scholarly journals A Wet-Spinning Process for Producing Carbon Nanotube/Polyvinylidene Fluoride Fibers Having Highly Consistent Electrical and Mechanical Properties

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 4048
Author(s):  
Ki-Weon Kang ◽  
Chan-Woong Choi ◽  
Ji-Won Jin
Keyword(s):  
Carbon Nanotube ◽  
Polyvinylidene Fluoride ◽  
Structural Variation ◽  
Initial Conditions ◽  
Bath Temperature ◽  
Wet Spinning ◽  
Longitudinal Variation ◽  
Cross Sectional ◽  
Spinning Process ◽  
Dope Solution

Studies of polymer/carbon nanotube (CNT) fibers typically focus on optimizing the overall properties, and the effects of structural variation on these properties are ignored. Thus, we investigated the longitudinal variation in the properties of CNT/polyvinylidene fluoride (CNT/PVDF) fibers prepared by wet spinning a solution of multi-walled nanotubes, PVDF, and dimethylacetamide. To this end, materials for the CNT/PVDF fiber were selected, and a dope solution was prepared using MWNT, PVDF, and dimethylacetamide (DMAc). To consider the process parameters that would affect the performance of the CNT/PVDF fiber during the wet-spinning process using the dope solution, the initial conditions for wet spinning were selected, including bath concentration, bath temperature, drying temperature, and elongation, and the CNT/PVDF fiber was spun under the corresponding conditions. Additionally, three performance stabilization processes were proposed to improve the initial conditions for wet spinning and manufacturing the fiber. Lastly, to confirm the reliability of the CNT/PVDF fiber in all sections, tensile strength, electrical conductivity, and cross-sectional images were analyzed for the 30 m, 60 m, and 90 m sections of the fiber, and the reliability of the wet-spinning process was verified.

Theoretical and experimental investigation of the wet-spinning process for mechanically strong carbon nanotube fibers

2021 ◽  
Vol 412 ◽  
pp. 128650
Author(s):  
Hyeon Dam Jeong ◽  
Seo Gyun Kim ◽  
Gyeong Min Choi ◽  
Minji Park ◽  
Bon-Cheol Ku ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Carbon Nanotube ◽  
Wet Spinning ◽  
Spinning Process ◽  
Carbon Nanotube Fibers

Highly stretchable multi-walled carbon nanotube/thermoplastic polyurethane composite fibers for ultrasensitive, wearable strain sensors

Nanoscale ◽  
2019 ◽  
Vol 11 (13) ◽  
pp. 5884-5890 ◽  
Author(s):  
Zuoli He ◽  
Gengheng Zhou ◽  
Joon-Hyung Byun ◽  
Sang-Kwan Lee ◽  
Moon-Kwang Um ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Thermoplastic Polyurethane ◽  
Strain Sensor ◽  
Strain Sensors ◽  
Wet Spinning ◽  
Polyurethane Composite ◽  
Multi Walled Carbon Nanotube ◽  
Highly Sensitive ◽  
Spinning Process ◽  
Highly Stretchable

In this manuscript, we report a novel highly sensitive wearable strain sensor based on a highly stretchable multi-walled carbon nanotube (MWCNT)/Thermoplastic Polyurethane (TPU) fiber obtained via a wet spinning process.

Research on the multi-scale microstructure of polyacrylonitrile precursors prepared by a dry-jet wet spinning process

2018 ◽  
Vol 31 (6) ◽  
pp. 662-670 ◽  
Author(s):  
Meiling Chen ◽  
Chengguo Wang ◽  
Quan Gao ◽  
Yanxiang Wang ◽  
Min Jing ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Performance ◽  
Nitrogen Adsorption ◽  
Coagulation Bath ◽  
Wet Spinning ◽  
Carbon Fibres ◽  
Cross Sectional ◽  
Multi Scale ◽  
Transmission Electron ◽  
Spinning Process

An understanding of the properties of polyacrylonitrile (PAN) precursors is an essential precondition for manufacturing high-performance carbon fibres, and the structure of the precursors has a direct and profound effect on the performance of carbon fibres. In this study, PAN precursors, formed in a multistage coagulation bath, were spun by a dry-jet wet spinning process, and the multi-scale microstructure and morphology of the precursors were investigated by separating the fibrils from the precursors. Scanning electron microscopy and high-resolution transmission electron microscopy were employed to examine the surface morphology, cross-sectional morphology and microstructure of the precursors. X-ray diffraction was used to characterize the crystal structure. The micropore sizes of the precursors were determined with nitrogen adsorption experiments; the adsorption increased after ultrasonic etching and decreased with an increase in the treated concentration. All the results demonstrated that the PAN precursors had a multi-scale microstructure, the precursors consisted of fibrils with diameters of 80–200 nm and the fibrils consisted of some microfibrils with diameters of 20–40 nm, including the periodic tissues with thicknesses of 16–30 nm perpendicular to the fibre axis.

PHASE INVERSION PREPARATION AND MORPHOLOGICAL STUDY OF POLYVINYLIDENE FLUORIDE ULTRAFILTRATION MEMBRANE MODIFIED BY NANO-SIZED ALUMINA

2009 ◽  
Vol 02 (03) ◽  
pp. 113-119 ◽  
Author(s):  
A. M. BAZARGAN ◽  
Z. GHOLAMVAND ◽  
M. NAGHAVI ◽  
M. R. SHAYEGH ◽  
S. K. SADRNEZHAAD
Keyword(s):  
Polyvinylidene Fluoride ◽  
Phase Inversion ◽  
Membrane Surface ◽  
Bath Temperature ◽  
Contact Angles ◽  
Coagulation Bath ◽  
Alumina Powder ◽  
Effective Parameters ◽  
Precipitation Bath ◽  
Cross Sectional

In this study, polyvinylidene fluoride (PVDF) membranes with various structures ranging from dense to highly asymmetric morphologies were obtained by changing the effective parameters in the phase inversion process. The effect of some important processing parameters such as solution concentration, harshness of the precipitation bath, exposure time before immersion in coagulation bath and bath temperature was studied and the mentioned parameters were optimized. The membranes were then modified with nano-sized alumina powder in order to improve the hydrophilicity of the PVDF membranes. The surface morphology, surface and cross-sectional structures of the membranes were examined by scanning electron microscope (SEM) and atomic force microscope (AFM). The specific surface area of the membranes was determined using the Brunauer–Emmett–Teller (BET) method. The contact angles between water and the membranes' surfaces were measured in order to study the hydrophilicity changes of the membrane surface. The results indicated that the addition of nano-sized alumina to the casting dope increased the hydrophilicity of the PVDF membrane surface.

scholarly journals Exploiting the Interplay between Liquid-Liquid Demixing and Crystallization of the PVDF Membrane for Membrane Distillation

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
N. I. M. Nawi ◽  
M. R. Bilad ◽  
N. A. H. M. Nordin ◽  
M. O. Mavukkandy ◽  
Z. A. Putra ◽  
...  
Keyword(s):  
Polyvinylidene Fluoride ◽  
Water Flux ◽  
High Water ◽  
Membrane Distillation ◽  
Degree Of Crystallinity ◽  
Solution Temperature ◽  
Hydrophobic Membrane ◽  
Sem Images ◽  
Cold Temperatures ◽  
Dope Solution

Membrane distillation (MD) purifies water by transporting its vapor through a hydrophobic membrane. An ideal MD membrane poses high water flux and high fouling, scaling, and wetting resistances. In this study, we develop polyvinylidene fluoride (PVDF) membranes for MD by focusing on reduction of PVDF degree of crystallinity. We explore the roles of dope solution temperature in dictating the phase separation mechanisms as well as the structure and the performance of semicrystalline PVDF membranes. DSC spectra show that higher dope solution temperature depresses crystallinity via formation of imperfect crystal. Such findings were also supported by FTIR and XRD results. The SEM images reveal formation of spherulite-like morphology in the membrane matrices for membranes prepared from high temperature dope solutions. A good balance between solid-liquid and liquid-liquid phase separations that offers low degree of crystallinity was found at a dope solution temperature of 60°C (PVDF-60), which showed the MD flux of 18 l/m2 h (vs. 6 l/m2 h for temperature of 25°C, as a benchmark) and nearly complete salt rejection when run at hot and cold temperatures of 65°C and 25°C, respectively. The PVDF-60 shows a high wetting resistance and stable MD flux of 10.5 l/m2 h over a 50 h test for treating brine solution as the feed (70 g NaCl/l).

Fanno Design of Blow-Off Lines in Heavy Duty Gas Turbine

2013 ◽  
Author(s):  
Marco Cioffi ◽  
Enrico Puppo ◽  
Andrea Silingardi
Keyword(s):  
Gas Turbines ◽  
Gas Flow ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Design Procedure ◽  
Flow Equation ◽  
Heavy Duty ◽  
Cross Sectional ◽  
Pipe Length ◽  
Choked Flow

In typical heavy duty gas turbines the multistage axial compressor is provided with anti-surge pipelines equipped with on-off valves (blow-off lines), to avoid dangerous flow instabilities during start-ups and shut-downs. Blow-off lines show some very peculiar phenomena and somewhat challenging fluid dynamics, which require a deeper regard. In this paper the blow-off lines in axial gas turbines are analyzed by adopting an adiabatic quasi-unidimensional model of the gas flow through a pipe with a constant cross-sectional area and involving geometrical singularities (Fanno flow). The determination of the Fanno limit, on the basis of the flow equation and the second principle of thermodynamics, shows the existence of a critical pipe length which is a function of the pipe parameters and the initial conditions: for a length greater than this maximum one, the model requires a mass-flow reduction. In addition, in the presence of a regulating valve, so-called multi-choked flow can arise. The semi-analytical model has been implemented and the results have been compared with a three-dimensional CFD analysis and cross-checked with available field data, showing a good agreement. The Fanno model has been applied for the analysis of some of the actual machines in the Ansaldo Energia fleet under different working conditions. The Fanno tool will be part of the design procedure of new machines. In addition it will define related experimental activities.

Hemodynamic Measurements in Human Arterial Casts, and Their Correlation With Histology and Luminal Area

1980 ◽  
Vol 102 (3) ◽  
pp. 247-251 ◽  
Author(s):  
M. H. Friedman ◽  
C. B. Bargeron ◽  
G. M. Hutchins ◽  
F. F. Mark ◽  
O. J. Deters
Keyword(s):  
Laser Doppler Anemometer ◽  
Longitudinal Variation ◽  
Sectional Area ◽  
Vascular Response ◽  
Velocity Measurements ◽  
Cross Sectional ◽  
New Approach ◽  
Flow Acceleration ◽  
Luminal Area ◽  
Hemodynamic Measurements

A new approach is presented for studying the vascular response to hemodynamic stress. A laser doppler anemometer is used to make velocity measurements very near the walls of human arterial casts; these measurements are then correlated with the histology of the artery from which the cast was made. Several illustrative results are given which suggest that the velocity profiles along the outer walls of aortic bifurcations may be significantly determined by the longitudinal variation of cross-sectional area. The shapes of these profiles were qualitatively different for each cast studied. In one specimen, the location of initial lipid deposits appeared to correlate with flow acceleration.

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