scholarly journals Cellulose Submicron Fibers

2011 ◽  
Vol 6 (4) ◽  
pp. 155892501100600 ◽  
Author(s):  
Rohit Uppal ◽  
Gita N. Ramaswamy
Keyword(s):  
Aqueous Solution ◽  
Applied Voltage ◽  
Fiber Diameter ◽  
Solvent Mixture ◽  
Degree Of Crystallinity ◽  
Cellulose Solution ◽  
Average Fiber Diameter ◽  
Water Solvent ◽  
Urea Aqueous Solution ◽  
The Degree Of Crystallinity

In order to manufacture cellulose submicron fibers, electrospinning of cellulose was tried with different solvents. Alpha-cellulose did not dissolve in 6% (w/w) sodium hydroxide/4%urea aqueous solution. Alpha-cellulose solution in 85% phosphoric acid was not spinnable at an applied voltage between 15kV to 25 kV and at a spin length of 4 to 6 inches. Electrospinning of alpha-cellulose in N-methylmorpholine-N-oxide/N-methyl-pyrrolidinone/water solvent mixture could be performed at an applied voltage of 28 kV and at a spin length of seven inches during spinning and at an ambient temperature of 380C. The degree of crystallinity of the cellulose submicron fibers was found to be 37.88%. The number average fiber diameter of cellulose submicron fibers from 1.25% (w/w) cellulose solution in the N-methylmorpholine-N-oxide/N-methyl-pyrrolidinone/water solvent was found to be 207 nm and the number average fiber diameter of cellulose submicron fibers from 2.5% (w/w) cellulose solution in the N-methylmorpholine-N-oxide/N-methyl-pyrrolidinone/water solvent mixture was found to be 243 nm.

Prediction and optimization of process parameters of electrospun polyacrylonitrile based on numerical simulation and response surface method

2021 ◽  
pp. 004051752110039
Author(s):  
Peng Chen ◽  
Qihong Zhou ◽  
Ge Chen ◽  
Qian Zhang ◽  
Shaozong Wang
Keyword(s):  
Response Surface ◽  
Response Surface Method ◽  
Process Parameters ◽  
Applied Voltage ◽  
Feed Rate ◽  
Fiber Diameter ◽  
Average Fiber Diameter ◽  
Volume Force ◽  
Surface Method ◽  
Multiple Process

There is a strong coupling relationship between the process parameters of electrospun polyacrylonitrile (PAN) and its fiber diameter. By examining the mechanism of influence, the quality of electrospun products can be significantly improved and controlled. In this study, a novel idea for predicting and optimizing electrospun PAN process parameters was proposed. First, the control equation of the electrospun PAN was established based on the incompressible Navier–Stokes equation, and the volume force (generated via electric field force, gravity, and surface tension) and jet velocity during electrospinning were solved and analyzed via simulation software. Then, grey correlation analysis was used to calculate the correlation among the three process parameters (applied voltage, feed rate, and distance between the needle and collector) of the electrospun PAN, volume force, jet velocity, and average fiber diameter. Subsequently, the effect of simultaneous changes in multiple process parameters on the average fiber diameter was examined based on the response surface method, and a prediction model was established. Finally, the experimental results indicated that the model can predict the average fiber diameter when multiple process parameters are simultaneously changed. The model predicted the average fiber diameter with an error of only 0.28%, and the optimized minimum fiber average diameter was 235.3 nm (the applied voltage was 12 kV, the distance between the needle and collector was 15.6 cm, the feed rate was 0.37 mL/h). This study provides a theoretical basis for the on-line monitoring of the electrospun PAN.

scholarly journals Fabrication and characterization of polyvinylidene fluoride nanofibers prepared by electrospinning technique

2021 ◽  
Vol 63 (1) ◽  
pp. 49-54
Author(s):  
Thi Thu Thuy Nguyen ◽  
◽  
The Huu Nguyen ◽  
Thi Hai Trinh ◽  
Thi Thu Trang Bui ◽  
...  
Keyword(s):  
Applied Voltage ◽  
Feed Rate ◽  
Polyvinylidene Fluoride ◽  
Fiber Diameter ◽  
Average Diameter ◽  
Solution Concentration ◽  
Solvent Mixture ◽  
Gas Filtration ◽  
Hydrophobic Property ◽  
Electrospinning Technique

Electrospinning is a technique that produces polymer fibers with diameters in the submicron range. In this study, some electrospinning parameters affecting the morphology, average diameter, and distribution of the diameter of polyvinylidene fluoride (PVDF) fibers were investigated by using scanning electron microscopy (SEM). These electrospinning parameters include solution concentration, applied voltage, the feed rate of solution, distance from the needle to the collector, and solvent mixture. PVDF fibers have a fine structure, narrow distribution of fiber diameter, and average fiber diameter of 736 nm at a solution concentration of 20 wt%, solvent mixture with 60/40 weight of N,N-dimethylacetamide (DMAc) and acetone (Ac), an applied voltage of 11 kV, the feed rate of 1 ml/h, and the distance from the needle to the collector of 17 cm. The hydrophobic property and tensile strength of the PVDF nanofiber membrane were also reported. PVDF nanofibers have the potential to apply in several areas such as water or gas filtration, catalyst, lithium battery, ect.

Effect of Crystalline Morphology on Mechanical Properties of PPB Polymer Nanofiber Composite

2012 ◽  
Vol 506 ◽  
pp. 262-265
Author(s):  
S. Sangthaiyarak ◽  
N. Tawichai ◽  
Kamonpan Pengpat ◽  
Gobwute Rujijanagul ◽  
Tawee Tunkasiri ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Applied Voltage ◽  
Degree Of Crystallinity ◽  
Crystalline Morphology ◽  
X Ray Diffraction ◽  
Electrospinning Technique ◽  
Nanofiber Composite ◽  
X Ray ◽  
Polymer Nanofiber ◽  
The Degree Of Crystallinity

In this work, the effects of crystalline morphology on the mechanical properties of polycaprolactone/polyvinyl alcohol/ butterfly pea extract (PPB) nanofiber composite were investigated. Biopolymer nanofiber composite of PPB was fabricated by electrospinning technique using polycaprolactone concentration and distance of nozzle to ground collector of 7 wt% and 20 cm, respectively. The influence of applied voltage (vary from 15-25 kV) on the stress-strain curves was also observed. The structure and morphology of electrospun PPB nanofibers were investigated by x-ray diffraction (XRD) and scanning electron microscopy (SEM). It was found that, the degree of crystallinity increased with applied voltage and the mechanical properties was affected by the morphology of PPB nanofiber.

Effect of Processing Parameters on the Diameter and Morphology of Electrospun Iron-Modified Montmorillonite (Fe-MMT)/Polycaprolactone Nanofibers

2020 ◽  
Vol 846 ◽  
pp. 14-22
Author(s):  
Gianina Martha A. Tajanlangit ◽  
Leslie Joy L. Diaz
Keyword(s):  
Flow Rate ◽  
Applied Voltage ◽  
Low Voltage ◽  
Fiber Diameter ◽  
Significant Loss ◽  
Fractional Factorial ◽  
Average Fiber Diameter ◽  
Fiber Morphology ◽  
Modified Montmorillonite ◽  
Needle Diameter

Iron-modified montmorillonite-filled polycaprolactone nanofiber mats were produced via electrospinning with varying applied voltage, flow rate, needle-tip-to-collector distance, and needle diameter. Scanning electron microscopy (SEM) was used to observe fiber morphology and characteristics. The effects of varying process parameters on various fiber characteristics were evaluated using a two-level fractional factorial experimental design. The effect of voltage on fiber diameter differed with varying flow rate. At 32 ml/hr, the average fiber diameter decreased from 518.38 nm ± 289.37 nm to 466.43 nm ± 312.36 nm when the voltage is increased. At 42 ml/hr the effect of voltage on fiber diameter was reversed. The average fiber diameter was also found to decrease from 516.03 nm ± 283.48 nm to 467.96 nm ± 318.07 nm with decreasing tip-to-collector distance at 32 mL/hr flow rate. The variation of the effect of the factors on fiber diameter was mainly due to a significant loss of material observed at 12 kV and 15 cm tip-to-collector distance. Bead formation was observed for all runs with more beads being formed at 12 kV applied voltage and 15 cm tip-to-collector distance. Spherical beads were observed at 12 kV and 15 cm tip-to-collector distance while spindle-like beads were present in nanofiber membranes spun at high voltage and at the combination of low voltage and low tip-to-collector distance. The parameter setting combination of 19 kV, 32 ml/hr flow rate, 10 cm tip-to-collector distance, and 0.514 mm needle diameter yielded the lowest fiber diameter with the least amount of beading and small bead size. Small fiber diameters and less beading provide larger surface area and more exposure of the Fe-MMT particles for more efficient adsorption.

PVA/PVAm Hydrogel Membranes for Removal of Metal Ions from Aqueous Solution

2011 ◽  
Vol 130-134 ◽  
pp. 1507-1510 ◽  
Author(s):  
Qiang Chen ◽  
Lin Zhu
Keyword(s):  
Aqueous Solution ◽  
Metal Ions ◽  
Degree Of Crystallinity ◽  
Poly Vinyl Alcohol ◽  
Degree Of Ionization ◽  
Hydrogel Membranes ◽  
Swelling Studies ◽  
Removal Of Metal ◽  
Removal Of Metal Ions ◽  
The Degree Of Crystallinity

Glutaraldehyde cross-linked Poly (vinyl alcohol)/Polyvinylamine (PVA/PVAm) membranes for removal of metal ions from aqueous solution were prepared by solution casting and solvent evaporation techniques. The membranes were characterized using XRD, Swelling studies and metal ions adsorption experiments. The results show that PVA/PVAm membranes exhibit semi-crystalline natures as PVA macromolecular, however, the degree of crystallinity of membranes decrease as PVAm increased. The membranes were pH-sensitive and the swelling ability of membranes was significantly enhanced. It was found that the change of swelling behavior versus pH was consistent with the change of degree of ionization versus pH. The amount of Cu2+ions adsorbed increased as PVAm increased as well as increasing pH of solution in the range of 2.5~6.0.

scholarly journals Estimation of the Age of Architectural Heritage Objects by Microstructural Changes of Calcite in Lime Mortars of Ancient Brickwork and Masonry

Buildings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 240
Author(s):  
Vladimir Kotlyar ◽  
Victoria Pishchulina ◽  
Alexey N. Beskopylny ◽  
Besarion Meskhi ◽  
Yury Popov ◽  
...  
Keyword(s):  
18Th Century ◽  
Degree Of Crystallinity ◽  
Architectural Heritage ◽  
Natural Conditions ◽  
Relative Age ◽  
Lime Mortars ◽  
Powder Samples ◽  
Diffraction Patterns ◽  
Cultural Monuments ◽  
The Degree Of Crystallinity

Determining the age of ancient architectural and cultural monuments is a significant scientific problem. An approach based on the transformation of portlandite into calcite and subsequent recrystallization of calcite is considered, which allows for estimating the relative age of ancient brickworks for local groups of historic buildings based on the results of diffraction studies of powder samples of carbonate mortars and measurements of samples with a known age. This article presents the results of the study of lime mortars of ancient brickwork. Under natural conditions, the process of transformation of portlandite into calcite takes from 100 to 200 years. The rate of this process is influenced by temperature, humidity, peculiarities of interaction with carbon dioxide contained in the air, etc. Examples show that portlandite is completely transformed into calcite in masonry mortars of the 18th century and that portlandite is not found in older mortars. It was determined that after the transformation of portlandite into calcite, an increase in the degree of recrystallization of calcite is observed, which manifests itself in powder diffraction patterns in the relative broadening of the diffraction peak of calcite hkl 104. In a detailed study, an estimate of the peak width at half maximum (FWHM) associated with the degree of crystallinity is effective. The actual data are given, which show that in older lime mortars the degree of recrystallization of calcite is higher than in younger ones. This fact makes it possible to indirectly determine the relative age of brickwork and masonry of various buildings of architectural heritage, which is especially relevant for the objects with the use of lime mortars of the northern provinces of the Byzantine Oecumene and other periods of various cultures.

scholarly journals Radiation-initiated high strength chitosan/lithium sulfonate double network hydrogel/aerogel with porosity and stability for efficient CO2 capture

RSC Advances ◽  
2021 ◽  
Vol 11 (33) ◽  
pp. 20486-20497
Author(s):  
Zhiyan Liu ◽  
Rui Ma ◽  
Wenjie Du ◽  
Gang Yang ◽  
Tao Chen
Keyword(s):  
Aqueous Solution ◽  
High Strength ◽  
Beam Radiation ◽  
Chitosan Hydrogel ◽  
Double Network ◽  
Electron Beam Radiation ◽  
Freeze Dried ◽  
Urea Aqueous Solution ◽  
Capture Capacity

Chitosan hydrogel is regenerated from alkali/urea aqueous solution and the lithium sulfonate second network is introduced by electron beam radiation-initiated in situ free radical polymerization. The freeze-dried aerogel has CO2 capture capacity.

scholarly journals Preparation and Characterization of Talc Filled Thermoplastic Polyurethane/Polypropylene Blends

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Emi Govorčin Bajsić ◽  
Vesna Rek ◽  
Ivana Ćosić
Keyword(s):  
Thermal Properties ◽  
Thermoplastic Polyurethane ◽  
Mechanical Analysis ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Polypropylene Blends ◽  
Pp Blends ◽  
The Degree Of Crystallinity ◽  
Better Than

The effect of the addition of talc on the morphology and thermal properties of blends of thermoplastic polyurethane (TPU) and polypropylene (PP) was investigated. The blends of TPU and PP are incompatible because of large differences in polarities between the nonpolar crystalline PP and polar TPU and high interfacial tensions. The interaction between TPU and PP can be improved by using talc as reinforcing filler. The morphology was observed by means of scanning electron microscopy (SEM). The thermal properties of the neat polymers and unfilled and talc filled TPU/PP blends were studied by using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The addition of talc in TPU/PP blends improved miscibility in all investigated TPU/T/PP blends. The DSC results for talc filled TPU/PP blends show that the degree of crystallinity increased, which is due to the nucleating effect induced by talc particles. The reason for the increased storage modulus of blends with the incorporation of talc is due to the improved interface between polymers and filler. According to TGA results, the addition of talc enhanced thermal stability. The homogeneity of the talc filled TPU/PP blends is better than unfilled TPU/PP blends.

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