabric to the needle. It revealed the puncture force varies with the needle gauge when sewing on the same fabric (Tab.2), and with different fabrics at the same needle gauge. The strain produced by the same needle gauge when piercing fabrics varied with different Poisson's ratios (Fig.11). The strain increased with the increase in the Poisson's ratio, and the largest strain of 0.106 mm was found for a Poisson's ratio of 0.25 and the smallest strain of 0.095 mm for a size 12 needle. On the experimental platform, six knitted weft fabrics were tested using six different pressures and tensile forces, and the relationship between them was described in two sets of graphs (Fig.14(a) and Fig.15(a)), the higher the coefficient of friction, the higher the frictional force to which it is subjected. The higher the coefficient of friction of the fabric, the higher the resulting frictional force and the higher the strain that occurs when the fabric was subjected to the same pressure (Fig.14(b) and Fig.15(b)). It shows the numerical models of the relationship between the tensile force applied to the fabric and the deformation it undergoes in the form of force-deformation curve (Fig.14(c) and Fig.15(c)). As the Poisson's ratio of the fabric increases, the results indicated that the greater the amount of strain was produced for the same tensile force. The fabric sewing shrinkage curves are shown (Fig.16). When comparing the same tensile strengths, No. 12 has the greatest effect on the sewing shrinkage of the fabric and No.11 has the least effect on the sewing shrinkage of the fabric. When comparing adjacent tensile strengths, the sewing shrinkage of the fabric changes significantly when the fabric was subjected to tensile strengths between 100 cN and 150 cN, while the sewing shrinkage of the fabric changes less when the tensile strength was between 150 cN and 200 cN. The sewing crinkle rate tends to increase when the pulling force was greater than 200 cN, indicating that the use of a pulling force greater than 200 cN stretches the fabric and causes the fabric to suffer from excessive pinholes.

Conclusion The greater the radius of the sewing needle when piercing the fabric, the greater the holding force of the yarns during the sewing process, the tighter the fabric structure, and the greater the sewing resistance. Applying a certain amount of tension during the sewing process changes the density of the fabric, thus moderating the effect of the holding force of the yarns and the frictional resistance on the sewing needle. The tension applied to the fabric during the sewing process has a greater impact on the sewing quality of the fabric, and by applying different tensions to different fabrics and choosing the sewing conditions reasonably, the quality of the sewing can be improved and the shrinkage rate of the fabric reduced. In contrast to workers' experience in sewing fabrics with needles and the study of fabric stress and fabric deformation during sewing, modelling and selection of suitable processing parameters for sewing fabrics on a collaborative automatic sewing experiment platform can improve the quality of fabric sewing and provide data for future sewing processes in fully automatic and unmanned production lines.

Human contour and parameter extraction from complex background

GU Bingfei, ZHANG Jian, XU Kaiyi, ZHAO Songling, YE Fan, HOU Jue

Journal of Textile Research. 2023, 44(03):  168-175.  doi:10.13475/j.fzxb.20220102308

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Objective For the collection of human body images in non-contact two-dimensional measurement systems, most of the early studies reduced the difficulty of human contour extraction by means of restricting the shooting background. In order to acquire human contour and parameter information quickly and easily from photographs with a complex background, this study proposes the use of holistically-nested edge detection (HED) deep learning model to achieve the extraction of human contours and perform parameter extraction analysis.

Method A training set of 43 200 images was established by creating a human contour label map, data enhancement and pre-processing with 450 human photos with different backgrounds as the original image dataset. A deep learning network model was used for training and learning, and the optimal edge detection model was constructed after repeated training and tuning to achieve automatic human contour extraction. In addition, in order to verify that the extracted human silhouette form is consistent with the real human form, 13 human parameters are selected for error analysis.

Results After training and tuning the deep learning model to obtain the optimal model for human contour extraction, the test-set images were subsequently output (Fig.5), which shows that the optimized HED network model training extracteds clear human contours without other cluttered background information, but the human contour edge lines was thick. Therefore, the Zhang-Suen edge refinement algorithm was adoptrd to refine the human contours (Fig.5(d)). It can be seen that after the edge refinement, not only the edges of the human contour can be detailed and clear with no break in continuity, but also some non-human contour details in the original contour map can be removed to make the background cleaner. In addition, in order to verify the accuracy of extracting human contours, 40 subjects were selected and subjected to 3-D anthropometric measurements and 2-D photographs, respectively. Based on the human body photograph to extract the human body contour and feature point identification positioning, 13 measurements were extracted and compared with the corresponding 3-D point cloud manual measurements (Tab.3). It can be seen that the error range of 3 angle parameters are between 0.125 3°and 1.862 2°, and the error range of 10 ratio parameters are between 0.000 2 and 0.081 7. The data indicated that there was no significant difference between the contour measurements and the 3-D real values, and a high consistency was maintained between them, which further verified the feasibility and accuracy of extracting human contours based on 2-D photographs.

Conclusion This paper proposed a deep learning-based method for human contour extraction from complex backgrounds, use the HED network optimization model as the main framework to train and learn the human photo dataset, achieving the contour extraction and edge refinement of human photos based on complex backgrounds. Meanwhile, in order to verify the authenticity of the photo-extracted contours, 13 scale and angle parameters that can reflect the human body shape were selected, and error analysis was performed on the contour extraction values and 3-D point cloud measurements of 40 subjects. The results show that the improved HED network model can accurately extract clear and continuous human contours based on complex backgrounds with cleaner backgrounds; and there is no significant difference between the extracted values of contour-based parameters and 3-D point cloud measurements. This research proves the feasibility and accuracy of the method adopted in this research, and the research results can provide technical support for the research of non-contact 2-D measurement technology.

Personalized clothing matching recommendation based on multi-modal fusion

LIU Junping, ZHANG Fuhong, HU Xinrong, PENG Tao, LI Li, ZHU Qiang, ZHANG Junjie

Journal of Textile Research. 2023, 44(03):  176-186.  doi:10.13475/j.fzxb.20211106611

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Objective In the context of fast fashion, most consumers do not have the keen insight of professional designers on fashion clothing matching, which leads to their capability of quickly selecting a set of appropriate, harmonious and suitable clothing from a large number of clothing. In order to better improve users' online shopping experience and help them accurately express their unique personality characteristics, professional identity, status and other image positioning to the outside world, this paper aims to achieve high-precision recommendation by improving the clothing matching degree, so as to meet the huge demand of consumers for personalized clothing matching recommendation.

Method By studying the highly nonlinear complex attribute interaction from clothing color to category, and based on the quantitative standard of matching degree of clothing matching, an embedded model of the potential feature representation space of an item was built. By building a matrix decomposition framework model that integrates multimodal information, the shortcomings of existing multimodal feature fusion algorithms were further analyzed, and the clothing style preferences of different users were depicted. Through feature extraction, multimodal feature fusion match degree was calculated and other operations were carried out to establish personalized clothing matching scheme.

Results PCMF (personalized clothing matching recommendation based on multi-modal fusion) with some conventional clothing matching methods were qualitatively compared. Compared with all baselines, the clothing matching degree calculated by this model reached 0.81, which is 1.25% higher than the AUC (area under curve) value of conventional methods (Tab.2). It is confirmed that the transposition fusion method of text features and visual features used in PCMF improves the correlation between features, making the presentation of individual style more accurate. In order to compare the difference of contribution of different modal information to the matching degree of PCMF modeled clothing, experiments under three different modal combinations were conducted, i.e. PCMF-T (only exploring the text information of items), PCMF-V (only exploring the visual information of items), and PCMF-TV (exploring the visual and text information of items) (Tab.3). The AUC value of PCMF-T reached 0.775, higher than that of PCMF-V (0.763), indicating that the text information of the piece can more succinctly summarize the key features of the piece, such as patterns, materials and brands. PCMF-TV shows better performance than PCMF-T and PCMF-V, which indicates the necessity of combining multi-modal information of items, and verifies the effectiveness of adding user factors to the general clothing matching modeling to make personalized clothing matching recommendation. In order to effectively evaluate the practical application of the PCMF model, the PCMF model was deployed in the complementary item retrieval task (Fig.5). It is demonstrated that the PCMF model can complete the personalized clothing matching recommendation task according to the user's preferences. In addition, the MRR (mean reciprocal rank) measurement method was used as the evaluation index to further evaluate the model. PCMF performs better than other models regardless of the number of clothing candidates (Fig.6).

Conclusion Through the combination of IGCM (item-item general clothing match modeling) and UPCM (user-item personalized clothing match modeling), a personalized clothing matching recommendation model based on multi-modal fusion is constructed, which facilitates high-precision personalized clothing matching recommendation. Specifically, the purpose is to match a lower garment that not only has a good match with a given user's top, but also meets the user's taste. In general, the research results show the necessity and effectiveness of combining visual and text modal information and introducing user factors in personalized clothing matching recommendation and the practical application value of PCMF in real scenes is verified. In the future, the clothing matching recommendation problem of two examples will be transformed into a multi-instance learning problem to provide users with personalized package recommendation including shoes and accessories.

Influence of local electric heating on overall thermal response of human body in cold environment

ZHANG Zhaohua, CHEN Xue, NI Jun, YANG Yutong, ZOU Yifan

Journal of Textile Research. 2023, 44(03):  187-194.  doi:10.13475/j.fzxb.20211109608

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Objective Cold environments threaten the life and health of the human body, and active heating of the human body can reduce heat loss from the body in a cold environment. This research aims to explore the influence of local heating of various body parts on the local thermal sensitivity and overall thermal comfort in a cold environment, which provides a theoretical basis for the design of local electric heating garment against cold environment.

Method For the first part of the experiments, 12 subjects were invited to apply 8 body parts thermal stimulation (chest, back, abdomen, waist, hands, elbows, knees and feet) separately using carbon fiber heating patches in a chamber with temperature of 5 ℃ and relative humidity of 50%. The local skin temperature, the scores of thermal and comfort sensations were collected during the tests to calculate the local thermal sensitive level of each body part. The second part of the study were carried out by heating simultaneously two body parts located at the same sensitive level to examine the differences between single-area heating and two-areas heating.

Results The results of local electrical heating showed a significant difference in the heating demand among eight body parts (P<0.05), the order of influencing degrees on the overall thermal sensation (OTS) was ranked from highest to lowest as feet / back / chest / abdomen / waist / elbows / knees / hands, and heating the feet has the greatest influence on the OTS (the impact factor is 0.112). In terms of heating temperature, the skin temperature of each body part finally converged to 39.8 ℃ at the end of local heating, indicating that the local skin temperature tolerance value is 39.8 ℃ under the experimental conditions. The heating temperature of the heating patches at the end of local heating was defined as the local preference temperature, which was found in the range of 46-49 ℃ for the limbs and 43-46 ℃ for the torso. The eight body parts can be divided into three sensitive regions, namely the highly sensitive regions (upper back and feet), the medium sensitive region (chest, abdomen and waist) and the low sensitive region (elbows, knees and hands). The results of two-area heating revealed a significant effectiveness of combined heating two parts in highly sensitive regions over that of low sensitive regions, and the combined heating of high sensitive regions can achieve the full-body thermal comfort. The heating energy consumption of each part was abdomen (11.1 W), chest and back (11.5 W), waist (11.6 W), elbow (16.9 W), knee (17.0 W), hand (17.1 W) and foot (17.2 W), more energy was consumed to heat the limbs than torso for the same heating duration.

Conclusion For local heating of the stationary standing human body, heating the feet alone is the most effective way to improve the comfort of the human body in a cold environment, while heating other single body part cannot make the whole body reach thermal comfort. This finding suggests the necessity of the combined heating. Among them, the combination of heating the feet and back, chest and waist, waist and abdomen demonstrated a better effect in achieving the full-body thermal comfortable and satisfactory state. For comprehensive consideration of energy consumption, it is recommended heating the chest and waist, or waist and abdomen to save electricity. To avoid local scalding, the local skin temperature of 39.8 ℃ has been suggested as the reference for designing the local electric heating garment. The number of subjects can be further increased in subsequent studies, more heating sites will be selected, and the influences of gender, age, occupational characteristics on human local thermal sensitivity and heating preference will be comprehensively considered.

Characterization of lower extremity skin deformations based on biomechanical simulation of running motion

ZHANG Longlin, SHI Xi, ZHANG Min, ZHOU Li, LI Xinrong

Journal of Textile Research. 2023, 44(03):  195-200.  doi:10.13475/j.fzxb.20211204306

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Objective Skin deformation refers to the range of skin change measured when key body parts are in motion, including the value of skin surface change rate and the difference between each movement change rates. Obtaining the rules of skin deformation of different parts, which is in the subdivision curved surface of the static and dynamic model of running lower limbs, is to solve the design requirements of the clothing pattern design of running tight functional clothing. A reference is provided for the running pants, and also for design and improvement of related pants pattern.

Methods A biomechanical simulation system was adopted to analyze the muscle fiber dynamics of the lower limb muscles during periodic running, and a hand-held 3-D scanner was adopted to scan the skin of the lower limb for selected key frame movements. After analyzing the difference of skin deformation data and comparing with the static and dynamic human model subdivision surface, a more scientific and perfect scheme for acquiring the whole skin deformation was obtained.

Results The biomechanical simulation system was adopeed to analyze the muscle fiber active force of human lower limb muscles during periodic running (Tab.1). According to the systematic sampling method, 61 samples of muscle initiative data in one running cycle were selected and processed, and the muscle fiber initiative curve was obtain (Fig.1). The muscle with obvious mean of muscle fiber active force was selected, and the action corresponding to the time frame of its peak value was taken as the key frame action (Fig.2). The hand-held 3-D scanner was adopeed to scan the skin of the lower limbs in key frame movements. The skin deformation of the left and right sides of the body was taken into account to analyze the differences of the skin deformation data of the lower limbs in different movements. The transverse change rate of skin surface deformation was analyzed (Fig.4), and the longitudinal change rate of skin surface deformation was analyzed (Fig.5). Meanwhile, the dynamic and static subdivision surfaces of the human model were compared, and it was found that the changes of the body back from the hip circumference to the middle leg circumference area and the body front from the hip circumference to the thigh circumference area are the largest, and the changes of the area around the knee joint are the largest, too. The other areas show no significant changes (Fig.6).

Conclusion The dynamic and static human models are expanded and compared, which enables quick and effective observations of skin deformation of various parts of the human body. This method can be applied for multiple purposes. The rule of skin deformation in static and dynamic model subdivision surface contrast map is consistent with that of skin deformation calculated after measuring the area or length. At the same time, the rules of skin deformation obtained by the two methods can be verified with each other, which make the scheme of acquiring the whole skin deformation more scientific and perfect.

Comprehensive Review

Research progress in electrospun nanofibers in interfacial solar steam generation

HE Mantang, WANG Liming, QIN Xiaohong, YU Jianyong

Journal of Textile Research. 2023, 44(03):  201-209.  doi:10.13475/j.fzxb.20210700509

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Significance Solar steam generation is a method to generate steam from solar energy to obtain clean water resources which can convert solar energy into heat energy and solve the problem of clean water shortage with minimal environmental impact. Electrospun nanofibers have been used as the substrate of interfacial solar steam generator by means of its structural features. Electrospinning can provide nanofibers with high specific surface area to enhance the evaporation process, continuous fibers can transport water over long distances, which can ensure adequate water supply, and the porosity and pore structure of the film can be adjusted to achieve higher vapor diffusion by adjusting the parameters of the electrostatic spinning device. Moreover, many reports confirmed that the electrospun nanofiber-based evaporator can achieve seawater desalination, wastewater purification and other purposes by using interfacial solar steam generation.

Progress In this paper, four main ways of combining electrospun nanofibers with photothermal materials in two-dimensional nanofiber membrane and three-dimensional nanofiber aerogel evaporator were introduced, with their principles, properties and process methods systematically summarized. The performance of different types of solar evaporators using electrospun nanofiber-based was compared and discussed. It is showed that these evaporators can achieve a maximum evaporation rate of 3.81 kg/(m²·h) with a conversion efficiency of 90.1% and salt resistance of 99% under one sun irradiation. The conventional methods of two-dimensional surface modified electrospun nanofiber membrane, the principles of two-dimensional blending electrospun nanofiber membrane, two-dimensional Janus electrospun nanofiber membrane and three-dimensional electrospun nanofiber aerogel were scutinized. The surface modification of electrospun nanofiber membrane leads to many functional materials, such as loading conductive materials for sensors, spraying antibacterial agents for antibacterial properties, depositing photothermal materials to make solar steam generators. Surface modification is mainly divided into physical methods and chemical methods. Electrospun nanofiber membrane is prepared by mixing polymer and photothermal materials into uniform spinning solution through electrospinning. The preparation of Janus electrospun nanofiber membranes is generally carried out by surface modification on the upper and lower sides of the nanofiber membranes or by step spinning on different spinning fluids, so as to achieve the effect of different characteristics on both sides of the nanofiber membranes. Electrospun nanofiber-based aerogel is prepared by freeze-drying of nanofibers, photothermal materials and crosslinking agents in the nanofiber membrane. The three-dimensional aerogel prepared by nanofiber offers larger volume and higher specific surface area, which not only can improve the binding strength between nano-fiber and photothermal materials, but also fully improve the evaporation rate and salt resistance of solar evaporator.

Conclusions and Prospect The electrospun nanofiber-based solar steam generator makes use of the characteristics of electrospun nanofibers, enriches the combination of nanofibers and photothermal materials, and effectively expands the application of nanofibers in the field of photothermal energy. However, there are still some challenges, such as low strength, poor adhesion with photothermal materials and insufficient function, which limit the development of electrospun nanofibers in the application of solar steam generation. Practical application process of solar steam generator often faces issues such as complex water environment (such as seawater, acid and alkali wastewater) where strengthened adhesion between electrospun nanofibers and photothermal materials is necessary to impart multi-functions such as bacterial resisting and self-cleaning. The thickness of two-dimensional planar solar evaporator directly constructed by electrospun nanofiber membrane is small which makes the thermal management, and hence water supply and vapor diffusion in the process of water evaporation cannot be carried out faster. In order to solve this problem, solar steam generators need to focus on constructing two-dimensional nanofiber membranes into three-dimensional structures, optimize the structure design, and make full use of solar energy to improve the ability of photothermal steam conversion. In addition, photothermal materials and nanofibers still have problems such as high production cost and long technological process at present. It is believed that developing simple preparation methods and low-cost materials for high-performance solar steam generators represent a key perspective in future development.

Research progress in tissue engineering scaffolds by 3D bioprinting

WANG Shudong, MA Qian, WANG Ke, GU Yuanhui

Journal of Textile Research. 2023, 44(03):  210-220.  doi:10.13475/j.fzxb.20210705311

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Significance Tissue engineering is a new interdisciplinary field with great potential. It aims to solve the problems of repair, maintenance, improvement and replacement of tissue functions through the integration and innovation of engineering and life sciences. At present, planting functional cells into scaffolds with good biocompatibility and degradability, culturing in vitro for a period of time, and implanting into the body after maturation is the main way to repair or reconstruct tissue defects. 3D printing technology can synchronize the accumulation and forming of cells and biological materials, ensure the proliferation of cells in biological scaffolds and the transfer of nutrients and metabolic wastes, and have the advantages of stable structure and controllable shape, which is one of the most potential methods to realize the industrial manufacturing of tissue scaffolds. However, different from industrial 3D printing technology, 3D bioprinting requires special materials and processes, which are the basis for forming three-dimensional, porous network structures. In view of the characteristics of 3D bioprinting, this paper reviews the progress of 3D bioprinting technology, materials and applications for tissue engineering, so as to provide a reference for further promoting the development of 3D bioprinting technology for tissue engineering and the research in related fields.

Progress Based on the current 3D bioprinting methods and the formation mechanism of related materials, this paper reviews the research progress of tissue engineering scaffolds prepared by 3D bioprinting in detail. There are four categories of 3D bioprinting technology: inkjet printing, extrusion printing, laser assisted printing and stereo lithography. Inkjet printing ink has low density with long curing time, which tends to cause cell drying and death after printing. Extrusion printing with high viscosity may cause nozzle blockage. The combination of biological materials with good rheological and mechanical properties and natural materials with good biological properties can effectively solve this problem. Laser assisted stereo lithography avoids the problem of nozzle blockage, but it also has the problems of high cost and residual biotoxic materials. As for the 3D biological printing materials, biological ceramic materials and polymers are mainly introduced, including their characteristics, curing mechanism and the application range. Chemical modification of natural materials or combining them with synthetic polymers can effectively adjust the mechanical property and biocompatibility of scaffolds, such as meth acrylic anhydride, gelatin (GelMA) in recent years has become a commonly used material in 3D biological printing. As a densifier, polyethylene oxide (PEO) can not only improve the printability of GelMA and other materials, but also flexibly regulate the pore size and void structure of the printing scaffold because of the water solubility of PEO through removing it. Aiming at the application of 3D bioprinting, this paper mainly introduces the latest research progress of 3D bioprinting in the construction of functional tissues such as blood vessels, bone, ears and hearts, which provides theoretical and practical reference for further promoting the development of 3D bioprinting technology for tissue engineering.

Conclusions and Prospect This paper mainly introduced the 3D printing technology, materials and application and expounds the principles, operation process and the advantages and disadvantages of the inkjet printing, extrusion printing, laser assisted and stereo lithography printing technology. The technology problems such as speed, accuracy, cell survival and activity still need to be solved, especially for inkjet and extrusion biological print, in which cells are to be blocked by nozzles, and how to balance cell viability (requiring a large nozzle size) and printing accuracy (requiring a small nozzle size) is the main challenge. In terms of materials, the research of 3D bioprinting materials still has a great development space, including endowing materials with more abundant molding methods (such as light/thermal, physical/chemical double cross-linking, etc.) to improve their mechanical properties and printability, thereby improving the structural plasticity and stability of scaffolds. Based on the biomimetic principle, multi-material materials, cells and bioactive factors are combined to improve biocompatibility. Heterogeneous and gradient composite 3D bioprinting materials are expected to meet the needs of complex biological tissues. It will be an important research direction in the future to regulate the degradation properties of materials and further study the structure and properties of 3D bioprinted scaffolds with time. At present, although the use of 3D bioprinting technology has successfully constructed functional tissues such as blood vessels, bone, ears, and heart, its clinical application is still in the initial stage. How to maintain cell activity, achieve organ function reconstruction, and solve the internal vascularization problem will be an important development direction in the future. It is believed that with the continuous improvement of 3D bioprinting technology and materials, 3D bioprinting will bring revolutionary changes to tissue engineering.

Research progress in wearable electrochemical sensor for sweat detection

TANG Liqin, LI Yan, MAO Jifu, WANG Jun, WANG Lu

Journal of Textile Research. 2023, 44(03):  221-230.  doi:10.13475/j.fzxb.20210901210

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Significance Sweat as a typical body fluid for analysis can provide rich biochemical information and is easy to collect. Electrochemical sensors with the advantages such as easy miniaturization, high sensitivity, and low cost stand out from other sensors, and the detection of various body fluids by wearable electrochemical sensors can achieve a non-invasive and non-invasive, simple operation, integrated diagnosis and treatment, and personalized medical process. By reviewing the research of flexible wearable electrochemical sensors in sweat composition analysis and its application status, the integration of wearable electronic devices with textile field is promoted and the future development of smart textile technology is driven. It also drives the huge demand and potential of sweat wearable electrochemical sensors in molecular chemistry, analytical chemistry, medical-military and aerospace fields.

Progress This paper provides an overview of the advances in sweat extraction strategies, different analytes and electrochemical sensor substrate materials, respectively. Among them, sweat extraction strategies have evolved from conventional external stimulation or exercise sweating to microfluidic collection of sweat, even sitting still. For complex analytes in sweat, endogenous analytes are the initial targets for detection, especially glucose, a substance abundant in sweat, its sensors have been evolved from enzymatic to non-enzymatic, addressing the drawback that biological enzymes are easily inactivated. However, with the development of personalized medicine needs, monitoring the metabolic concentration of some oral or injectable clinical drugs in body fluids has become necessary. In addition to drug molecules, sweat detection of some prohibited drugs can also help police officers and other law enforcement. Finally, electrochemical sensor substrates were initially commonly used materials for rigid electrodes, and since the comfort of wearing them was greatly hindered, the construction of electrochemical elements on flexible substrates (polydimethylsiloxane, polyethylene terephthalate, etc.) was investigated, however, the most ideal was always textile-based materials that fit the human body perfectly, so the final development was to give textiles conductivity before constructing electrochemical sensors, which has led to significant progress in wearable e-textiles.

Conclusions and Prospect Nowadays, wearable devices are gradually evolving from single-modal sensing to multimodal sensing capabilities. They can detect signals such as strain, bioelectricity and pressure in the skin along with numerous markers in sweat. The integration of electrochemical sensors for multiple target substances also relies on external power supplies, circuit boards, etc., which increases the rigidity of the sensors to some extent and also requires the development of flexible, long duration power supply devices. Sensors constructed on flexible stretchable substrates mostly rely only on screen printing technology, with relatively poor conductivity and stability. Research on paper-based and textile-based electrochemical sensors is still in its infancy, and the poor electrical conductivity of substrates leads to low sensitivity for the detection of substances with low concentration, and high-precision, high-sensitivity textile-based wearable electrochemical sensors are yet to be tapped for innovation. In addition, the challenges for e-textile sweat biosensors in the textile and electronic fields remain the synthesis and construction of textile-based biosensing materials, skin-sensor interface design, and embedded wireless data acquisition and transmission. With the demand for multi-matter sensing, wearable e-textile devices need to focus more on breathability, portability, and performance stability, and also consider cost and simple and economical preparation strategies to make a long effort to realize wearable smart textiles.

Research progress of supervision and inspection system for recycling waste textiles

HAN Fei, LANG Chenhong, QIU Yiping

Journal of Textile Research. 2023, 44(03):  231-238.  doi:10.13475/j.fzxb.20211111408

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Significance The direct disposal of textiles for daily use leads to double pressures of environmental pollution and resource waste. Under the macro environment of national promotion for energy conservation and emission reduction and public participation in waste sorting, the recycling of waste textiles becomes a necessary condition for the sustainable development of the textile industry. Relevant policies were issued nationally, but the management of waste textiles was different from place to place. Coupled with the occurrence of market chaos, many consumers have insufficient understanding on recycling waste textiles, and low support for the products made from tecycled textiles. The quality of the recovered waste textiles and the quality of products from recycled textiles seem to be the key to the sound development of circular economy in the textile industry. With the aim to stabilize the quality of remanufactured products from waste textiles, standardize market order, and improve the credibility of the public, it was of great significance for a supervision and inspection system for recycling waste textiles to be established.

Progress According to an in-depth analysis of the present situation about the waste textiles legal system, waste textiles were classified as solid wastes, which are regulated by laws of environmental protection. Based on international experience and the present domestic situation of recycling, a strategy to further improve the system was put forward. It is more appropriate for waste textiles to be separated at the household level and collected separately. The existing standard system cannot fully cover the categories of remanufactured products. Some national mandatory standards explicitly prohibit the use of waste textiles, which hinders the re-use of waste textiles. The latest research achievements of the inspection and testing technology of waste textiles were described, including the application of infrared spectroscopy in sorting process and qualitative analysis of regenerated fibers. In some studies, it was found that infrared spectroscopy has good applicability in the rapid detection of cotton, polyester and wool/cashmere fibers in waste textiles, which is able to effectively improve the detection efficiency and reduce the labor cost. Furthermore, industry autonomy based on school uniforms, military uniforms and work uniforms was introduced. It is necessary to realize industry autonomy through the extension of producer responsibility.

Conclusions and Prospect The management of waste textiles in China is still at the primary stage of the legal system, and the quality control of waste textiles in standard specifications has not formed a close-loop management. Therefore, the laws and regulations of waste textiles need to be specialized and the standard specifications need to be systematized. The regulations on recycling of waste textiles should be formulated, the application of waste textiles should be widened, and the inspection and testing methods of waste textiles should be strengthened. For the future development trend of recycling waste textiles, the detection technology should be innovated with accuracy, timeliness and online as the main factors. The social supervision comes from the consciousness of the industry and even the whole people. Finally, the review pointed out that the legal system, standardization system and social supervision are whole, and accelerating the improvement of national environmental protection awareness is the key to promote the development of waste textiles recycling economy and realizing remote cloud automated production.