Table of Content

15 July 2023, Volume 44 Issue 07

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Fiber Materials

Synthesis and solid-state polymerization of flame retardant copolyester containing phosphorus side groups

SHANG Xiaoyu, ZHU Jian, WANG Ying, ZHANG Xianming, CHEN Wenxing

Journal of Textile Research. 2023, 44(07):  1-9.  doi:10.13475/j.fzxb.20220101601

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Objective Poly(ethylene terephthalate) (PET), as the major polyester material, has excellent performance but is flammable, and hence it is important to improve the flame retardant properties of PET to satisfy the requirement for various applications. Introducing phosphorus-based flame retardants into PET molecular chains by copolymerization is one of the effective flame retardant modification methods at present. The flame retardant copolyester produced by melt polymerization has a intrinsic low viscosity of 0.6-0.7 dL/g, which cannot meet the flame retardant specifications of copolyester in fields such as engineering plastics, bottles, and industrial filament. This research represents an effort to increase the intrinsic viscosity of copolyester by polycondensation so as to expand the applications.

Method The side group phosphorus-containing flame retardant 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl] 10-phosphorus-phenanthrene-10-oxide (DDP) was copolymerized into PET molecular chain to obtain copolyester (PETD). Nuclear magnetic resonance hydrogen spectroscopy(¹H NMR) and Fourier transform infrared spectrometer characterization methods were adopted to measure the success of copolyester synthesis. The intrinsic viscosity of copolyesters was determined by using viscosity test. The thermal stability, crystallinity, carbon formation capacity, flame retardant properties, actual phosphorus content and carboxyl end-group content of copolyesters were characterized by differential scanning calorimetry, thermogravimetric analysis, limiting oxygen index (LOI) test, inductively coupled plasma-optical emission spectrometer test and carboxyl end-group concentrations test. In order to investigate the intrinsic viscosity changes of flame retardant copolyester containing phosphorus side group after solid-state polycondensation reaction under different reaction conditions, different amount of side group phosphate-containing flame retardant were used for optimisation. Reaction rate constants and activation energy were calculated by analyzing the viscosity increasing effect and reaction kinetics.

Results The flame retardant copolyester containing phosphorus side group was synthesized by copolymerization method. The reaction process of solid-state polycondensation (SSP) of flame retardant copolyester containing phosphorus side groups and the reaction kinetics were studied to establish understanding of mechanism governing the polycondensation technology of flame retardant copolyester. The results showed that the intrinsic viscosity of the prepared PET and copolyester reached 0.6-0.7 dL/g (Tab. 1), meeting the requirements of conventional polyesters. The increase of the DDP content of the flame retardant caused the carboxyl end-group concentrations to increase, the crystallization capacity to be worsened, and the carbon forming capacity and flame retardant property to increase. PETD₅ deminstrated good thermal stability and mechanical properties, and showed 13.6% of carbonization capacity (Tab. 2 and Fig. 6), 15% of crystallinity, and 31.8% of LOI (Tab. 1), proving successful preparation of flame retardant copolyester containing phosphorus side group in preparation for subsequent polycondensation reactions. The research showed that all polyesters achieved the intrinsic viscosity of 1.0 dL/g or higher within 10 h of solid-state polycondensation reaction at 200 and 210 ℃ (Fig. 8), and that the intrinsic viscosity of all polyesters increased with the increase of temperature and reaction time. Correspondingly, the concentration of carboxyl end-group concentrations decreased gradually with the increase of reaction temperature and reaction time. Compared with conventional PET, the reaction rate constant of flame retardant copolyester PETD increased with increasing temperature and decreasing flame retardant amount, and the activation energy increased when increasing flame retardant amount.

Conclusion It is found that the solid-state polycondensation reaction conditions are mild even with prolonged reaction time, and the copolyester demonstrates satisfactory thermal stability. It is easy to adjust the reaction conditions according to different demands in production, and therefore the study of solid-state polycondensation and condensation and adhesion reaction of flame retardant copolyester containing phosphorus side groups is of certain value for its industrial development. There are still many concerns calling for further study on the adhesion reaction of flame retardant copolyesters, and many aspects can be further explored, such as the influence of different reaction factors (vacuum degree, reaction atmosphere, particle size, crystallinity) on the adhesion of flame retardant copolyester. The changes of flame retardant properties, thermal stability, crystallization capacity and mechanical properties of flame retardant copolyester after polycondensation need to be studied in depth. The flame retardant and mechanical properties of the tackified flame retardant copolyesters needs to be evaluated.

Spinning and microstructure and properties of photochromic polylactic acid fibers

ZHAO Mingshun, CHEN Xiaoxiong, YU Jinchao, PAN Zhijuan

Journal of Textile Research. 2023, 44(07):  10-17.  doi:10.13475/j.fzxb.20220203301

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Objective In response to the national theme of low-carbon environmental protection, replacing conventional petroleum-based fibers with degradable polymer fibers has become necessary. However, it seems to be a great challenge to obtain degradable polymer fibers photochromic properties while maintaining their mechanical properties. It is therefore necessary to develop photochromic fibers with mechanical properties and discoloration effects.

Method The photochromic polylactic acid(PLA) fibers were prepared from PLA, and photochromic microcapsules by melt spinning and hot stretching processes, and their morphological, crystallographic, and thermal properties were systematically analyzed, with emphasis on the effect of photochromic microcapsules on the mechanical and reversible discoloration behavior of the fibers, so as to reveal the effect of the difference in fiber properties and their internal structure.

Results The fiber morphology structure showed that the smooth cross-sections and surfaces (Fig. 1, Fig. 2) the pure PLA fibers. As the dosage of added photochromic microcapsules increased, the fibers were found to form more and more pores and defects, leading to the deterioration of the mechanical properties of the fibers. The photochromic PLA fibers prepared in this research demonstrated a breaking strength of 3.54-4.18 cN/dtex, an elongation at break of 19.27%-27.01%, and a modulus of elasticity of 55.67-58.66 cN/dtex (Fig. 3). With the increase in dosage of photochromic microcapsules, the breaking strength and elongation at the break of the fibers illustrated a decreasing trend. Even so, when the mass fraction of microcapsules was 6%, the breaking strength and elongation at the break of the fibers were still 3.54 cN/dtex and 20.21%, which could meet the requirements of subsequent processing. Furthermore, the crystallinity of fibers with the increase in dosage of photochromic microcapsules tended to rise and then fall (Fig. 5). The crystallinity of fibers without microcapsules addition was 50.22%. The maximum crystallinity of 55.42% was reached when the mass fraction of microcapsules was 2%. With the continuous increase of photochromic microcapsules, the crystallinity decreased to 47.62%. The photochromic properties of the photochromic PLA fibers (Fig. 6-8) showed high sensitivity, excellent photobleaching (Fig. 9) and photostability (Fig. 10) with the color change completed within 1 s and returning to the original color within 50 s. The fibers' photochromic intensity varied with the microcapsules' mass fraction. The discoloration intensity of the fibers increased with the mass fraction of photochromic microcapsules, but not linearly. In addition, the fiber has excellent durability, maintaining a stable color intensity during 50 cycles of discoloration.

Conclusion Photochromic PLA fiber was successfully prepared by melt spinning technology, which has excellent mechanical properties, with a tensile breaking strength of 3.54-4.18 cN/dtex, elongation at break of 19.27%-27.01%, modulus of elasticity of 55.67-58.66 cN/dtex. Cut-in photochromic function presents high sensitivity, excellent photobleaching performance and photostability. The mechanical properties of fibers and the photochromic effect are closely related to the dispersion or aggregation state of photochromic microcapsules in the PLA matrix. When the mass fraction of microcapsules is low, their distribution in the PLA matrix is uniform, which is conducive to the orderly arrangement of PLA molecular chain segments and has a beneficial effect on the mechanical properties of fibers. When the mass fraction of microcapsules is high, the orderly arrangement of PLA molecular chain segments is hindered, which is the main factor affecting the mechanical properties of fibers. By adjusting the mass fraction of photochromic microcapsules, mutual coordination of fiber color change function was reached, leading to the possibility of achieving the mechanical properties of fibers. The fibers can be mass-produced by melt spinning, which has a broad application prospect in photochromic fabrics, anti-counterfeiting and military.

Preparation and properties of superhydrophobic thermal insulating polyester nanofiber/silica aerogel composite membranes

LIU Dunlei, LU Jiaying, XUE Tiantian, FAN Wei, LIU Tianxi

Journal of Textile Research. 2023, 44(07):  18-25.  doi:10.13475/j.fzxb.20220301301

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Objective Polyester fiber has the advantages of high strength, high elasticity, good conformability and low cost, which occupies an important position in the modern textile industry. Especially, polyester nanofiber membranes prepared by electro-spinning have a three-dimensional porous structure, excellent air permeability and high production efficiency, and received extensive attention. However, polyester nanofiber membranes have high hydrophilicity, high thermal conductivity and poor thermal stability, which are regarded as disadvantages. Therefore, it is of great importance to develop thermal insulating polyester membranes with low thermal conductivity, superhydrophobicity and flexibility for the thermal protection of workers in extreme hot and humid environments.

Method Superhydrophobic thermal insulating polyester nanofiber/silica (PETS) aerogel composite membranes were prepared by in-situ condensation of silica aerogel in the polyester nanofiber, followed by hydrophobic treatment, solvent exchange and ambient pressure drying. The structural and mechanical properties of PETS aerogel composite membrane were characterized and analyzed by scanning electron microscopy, and a universal tensile testing machine. Thermal insulating properties of PETS aerogel composite membranes were characterized by infrared thermal imager and hot disk thermal analyzer in humid environments.

Results PET and PETS aerogel composite membranes were shown to have the construction of silica aerogels in the polyester nanofibers created by in-situ condensation (Fig. 2). Within the polyester nanofiber membrane, the silica aerogel gradually developed a continuous three-dimensional porous structure as the molar ratio of ethanol to tetraethyl orthosilicate increase to 10∶1 (Fig. 4). As the content of silica aerogel increased, the tensile break strength of PETS aerogel composite membrane demonstrated a gradually decrease. Notably, the PETS₁₀ aerogel composite membrane had a stable structure in high temperature environment because the silica aerogel was tightly bound to the surface of PET nanofibers as an inorganic protective layer, which effectively inhibited the structural collapse of polyester nanofibers. Furthermore, the thermal conductivity of PETS₁₀ aerogel composite membrane was only 66.5 mW/(m·K) at 150 ℃, while the pure polyester nanofiber membrane was seriously deformed and its thermal conductivity was as high as 135.6 mW/(m·K) (Fig. 7). This was attributed to the three-dimensional nanopore structure of silica aerogel, which effectively inhibited heat transfer and endued the PETS aerogel composite membrane excellent thermal insulating properties. Benefiting from the replacement of hydrophilic Si—OH by hydrophobic Si—CH₃ in silica wet gels, the PETS aerogel composite membrane exhibited superhydrophobi-city (water contact angle of 153°) compared to the polyester nanofiber membrane (water contact angle of 17°) (Fig. 8). Therefore, the superhydrophobic PETS could effectively prevent the adsorption of water molecules, and its thermal conductivity was 74.5 mW/(m·K) at 50 ℃ and 100% high humidity, while the thermal conductivity of pure polyester nanofiber membrane was as high as 170.6 mW/(m·K) (Fig. 9). Compared with silica aerogel composites previously reported, PETS aerogel composite membrane showed a lower thermal conductivity, indicating its great potential for thermal insulation in high-temperature and humid environments.

Conclusion The PETS aerogel composite membrane is found to exhibit excellent temperature resistance, superhydrophobicity, and thermal insulation capabilities. The interfacial bonding between SiO₂ aerogel and PET nanofiber can be optimized by controlling the functional groups of the silica wet gel, thus further optimizing the mechanical properties of the PETS aerogel composite membrane. Furthermore, this strategy can also be used for modifing other nanofiber membranes with good generalizability.

Preparation and performance of poly(vinylidene fluoride-trifluoroethylene) piezoelectric modified fiber membrane for long-lasting protective masks

ZHANG Jin, ZHANG Linjun, XIE Yunchuan, WANG Jian, JIA Yinfeng, LU Tao, ZHANG Zhicheng

Journal of Textile Research. 2023, 44(07):  26-32.  doi:10.13475/j.fzxb.20220203601

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Objective Polypropylene (PP) melt-blown fabric has an electrically charged surface that generates an electrostatic field to adsorb micron-sized particles and is widely used as a filter layer in disposable protective masks. However, the free charge was found to be easily lost in the presence of moisture, leading to rapid failure of the filter layer and mask. Disposing of large numbers of masks also puts enormous pressure on environmental protection efforts. Therefore, there is an urgent need to develop masks with high protection capacity and long service life.

Method A piezoelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) fiber layer was prepared by electrospinning on a PP melt-blown fabric substrate, resulting in a PP melt-blown fabric/P(VDF-TrFE) modified filter layer. The modified filter layers took advantage of the fact that piezoelectric materials can generate a bound charge under external forces, providing the mask with a durable electrostatic adsorption capability. The influence of spinning process on the morphology and structure of piezoelectric fibers was studied, and the research further investigated the changes in static voltage, smoke filtration efficiency and breathability of the modified filter layer after durability treatment such as water washing and steam treatment.

Results An optimized electrostatic spinning process was found to prepare excellent-performance piezoelectric P(VDF-TrFE) fiber membranes. The fibers prepared by spinning were free of beads and uniform diameter, with a distinct piezoelectric crystal phase structure, which ensures the breathability of the fiber membrane while providing the mask with a stable load of charge and a durable electrostatic adsorption capacity (Fig. 2, Fig. 3). The piezoelectric fiber layer showed a 25% higher filtration efficiency for PM_2.5 than the ordinary PP melt-blown fabric in the smoke filtration effect test. In the standard test of medical masks, the filtration efficiency of the modified filter layer was improved by 10.5% and 27.5% at an inlet airflow of 32 and 85 L/min, respectively (Fig. 6). The static voltage on the surface of the ordinary mask and the modified filter layer was reduced after treatment by water washing, alcohol washing, and steam sterilization. Owing to the presence of the piezoelectric fiber membrane in the modified filter layer, the piezoelectric fiber is still able to recover the static surface voltage of the filter layer well after being subjected to the mechanical effects of bending and pressing several times (Fig. 4). After the durability treatment, the modified filter layer maintained a filtration efficiency of 90% at a both inlet airflow of 32 and 85 L/min, respectively, exceeding the filtration efficiency of the melt-blown fabric itself. However, the organic solvent could destroy the structure of the piezoelectric fibers, resulting in a significant reduction in the filtration efficiency of the ethanol-treated modified filter layer(Fig. 7).

Conclusion As fossil energy sources become depleted and environmental pollution increases, it is necessary to develop and use more effective and durable masks to prevent infectious diseases. The innovation of this work is the introduction of piezoelectric polymer material in the production of masks by an electrostatic spinning process, which significantly improves the difficulty of maintaining the electrostatic adsorption capacity of PP melt-blown fabrics over a long period. Experiments have demonstrated that the modified masks can maintain electrostatic adsorption capacity after washing and steam treatment. The application of the piezoelectric polymer material not only improves the filtration performance of the mask but also endues the mask a long-lasting protection capability. The prolonged service life of the masks can effectively solve the problem of poor utilization of materials.

Interfacial polymerization modification of chlorinated polyvinyl chloride/polyvinyl butyral blend membrane

FAN Yangrui, QIAN Jianhua, XU Kaiyang, WANG Ao, TAO Zhenglong

Journal of Textile Research. 2023, 44(07):  33-41.  doi:10.13475/j.fzxb.20220507501

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Objective In order to improve the ion separation efficiency of nanofiltration (NF) membrane and improve hydrophilicity and surface smoothness of chlorinated polyvinyl chloride/polyvinyl butyral (CPVC/PVB) blend membrane, this research investigated the modification of CPVC/PVB blend membrane, and the structure and properties of nanofiltration membrane before and after modification were analyzed to broaden the application of CPVC/PVB blend membrane.

Method CPVC/PVB blend membranes were used as the base membrane, and the surface of the base membranes were modified to improve hydrophilicity using the additives of polyethylene glycol (PEG) and 1,2-propanediol (PG). Using the modified CPVC/PVB blend membranes as the support layer, water phase monomer m-phenylenediamine (MPD) and the oil phase monomer trimesic acid chloride (TMC) were polymerized on the support layer interfacial, by the reaction assistant N-ethylamine piper under the catalysis of azinepropyl sulfonate (AEPPS). The Influences of mass fractions of MPD, TMC and AEEPS on the structure and performance of composite nanofiltration membranes were studied. A series of experiments were carried out using Fourier infrared spectrometer, field emission scanning electron microscope, ultraviolet and visible spectrophotometer, energy spectrum analyzer, Zeta potential tester, and water flux tester. The influences of the infrared spectrum of the blend membrane, surface elements, the cross-section structure of the surface microstructure, the Zeta potential of the membrane surface, and the monomer mass fraction required for the interfacial polymerization on the water flux and desalination performance of the nanofiltration membrane were obtained.

Results After the interface polymerization of CPVC/PVB blend membrane, two characteristic peaks and amino groups were added to the infrared spectrum (Fig. 3). With the increase of the mass fraction of MPD monomer, the proportion of N elements on the membrane surface first increased and then decreased (Tab. 1).The increase in N element is due to the introduction of amino groups on the membrane surface. The decrease in N element content is due to the fact that the surface of the nanofiltration membrane becomes dense with the introduction of amino groups, making it impossible to introduce more amino groups. The surface of the modified nanofiltration membrane became smoother and the pore size became smaller, resulting in the formation of a dense layer, while the section structure had no obvious change (Fig. 4, Fig. 5). According to the Zeta potential test, when pH value was equal to 7, the Zeta potential of the unmodified nanofiltration membrane was negative, and the zeta potential of the modified membrane surface turned positive (Fig. 6). With the increase of the mass fractions of MPD and TMC, the water flux first decreased and then increased. The reason for the decrease in water flux is the formation of a dense functional thin layer on the membrane surface, making it more difficult for water to pass through. The reason for the increase in water flux is that as the content of MPD, TMC and AEEPS increases, the functional thin layer on the surface of the nanofiltration membrane has stabilized and will not become denser. AEEPS contains hydrophilic groups, which can improve the water flux of the membrane.With the increase of the mass fraction of MPD, TMC and AEEPS, the desalination efficiency of nanofiltration membrane was increased first and then decreased (Fig. 7-Fig. 9). After the interfacial polymerization reaction occurs, the positively charged nanofiltration membrane improves the filtration efficiency of divalent cations, thereby improving the desalination efficiency of the nanofiltration membrane. However, with the increase of MPD and AEEPS, excessive amino and hydrophilic groups were introduced, making the surface of the nanofiltration membrane more porous, resulting in an increase in water flux and a decrease in desalination efficiency.

Conclusion After interfacial polymerization, a dense polyamide separation layer was formed on the surface of the CPVC/PVB blended membrane, more amino groups were introduced, the membrane surface was positively charged, and the water flux was improved. When the mass fractions of MPD, TMC and AEPPS were 0.6%, 0.5% and 0.6%, respectively, the three-dimensional morphology of the nanofiltration membrane surface became complete, the surface roughness was reduced, and the structure was more compact, showing the best desalination performance and the best separation performance for divalent cations. Therefore, the nanofiltration membranes have further development and application prospects in the fields of water softening, seawater desalination, and industrial wastewater treatment.

Preparation and oil-water emulsion separation performance of amidoximated polyacrylonitrile nanofiber membrane

WANG Yuzhou, ZHOU Mengjie, JIANG Yuanjin, CHEN Jiaben, LI Yue

Journal of Textile Research. 2023, 44(07):  42-49.  doi:10.13475/j.fzxb.20220106501

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Objective Efficient treatment of oily wastewater is of great significance for environmental and economic needs. The conventional separation technology can effectively separate oil from oil-water emulsion, but its separation efficiency is relatively low. Membrane separation technology can achieve the separation of oil-water emulsion by adjusting the pore size and changing the wettability of membrane materials. Nanofiber membrane prepared by electrospinning technology has been widely used to separate oil-water emulsion due to its high porosity, high connectivity, large specific surface area, adjustable wettability and other comprehensive characteristics. This research aims to enhance the oil-water emulsion separation performance of nanofiber membrane and to explore the influence mechanism of membrane materials on the hydrophilicity of fiber membrane.

Method Amidoxime (PAO) was synthesized from polyacrylonitrile (PAN), and then the PAO nanofiber membrane was prepared by electrospinning method. The surface morphology, fiber diameter, average pore diameter, surface roughness, surface wettability, mechanical properties, functional group composition of fiber membrane and oil-water emulsion separation performance were tested and analyzed.

Results The mass fraction of PAO directly was found to affect the surface morphology of the PAO membrane. The results showed that when the mass fraction of PAO in the spinning solution was 10%, the average fiber diameter was 0.21 μm and the diameter distribution of PAO membrane was relatively uniform with an average pore size of 0.88 μm (Fig. 2, Fig. 3). It was demonstrated that the surface roughness played an important role in influencing the wettability of the membrane surface. The surface roughness of the nanofiber membrane prepared after amidoximation was significantly improved, attributing to the increase in the diameter of the electrospun fiber (Fig. 4). The fabricated PAO nanofiber membranes were found to have abundant —NH₂ and —OH hydrophilic groups, the 10%PAO nanofiber membrane exhibited excellent surface wettability with an initial water contact angle of 15.6° and an underwater oil contact angle of 157° (Fig. 5, Fig. 6). The stress and strain of the original PAN nanofiber membrane was 2.25 MPa and 25.15%, respectively. After amidoximation, the mechanical properties of the 10%PAO membrane did not decrease, remaining at 2.47 MPa and 26.64%, respectively, proving that direct amidoximation of the spinning solution can maintain various properties after amidoximation treatment and keep the flexibility and strength (Fig. 7). The permeation fluxes of the 10%PAO nanofiber membrane for silicone oil water, n-hexane water, petroleum ether water and edible oil water emulsion were 1 362.9, 1 658.9, 1 614.2 and 1 425.9 L/(m²·h), respectively, and the corresponding oil rejection rates were 99.1%, 98.5%, 99.3% and 98.6%, respectively (Fig. 12). This shows that PAO nanofiber membrane has good oil-water emulsion separation performance. It can separate various oil water emulsion only under gravity conditions, and shows excellent separation efficiency and precision, showing a good prospect for oil-water separation.

Conclusion When the content of the PAO spinning solution was 10%, the PAO nanofiber membrane showed good surface wettability and oil-water emulsion separation performance. The initial water contact angle is 15.6° and the underwater oil contact angle is 157°, and its permeation flux of silicone oil emulsion is 1 362.9 L/(m²·h), and the rejection rate is 99.1%. The surface hydrophilicity and oil-water emulsion separation performance of the fiber membrane are significantly improved compared with the PAN fiber membrane without amidoxime treatment which shows good prospects for the separation of oily wastewater.

Textile Engineering

Influences of twist and twist direction arrangement on properties of double covered yarns

AO Limin, TANG Wen

Journal of Textile Research. 2023, 44(07):  50-56.  doi:10.13475/j.fzxb.20220305901

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Objective In order to explore the influence of the twist direction and twist configuration of the double wrapping on the structure and properties of the double covered yarns, the influences of twist and twist direction arrangement on the structure, tensile fracture performance and twist balance of covered yarns were experimentally investigated and analyzed, which were produced using the hollow spindle method with double wrapping.

Method Three 111 dtex (48 f) untwisted polyester draw texturing yarn (DTY) filament yarns with different colors were employed as raw materials with unchanged wrapping twist, double covered yarns with SZ cross-wrapped and SS co-wrapped were spun separately each with 6 twist ratios, using hollow spindle covering machine. The covering structures of the covered yarns were analyzed by visual observation of the partial enlarged photographs of covered yarns, while the twist balance indexes were tested by open loop method and the tensile mechinical properties were tested by yarn tensile tester.

Results The spinning principle of double covered yarns was explained, and the structural model of the two twist direction arrangement of the same direction wrapping and the reverse (cross) wrapping were establi-shed (Fig. 1 and 2). Partial enlarged views of two types of double covered yarns showed that both types of covered yarns presented mixed color of core yarn and wrapped yarn, and it was found that with the increase of secondary wrapped twist, the finer the degree of color block segmentation mixed and the finer the texture of covered yarn. Meanwhile, the cross-wrapped was found to be able to form a clear layered wrapping structure. Double covered yarns and raw filament yarn showed similar force-extension curves, and the differences were only in the characteristic values like yield load and yield elongation, breaking strength and elongation at break, based on 50 core yarn tests. SZ cross-wrapped and SS co-wrapped covered yarns were produced with twist ratio of 0.9. The tensile test results of three types of raw yarn and two types of 12 covered yarns presented the changes of breaking strengths and their CV value, elongations at break and their CV value and strength efficiencies along with the changes of twist direction and twist ratio of twice wrapping (Tab. 1). Different twist direction and twist ratio arrangement produced different twist balance in the double covered yarn, the snarl index test results of 12 composite yarns showed the self-twisting direction, mean values of snarl indexes and their CV value for 10 tests of the two types of double covered yarns with different twist directions and twist ratios (Tab. 2).

Conclusion It was discovered that co-wrapped can not form a layered wrapping structure similar to cross-wrapped, and the strength efficiencies of the two types of covered yarns are greater than 1. The elongations at break are increased by more than 25%, and the strength of covered yarns increase first and then decrease with the increase of twist ratio, but the change range are small. The residual torques of the twice wrappings are not a simple superimposition. The second wrapping has a consolidation effect on the residual torque of the primary wrapping, and the snarl index of co-wrapped covered yarn is much larger than that of cross-wrapped. Reasonable configurating of the twist ratio of the twice wrapping can significantly reduce the snarl index of the cross-wrapped covered yarn. This paper would provide reference for the process design of double wrapped covered yarn.

Design and color simulation evaluation of multi-color dot structured jacquard fabrics

ZHANG Aidan, GUO Zhenni, YE Jingjing

Journal of Textile Research. 2023, 44(07):  57-63.  doi:10.13475/j.fzxb.20220405801

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Objective Shaded weaves are extensively used in the design of figured full-color simulation of jacquard fabrics, to the extent that this design pattern is solidified into a certain mind-set. In order to overcome this situation, a design method of multi-color dot superposition combination is proposed for motivating the diversified development of the design technology for color simulation jacquard fabrics.

Method The digital screen technology was adopted to discretize the digital color image with continuous tone into a multi-color dot image, which directly became the weave structure of a jacquard fabric. The multi-color dot image was composed of no more than 6 to 8 fixed colors (Fig. 1(b)). In order to investigate the color simulation performance of jacquard fabrics based on multi-color dot image, six jacquard fabric samples were woven by using two design method respectively for representing three different pictures (Fig. 3). Three color measurement point templates were designed for collecting the color data of the jacquard fabric samples (Fig. 4). The templates were fixed on the jacquard fabrics, and then the Lab values of each color measurement point were measured by using the American X-rite Color i7 desktop spectrophotometer. By comparative analyzing the color difference between the images of jacquard fabric samples and the original images, the color simulation performances of the jacquard fabric applying the multi-color dot image were demonstrated.

Results The average total color differences (ΔE_ab) among the six jacquard fabric samples and the corresponding original image were calculated (Tab. 2). The data of three multi-color dot structure jacquard fabrics was 14.31, 24.09 and 16.10, representing improved color simulation performance of 13.11%, 19.49% and 4.28% over that of shaded weave jacquard fabric images, respectively. In addition to comparing the total color difference of single jacquard fabrics, the measured color data of six jacquard fabrics were classified into two groups according to the two different design method of multi-color dot images and shaded weaves, and then comparatively analyzed in terms of lightness, total color difference, red value, green value, yellow value and blue value (Tab. 3). The six terms of color difference data of multi-color dot jacquard fabrics were reduced in varying degrees comparing with that of shaded weave jacquard fabrics. At last, the ΔE_ab between the color measurement points of the original images and the multi-color dot images were taken as the dependent variable, and the lightness, red-green value and yellow-blue value of all the color measurement points of the three original images were taken as the independent variables. The polynomial regression equation was used for fitting, the results (Fig. 6 and 7) showed that the color simulation effect of multi-color dot jacquard fabric was better for neutral color, medium brightness color and low saturation color, while the simulation effect of vivid, bright or extremely dark color was relatively not so well.

Conclusion According to the comparative investigations of the color differences of the images of the multi-color dot structure jacquard fabrics and that of the shaded weave jacquard fabrics, it proves that the jacquard fabrics by using the method of discretizing the continuous tone color image into a multi-color dot image can improve the color simulation performance. Because the color number of image is significantly reduced without obvious affecting the image color quality, the large number of fabric weaves are no longer needed, which realizes overcoming the limitations of fabric weave in color simulation and provides a new way for the design of color simulation jacquard fabrics. For expressing image color, the jacquard fabrics depend upon the design factor of weave but excessive reliance on the weave would also have a negative impact on the expression of image color, which is also worth thinking about.

Preparation and conductive stability of knitted circuit using cotton/stainless steel wire core-spun yarn

WANG Kai, WANG Jin, NIU Li, CHEN Chaoyu, MA Pibo

Journal of Textile Research. 2023, 44(07):  64-71.  doi:10.13475/j.fzxb.20220100901

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Objective The development of intelligent wearable products has put forward new requirements for conductive circuit, in which high flexibility and outstanding adaptation to the human body are essential. Flexible textile circuit made with metal wire guarantees reliable electric conduction, but faces challenges in processibility, wearing comfort, safety and conductive stability. The purpose of this paper is to improve the flexibility and stability of textile circuit made from cotton/metal wire core yarns to establish a flexible wearable sensing network.

Method This paper proposed a flexible circuit based on knitting structure that integrates sirospun technology with knitting technology. By exploring different spinning parameters including stainless steel wire diameter, twist factor and draft ratio, siro core-spun yarns were prepared from stainless steel wire and cotton. The non-conductive part of flexible knitted circuit was fabricated with polyamide/spandex yarn as plating yarn and polyester yarn as ground yarn. The conductive part was integrated by intarsia knit with polyamide/spandex yarn as plating yarn and conductive core-spun yarn as ground yarn. Then, mechanical properties, electrical stability under various mechanical conditions and conductive durability of flexible knitting circuit were characterized and analyzed.

Results The yarn used stainless steel wire as core and cotton fibers as the sheath (Fig. 3). Research on spinning parameters showed that increase in stainless steel wire diameter, reduction in draft ratio and proper twist factor have positive effects to conductive core-spun yarn appearance (Tab. 3). Considering the exposed core length and strength of the yarn, the twist factor of 400, the draft ratio of 17.28 and the stainless steel wire diameter of 0.05 mm were selected as the final spinning parameters. The break strength of the prepared conductive core-spun yarn is about 7.6 times that of bare stainless steel wire, but the elongation at break decreases about 2.8-3.6 times (Fig. 4). It was confirmed that the resistance of the yarn was affected by the strain and the structure of core-spun yarns caused reduction in the resistance change rate compared to bare stainless steel wire (Fig. 5). The prepared conductive core-spun yarn can be knitted on the knitting machine, exhibiting good processibility. In order to increase elasticity of the knitted circuit, polyamide/spandex yarn was introduced as plating yarn under conductive core-spun yarn and polyester yarn which increases circuit breaking force, breaking strain and maximum resistance change rate (Tab. 4). The trend of resistance change rate of knitted circuit in extended state is similar to that of conductive core-spun yarn, but the resistance change value is smaller than that of core-spun yarn, attributing to knitted structure (Fig. 7). The knitted structure also offered the knitted circuit good transverse mechanical property, with the transverse resistance change rate of the knitted circuit below 0.38%, which is smaller than the longitudinal resistance change rate (Fig. 8). The electrical durability test showed a resistance change rate of 0.61% after 5 000 cycles of 20% longitudinal strain, confirming circuit with knitted substrate has good durability after repeated deformation (Fig. 10). When bursting test was carried out to simulate complex three-dimensional strains on the knitted circuit, the resistance change rate was lower than 0.38% when the mean strain was lower than 150%. The load was then concentrated on the conductive core-spun yarn, the resistance change rate increases linearly with mean strain after elongation took place in the yarn (Fig. 12).

Conclusion Sirospun technology was adopted to prepare core-spun yarn with stainless steel wire as the core and cotton as the sheath. The spinning parameters were determined based on better covering degree and higher yarn strength by exploring the influences of twist factor, draft ratio and stainless steel wire diameter on the performance of core-spun yarn. The prepared conductive core-spun yarn was found to have good processibility. The research on the conductive properties of knitted circuit with different conductive core-spun yarns and fabric specifications shows that the conductivity is related to fabric elasticity, stainless steel wire diameter and tensile direction. The resistance change rate of the fabricated circuit can be less than 0.31% indicating good conductive stability of the knitted circuit. Similar conductive stability was also observed in three-dimensional bursting test under 150% mean strain. The knitted circuit has good electrical durability and can maintain stable resistance during 5 000 cycles of longitudinal tensile tests with an average strain of 20%.

Design and application of functional knitted fabric imitating nepenthe mouth structure

YU Xuliang, CONG Honglian, SUN Fei, DONG Zhijia

Journal of Textile Research. 2023, 44(07):  72-78.  doi:10.13475/j.fzxb.20211101201

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Objective Studies show that moisture transferring fabric plays an important role in achieving the balance of heat and humidity of the whole garment. Sweat can be quickly conducted in the moisture transferring fabric, which help concentrate or drive sweat to the designated area, thus strengthening the ability of clothing to control sweat. In order to achieve the rapid conduction of moisture on the surface of fabric and improve the thermal and moisture comfort of clothing, an effort was made to combine the biological system with textiles in a multidisciplinary way to form a more characteristic biomimetic structure fabric. By referring to the liquid single-direction continuous transport mechanism on the surface of the nepenthe plant mouth edge area, a biomimetic structure fabric with a single-side moisture transfer function was designed aiming to optimize the structure design of fabric and the principle of moisture conduction.

Method By studying the three-layer micro-groove structure in the mouth edge area, it was found that the "duck-bill" pit with gradient wedge angle characteristics was the key to the liquid directional transport movement of nepenthe plants. The gradient wedge angle produced gradient tailor ascending effect in the micro-groove, which promoted the liquid climbing transport movement. Therefore, SM-DJ-2TS double-sided electronic circular knitting machine was adopted to produce a fabric with 18 stitches/(25.4 mm) and 912 stitches using single-sided and double-sided structure, and the 150 dtex(24 f) polyester low-elastic yarn and the 20/50 blending ratio of spandex/polyamide coated yarn were selected as raw materials. The structure fabric with the same shape as the bionic structure was designed to form the concave and convex fabric with the "duck bill" arch structure. Meanwhile, the structure model of the same shape was established, and the fluid finite element analysis was carried out with ANSYS software to simulate the movement scene of sweat on the surface of the structure fabric.

Results Simulation analysis showed that more water flow through the surface structure of the model would lead to faster flow velocity. The channel structure model would increase the flow velocity by about 43%, suggesting that the structure model was able to transport water and enhance the liquid wicking. Meanwhile, the experimental test of the wicking height showed that the bionic structure pit channel can enhance the core absorption effect of reagents. At 600 s of the experiment, the difference between the bionic structure fabric and the plain fabric was more obvious. The experimental results of bionic fabric wicking height test validated the simulation results. Besides, its surface diffusion area and diffusion speed also showed unique advantages. The liquid further diffused along the direction of the arch pit in the channel on the groove structure. Finally, the wetting and diffusion effect on the bionic structure fabric was irregular, but it was obviously different from plain fabric. On the plain fabric, the reagent diffused around the dripping point as the center, and finally formed a circular or oval wetting diffusion area. This indicates that the moisture can be diffused more rapidly in the pit channel of the bionic fabric structure, and the longer distance transmission showed the rapid and efficient one-way water transfer function effect.

Conclusion The design and development of moisture transferring fabric with structure at the edge of nepenthe plants can satisfy the application needs of functional products such as water guiding vamps, moisture controlling sports clothes and moisture conducting socks, which can optimize the moisture transferring of fabric and improve the comfort of heat and humidity of clothing, providing certain references for the design and development of moisture transferring fabric.

Influencing factors for thermal insulating properties of cotton gauze quilts

ZHANG Luyang, SONG Haibo, MENG Jing, YIN Lanjun, LU Yehu

Journal of Textile Research. 2023, 44(07):  79-85.  doi:10.13475/j.fzxb.20220606401

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Objective Studies on thermal insulating properties of quilts have been carried out aiming to improve the thermal comfort and sleep quality. Previous studies mainly focused on quilts with filling materials, and few research focused on non-filling quilts such as gauze quilt. In order to provide more understanding on comfortable sleeping microclimate, a systematic investigation on thermal insulating properties of several gauze quilts with different parameters was conducted.

Method 41 samples in total were provided, including 22 unwashed cotton gauze quilt fabric samples, 4 washed cotton gauze quilt fabric samples, 3 spunlaced cotton wadding samples, 6 cotton gauze quilt samples. The influences of air permeability, surface density and number of layers on heat resistance of cotton gauze quilts were analyzed by sweating hot plate tests and thermal manikin tests. The correlation between heat resistance of fabric and quilt was also established.

Results It was found that the heat resistance of both cotton gauze quilt samples and cotton spunlaced wadding samples have significant positive linear relationships with surface density. The heat resistance rose with the increase of surface density. The growth rate of the spunlaced cotton wadding quilts (0.006 1) was higher than that of cotton gauze quilts (0.001 7). Heat resistance of cotton gauze quilt samples decreased with the increasing of air permeability, exhibiting a low correlation, but the influence on thermal insulation was obvious when the air permeability was below 1 000 mm/s. The heat resistance of the spunlaced cotton wadding quilt showed a significant negative linear relationship with its air permeability. In addition, the air permeability and surface density presented an exponentially negative correlation. The change rate was constantly decreasing when surface density was more than 450 g/m². Generally, the air permeability of each cotton gauze quilt was above 500 mm/s, higher than that of the spunlaced cotton wadding quilt. The surface fitting results (thermal insulation as dependent variable, air permeability and surface density as independent variables) revealed that heat resistance and air permeability exhibited a low correlation. The surface density demonstrated a significant influence on heat resistance, and the heat resistance of cotton gauze quilt exhibited a positive linear relationship with the number of cotton gauze fabric layers. The air permeability of cotton gauze quilt showed power function relationship with the number of fabric layers. The heat resistance of cotton gauze quilt was increased after washing, with the average increase of about 20%. After once machine washing in 20 ℃ water, the thickness and surface density of cotton gauze quilt was increased by 26.6% and 13.6% in average, respectively, whereas the air permeability was decreases by 8.7% in average. A significant non-linear relationship exists between the heat resistance of fabric samples and quilt samples (p<0.05), which can be approximately expressed by an exponential function. In particular, they show approximate a linear relationship when the heat resistance of fabric was less than 1.8 clo.

Conclusion The heat resistance of the cotton gauze quilts has a significant positive linear relationship with the surface density, exhibiting a negative and low correlated relationship with the air permeability. Therefore, surface density is more appropriate for the prediction of heat resistance value in engineering application. Under the same surface density, spunlaced cotton wadding quilt provides higher thermal insulating properties, while cotton gauze quilt provides bigger air permeability. The superimposition of cotton gauze fabric layers can produce thicker air gaps, resulting in higher thermal insulating property of cotton gauze quilt. Once machine washing has a positive effect on thermal insulating property of cotton gauze quilt by virtue of the increase of thickness and surface density after washing. Moreover, heat resistance of fabric samples can be adopted to predict the heat resistance of quilt, showing a significant non-linear correlation. These research findings can provide evidence for the design of cotton gauze quilts and usage guideline to achieve thermal comfort during sleeping.

Defect detection of jacquard knitted fabrics based on nonlinear diffusion and multi-feature fusion

SHI Weimin, JIAN Qiang, LI Jianqiang, RU Xin, PENG Laihu

Journal of Textile Research. 2023, 44(07):  86-94.  doi:10.13475/j.fzxb.20220406301

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Objective Supervision and inspection are important parts in quality control of the knitted fabric production process. The defect detection by automation and machine vision technology can effectively improve the detection efficiency. Jacquard knitted fabrics have prominent yarn edges, obvious loop characteristics and patterns, which have a strong interference to the defect detection process. Therefore, it is necessary to design an effective and accurate pretreatment and defect detection method for the complex texture of jacquard knitted fabrics.

Method Improved PM (perona-malik)model was adopted to suppress the strong texture edge of jacquard knitted fabric. Firstly, the image was divided into texture and defect region by gradient difference before selecting the corresponding diffusion equation. The gradient threshold was determined according to the probability subset calculated by the gradient matrix and the relevant criteria to achieve regional diffusion. According to the texture distribution characteristics, the improved local binary pattern(LBP), entropy and correlation were extracted, and then the defect regions were further highlighted by neighborhood normalization and multi-feature fusion. Finally, the defect morphology was located and segmented by region growth method.

Results The effectiveness of the preprocessing method and the defect detection method for texture suppression was experimental investigated and analyzed, and defect information extraction of jacquard knitted fabric was demonstrated exhaustively. In addition, several different preprocessing algorithms and defect detection algorithms were compared and demonstrated. Comparison of defect image before and after preprocessing showed that the gray fluctuation amplitude of the image after preprocessing was smaller and the texture distribution was more concentrated. It was seen from the pretreatment experimental images and from the comparison effect with other preprocessing algorithms that the abrupt change of the texture edge area was still obvious, and the yarn spacing area of the fabric was still obvious in the visual effect. However, the proposed preprocessing algorithm effectively suppressed the strong texture edges and yarn spacing of patterns, and the intensity of texture edge filtering was greater. At the same time, in order to prove the robustness of the preprocessing effect more intuitively, the background suppression factor BSF, structure similarity SSIM and signal-to-noise ratio gain ISNR were used for index evaluation (Tab. 1). From characteristic reconstruction diagrams and normalized characteristic diagrams, the texture features selected in this paper effectively described the gray difference and gray distribution difference between defects and textures. In addition, the normalization of the row mean value without neighborhood effectively weakened the eigenvalue of the texture region and increased the difference between the texture and the defect. The effect of different defect detection algorithms on the defect image of jacquard knitted fabric was showed that, the algorithm in docoment [3] may misjudge the fabrics with single pattern or similar patterns, while the fabrics with multiple patterns may be interfered by complex patterns, resulting in false detection. The algorithm adopted in docoment[4] was not able to rule out that the interference of yarn coil spacing, which lead to missed inspection and false inspection. The algorithm in this paper achieved the localization of the defect area and extracts a relatively complete defect shape contour. The comparison results of the detection accuracy of each detection algorithm for 100 experimental images were obtained (Tab. 2). The false detection rate of the algorithm was 3.3% for normal fabric images and 98.6% for defective fabric images, further illustrating the effectiveness of the algorithm.

Conclusion Aiming at the complex texture of jacquard knitted fabric, this paper proposed a defect detection algorithm based on nonlinear diffusion and multi-feature fusion. The improved nonlinear diffusion model was used as the pretreatment means, and the single diffusion mode of the conventional PM model was improved to the regional diffusion by selecting the best diffusion equation and gradient threshold. At the same time, multi-feature extraction and fusion were used as detection means to further highlight the defect area by using without neighborhood normalization and weighted fusion methods, and finally the defect shape was segmented by using region growth method. The experimental results show that the improved PM model effectively weakens the complex texture of jacquard knitted fabric and eliminates the interference caused by texture. Feature extraction method and normalization method increase the difference between texture and defect, and further highlight the defect. Compared with other detection methods, the detection accuracy of this paper is higher for jacquard knitted fabric defect image, and the defect region segmentation is more perfect and accurate.

Real-time detection of fabric defects based on use of improved Itti salient model

YAN Benchao, PAN Ruru, ZHOU Jian, WANG Lei, WANG Xiaohu

Journal of Textile Research. 2023, 44(07):  95-102.  doi:10.13475/j.fzxb.20220308301

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Objective Conventional manual testing relies on the subjective experience and rating standards of inspectors to complete the appearance quality testing and evaluation of fabrics, which has problems such as backward productivity, poor detection accuracy, low efficiency and easy fatigue. Fabric defects automatic detection technology is one of the key links for textile enterprises to develop into intelligent manufacturing. Thus, this paper intends to develop a real-time detection system in order to achieve the automatic detection of fabric defects so as to overcome the disadvantages seen in manual detection.

Method The system adopts the motor drive to realize the fabric winding and the automatic transfer of the roll. Unwinding and transmission can be stably, with high automation and accuracy. In order to meet the different lighting requirements, three rows of LED lights are installed, and they have more lighting modes than other systems. Eight industrial cameras are arranged side by side to realize the image acquisition of the fabric. The acquired images were rapidly detected by the image defects based on an improved Itti salient model fault detection algorithm. The model has shorter detection time for fabric image and has higher accuracy, which can meet the real-time detection requirements of fabric defects.

Results The schematic diagram of the fabric image acquisition system is established (Fig. 1). The fabric is rewound by the motor and can be stably transmitted to the image acquisition area in a specific route. In the image acquisition area, fabric images of different thickness fabrics with different light sources are obtained (Fig. 3). It can be seen that the sharpness of the images taken by different light sources is different, which meets the detection requirements of different thickness fabrics. It also indicates that the installed camera has a high shooting definition. The images were detected based on the improved Itti salient model. Different directions can effectively extract the features of the fabric image and detect the edge information inside the image. The fabric fault significance graph is obtained by manipulating the normalized brightness and orientation feature, and the significant graph is divided by the custom threshold to effectively detect the defect information(Fig. 8, Fig. 9). It can effectively detect fabric defects in industrial grey fabric and denim, such as oil and holes. The defect detection rate is 93%. Compared with other fabric defect detection algorithms, the detection accuracy is higher. At the same time, it can be seen that the detection time of this method is short (Tab. 3), and the detection speed is 48 m/min. The real-time detection speed is further improved.

Conclusion In order to improve the disadvantages of the convenitional artificial fabric fault detection, a fabric image acquisition platform and a real-time fabric fault detection system based on the significance detection algorithm are proposed. The fabric platform can be driven by a motor, which is more stable than the previous roll transmission system and takes clearer photos. The improved significance detection algorithm detects the images and achieves good detection results. By comparison, the method has high detection accuracy and real-time performance, and the detection time of the algorithm meets the requirements of dynamic detection. The designed fabric real-time detection platform can run effectively and stably, and have higher real-time detection performance.

Defect reconstruction algorithm for fabric defect detection

FU Han, HU Feng, GONG Jie, YU Lianqing

Journal of Textile Research. 2023, 44(07):  103-109.  doi:10.13475/j.fzxb.20220405401

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Objective Defect has great influence on the accuracy of fabric quality evaluation. At present, the detection methods of fabric defect utilizing deep learning method, such as region convolutional neural networks (R-CNN) and YOLO, have insufficient detection accuracy for complex pattern fabric defects and are heavily dependent on the number of training samples. In order to solve the problem that the number of fabric defect samples with complex patterns has a large impact on the detection accuracy, a reconstruction method of fabric defect image is proposed for fabric defect detection.

Method The core idea of the proposed method is to consider the defect as a damage to the fabric texture. Firstly, the conditional generative adversarial neural network(CGAN) is adopted to repair the defective area of the image. Then, the difference is calculated as pixels-by-pixels comparison between the reconstructed image and the defect image. Lastly, the detection of fabric defect is perform by the image division of difference result.

Results In order to enhance reconstruction accuracy of the defect image by the generator, a self attention mechanism is used in the constitutional neural network, which can establish connections between distant pixels in the defect image. To solve the problem that the loss function of the generative adversarial neural network is weak in processing image details, the L1 loss function and the improved structural loss function are employed to construct the target loss function to improve the network's ability to process image details. Since the self attention mechanism is added to the generator, the neural network has the capability to coordinate the global features of the pattern fabric image and the local features around the defect area. The network is encouraged to reconstruct the defect according to the global features, so that the accuracy of image reconstruction is higher. Through the reconstruction experiment of oil defect images, the effectiveness of the method is proved (Fig. 1). The image reconstruction quality and image detail processing capability of the network are improved by introducing L1 loss function and improved structure loss function. L1 loss function can improve the image reconstruction quality of the network. The structural loss function can enhance the detail processing ability of the network. Two functions were simultaneously a dopted to strengthen the detection capability of defect edges and small defects (Fig. 3). ReNet-D method, SDDM-PS method and the proposed method are respectively used for the comparative experimental study of five kinds of fabric defects with different complex patterns. The results show that the ReNet-D method has a very poor performance in the detection of various defects of complex pattern fabrics, and can hardly detect the defects. The SDDM-PS method had a good detection effect on obvious defects such as oil stains and holes, but there were some cases of missed detection and false detection, and the detection effect was poor for defects such as rubbing damage and gaps with small differences from the background. It can be seen that the proposed method provides complete detection of oil, foreign matter, holes, rubbing damage and warp loss defects in the fabric (Fig. 6-Fig. 10). In terms of detection efficiency,our method takes 46.15 ms to detect an image, which is only a small increase in time consumption compared to 38.25 ms for ReNet-D and 43.82 ms for SDDM-PS.

Conclusion A defect detection method based on defect image reconstruction is proposed. This method combines GAN network and self attention mechanism, and makes full use of the advantages of both to improve the reconstruction accuracy of defect images. At the same time, aiming at the problem of weak image detail processing in the generation of adversarial neural network loss function, L1 loss function and improved structure loss function are introduced to construct the target loss function, so as to improve the ability of CGAN network to process image details. The experimental results show that the ReNet-D method has poor detection accuracy for all kinds of defects, and even the original background of the image is used as a defect. SDDM-PS method has certain detection ability for oil, foreign matter and holes, but there are cases of missed detection and false detection, and it can hardly detect rubbing damage defects, and the detection integrity of warp loss defects is also very low. Although there is some error in the detection of rubbing damage and warp loss defects, the proposed method has a high degree of completeness and accuracy compared to the above two methods.

Development of three-jacquard spacer shoe fabrics with three-dimensional mesh structure and three-jacquard color

SUN Yuanyuan, ZHANG Qi, ZHANG Yanting, ZUO Lujiao, DING Ningyu

Journal of Textile Research. 2023, 44(07):  110-115.  doi:10.13475/j.fzxb.20220406001

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Objective At present, the warp knitted shoe fabrics on the market are mainly single- and double-jacquard shoe fabrics. However, due to the limitation of the number and configuration of the jacquard guide bars, it is difficult for single- and double-jacquard shoe fabrics to form the mesh structure both on the front layer and the back layer, and the color effect is singular. Therefore, by analyzing the process difficulties of knitting the target shoe fabrics with double-jacquard guide bar configuration, a three-jacquard bar arrangement scheme was proposed. The three-jacquard knitting process was further studied, and the three-jacquard shoe fabrics with both three-dimensional (3-D) mesh structure and three-jacquard color effect were created, which enriches the product variety of warp knitted shoe fabrics, and a design method reference for the development of other three-jacquard shoe fabric was provided.

Method By analyzing the jacquard guide bars configuration schemes of RDPJ6/2 and RDPJ7/2 warp knitted jacquard machines, the knitting function of every jacquard guide bar and general guide bar was studied, the technical difficulty of knitting the 3-D mesh structure and three-jacquard color effect was explored, and the configuration scheme of three-jacquard guide bars was proposed. Based on the RDJ6/3 guide bar configuration scheme, the jacquard process principle of three-dimensional mesh structure was studied, including the design of jacquard structure and jacquard offset information. At the same time, the process principle of using polyester, cationic modified polyester and polyamide to form three-jacquard color effect was studied, and the raw material piercing scheme and specific jacquard effect were analyzed in combination with the guide bar configuration of RDJ6/3. By using WKCAD design software and RDJ6/3 warp knitting machine, the three-jacquard spacer shoe fabrics with 3-D mesh structure and three-jacquard color effect were knitted on the machine according to the jacquard structure design, raw material threading design and lapping process design of shoe fabrics.

Results The configuration of three-jacquard guide bars are able to obtain three-layer shoe fabrics with double layers jacquard effect with the new configuration scheme RDJ6/3(Fig. 1). Among them, a back layer with mesh structure could be formed by GB1 and JB2, the spacer layer could be formed by GB3, and the three-jacquard color effect could be formed by JB4 and JB5 with different yarns, with a front layer with mesh structure could be formed by JB5. On the RDJ6/3 warp knitting machine mentioned above, the first jacquard guide bar (JB2) was designed to form a back layer mesh in the front needle, the third jacquard guide bar (JB5) was designed to form a front layer mesh with the same position and size as the first jacquard. The spacer guide bar GB3 was located in the middle of the first and third jacquard guide bar, connecting the non-mesh area of the both layers to form a 3-D mesh structure. The jacquard principle of three-jacquard color effect was to use the difference of dyeing properties of polyester, cationic modified polyester and polyamide into different half-size jacquard guide bars, and then form color patterns through the change of jacquard stitch.

Conclusion Combined with WKCAD software, the drawing of jacquard pattern and the design of jacquard structure were achieved, and 111.11 dtex(36 f)polyester, 111.11 dtex(48 f)cationic modified polyester, 33.3 dtex polyester monofilament and 77.78 dtex(48 f)polyamide were selected as yarns. The knitting of shoe fabrics with three-dimensional mesh structure with double-sided mesh and white, blue and black three-jacquard color effect was realized on RDJ6/3 warp knitting machine, which truly integrated structural functionality and color decoration with new warp knitted shoe fabrics. The breakthrough of the key technology of three-jacquard was achieved, the product style library of warp knitted three-jacquard shoe fabric was expanded, and theoretical and practical reference for the further development of three-jacquard shoe fabric was provided.

Analysis of interlayer damage acoustic emission characteristics of oxygen plasma modified ultra-high molecular weight polyethylene fiber composite materials

CHEN Lu, WU Mengjin, JIA Lixia, YAN Ruosi

Journal of Textile Research. 2023, 44(07):  116-125.  doi:10.13475/j.fzxb.20220301701

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Objective As a lightweight fiber-reinforced composite material with high strength and modulus, ultra-high molecular weight polyethylene (UHMWPE) plays an important role in modern aviation, aerospace, marine defense equipment, and other fields. Because its smooth surface is chemically inert and does not contain polar groups, the poor binding with the resin matrix would affect its interface performance. The chemical composition reconstruction on the surface of UHMWPE fiber was carried out by oxygen plasma modification, which effectively provided more polar sites for the interface layer to improve the interface binding performance between UHMWPE fiber and resin matrix.

Method In order to investigate the influence of damage mode on interlayer fracture toughness of oxygen plasma modified UHMWPE/vinyl ester composites. UHMWPE plain fabrics with a weft density of 200 picks/(10 cm) and warp density of 160, 200 and 240 picks/(10 cm) were woven and modified by oxygen plasma. UHMWPE/vinyl ester composites were prepared by vacuum-assisted resin infusion molding (VARI). Mode I (G_ⅠC) and mode Ⅱ (G_ⅡC) interlayer fracture toughness tests were carried out. The damage patterns were analyzed by the acoustic emission (AE) technique.

Results After oxygen plasma modification of UHMWPE fabrics, the water contact angle of the fiber surface was found to be reduced (Fig. 2), improving surface energy. For G_ⅠC, the maximum loads of G_ⅠC of samples U03 and P03 were 19.49 and 27.05 N, respectively. It was found that the plasma modified G_ⅠC of sample P03 by 36.8%, and the mode Ⅰ interlayer fracture angles of samples P01 and P03 were 26° and 10°, respectively (Fig. 3). P01 displayed the greatest change in interlayer fracture angle. The G_ⅠC of UHMWPE/vinyl ester composites was mainly related to the interfacial bonding properties, the woven fabrics structure, the state of the pre-crack tip, and the brittleness of the matrix. During the G_ⅠC test, AE cumulative energy of UHMWPE/vinyl ester composites increased as the warp density of UHMWPE fabric increased (Fig. 4). Because of the influence of the compact structure of UHMWPE fabric on the uniformity of modification, the interface bonding appeared to be poor. The three damage modes in the process of the G_ⅠC test responded to acoustic emission of three types of signals, respectively, i.e. Class-1 signal indicating matrix cracking, Class-2 signal fiber/matrix debonding, and Class-3 signal fiber fracture (Fig. 5). After oxygen plasma modification, the intensity of the Class-2 signal was reduced, suggesting improvement in the fiber/matrix bonding. For G_ⅡC, the maximum loads of G_ⅡC of samples U03 and P01 were 106.99 and 244.58 N. The plasma modification improved G_ⅡC of sample U01 by 1 120%, and the minimum crack propagation length of sample P03 became 0.8 mm. The maximum bending fracture angle was 145° (Fig. 7). Sample P01 showed good G_ⅡC after oxygen plasma modification, and sample P03 demonstrated the smallest crack propagation length and flexural fracture angle. The G_ⅡC of UHMWPE/vinyl ester composites was mainly related to the interfacial bonding properties, stiffness, the state of the initial crack tip, and the brittleness of the matrix. During the G_ⅡC test, UHMWPE/vinyl ester composites modified by oxygen plasma delayed the start time of AE as cumulative energy, and different damage modes were reduced or eliminated (Fig. 8). The three AE signals generated by the damage modes during the G_ⅡC test were the same as those in the G_ⅠC test (Fig. 9). After oxygen plasma modification, the signal intensity of Class-3 in the sample was reduced, and the fiber fracture was reduced.

Conclusion UHMWPE/vinyl ester composites are prepared by oxygen plasma modification of UHMWPE fabrics with different warp densities, and G_ⅠC and G_ⅡC were evaluated. The oxygen plasma modified UHMWPE/vinyl ester composites can effectively strengthen the G_ⅠC and G_ⅡC, improve the interface bonding strength and prevent crack propagation. For the loose structure of UHMWPE fabric with low warp density, the uniformity of oxygen plasma modification is the best, which has the effect of interlayer toughening. Three damage modes of UHMWPE/vinyl ester composites in G_ⅠC and G_ⅡC tests are detected by acoustic emission testing, which are matrix cracking, fiber/matrix debonding, and fiber fracture. The overlapped signals of the three damage modes in the amplitude distribution interval indicate that the damage does not appear alone, and the appearance of new damage is usually accompanied by the expansion of the previous damage, leading to the simultaneous appearance of different damage modes. Oxygen plasma modification can effectively weaken or eliminate interlayer damage and inhibit interlayer crack propagation.

Mechanical properties of carbon fiber reinforced epoxy resin woven composites based on DIGIMAT

DUAN Chenghong, WU Gangben, LUO Xiangpeng

Journal of Textile Research. 2023, 44(07):  126-131.  doi:10.13475/j.fzxb.20220103101

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Objective Braided composites have many advantages such as high specific strength, high specific stiffness, high impact damage tolerance and designable mechanical properties, and have been widely used in aerospace, machinery and other fields, and it is particularly important to optimize or design their mechanical properties. In this paper, based on a new composite simulation software DIGIMAT, a representative volume element (RVE)considering the kink defects of fiber bundles with fiber path is established to accurately and quickly predict the equivalent elastic properties of the material at different braiding angles and to explore the influence of the weaving angle on them; and then the stress distribution of two-dimensional triaxially braided composite RVE is obtained to provide a basis for further study of its damage and failure.

Method Although the internal structure of two-dimensional triaxially braided composites is relatively complex, it has a certain periodic distribution on the mesoscale. Therefore, an RVE considering the kink defects caused by fiber bundles along the fiber path was established by using the nonlinear composite modeling platform DIGIMAT, and the equivalent elastic properties of materials were predicted based on the DIGIMAT-MF module mean field homogenization method. Based on the strength failure criterion, the DIGIMAT-FE module was adopted to predict the mechanical properties of braided composites with different braiding angles under uniaxial tensile loading (peak strain of 0.5%).

Results The equivalent engineering constants of two-dimensional triaxial braided composite RVE were predicted with the longitudinal tensile modulus E₁ of 48.33 GPa, the transverse tensile modulus E₂ of 6.70 GPa, and the longitudinal Poisson's ratio μ₁₂ of 0.71, the transverse Poisson's ratio μ₂₃ of 0.45, and the shear modulus G₁₂ of 6.77 GPa. In addition, nine braiding angles of 15°, 19°, 23°, 27°, 30°, 35°, 37°, 41° and 45° were selected to analyze their influence on the equivalent engineering constant. The longitudinal tensile modulus E₁ was inversely proportional to the braiding angle. With the increase of braiding angle, E₁ demonstrated a gradual decrease, whereas the transverse tensile modulus E₂ showed an opposite trend. With the increase of braiding angle, the longitudinal shear modulus G₁₂ firstly increased and then decreased, while the transverse shear modulus G₂₃ remained virtually unchanged (Fig. 3). With the gradual increase of braiding angle, the longitudinal Poisson's ratio μ₁₂ first increased and then decreased, while the transverse Poisson's ratio μ₂₃ shows a decreasing trend (Fig. 4). The longitudinal uniaxial tensile simulation of two-dimensional triaxially braided composite RVE with different braiding angles showed that the elastic modulus of the material decreases with the increase of braiding angle, while the fracture strain is the opposite (Fig. 5). From the contour, it can be observed that the overall stress distribution is not uniform, and the stress peak tends to appear at the yarn, while the stress valley appears at the matrix, and a large stress gradient exists in the contact area between the two (Fig. 6 and Fig. 7). This is mainly because under the longitudinal tensile load, the axial fiber bundle bears most of the load, and the warp and weft yarns also bear part of the load, while the matrix basically does not bear the load effect, the warp and weft yarns improve the longitudinal bearing capacity of the material, so that the structure bears the load more uniformly. There are obvious stress concentrations in the mutual twist zone and the contact zone between the yarns and the matrix, which may lead to local deformation and crack expansion, and then cause material failure.

Conclusion The effect law of braiding angle on the equivalent engineering constant derived in this study is consistent with the law derived by experimental methods in the documents, the accuracy of the finite element model developed in this paper is verified. Based on this finite element model, the stress distribution of the two-dimensional triaxially braided composite RVE was predicted. The overall stress distribution is not uniform, and the stress of the yarn is significantly higher than the stress of the matrix. There are obvious stress concentrations in the yarn mutual kink area and the contact area between the yarn and the matrix, which may lead to the occurrence of local deformation and crack expansion, and then cause the material failure.

Preparation and tensile properties of glass fiber weft-knitted biaxial tubular fabrics

ZHOU Mengmeng, JIANG Gaoming

Journal of Textile Research. 2023, 44(07):  132-140.  doi:10.13475/j.fzxb.20220309801

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Objective Glass fiber is an important material for the preparation of tubular textile reinforcements because of its high strength, high modulus and high cost performance, but its brittleness, small fracture elongation and poor torsion resistance limit its textile processability. In order to obtain glass fiber weft-knitted biaxial tubular (WKBT) fabrics with stable and compact structure to meet industrial requirement for integrated tubular fabric formation with high strength, high modulus and low ductility, glass fiber WKBT fabric with warp and weft lining yarns constructed using 1×1 rib structure was designed and discussed, and the tensile properties of WKBT fabric were evaluated.

Method Four types of WKBT fabrics, i.e., PET₁-GF-GF, PTFE-GF-GF, PE {\mathrm{T}}_2^{\mathrm{F}\mathrm{B}}-PET₁-GF-GF, and PTFE^FB-PTFE-GF-GF, with different stitch structures and binding yarns were prepared by plaiting technology and spreading device, and their appearance morphology, transverse and longitudinal density and tensile properties were analyzed. The shrinkage was introduced to discuss the dimensional stability of WKBT fabric influenced by the stitch structure and the binding yarns. The strength efficiency of lining yarn was defined to describe the influence of different stitch structure and binding yarns on the strength efficiency of glass fiber.

Results According to the definition of "binding yarn-warp yarn-weft yarn", three types of WKBT fabrics were prepared by different binding yarn and insertion yarns, which were PET₁-PET₁-PET₁、PET₁-GF-GF、PTFE-GF-GF, respectively. The WKBT fabric was stretched in the 0° direction on the machine, and the diameter of the WKBT fabric was approximately equal to the diameter of the weft yarn along the circumferential direction of the fabric. Under the pulling force, the sinker loop transfer to leg causing loops to shrink and densely arranged along the circumferential direction, and the diameter of the WKBT fabric becomes smaller. The weft lining yarns were bent and arched on the front of the fabric under the shrinkage force of the adjacent binding loop, resulting in the phenomenon of "lining yarns buckling". "Plaiting yarn-binding yarn-warp yarn-weft yarn" was defined to describe the WKBT fabric, and the plaiting yarn on the front side of fabric (F), back side (B), and front and back (FB), respectively. Two WKBT fabrics were prepared, which are PE {\mathrm{T}}_2^{\mathrm{F}\mathrm{B}}-PET₁-GF-GF and PTFE^FB-PTFE-GF-GF. The dimensional stability and appearance of fabric was improved by the plaiting yarn, but the buckling of lining yarns still existed. Compared to the 1+1 rib, the plaiting yarn prevented more effectively the shrinkage of fabric along the circumferential direction. The total shrinkage of the WKBT fabric was small, and the fabric was stable and compact. The weft lining yarns were straightened after the WKBT fabrics were spreading, the buckling of lining yarns decreased. The WKBT fabric was more compact which was bond by the PTFE fiber. The elasticity of PTFE fiber was smaller and the fabric shrank along the 0° direction after spreading. Compared with 1+1 rib structure, the longitudinal density of WKBT fabric increased which was bond by the plaiting structure and the fabric is more compacter. Four WKBT fabrics had good tensile properties, and the strength efficiency of warp lining yarn were 70.48%, 69.14%, 63.88% and 46.02%, respectively, and the strength efficiency of weft lining yarn were 70.50%, 81.40%, 84.68% and 62.09%, respectively. The structure and tightness of stitch structure were shown to be important factors affecting the elastic modulus of WKBT fabric.

Conclusion The plaiting stitch can prevent the circumferential shrinkage of the binding stitch structure, but there is still the lining yarns buckling. The buckling of lining yarns can be solved by using the spreading device. Combined with the plaiting technology, the WKBT fabric with stable and compact structure can be prepared. The lining yarns of the four WKBT fabrics still have high elastic modulus and strength efficiency, meaning that the WKBT fabrics with excellent performance can be prepared by plaiting technology and spreading device while eliminating shrinkage.

Dyeing and Finishing & Chemicals

Multi-component quantitative analysis method for dyeing with reactive dyes

GUO Yuqiu, ZHONG Yi, XU Hong, MAO Zhiping

Journal of Textile Research. 2023, 44(07):  141-150.  doi:10.13475/j.fzxb.20221100501

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Objective Color matching dyes in the dyeing process has been attracting more attention, and more research efforts have been made to explore the principle and technology of color matching dyeing. The key to study the dyeing principle and promote the dyeing technology is to monitor the change of dye concentration in the dyeing process. At present, there is a lack of a mature and systematic online detection method and detection equipment. The difficulty lies in how to achieve fast and accurate online detection which offers strong applicability and a wide range of concentration detection.

Method A simple, sensitive and accurate multi-component quantitative analysis method was established by combining Raman spectroscopy with chemometrics method (partial least squares method), for simultaneous quantitative analysis of multi-components in mixed liquids. This detection method was adopted to construct a rapid detection and quantitative analysis model for the concentration of each component in the mixed dye solution of Reactive Violet 4 (RR4), Reactive Orange 4(RY4) and Reactive Black 5(RB5), and the process of dyeing cotton fabrics with different concentration ratios was monitored online. The detection limit of the components to be tested was determined according to the linear relationship between the characteristic peaks of Raman spectroscopy and the dye concentration, and the applicable concentration range of the quantitative components was determined.

Results The detection ranges of RR4, RY4 and RB5 were 0.08-15 g/L, 0.08-20 g/L and 0.05-20 g/L, respectively (Fig. 1 and 2). The quantitative analysis model of multi-component mixed system was constructed. The results showed that the correlation coefficient (R²) between the fitting value of the model and the standard value was greater than 0.99, and the values of root mean square error(RMSECV) and root mean square error of prediction (RMSEP) were smaller than 0.2. The multi-component quantitative analysis model constructed by this method offered high accuracy. Finally, the compatibility of dyes was further evaluated by detecting the concentration change of each component and the dyeing efficiency of fibers during the adsorption process of reactive dyes with divinylsulfone active group structure. Under the condition of dye dosage of 1% (o. w. f), in the RR4/RY4 mixed system, the dyeing percentage curve and S value of the two dyes were significantly different from those of the single component dyeing, but the dyeing consistency of the two dyes was stable under the experimental concentration ratio. The dyeing behaviors of RY4/RB5 and RR4/RB5 were consistent, and the difference was not significant compared with that of the single component dyeing. Therefore, it was generally believed that the three dyes selected showed good compatibility in the process of color matching and dyeing at lower dye dosage. In the mixed system of RR4/RY4, RR4 and RY4 still showed a competitive relationship when the dye dosage was 2% (o. w. f), but the dyeing synchronicity was not much different and the compatibility was still good. In the mixed system of RY4/RB5 and RR4/RB5, the dyeing percentage of single component fluctuated greatly and the compatibility became worse.

Conclusion The concentration range of Raman spectroscopy is found limited. When the dye concentration is too low, the sample content is low and the spectral signal is weak. When the dye concentration is too high, the fluorescence characteristics of the dye itself will affect the intensity and accuracy of the Raman spectral signal, and even fluorescence quenching occurs, making the Raman spectral signal annihilate, and limiting the detectable concentration range. Then, the study on the compatibility of reactive dyes with divinylsulfone active group structure shows that the structure and mass ratio of the mixed dyes will affect the dyeing process of a single component. Therefore, the compatibility can be evaluated according to the actual dyeing process of each component dye, so as to further guide the dye formulation design.

Preparation and properties of internal crosslinking self-matting waterborne polyurethane resin

SUN Guoqiang, YANG Jianjun, WU Qingyun, WU Mingyuan, ZHANG Jian'an, LIU Jiuyi

Journal of Textile Research. 2023, 44(07):  151-158.  doi:10.13475/j.fzxb.20220600201

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Objective The conventional matting resin is prepared by adding matting agent, however, this method has some shortcomings, such as easy sedimentation and insufficient stability when added in high dosoges, which is not conducive to storage and use. This research aims to prepare self-matting waterborne polyurethane without adding extra matting agent.

Method A series of internal crosslinking self-matting waterborne polyurethane emulsions and films were prepared from isophorone diisocyanate (IPDI) and polypropylene glycol (PPG) as monomers, 1,4-butane-diol (BDO) and 2,2-dimethylolbutyric acid (DMBA) as chain extenders, dipentaerythritol (DPE) as crosslinking agent, and hydrazine hydrate as post chain extender. The chemical structure of the film was characterized by Fourier transform infrared spectrometer. The surface morphology of the films was observed by scanning electron microscope. The thermodynamic properties of the films were tested. The Influences of DPE and hydrazine hydrate on the surface glossiness of the films were investigated. The influences of DPE dosage on the particle size, storage stability, mechanical properties, water resistance and thermal stability of the film were studied.

Results The glossiness of the films decreased with the increase of DPE dosage, indicating that the self-matting property of waterborne polyurethane could be improved by internal crosslinking modification. When the mass fraction of DPE was 1.75%, the glossiness of the film surface reached 4, which was consistent with the self-matting mechanism. In addition, the self-matting property of waterborne polyurethane resin was also affected by post chain extension. With the increase of the mole fraction of hydrazine hydrate, the 60° glossiness of the films surface decreased gradually, and when the mole fraction of hydrazine hydrate reaches 40%, the 60° glossiness of the film reached the minimum, indicating that the glossiness was also affected by the degree of post chain extension. The average particle size of the emulsion reached 1 192 nm, indicating that crosslinking modification can effectively increase the average particle size of the emulsion. The water absorption of the films was decreased from 65.2% to 7.1%, suggesting that the water resistance of the films was significantly improved. With the increase of DPE mass fraction, the break strength of the films was gradually increased while the elongation at break gradually was decreased, when the DPE mass fraction was set to 1.75%, the tensile strength reached 20.24 MPa, and the elongation at break was decreased to 420%. Compared with the pure waterborne polyurethane film, the break strength was increased by 122.2% while the elongation at break was decreased by 39.9%, indicating that the physical properties of the films were improved. The temperatures of 10% and 50% thermal weight loss were increased by 6.5 ℃ and 8.0 ℃, respectively, indicating that the same percentage of weight loss of the films require a higher temperature, and the thermal stability of the films was enhanced.

Conclusion The self-matting property of waterborne polyurethane resin can be effectively improved by internal crosslinking modification and post chain extension. In addition, the mechanical properties and water resistance of resin were significantly enhanced by crosslinking modification, but excessive crosslinking agent is not conducive to the stability of the emulsion. Finally, the decomposition temperature corresponding to the same percentage of weight loss of the films was increased, indicating the thermal stability of the films was improved.

Research and application of ink jet printing on cotton fabrics

CHEN Jiahui, LIANG Yueyao, CHEN Ni, FANG Kuanjun

Journal of Textile Research. 2023, 44(07):  159-166.  doi:10.13475/j.fzxb.20220602301

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Objective Because of the different surface properties of printing materials, the spreading and penetration of ink on the substrate are different. Fabrics are composed of regular fiber structure, which makes its interface have a directional diffusion path. The spreading and penetration behavior of ink on fabrics would causes the diffusion area of ink to be much larger than the theoretical area, known as the dot gain phenomenon, which leads to blurred edges of printing images, changes in color scales, and seriously affects the image restoration effect. Therefore, it is particularly important to reduce the excessive diffusion of ink on fabric and improve the quality of image printing.

Method In order to solve the problem of poor image restoration caused by excessive diffusion of ink on the fabric, this research proposed a method of cluster dot printing, which uses image processing software to gather and print the originally scattered printing points according to certain rules, which could effectively reduce the excessive diffusion of ink and achieve the effect of high-precision image reproduction.

Result Because of the difference in the material and structure of the printing medium, the diffusion of ink is different (Fig. 3). The perimenter of a single ink drop on the cotton fabric is 2.26 times that on the copper proofing paper, and the area is increased by 36% (Tab. 1). The ink expansion rate on cotton fabric was significantly higher than that on copper proofing paper, which results in that the printing method applicable to the paper may not be applicable to the cotton fabric. Different printing methods were adopted to print on cotton fabric. The area expansion rate of scattered printing points on cotton fabric was as high as 40%, while the area expansion rate of clustered printing ellipse points on cotton fabric was only 16%, and the area expansion rate is reduced by 24%. Therefore, the clustered printing mode was shown to be effective in reducing the diffusion of ink on cotton fabric (Fig. 5). The change of printing mode could improve and reduce the ink diffusion and thus the printing effect. Lines are the units that constitute patterns. When printing lines of 0.5 mm, the difference in line thickness formed by clustered printing is less than 10%, far less than the 30% of scattered printing, greatly improving the uniformity of the print line, and making the print spacing closer to the ideal spacing (Fig. 6). Clustered printing could better restore the color scale of the image. Compared with scattered printing, the reflection rate of light was reduced by 9%. Compared with the points used for clustered printing, the light absorption rate of dispersion printing was significantly enhanced. This indirectly suggests that the point expansion of scattered printing may lead to the contact between adjacent points, which increases the actual ink area, thus increasing the light absorption (Fig. 8). The use of clustered printing would better restore the image and improve the printing effect. The final image of scattered printing would be much darker than the original image with some noise, which affect the printing quality. Compared with scattered points, the pattern printed in clustered printing mode would be brighter and reduce noise. This is because polymerization printing can effectively reduce the diffusion of ink on the fabric and improve the printing quality (Fig. 9).

Conclusion From the perspective of ink diffusion on the substrate, the diffusion of a single ink drop on the cotton fabric is greater than that on the copper proofing paper, which results in that the printing method applicable to the paper may not be applicable to the cotton fabric. Compared with scattered printing, the clustered printing technology gathers randomly printed dots to form dots of different shapes according to certain rules, which can effectively reduce the diffusion of ink on cotton fabrics, reduce the dot gain of ink drops, and thus improve the resolution of image repruduction. When printing lines, clustered printing can effectively avoid the uneven thickness of lines, and make the actual line width closer to the theoretical width. When printing images with different grayscales, the clustered printing can effectively avoid the grayscale darkening of the image caused by dot enlargement, and reduce the noise in the printing process, so as to improve the printing quality.

Preparation and properties of multichromatic thermochromic cotton fabrics using SiO₂ microcapsules

TAN Jialing, LIU Jiayin, YU Weidong, YIN Yunjie, WANG Chaoxia

Journal of Textile Research. 2023, 44(07):  167-174.  doi:10.13475/j.fzxb.20220307401

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Objective Low-temperature reversible thermochromic textiles are not only fashionable and attractive, but also applicable for temperature indication and anti-counterfeiting, showing the potential economic and social benefits of thermochromic textiles. However, the majority of thermochromic textiles are currently available for single-color change, e.g. from colored to colorless or colored to colored. In order to broaden the color change range of thermochromic textiles and achieve multichromatic thermochromic color change, SiO₂ shell thermochromic microcapsules with various colors were prepared and finished on cotton fabrics to obtain multichromatic thermochromic cotton fabrics.

Method In this research, tetraethyl orthosilicate was used as the silica source and fluorane-diphenyl sulfone-aliphatic alcohol as the core material to prepare multi-color SiO₂ shell thermochromic microcapsules by sol-gel method. After blending and dyeing cotton fabrics, cotton fabrics with continuous chromatographic color change with temperature change were obtained. Scanning electron microscopy was adopted to observe the morphological features of microcapsules. The chemical structure of the microcapsules was characterized employing infrared spectroscopy. The thermal stability of the microcapsules was tested with a thermogravimetric analyzer. The color change of thermochromic cotton fabrics was characterized by colorimeter.

Results The SiO₂ shell thermochromic microcapsules prepared by sol-gel method had uniform size dispersion and smooth surface (Fig. 2). The average particle size was about 0.9 μm (Fig. 3). The microcapsules demonstrated excellent thermal stability, where thermal degradation temperature was shown up to 200 ℃ (Fig. 5), much higher than daily service temperature. The microcapsules are finished onto the surface of the cotton fabric using the dip-roll method. After 50 heating-cooling cycles, the change of K/S value is only 0.01, showing the thermochromic microcapsules possess excellent thermal cycling durability (Fig. 7). The color change of cotton fabric in response to heat was still obvious. The excellent thermal stability and cycling durability could be attribute to fluorene, the developing agent, with sensitive color development, good stability and abundant color. The single-color change of thermochromic cotton fabric was obvious (Fig. 9), and the reflectance demonstrated an overall upward shift with temperature increasing, with the cotton fabric changing from colored to colorless (Fig. 8). It was possible to obtain thermochromic textiles with different color change temperatures by changing the solvent phase change point (Tab. 1). After different color-change thermochromic microcapsules of red, yellow and blue compound were coated onto the cotton fabric, the obtained multichromatic temperature sensitive color change cotton fabric was able to achieve step color change (Fig. 10). The color change performance of polychromatic color-change cotton was reliable and color change effect was obviously.

Conclusion Thermochromic microcapsules with SiO₂ shell have been successfully prepared by sol-gel method on fluorane-diphenyl sulfone-aliphatic alcohol core material. The prepared thermochromic microcapsules indicate superb microscopic morphology and uniform size dispersion. The prepared thermochromic fabric has good thermal stability and thermal cycling durability and can meet the requirements of daily use, which broadens the temperature variation range of thermochromic cotton textiles. The prepared multichromatic thermochromic textiles can respond to temperature from 20 to 55 ℃. Since the prepared thermochromic cotton fabric can achieve gradient color change, it can be utilized to indicate the temperature. It is expected that the multichromatic thermochromic cotton fabrics would be employed in the fields of food safety for temperature indication to indicate suitable storage temperature. It also can be used on anti-counterfeiting and building for environmental temperature indication. However, further increase of the temperature sensing accuracy of thermochromic materials still need further attention. Compared to inorganic thermochromic materials, organic thermochromic materials is non-toxic, and excellent in temperature sensitivity and color density. However, the color change performance of organic reversible thermochromic materials in the high temperature region is still a major problem, which is a hot spot in future research.

Decolorization properties and mechanism of waste cotton fabrics for preparing cotton pulp

WANG Wei, WU Jiaxin, ZHANG Xiaoyun, ZHANG Chuanjie, GONG Zhaoqing

Journal of Textile Research. 2023, 44(07):  175-183.  doi:10.13475/j.fzxb.20220202401

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Objective It is urgent to adopt the mild decolorization technology for waste cotton fabrics to achieve clean pulping to resolve the problems that the high consumptions of energy, as well as severe degradation of cellulose during preparation of cotton pulp from waste cotton fabrics.

Method Due to the violent reaction when decolorizing cotton fabric with oxidant, the breaking strength of the decolorized cotton fabric is lost more, and the molecular chain is broken seriously. While the reaction when decolorizing cotton fabric with reductant is relatively mild. A method for decolorizing was conducted to black mercerized cotton fabric, named as the sodium hydroxide-sodium hydrosulfite system through orthogonal experiment and single factor experiment. The role of decolorization parameters, influence of decolorization treatment on the structure and properties of cotton fabrics and mild decolorization mechanism were investigated.

Results Sodium hydroxide can improve the stability of sodium hydrosulfite (Fig. 1), and can hydrolyze and destroy the covalent bond between reactive dyes and black mercerized cotton fabric, so that the dyes on cotton fabric can hydrolyze and diffuse into the decolorization solution(Fig. 2). At the same time, the dye chromophore group on the cotton fabric and in the solution will be destroyed under the reduction of sodium hydrosulfite (Fig. 3). Because sodium hydrosulfite itself will undergo invalid decomposition, sodium hydrosulfite is added in a two-step process decomposes more active substances for decolorization and shorten the time of decolorization reaction (Fig. 5 and Fig. 6), and the lightness value of the decolorized cotton fabric is increased from 16.52 to above 70.00 by adopting the best two-step decolorization process. Almost no dye remains on the cotton fibers under the synergistic effect of sodium hydroxide and insurance powder (Fig. 7). The decolorization system has been proved to be able to reduce the strength loss of the cotton fabric after bleaching, and the break strength retention rate of the cotton fabric after decolorization in both warp and weft directions is more than 98% by adopting the best two-step decolorization process(Fig. 8). The chemical structure and crystal structure of cotton fabric are hardly affected during the decolorization process. Among which, sodium hydrosulfite will destroy the chromophore group of the dye without destroying the covalent bond between the dye and the cotton fiber. sodium hydroxide will hydrolyze the covalent bond between the dye and the fiber, and the hydrosulfite will promote the hydrolysis of the covalent bond by sodium hydroxide (Fig. 9). Only a small amount of the crystal area of cotton cellulose has been damaged, and most of the crystal area and crystal structure are not affected during the decolorization process of sodium hydroxide-sodium hydrosulfite system (Fig. 10), and the position of the diffraction peak of cotton cellulose has not changed before and after decolorization. Finally, it has been found that the molecular weight and its distribution of cotton fiber were almost unchanged before and after decolorization by gel liquid chromatography (Tab. 3).

Conclusion In summary, sodium hydroxide can promote the hydrolysis of covalent bond between reactive dyes and cotton fabric, and transfer dyes on cotton fabric to decolorization solution; and sodium hydrosulfite can destroy the chromophore group of the dye to achieve the purpose of decolorization. The coexistence of sodium hydroxide and sodium hydrosulfite in the decolorization solution can promote each other, thereby realizing the decolorization of cotton fabrics. Thus, the sodium hydroxide-sodium hydrosulfite system, which be adopted to decolorize cotton fabric under normal pressure and high temperature, can achieve mild decolorization of waste cotton fabric without affecting subsequent pulping.

Apparel Engineering

Body shape characteristics and classification of middle-aged and elderly women in eastern China

LIU Yongmei, LIU Siyi, YU Xiaokun, XUE Huixin, ZHANG Xianghui

Journal of Textile Research. 2023, 44(07):  184-191.  doi:10.13475/j.fzxb.20220504501

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Objective Nowadays, China's aging population is becoming increasingly severe, the size of middle-aged and elderly people is expanding, and so is the related clothing market. Middle-aged and elderly people put forward higher requirements for the comfort and aesthetetics of clothing, and the human body shape is closely related to the structure and shape design of clothing. Among them, the differences between middle-aged and elderly women and young women are significant in the shapes of chest, waist, abdomen and back. This research is proposed to study the body shape characteristics and classification of middle-aged and elderly women.

Method In order to further explore the body shape characteristics and distribution of middle-aged and elderly women, 207 middle-aged and elderly women aged 50-65 from eastern China were selected as research subjects, and 20 pieces of body size data were collected according Martin's measurement method. According to the national women's size standard, the collected data of body shape of middle-aged and elderly women were classified based on the difference of chest and waist and compared with the data of body shape proportion of the national standard to obtain the differences between the standard body shape of middle-aged and elderly women and the standard body shape of adult women. Further factoral analysis and correlation analysis were carried out on the collected data to acquire characteristic variables affecting the body shape of middle-aged and elderly women. Finally, based on the influence factor with the highest correlation, the body shape of middle-aged and elderly women was classified through rapid cluster analysis, and the value range of characteristic variables was calculated.

Results Compared with the national standard GB/T 1335.2—2008《Standard Sizing Systems for Garments-Women》, the proportion of Y and A types decreases while the proportion of B and C types increases, among which the proportion of B type is the highest (Tab. 2 and Tab. 3). The results of factor analysis showed that circumference factor was the main factor affecting the body shape difference of middle-aged and elderly women, the front and back waist section difference was the characteristic variable affecting the body shape of the torso, the waist ratio, the chest-waist difference, the hip-waist difference was the characteristic variable affecting the body height, slimness and fullness index (Tab. 4 and Tab. 5). Combined with factor analysis and extraction results of human characteristic variables, clustering was finally carried out from two perspectives, i.e. the difference between front and back waist section difference was taken as a clustering index, and waist, waist ratio, chest-waist difference and hip-waist difference were taken as clustering indexes. The results of K-means fast clustering showed that the human body shape was divided into humpback body, slight humpback body, normal body and chest pull-out body by using the difference of front and back waist as the benchmark. Based on waist circumference, waist ratio, chest-waist difference and hip-waist difference, human body shape was classified into X type, H type, small A type and A type. Finally, the value range of clustering indicators of each body type was obtained (Tab. 11 and Tab. 12).

Conclusion The body shape of middle-aged and elderly women shows an obvious trend of obesity, and the coverage rate for their body shape in the national standard is low, which calls for targeted clothing size standards to be established. Circumference factor is the main factor affecting the body size difference of middle-aged and old women. Through cluster analysis, the body shape of middle-aged and elderly women are divided into four categories from the aspects of trunk shape, and body height, thinness and fullness, and their body shape are subdivided more accurately, providing reference for the establishment of clothing type of middle-aged and elderly women. For future research, it is suggested to increase the sample size of the research subjects to better represent body shape of middle-aged and elderly women, so as to improve the accuracy of body type classification.

Three-dimensional virtual try-on network based on attention mechanism and vision transformer

YUAN Tiantian, WANG Xin, LUO Weihao, MEI Chennan, WEI Jingyan, ZHONG Yueqi

Journal of Textile Research. 2023, 44(07):  192-198.  doi:10.13475/j.fzxb.20220508401

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Objective Three-dimensional (3-D) virtual try-on can provide an intuitive and realistic view for online shopping and has great potential commercial value. However, there are some problems in the existing 3-D virtual try-on network, such as inaccurate generated 3-D human models, unclear model edges and excessive clothing deformation in the virtual fitting, which greatly limit the application of this technology in real scenarios.

Method In order to solve the above problems, this research proposed the network named T3D-VTON, a deep neural network introducing convolutional attention mechanism and vision transformer. The network was designed to have three modules: 1) a convolutional block attention module that was added to the feature extraction module to make the network focus on the key information and reduce the influence of irrelevant information; 2) a depth estimation network which was created to adopt an encoder-decoder structure for the establishment of a multi-scale neural network combining Resnet and transformer; 3) a feature fusion module that aimed to fuse 2-D and 3-D information to obtain the final 3-D virtual fitting model. The effect of adding the convolution attention mechanism and vision transformer module on the performance of the network was investigated in details. The performance of the network is mainly expressed by the virtual fitting results and the accuracy of the human body model. Qualitative and quantitative comparative analyses were conducted between this experiment and the benchmark network.

Results The quantitative experimental results showed that the structure similarity index measure (SSIM) was improved by 0.015 7 compared with the baseline network, and the peak signal-to-noise ratio (PSNR) improved by 0.113 2. The above results indicated that the image generation quality is improved without much loss of information. In terms of human model generation accuracy, compared to the baseline network, absolute relative error was reduced by 0.037 and square relative error was reduced by 0.014 in the results of depth estimation, indicating that the 3-D human model generated by this network was more accurate and the depth in the depth map was more consistent with the original given ground truth. The qualitative experimental results showed that the deformation of the garment fitted the original area of the target body more closely without excessive deformation and reduced the generation of garment artifacts. When dealing with complex textures, the network was able to better preserve the pattern and material of the garment fabric. The generated 3-D human body try-on model showed the front and side effects of the human body model, suggesting that the 3-D human body model generated by the network presents clearer contour edges and effectively eliminates the adhesion between the arms and the abdomen. When the knees are close to each other for example, the network would be able to eliminate the adhesion between the knees.

Conclusion The convolutional block attention module and vision transformer introduced by the T3D-VTON network are able to preserve the textural patterns and brand logos on the garment surface when dealing with complex textures. The structure can effectively regulate the garment deformation and blend reasonably with the dressing area of the target character. When generating the 3-D human body model, the network can produce a clearer edge and has more accurate shape generation capability. The method can finally present a 3-D human body model with richer surface texture and more accurate body shape, which provides a fast and economical solution to realize a single image to 3-D virtual application.

Machinery & Accessories

Modeling and control strategy of composite braiding-winding-pultrusion system

YANG Jin, LI Qiyang, JI Xia, SUN Yize

Journal of Textile Research. 2023, 44(07):  199-206.  doi:10.13475/j.fzxb.20220500101

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Objective The load uniformity of braiding machine motor and the co-control of braiding, winding and pultrusion system seriously affect the stability of production systems, thus affecting the mechanical properties of formed parts. Therefore, in order to ensure the load uniformity of the motor and the system cooperative control among the weaving machine, the winding machine and the traction device is crucial to control the quality of the molding parts.

Method The dynamic uniform load control method based on the model predictive control (MPC) is proposed and applied to the braiding electromechanical unit, and the integrated mathematical model of the braiding-winding-pultrusion production system is established. The proportional synergistic deviation coupling control strategy is adopted to improve the collaborative working accuracy of the production system. The simulation and experiments were carried out to verify the proposed modeling and control strategy.

Results It was showed that the braiding machine motor speed can reach the stable state within 0.05 s under both two control strategies. The fluctuation of the motor speed under the dynamic uniform load control condition is within 2%, while the fluctuation of the motor speed under the parallel control condition is within 1%. Braiding machine motor torque showed that the output torque reaches the stable state within 0.05 s. For the same time, the maximum deviation of the output torque under the parallel control model is nearly 1 N·m, while the maximum deviation of the output torque of the dynamic uniform load control is about 0.2 N·m. Simulation results before model coupling shows the duration to the stable state for the braiding machine, winding machine and traction device. Since the three devices are independent of each other and have no direct physical connection, the times to steady state of these three devices are different. The motor speed of the braiding machine and the winding machine can be stabilized within 0.03 s, while the motor of the traction unit can be stabilized at about 0.08 s. Simulation results after model coupling shows the time to the stable state for the three devices under the proportional synergistic deviation coupling control model. The motor of the three devices reached the stable state within 0.08 s. The measured motor speed of the three devices under the proportional synergistic deviation coupling control condition showed good agreement with the simulation results. Braid angle comparison before and after control strategy optimization showed the braid angle fluctuates greatly before the optimization, while the weaving angle fluctuates little after the optimization.

Conclusion 1) The dynamic uniform load control method based on MPC effectively solves the problem of uneven load of the motor in the braiding process. In addition, the output torque is significantly reduced while the motor speed of the braiding machine is synchronized. 2) The proportional synergistic deviation coupling control strategy significantly improves the accuracy of the collaborative work of the production system. 3) The dynamic uniform load control method based on MPC and the proportional synergistic deviation coupling control strategy can effectively improve the stability of the braid angle, which will improve the mechanical properties of the forming parts. This research will provide support for industry production.

Design of needling robot system for quasi-rotary preforms

LI Jiao, CHEN Li, YAO Tianlei, CHEN Xiaoming

Journal of Textile Research. 2023, 44(07):  207-213.  doi:10.13475/j.fzxb.20220502201

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Objective Quasi-rotary composite preforms are increasingly used in high-speed aircrafts. The shape and structure of the quasi-rotary composite preform are complex, and the current 4-axis needling system and 6-joint robot needling system cannot meet its weaving requirements. A 7-axis linkage needling system based on a robot platform was proposed for needling of the quasi-rotary preforms.

Method The mechanical structure design, control system design, and needling trajectory planning method of the 7-axis needling system were carried out, and the feasibility of the system was verified by motion simulation and experiment. The needling end-effector adopted apneumatic actuator, which had simple structure, easy maintenance, and light weight. Considering the high-quality needling requirements of large size preform components, a computer numerical control (CNC) rotary table with large load capacity and high accuracy was selected. The needling trajectory planning software was developed to facilitate the generation of the control program of the quasi-rotary preform needling robot.

Results The quasi-rotary composite preform needling robot was composed of a 6-joint mechanical arm, a needling end-effector, and a CNC rotary table. A Kawasaki RS050N mechanical arm was adopted for 6-joint mechanical arm, with end load of 50 kg. Universal TK13250Q CNC vertical and horizontal rotary table was selected as the rotary table. The reduction ratio was 90, and the maximum allowable inertia was 1.2 kg/m², which meet the system operation requirements. The continuous milling program development function of Powershape and Powermill was adopted to design the needling trajectory and output the position and posture information of continuous points on the trajectory. Based on Python language and QT Designer, the post-processing software of 7-axis linkage needling robot program was developed (Fig. 7). Through the simple user interface, the 7-axis needling program was designed, which reduced the workload and the human error caused by the tedious generation process. The main work of converting 6-axis program to 7-axis program was to transform the position and posture of needle points in the plane. The experiment verification results showed that the system achieved the integral needling formation of the quasi-rotary preform, the needling experimental trajectory of the quasi-rotary body was highly consistent with the theoretical design trajectory, the needling trojectory was uniform, and the surface of the preform was flat, which proved the feasibility of the 7-axis linkage needling system (Fig. 10). It was proved feasible to use Powershape and Powermill software for continuous trajectory design and robot 6-axis program output, and the 7-axis linkage needling robot independently developed based on Python could execute the program post-processing. The algorithm for converting programs into 7-axis programs was reliable.

Conclusion This paper presented a 7-axis robot needling system for manufacturing composite preforms with quasi-rotary structures. The needling robot system realized the needling formation of the quasi-rotary preforms. The needling experimental trajectory of the preform parts of quasi-rotary body was highly consistent with the theoretical design trajectory, the needle trajectory was uniform, and the surface of the preform parts was flat, which proved the feasibility of the 7-axis linkage needling system. It was feasible to use Powershape and Powermill for continuous trajectory design and 6-axis robot program output, which facilitated needling trajectory planning of complex special-shaped surfaces. The self-developed algorithm of transform the 6-axis program into the 7-axis program was reliable, and the self-developed post-processing software of the executable program of the 7-axis linkage needling robot based on Python was feasible. The system could be used for high-quality needling of radome preforms and cabin preforms for high-speed aircrafts.

Comprehensive Review

Research progress in preparation and application of conductive yarn materials

LI Long, ZHANG Xian, WU Lei

Journal of Textile Research. 2023, 44(07):  214-221.  doi:10.13475/j.fzxb.20211105002

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Significance The good conductivity of the material is the basis of manufacturing smart wearable devices. Because textile material is light, soft and good in air permeability and shape adaptability, textile-based flexible smart wearable devices have been attracting extensive attention from researchers. In recent years, the researchers have been using various techniques to integrate conductive materials with textile materials for manufacturing textile flexible intelligent wearable device for real-time monitoring of human health, friction power generation, personal thermal management, energy storage and so on. Conductive yarn is one of textile intelligent wearable materials, in order to further study the low-resistance and multi-performance conductive yarn for smart wearable devices, textile yarns was taken as the object. The methods of preparing conductive yarn materials were reviewed in relation to spinning technology, coating, coating combined with spinning technology and electrostatic spinning technology and application of the conductive yarns in electromagnetic protection, sensing device, energy storage device, transmission and power supply, artificial muscle, electric heating and thermal management device in recent years.

Progress The advantages and disadvantages of conductive preparation methods are analyzed. Both conventional textile fibers and conductive fibers are spun into yarns by blending or wrapping using spinning technology, which can produce conductive yarns in batches. Besides, the yarn has excellent textile characteristics. However the conductive yarn is seldom used in resistance strain sensing. It is difficult for the mass production of conductive yarn prepared by coating technology, and the yarn has poor performance stability and poor weaving property, the preparation process is complicated and coating waste liquid may cause environmental pollution. Compared with the spinning technology, the method of preparing conductive yarn by coating is flexible, and the yarn has wide application. The auxiliary technology of electrostatic spinning nanofibers plays an important role in developing conductive yarns, and the conductive yarn with sheath-core structure prepared by electrostatic spinning technology overcomes some problems existing in conventional conductive coating. However, it is difficult to mass-produce conductive yarn by this method. The conductive yarn prepared by coating combined with spinning technology has good textile characteristics, but the conductive coating waste liquid of textile fiber materials may also cause environmental pollution.

Conclusion and Prospect The future research and development trends of conductive yarn materials are proposed by combining the performance stability and the environmental safety of conductive yarn in its life cycle. It is proposed that the stability and service life of sensing performance under large strain needs to be further improved for the conductive yarn prepared used for resistance strain sensor. The conductive yarn needs additional flame retardant function,elasticity function and flexibility for their use in electric heating products so as to improve the use safety and wearing comfort. It is necessary to further study the change law of yarn conductivity under special environmental conditions (such as wet environment, high temperature environment, low temperature environment), so as to develop textile-based flexible smart wearable devices to be used in different temperature and humidity environments. It is still a research focus to develop conductive yarn materials with textile characteristics and lower linear resistance and good linear resistance uniformity. In order to popularize the practical application of textile flexible intelligent wearable devices, a development goal is that the whole life cycle of manufacturing, using and discarding of the conductive yarn has no negative impact on human health and environment. It is necessary to further optimize the structure of conductive yarn and innovate the integration technology of conductive materials and textile fiber materials, and improve the durability, sensibility, weaving property, biodegradability and mass production capacity of the conductive yarn.

Advances in regulations/standards and analytical methods of phenolic compounds in textiles

LUO Xin, DING Youchao, YE Xiwen, LI Xiaotong, GAO Yonggang, NIU Zengyuan

Journal of Textile Research. 2023, 44(07):  222-231.  doi:10.13475/j.fzxb.20220601702

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Significance Various types of colorants, chemicals and auxiliaries used during the production and processing progresses of textiles may eventually remain in the commercial products, causing potential hazardous risks to the environment and human health. Therefore, many countries and regions have prohibited or restricted their use in textiles. Furthermore, with the development of science and technology and the improvement of living standards, more attentions have been paid to the safety and environmental protection of textile and apparel, and the concept of green and ecological textiles has gradually gained popularity. Phenolic compounds, such as alkylphenols, were widely used in the textiles, leather, resins, dyes, pesticides, papermaking and petrochemical industries as preservatives, fungicides, adhesives, antioxidants, dye intermediates and flame retardants. In recent years, because of the increasing and stricter detection standards of phenolic compounds in textiles, the existing technologies are facing new challenges.

Progress This paper firstly reviewed the requirements of related textile regulations/standards from the aspects of limited amount of compounds, limit values, recommended testing methods, and risks of different materials. Considering the complexity of alkylphenols with a large number of isomers, this paper particularly discussed the restrictions of different regulations or standards on these substances. From the perspective of the source of regulatory material information, the analysis object of relevant environmental testing standards, and the actual industrial use, this paper provided suggestions on specific testing compounds of alkyl phenols in textiles. At the same time, this study reviewed the development progress of detection technology and detection standards for phenolic compounds, including chlorophenols, alkylphenols, bisphenols in textiles in terms of sample pretreatment and analysis methods. The extraction methods, including extractant, temperature, time and other parameters were compared in detail. Based on the requirements of regulations/standards for simultaneous determination of phenolic compounds, their salts and esters, the research and shortcomings of existing docoments in this field were discussed. As for instrument analysis, various instrumental methods for simultaneous determination of multiple phenolic compounds were described based on gas chromatography, gas chromatography-mass spectrometry, liquid chromatography, and liquid chromatography-mass spectrometry.

Conclusion and Prospect With the gradual improvement of the global chemical management system, as well as the increasing environmental protection awareness of consumers and manufacturers, some problems in the analytical field become emerging. Firstly, with the increasing number of controlled substances and the increasing severity of indicators, the conventional technology usually lags behind the regulatory requirements in terms of compound coverage, method sensitivity and selectivity. The conventional idea is to passively carry out the research of detection technology after the introduction of new regulations and requirements. Secondly, multiple classes and dozens of phenolic compounds were included in the regulations or standards, and most of the existing methods are only limited for single class of compounds. Moreover, since the risk level of the product cannot be fully understood, the detection of all classes of chemicals in ecological textiles leads to the problems of high cost and high time consumption. Thirdly, the convenitional detection model for banned substances in ecological textiles is all about the analysis of target compounds, which lacks the identification and discovery of harmful chemicals that are misused and abused in the supply chain, and the risk identification of new or alternative textile chemicals. Finally, the vast majority of textile chemical safety tests are carried out in the laboratory with large chromatographic instruments or mass spectrometers, however, methods with low-cost and rapid detection are still very rare. In addition, according to the latest research reports, some scholars are conducting extensive and in-depth research in the field of human exposure risk assessment of textile chemical residues. This direction will also be a good combination and development point of chemical analysis and environmental research of ecological textiles.

Research progress in recycling and reuse of waste textiles and clothing

SHEN Ya, CHEN Tao, ZHANG Lijie

Journal of Textile Research. 2023, 44(07):  232-239.  doi:10.13475/j.fzxb.20220306202

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Significance Sustained development is one of China's long-term strategies, and recycling and reuse of waste textile and clothing plays an important role in this policy. Recycling, sorting and reuse are main procedures for recycling and reuse of waste textile and clothing, and the ways to recycle and reuse waste textile and clothing influence the effect of recycling and reuse. This paper collates and reviews the current academic research and industry development in recycling and reuse of waste textile and clothing in detail, and expounds the whole recycling and reusing system of waste textile and clothing based circular economy 4R(reduce,reuse,recycle,remanufacture)principles aiming to enrich the theory and promote the high-value recycling and reuse of waste textile and clothing resources, hoping to realize efficient ecological economy.

Progress The current situation of the recycling and reuse of waste textile and clothing in China and abroad, the recycling and reuse technical methods and the market system are reviewed. The recycling and reuse patterns of waste textile and clothing are various. Compared with some overseas developed countries, China has some shortages in public policy, enterprise leadership and the cooperation among organizations. Sorting technology and reuse technology are the core technology of the recycling and reuse of waste textile and clothing, among which sorting technology consists of artificial method, general qualitative and quantitative analysis methods, near infrared spectroscopy and other technologies, reusing technology mainly covers clean technology, physical reuse methods and chemical reuse methods. Artificial method is the most common sorting method. Physical loosening method and remelting processing method are common high value-added physical reuse methods. The industrial chain of recycling and reuse of waste textile and clothing starts from the end of the traditional textile and clothing industry chain, and ends with the recycling-reusing products. Two organizational operation forms are adopted for the recycling and reuse of waste textile and clothing. One is the reverse organization operation mode of enterprises, the other is the social network organization operation mode. Each mode has its advantages and disadvantages. This paper analyzes the recycling and reuse system of waste textile and clothing based on the 4R principle of circular economy. The "reduce" principle is the first choice for the textile and clothing industry to solve the resource and environmental problems.

Conclusion and Prospect Recycling and reuse industry of waste textile and clothing is still in primary stage in China. It is still a long way for China to reach the level of developed countries. This paper proposes four suggestions for the future development in recycling and reuse waste textile and clothing in China. First, intensively cultivating second-hand textile and clothing market is essential, because second-hand textile and clothing market is valuable in recycling and reuse development. Second, standardizing recycling and reuse links is also important that could built standardization technical process and industry green assurance system. Third, focusing on core technology is also necessary. Technology development will greatly promote the recycling and reuse effect of waste textile and clothing industry. Beside all above, enhancing the awareness of resource recycling and reuse in all society is also a significant step by virtue of the fact that the improvement of the recycling-reusing awareness will help all recycling links become more active and initiative. In general, China needs to make suitable policies according to the national conditions to promote cooperation among all parties and organizations and scientific research activities to develop the waste textile and clothing industry. The social benefit of recycling and reuse of waste textile and clothing should be maximized, and the waste textile and clothing resources would be utilized profitably in ecology and economy!