Preparation and Properties of a Novel Cross-Linked Network Waterborne Polyurethane for Wood Lacquer.

Waterborne polyurethane (WPU) is a waterborne coating with excellent physicochemical properties. Its deficiencies of water resistance, chemical resistance, staining, and hardness have limited the wide application of polyurethane in the wood lacquer market. In this study, polycarbonate diols (PCDL) were used as soft segments and WPCU was modified by cross-linking using Trimethylolpropane (TMP) to prepare polycarbonate type WPU (WPCU) with cross-linked network structure. The new wood lacquer was prepared by adding various additives and tested by applying it on wood board. The successful synthesis of WPCU was determined by FTIR testing, and the cross-linking degree of WPCU was probed by low-field NMR. The viscosity of the cross-linked WPCU emulsion showed a decreasing trend compared to the uncross-linked WPCU emulsion, and WPCU-2 had the smallest particle size. Compared with the uncrosslinked WPCU film, the crosslinked WPCU film had lower water absorption (2.2%), higher water contact angle (72.7°), excellent tensile strength (44.02 MPa), higher thermomechanical, and better water and alcohol resistance. The effect of crosslinker content on the microphase separation of WPCU chain segments on the surface roughness of the film was investigated by SEM. The wood paint prepared by WPCU emulsion has good dry heat resistance, chemical resistance, and adhesion, and the hardness of the wood paint when the TMP content is 3% reaches H. It also has good resistance to sticky stains, which can be used to develop new wood lacquer.

High-Efficiency Electro/Solar-Driven Wearable Heater Tailored by Superelastic Hollow-Porous Polypyrrole/Polyurethane/Zirconium Carbide Fibers for Personal Cold Protection.

With the frequent occurrence of extreme weather, using massive energy inputs to maintain the thermal stability of the indoor environment or the human body has become common, and such excessive overuse of nonrenewable energy has created numerous significant problems for modern society. Personal thermal management textiles which can provide the better thermal comfort with less energy consumption than the room heating devices have attracted vast attention in recent years. A polypyrrole/polyurethane/zirconium carbide (PU/PPy/ZrC) fiber with superior electrothermal/photothermal conversion was fabricated via a simple two-step strategy. The surface temperature of PU/PPy/ZrC fibers can reach 51.7 °C under IR lamp irradiation and 55.8 °C at 2 V. In addition, excellent electrical conductivity can be maintained even though the fiber has been stretched to 150%. Due to the porous and hollow structure of the PU/PPy/ZrC fiber, the fiber exhibits outstanding thermal stability and can reach a temperature difference of 5.2 °C. The excellent quick-drying properties allow for fast and complete drying of the material in both modes. Combined with the considerable mechanical properties and hydrophobicity of the PU/PPy/ZrC fiber, it demonstrates the outstanding potential and broad development of this dual-driven fiber for basic research and practical applications in personal cold protection.

Composite Wadding of Down Fibers Encapsulated in Fabrics.

Down fiber is one of the most superior materials, with excellent thermal properties, that can be used in bedding, clothing, and so on. Down products are usually encapsulated in fabrics that are more compact and, therefore, impart an anti-drilling performance. In this study, down fibers were encapsulated in polypropylene melt-blown nonwoven fabric, and also in polyester woven cloth, to form two different kinds of composite waddings. The waddings made of down fiber encapsulated in melt-blown nonwoven fabrics have a superior moisture permeability, thermal insulation, and anti-drilling performance, and a slightly inferior air permeability compared to that of waddings made with traditional woven fabrics. The pore fractal dimensions of melt-blown nonwoven fabrics are larger than that of woven fabrics. The relationship between the fractal dimension and performance of waddings explains the difference.

Drug-loaded PLCL/PEO-SA bilayer nanofibrous membrane for controlled release.

The bilayer nanofibrous membrane fabricated via electrospinning technique can be considered as an ideal structure for the treatment of chronic skin diseases and exudative wound dressings. Wound exudate would affect healing and increases the likelihood of infection at the same time. Therefore, it is essential to produce a kind of wound dressing with relatively high hygroscopicity which could absorb wound exudate and provide a relatively dry healing environment. Bilayer nanofibrous membranes of poly(L-lactide-co-ε-caprolactone)/tetracycline hydrochloride- polyethylene oxide/sodium alginate-zinc oxide (PLCL/TCH-PEO/SA-ZnO) with drug delivery potential were prepared by electrospinning for wound healing. Then, a cross-linking which involved soaking the samples in an aqueous solution containing strontium ions for 4 h was conducted. SEM images showed that membranes still maintained the peculiar nanofibrous structure. The spinning aid (PEO) used was removed in the cross-linked alginate without affecting the PLCL/TCH outer layer gave the membrane good mechanical properties and manageability. The hydrophilicity of the mats was tested to evaluate the ability of the bilayer membrane to absorb exudate from the wound. In vitro drug release suggested that antibacterial agents TCH could release continuously more than 10 days. The cross-linked fibrous membrane has improved mechanical properties and fluid repellency, thus representing a barrier to the external environment and effective wound protection. Consequently, the bilayer fibrous scaffold with good hygroscopicity and drug release properties would have wide applications prospects for the treatment of chronic skin diseases and exudative wound dressings.

Moisture-Wicking and Solar-Heated Coaxial Fibers with a Bark-like Appearance for Fabric Comfort Management.

Maintaining the human body's comfort is a predominant requirement of functional textiles, but there are still considerable drawbacks to design an intelligent textile with proper moisture absorption and evaporation properties. Herein, we develop moisture-wicking and solar-heated coaxial fibers with a bark-like appearance for fabric comfort management. The cortex layer of coaxial fibers can absorb moisture via the synergistic effect of the hierarchical roughness and the hydrophilic polymeric matrix. The core layer containing zirconium carbide nanoparticles can assimilate energy from the body and sunlight, which raises the surface temperature of the material and accelerates moisture evaporation. The resulting coaxial fiber-based membrane exhibits an excellent droplet diffusion radius of 2.73 cm, an excellent wicking height of 6.97 cm, and a high surface temperature of 61.7 °C which is radiated by simulated sunlight. Moreover, the designed fabric also exhibits a significant UV protection factor of 2000. Overall, the successful synthesis of such fascinating fibrous membranes enables the rapid removal of sweat from the human body textile, providing a suitable and comfortable microenvironment for the human body.

3D microstructure reconstruction of nonwoven fabrics based on depth from focus.

The filtration properties of nonwoven fabrics mainly depend on the fiber structure and alignment, which is difficult to be determined by using traditional methods. It is necessary to develop some new imaging method to characterize the 3D microstructure of nonwovens instead of simple 2D imaging of fabric surface appearance. In this paper, a novel method based on depth from focus is introduced to reconstruct three-dimensional microstructure of nonwoven fabrics. Firstly, a self-developed micro imaging system is established to capture the image sequence of the nonwoven fabric specimen, to be used for further reconstruction of a 3D model. Secondly, a depth from focus algorithm is developed to generate the depth map from image sequences. Thirdly, each fiber segment is located and identified by regional growth and the missing parts caused by occlusion could be restored. Fourthly, central the axis of the fiber is extracted by a thinning algorithm and polynomial curve fitting. Finally, the fiber radius is calculated and 3D model reconstructed using a ball whose sphere center rolls along the central axis. Our experimental results show that the real three-dimensional microstructure of nonwovens can be reconstructed well by using this new depth from focus method, which is very useful for the accurate modeling and analysis of nonwoven fabrics.

BSA loaded bead-on-string nanofiber scaffold with core-shell structure applied in tissue engineering.

Beaded nanofiber is a promising fibrous structure could act as drug delivery system with sustained drug release for regulating cell behaviors used in tissue engineering. Poly (L-lactic acid-co-ε-caprolactone) (PLCL) beaded nanofiber with core-shell structure (130 ± 30 nm) was fabricated and bovine serum albumin (BSA) was encapsulated into the inner layer. The surface morphology and characteristic were evaluated by scanning electron microscopy (SEM), inverted fluorescence microscopy and water contact angle test. Degradation analyses suggested that PLCL/BSA core-shell @ beaded nanofibers could maintain the fibrous framework during 3 weeks. The biocompatibility was investigated by in vitro cultivation of human mesenchymal stem cells (hMSCs) on the surface of PLCL/BSA core-shell @ beaded nanofibers. The proliferation of hMSCs was tested using alamar blue reagent and the spreading morphology of cells was observed by SEM. Corresponding results suggested that beaded nanofibers with core-shell structure could effectively support the attachment and proliferation of cells. PLCL beaded nanofiber with core-shell structure would work as a promising candidate for drug release system and tissue engineering.

Preparation and characterization of wormwood-oil-contained microcapsules.

In recent years, wormwood has been successfully applied in various fields, such as flavouring agent, plant dye, insect repellent and medical product. Wormwood oil encapsulated microcapsules with continuous release behaviours would be further applied in the health care textiles. Here, wormwood oil encapsulated microcapsules with different core-wall materials ratios (gelatine: gum arabic: wormwood oil = 1:1:1, 1:1:2, 1:1:3, 1:1:4) were fabricated. The morphology and physicochemical properties of microcapsules were explored by scanning electron microscopy, ultrasonic wave particle size analysis, thermo gravimetric analysis and so on. The size analysis results indicated that the microcapsule diameter could be controlled less than 1 um. In vitro testing showed that the microcapsules were capable of extending the releasing period to over 6 days. The thermo gravimetric analysis proved that microcapsules had superior thermal stability compared with pure wormwood oil, showing broad application prospects in functional health care textile.

Flexible, portable and heatable non-woven fabric with directional moisture transport functions and ultra-fast evaporation.

Compared with previous textiles possessing a hierarchical roughness structure for accelerating moisture evaporation, the use of Joule-heating to prepare heatable textiles is a more novel and useful way to achieve ultra-fast evaporation. Herein, we report an assembly strategy to create a functional non-woven (NW) fabric for directional moisture transportation and ultra-fast evaporation, ameliorating previous shortcomings. The resulting functional NW fabric reaches a sheet resistance of 1.116 Ω â–¡-1, and the increased surface temperature (76.1 °C) induced by a low voltage (5 V) further results in an excellent ultra-fast evaporation rate (3.42 g h-1). Also, the moisture is transported to the outer surface of the designed fabric and spreads onto this surface. This desirable property can expand the contact area between sweat and the heatable fabric, further improving the evaporation efficiency, while maintaining the dry state of human skin. Generally, this functional textile with remarkable moisture management capabilities could be applied in winter outdoor sportswear to maintain human comfort.

Automatic identification of cashmere and wool fibers based on the morphological features analysis.

Identification of wool and cashmere extremely similar fibers is always an important topic in the textile industry. In order to solve this problem much better, a novel fiber identification method based on the extraction and analysis of the morphological features was proposed in this paper. Firstly, the original fiber images were captured by the self-developed system including the optical microscope and digital camera. The influence of the acquisition process may lead to the low contrast and impurities, so the original fiber images needed to be processed by the image enhancement and de-noise to obtain the available fiber images with a better quality. Then the hessian matrix of processed images was put into the Frangi filter to detect the edge of the fiber scales, and the binary images of filter output images were processed to obtain the signal-pixel scale skeleton. The connected region labeling algorithm can be adopted for the scale skeleton images to mark and extract every scale from the whole fiber according to the different color information. Next, the three morphological features including scale height, fiber diameter and their ratio can be calculated by the self-defined vertical line rotation analysis method, and the mean value of five different scales was calculated as the final features to describe one fiber. In the experiment, 500 fiber cashmere and 500 wool fiber images were collected for the whole research, and a Bayesian classification model for identifying wool and cashmere fibers was established based on the statistical assumptions of three morphological characteristics. The results show that the identification accuracy of the method proposed in this paper could reached the 94.2%. It also proves that this novel method can be used for the identification of cashmere and wool extremely similar animal fibers.

Electrospun meta-aramid/polysulfone-amide nanocomposite membranes for the filtration of industrial PM2.5 particles.

Filtering of industrial PM2.5 is a major challenge for global environmental and animal protection. Filtering of materials with excellent thermal stability and other comprehensive performances is required for the removal of fine particles in high-temperature operating industries such as steel, cement, metallurgy, incineration, etc. In this study, a meta-aramid/polysulfone-amide (PMIA/PSA) composite nanofibrous filtration membrane is prepared via solution electrospinning for the development of high-temperature-resistant filtering products. To maximize the merits of each component, PMIA/PSA composite nanofibrous membranes with different mass blending ratios are prepared to determine the optimal balance. It is found that the PMIA/PSA composite nanofibrous membranes show excellent thermal stability and thermal shrinkage performance. They also maintain superb mechanical retention ratios after 200 h treatment at 200 °C. In addition, they exhibit excellent removal efficiency of polystyrene aerosol (PSL) particles of various sizes. It is found that the removal efficiency of PMIA/PSA (3/7) is 96.7% for 0.1 µm, 98.3% for 0.2 µm and 99.6% for 0.3 µm particles and it possesses optimal filtration resistance (79 Pa), while other composite membranes can reach a removal efficiency of over 99.7%. Our experimental results illustrate that the filtration efficiency for PM2.5 of PMIA/PSA (7/3), (5/5) composite nanofibrous membranes is still kept as high as 99.9% even after being treated at 200 °C for 120 h. It indicates that the prepared composite nanofibrous membranes have potential for applications where high-efficiency filtration is desired, such as bag dust filters for use under high temperatures.

Nonwovens structure measurement based on NSST multi-focus image fusion.

In the digital optical microscope, the depth of field cannot clearly display all fibers in the same image, due to the thickness of nonwovens. A new multi-focus image fusion algorithm based on non-subsampled shearlet transform (NSST) is proposed to improve the quality of fused image, which realizes the fusion of a series of images taken from the same perspective and makes all fibers clearly within a single image. The rule of large absolute value is used to fuse the high frequency sub-band and the rule of large regional variance is used to fuse the low frequency sub-band. Comparing the method with other methods, the superiority of the method can be seen from several indicators of image quality evaluation. Based on the fused image, the diameter and orientation are measured by Hough transform and image preprocessing, and automatic measurement is realized. The porosity is measured by identifying pores, which is fast and convenient. Experiments show that the measurement of nonwoven fabric structure can be quickly achieved based on image processing.

Investigation of a novel automatic micro image-based method for the recognition of animal fibers based on Wavelet and Markov Random Field.

In the analysis of fiber recognition, the challenge lies in the texture feature extraction. The main aim of this paper is to present a novel texture feature analysis method based on wavelet multi-scale analysis to fully extract texture features of microscopic images resulting in better recognition of similar animal fibers. Thousands of three kinds of similar fiber images including cashmere, sheep wool and goat hair were captured by the optical microscope and the digital camera. They were pre-processed to obtain the enhanced images with background removed. Then the pretreated fiber images were decomposed by 3-layer wavelet transform, four sub-images under the third-layer wavelet decomposition scale were analyzed by Gauss Markov Random Field (GMRF) model and their model parameters were obtained. Through the difference analysis of different kinds of fibers, two model parameters were selected from each sub-image to generate an 8-dimensional feature vectors, which was used to describe the fiber images. The parameters, which were extracted from 1000 images of each kind of fiber, were copied three times and randomly arranged to generate the final data sets. Finally, the data sets were processed by 10-times cross validation method as the training set and testing set of support vector machine (SVM). Ten different recognition rates could be obtained through the experiment, and the mean value was used as the final recognition accuracy of wool and cashmere fibers. The experimental results indicated that the method had a great recognition rate with 90.07% and the performance was robust. It verifies that the method based on wavelet multi-scale analysis is effective for the recognition of similar fibers.

Preparation and characterization of multilayered superfine fibrous mat with the function of directional water transport.

Directional water transport in garment materials plays a pivotal role in maintaining human thermal and wet comfort. In the present work, a new type of multilayer fibrous mat with the specific function of directional water transport was prepared via the combination of melt-electrospinning and solution-electrospinning. The polypropylene (PP) fibrous layer prepared by melt-electrospinning technology was located in the inner layer (next to the skin), while the polyacrylonitrile-containing hydrophilic nano-silica particles (PAN-SiO2) layer with remarkable hydrophilicity was located in the outer layer, which could effectively transport water to the outer surface of the composites. Treatment of the as-prepared PAN-SiO2/PP with an alkaline aqueous solution of dopamine not only increased the wettability of the PP layer, but also further improved the hydrophilicity of PAN-SiO2. A layer of cotton woven mesh was added between the TPP layer and TPAN-SiO2 to form a sandwich structure in order to accelerate water transport in the bilayered fibrous mats. The directional water transport, mechanical flexibility, and permeability of the prepared multilayered superfine fibrous mat were characterized systematically. The experimental results exhibited that TPAN-SiO2/cotton mesh/TPP exhibited an excellent accumulative one-way transport index (AOTI, 1071%), remarkable overall moisture management capacity (OMMC, 0.88), and reasonably high water vapor transport rate (WVT, 11.6 kg d-1 m-2), indicating it is a promising candidate for the development of novel textile materials for use in the field of sportswear for fast sweat release applications.

Electrospun sandwich polysulfonamide/polyacrylonitrile/polysulfonamide composite nanofibrous membranes for lithium-ion batteries.

The demands for novel approaches that ensure stability in lithium-ion batteries are increasing and have led to the development of new materials and fabrication strategies. In this study, sandwich structure-like polysulfonamide (PSA)/polyacrylonitrile (PAN)/polysulfonamide (PSA) composite nanofibrous membranes were prepared via an electrospinning method and used as a separator in lithium-ion batteries. The spinning time of each polymer nanofiber layer of the composite membranes was respectively and precisely controlled to maximize the merits of each component. It was found that the PSA/PAN/PSA composite nanofibrous membranes exhibited superior thermal stability and excellent porosity, liquid electrolyte uptake and ionic conductivity, showing obvious enhancement as compared to those of the commercial microporous polyolefin separator (Celgard 2400), pure PSA and pure PAN membranes. In addition, they were evaluated in the assembled Li/LiFePO4 cells with an electrolyte solution, and good cycling performance and C-rate capacity were obtained; especially for the case of the PP6P membrane, the first discharge capacity of the battery reached 152 mA h g-1, and the discharge capacity retention ratio was 85.94% from 0.2C to 2C; moreover, the battery displayed highest capacity retention ratio after 70 cycles, which was found to be 96.2% of its initial discharge capacity. Therefore, the PSA/PAN/PSA composite nanofibrous membranes can be regarded as a promising candidate for application in lithium-ion batteries.

Preparation and Characterization of Electrospun PAN/PSA Carbonized Nanofibers: Experiment and Simulation Study.

In this study, we simulated the electric field distribution of side-by-side electrospinning by using the finite element method (FEM), and studied the effects of spinneret wall thickness, spinning voltage and receiving distance on the distribution of the electrostatic field. The receiving distance was selected as a variable in the experimental, a series of PAN/PSA composite nanofiber membranes were prepared by using a self-made side by side electrospinning device. The membranes were tested by Fourier-transform infrared (FTIR), thermogravimetric analysis (TG), and scanning electron microscope (SEM). The prepared membranes were also treated by high-temperature treatment, and the change of fiber diameter and conductivity of the membrane before and after high-temperature treatment were studied. It was found that the PAN/PSA carbonized nanofibers could achieve a better performance in heat resistance and conductivity at 200 mm receiving distance.

Effects of Jet Path on Electrospun Polystyrene Fibers.

In this study we investigated the effects of jet path on the morphology and mat size of synthetic polystyrene (PS) fibers during the electrospinning process. In addition, the mechanism of the fiber mats, which were prepared by varying the solution concentration, was evaluated. The straight jet length, envelope cone and whipping frequency of each electrospun jet were studied using images captured by a high-speed photography camera. The results showed that higher solution concentrations led to longer straight jet lengths, smaller envelope cones and lower whipping frequencies. The diameter and surface morphology of the PS fibers were also characterized by scanning electron microscopy (SEM). It was found that fibers spun with higher solution concentrations exhibited larger diameters and diameter distributions because of their jet path features. Furthermore, the electrospun jets with higher concentrations increased elongation and produced smaller fiber mats and higher breaking forces as a result of their different jet paths, which was a consequence of varying the solution concentration.