Wet Drawing Process Research Articles

Optimization of the Wet Drawing Process According to the Safety Factor Criterion

Optimization of the Wet Drawing Process According to the Safety Factor Criterion

Improved alignment and stress transfer in CNT fibre fabrics studied by in situ X-ray and Raman during wet-drawing

Translating the superlative mechanical properties of nanocarbons to the scale of structural components requires assembling them into highly aligned networks with uniform internal stress transfer. Continuous, non-woven fabrics are produced by winding multiple filaments of carbon nanotube fibres (CNTF) directly spun from the gas phase. The CNTF fabrics are drawn by stretching in regular solvents, which increases specific tensile strength to 1.2 GPa/SG and modulus to 44 GPa/SG, reaching ∼70% the strength and ∼50% modulus of the single filament. Tensile measurements of misaligned CNTF fabrics soaked in solvents show an increased strain-to-break, a large drop in tensile force, and shear-induced local deformation, analogous to a polymer wet-drawing process. In-situ small-angle X-ray scattering during wet-drawing shows a progressive and transient increase in porosity, attributed to the separation of adjacent bundles “wedged” by the ingress of solvent when the fabric is under load. Wet-drawing increases degree of alignment, reaching Herman's orientation parameter values <P2> = 0.54 and a narrower distribution of local alignment. Maps of the downshift of 2D Raman band during tensile deformation confirm a more homogeneous spatial distribution of local moduli after wet-drawing CNTF fabrics, evidencing more cooperative loading and stress transfer. Tensile mechanical properties of fabrics aligned after wet-drawing can be successfully described by the uniform stress transfer model.

Microstructure and Mechanical Properties of Polyacrylonitrile Precursor Fiber with Dry and Wet Drawing Process.

Polyacrylonitrile (PAN) fibers are typically used as precursor fibers for carbon fiber production, produced through wet-spinning processes. The drawing process of the spun fiber can be classified into dry and wet drawing processes. It is known that the drawing stability and stretching ratio differ depending on the drawing process; however, the elementary characteristics are approximately similar. In this study, the mechanical properties of PAN fibers have been examined based on these two drawing processes with the differences analyzed through the analysis of microstructures. Further, to examine the composition of the fiber, element analysis has been conducted, and thereafter, the microstructure of the fiber is examined through X-ray diffraction analysis. Finally, the characteristics of PAN fibers and its mechanical properties has been examined according to each drawing condition. There are differences in moisture content and microstructure according to the drawing process, and it affects the tensile behavior. The results obtained could have potential implications if the processes are combined, as it could result in a design for a stable and highly efficient drawing process.

Life cycle inventories of the commonly used materials for lithium-ion batteries in China

With the fast growing of the electric vehicle (EV) market and soaring production of the EV lithium-ion batteries (LiBs) in China, more and more life cycle assessment (LCA) studies has been focused on their impacts towards resources, energy and environment in recent years. As the indispensable background data, the life cycle inventories (LCIs) of the cradle-to-gate stage of the commonly used materials for the production of LiBs play an important role in the related LCA studies, since their accuracy and reliability can affect the results and conclusions greatly. However, LCIs of the LiB materials produced in China are in scarcity nowadays, which has become an obstacle for the further understanding of the eco-performances of EVs and LiBs. In this study, a general unit-process model was established firstly, and then a variety of foreground data were collected from the representative manufacturers of LiB materials in China. With a sequential calculation procedure carried out step by step, the targeted LCIs of the materials were obtained, along with the corresponding 95% confidential intervals through Monte-Carlo simulations. According to the inventories analysis, it was found that among the materials studied, the polyethylene separator made by wet drawing process, lithium hexafluorophosphate, carbon nanotubes, lithium nickel manganese cobalt oxide and nickel cobalt aluminum are with relatively higher primary energy demands and greenhouse gas emissions in their cradle-to-gate stage. Besides, among the cathode materials studied, lithium iron phosphate consumes the lowest non renewable mineral resources. In addition, through a comparison with GREET, we found that the energy consumptions and greenhouse gas emissions of the LiB materials in this study are significantly higher than that drawn from GREET. This will lead to 62–91% more greenhouse gas emissions from materials made in China than those in the United States in order to produce LiB cells of the same capacity. However, it was also found the discrepancies may be stemmed from many difference in the processes of modeling and data acquisition between this study and the supportive studies for GREET.

습식 연신공정에서 팽윤조건이 PVA 필름의 구조변화에 미치는 영향

습식 연신공정에서 팽윤조건이 PVA 필름의 구조변화에 미치는 영향

Piezoelectricity of wet drawn cellulose electro-active paper

Piezoelectricity is one major actuating mechanism of cellulose-based electro-active paper (EAPap). In order to increase the piezoelectricity of EAPap, wet drawing method with different stretching conditions was introduced in the fabrication process of cellulose film. Structural and mechanical characterizations of wet drawn and stretched cellulose film were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), high voltage electron microscope (HVEM) and mechanical pulling test setup. From the piezoelectric charge constant measurement, it was revealed that the performance of EAPap was sensitive to the drawing ratio of cellulose film and its material orientation. We found that optimized alignment direction along the cellulose fibers and drawing ratio during wet drawing process were very critical parameters to improve electro-mechanical properties of EAPap. Also we conclude that the simple wet drawing method is a very effective fabrication method to enhance the mechanical stiffness and the piezoelectricity of EAPap.

Failure mechanism of cemented tungsten carbide dies in wet drawing process of steel cord filament

Cemented tungsten carbide die has been used in wire drawing for almost a century. A combination of strength and wear resistance has made this material widely accepted in the steel wire industry, particularly in drawing steel cord filament. Used cemented tungsten carbide dies, collected from different sources where different lubricants were applied in the wet drawing process, were dissected with high speed diamond saw and examined by using scanning electron microscopy. Failure modes of cemented tungsten carbide dies were classified. Electrochemical properties of pure cobalt wire and cemented tungsten carbide were examined by anodic and cyclic polarization measurements to investigate the corrosion resistance of cobalt and cemented tungsten carbide in wire drawing lubricants. Results show that binding agent (cobalt) in cemented tungsten carbide might be selectively leached in certain lubricants, and the leaching rate increased as oxygen concentration decreased in the lubricants and pH was lowered inside the crevice. Contact of steel wire on the cemented carbide die due to the mismatch of slip during drawing could be the original source of stress. Synergic effect of stress and leaching could be the answer for the severe cracking of cemented carbide dies in the wet drawing process.

Study of the Texture of Steelcord during the Wet Drawing Process - Influence of the Patenting and the Friction on the Dies

Study of the Texture of Steelcord during the Wet Drawing Process - Influence of the Patenting and the Friction on the Dies