Direct-Write Fabrication of Polymer Nanocomposite Fibers

2008 ◽  
Vol 1143 ◽  
Author(s):  
Scott M. Berry ◽  
Santosh Pabba ◽  
Scott D. Cambron ◽  
Robert W. Cohn ◽  
Robert S. Keynton
Keyword(s):  
Cross Sections ◽  
Electromagnetic Interference ◽  
Electrical Transport ◽  
Fiber Length ◽  
Fiber Diameter ◽  
Polymer Concentration ◽  
Polymer Nanocomposite ◽  
Solution Viscosity ◽  
Drawing Rate ◽  
Direct Write

ABSTRACTThe unique properties of carbon-nanotube (CNT)-doped polymers have generated several promising applications including gas sensors, high-strength/light-weight materials, and electromagnetic interference shielding. The ability to process CNT-doped materials into complex architectures may enable further advancement of these devices. We have developed a direct-write technique for processing CNT-doped poly(methyl methacrylate) (PMMA) into 3D arrays of precisely-positioned fibers with micro- and sub-microscale diameters. In this method, a programmable micromanipulator-controlled syringe was loaded with solvated CNT/PMMA and utilized to draw an array of freely-suspended solution filaments on a substrate in a “connect-the-dots” fashion. As the filaments are drawn, they are thinned by surface tension-driven necking as they dry and form solid fibers. The degree of thinning can be controlled by varying the viscosity of the solution, which acts to resist the necking while the volatile solvent evaporates and solidification occurs. Multiple fibers were drawn to investigate the effects of several factors on fiber diameter and process yield. These variables included fiber length (4, 8, and 18 mm), fiber drawing velocity (5 and 20 mm/s), polymer concentration in solution (22 and 24% by wt.), and CNT concentration in solution (0, 0.5, 1, and 1.5% by wt.), with the latter two of these variables strongly influencing solution viscosity. Measurement of the fibers via scanning electron microscopy (SEM) revealed several trends: Fiber diameter was not influenced by CNT concentration, but increased with increasing PMMA concentration (P<0.001), increasing drawing rate (P<0.01), and decreasing fiber length (P<0.001), with fiber diameter ranging from 538 nm to >100 μm. Furthermore, fiber yield exceeded 75% for all tested solutions except for the lowest viscosity CNT-doped solution (24% PMMA/0.5% CNT, η=50.1 Pa*s), which experienced capillary breakup prior to solidification. The conductivities of direct-write PMMA/CNT fibers ranged from <10-7to 0.15 S/m, with shorter fibers having higher conductivities (P<10.005). Also, fibers drawn from solutions with 1.0% CNTs had higher conductivities that those drawn from solutions with 0.5% or 1.5% CNTs (P<0.01). This nonlinear trend was further investigated by cleaving fibers in liquid nitrogen and imaging their cross-sections with an SEM. This analysis illustrated that the CNTs, which were functionalized to remain dispersed in the solvent, tended to randomly aggregate within the polymer-fiber matrix, particularly for fibers drawn from solutions containing 1.5% CNTs. In conclusion, CNT/PMMA fibers were successfully drawn with the direct-write technique and CNT doping had no significant influence on fiber diameter or yield compared with fibers drawn from PMMA homopolymer. However, the CNTs were found to strongly aggregate when drawn from solutions loaded at high concentrations (1.5%), thereby hindering electrical transport.

scholarly journals Direct-Write Drawing of Carbon Nanotube/Polymer Composite Microfibers

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Scott M. Berry ◽  
Santosh Pabba ◽  
Robert W. Cohn ◽  
Robert S. Keynton
Keyword(s):  
Carbon Nanotube ◽  
Polymer Solutions ◽  
Fiber Diameter ◽  
Axial Strain ◽  
Polymer Concentration ◽  
Strain Rates ◽  
Direct Write ◽  
Composite Fibers ◽  
Capillary Thinning ◽  
Doped Polymer

Carbon-nanotube- (CNT-) doped polymer solutions were drawn into arrays of microfibers using a novel direct-write process. This process utilizes a micromanipulator-controlled syringe loaded with solvated polymer mixed with CNTs to “write” networks of composite fibers with precisely positioned endpoints. The diameters of these composite fibers are correlated to the degree of capillary thinning that occurs prior to the solidification of the directly written CNT-doped solution filament. The fibers had diameters ranging from 7 μm to over 100 μm and possessed conductivities as high as 0.1 Sm−1. Fiber diameter was found to increase with increasing polymer concentration and decreasing fiber length and can be controlled through modulation of these parameters. The presence of CNTs was found not to significantly affect fiber diameter, despite the CNTs significant effect on viscosity, which was previously reported to influence diameter. This discrepancy is likely related to the non-Newtonian effects of CNT/polymer solutions, including an apparent shear thinning at increasing axial strain rates.

scholarly journals Needleless Electrospinning of PA6 Fibers: The Effect of Solution Concentration and Electrospinning Voltage on Fiber Diameter

2020 ◽  
Vol 66 (7-8) ◽  
pp. 421-430
Author(s):  
Alexandra Aulova ◽  
Marko Bek ◽  
Leonid Kossovich ◽  
Igor Emri
Keyword(s):  
Electrical Conductivity ◽  
Surface Tension ◽  
Fiber Diameter ◽  
Polymer Concentration ◽  
Solution Concentration ◽  
Fine Tuning ◽  
Solution Viscosity ◽  
Diameter Distribution ◽  
Needleless Electrospinning ◽  
Pore Size Distributions

Needleless electrospinning is the process of forming thin material fibers from the open surface of its solution or melt in a strong electrostatic field. Electrospun non-woven materials are used in various applications that require specific fiber diameters and pore size distributions. Fiber diameter depends on the properties of the polymer solution and manufacturing conditions. A needleless electrospinning process using the Nanospider setup was investigated using the commonly used polyamide 6 (PA6) solution in a mixture of acetic and formic acids. Polymer solutions with different polymer concentrations were characterized by viscosity, surface tension and electrical conductivity. An increase in polymer content in the solution resulted in the exponential increase of the solution viscosity, polynomial increase of electrical conductivity and had almost no effect on surface tension. The effect of the polymer concentration in the solution, as well as electrospinning voltage on fiber diameter and diameter distribution, was investigated using scanning electron microscopy images. The average fiber diameter linearly increases with the increased polymer concentration and also demonstrates an increase with increased electrospinning voltage, although less pronounced. Therefore, a change in the PA6 solution concentration should be used for the robust adjustment of fiber diameter, while changes in electrospinning voltage are more appropriate for fine tuning the fiber diameter during the process of needleless electrospinning.

Effect of viscoelasticity on the soft-wall transition and turbulence in a microchannel

2017 ◽  
Vol 812 ◽  
pp. 1076-1118 ◽  
Author(s):  
S. S. Srinivas ◽  
V. Kumaran
Keyword(s):  
Molecular Weight ◽  
Reynolds Number ◽  
Reynolds Stress ◽  
Mass Fraction ◽  
Rectangular Cross Section ◽  
Pure Water ◽  
Polymer Concentration ◽  
Wall Turbulence ◽  
Solution Viscosity ◽  
Soft Wall

The modification of soft-wall turbulence in a microchannel due to small amounts of polymer dissolved in water is experimentally studied. The microchannels are of rectangular cross-section with height ${\sim}$160 $\unicode[STIX]{x03BC}\text{m}$, width ${\sim}$1.5 mm and length ${\sim}$3 cm, with three walls made of hard polydimethylsiloxane (PDMS) gel, and one wall made of soft PDMS gel with an elasticity modulus of ${\sim}$18 kPa. Solutions of polyacrylamide of molecular weight $5\times 10^{6}$ and mass fraction up to 50 ppm, and of molecular weight $4\times 10^{4}$ and mass fraction up to 1500 ppm, are used in the experiments. In all cases, the solutions are in the dilute limit below the critical overlap concentration, and the solution viscosity does not exceed that of water by more than 10 %. Two distinct types of flow modifications are observed below and above a threshold mass fraction for the polymer, $w_{t}$, which is ${\sim}$1 ppm and 500 ppm for the solutions of polyacrylamide with molecular weights $5\times 10^{6}$ and $4\times 10^{4}$, respectively. At or below $w_{t}$, there is no change in the transition Reynolds number, but there is significant turbulence attenuation, by up to a factor of 2 in the root-mean-square velocities and a factor of 4 in the Reynolds stress. When the polymer concentration increases beyond $w_{t}$, there is a decrease in the transition Reynolds number and in the intensity of the turbulent fluctuations. The lowest transition Reynolds number is ${\sim}$35 for the solution of polyacrylamide with molecular weight $5\times 10^{6}$ and mass fraction 50 ppm (in contrast to 260–290 for pure water). The fluctuating velocities in the streamwise and cross-stream directions are lower by a factor of 5, and the Reynolds stress is lower by a factor of 10, in comparison to pure water.

scholarly journals Short communication: Melatonin implantation during the non-growing period of cashmere increases the cashmere yield of female Inner Mongolian cashmere goats by increasing fiber length and density

2018 ◽  
Vol 16 (1) ◽  
pp. e06SC01 ◽  
Author(s):  
Ziyuan Wu ◽  
Chunhui Duan ◽  
Yan Li ◽  
Tao Duan ◽  
Fang Mo ◽  
...  
Keyword(s):  
Body Weight ◽  
Treatment Group ◽  
Fiber Length ◽  
Short Communication ◽  
Fiber Diameter ◽  
Contributing Factors ◽  
Initial Body Weight ◽  
Melatonin Treatment ◽  
Growing Period ◽  
Cashmere Goats

This study aimed to evaluate if melatonin implantation at the end of April and June was able to increase cashmere production in female Inner Mongolian cashmere goats and to search for contributing factors accounting for the melatonin increasing in cashmere production. One hundred and fifty female Inner Mongolian cashmere goats (initial body weight 37.2 ± 3.3 kg) were randomly assigned to either a control (n=75) or a treatment (n=75) group. Goats in the treatment group were implanted with melatonin (2 mg/kg of body weight) on April 30 and June 30, 2014 while goats in the control received no treatment. Melatonin implantation increased cashmere yield by 23.4% while increasing the length and density of the cashmere fiber by 19.8% and 11.4%, whereas it decreased cashmere fiber diameter by 4.4%. Melatonin treatment had no effect on doe growth, litter size or birth and weaning weights of kid. Melatonin implantation promoted cashmere yield by increasing fiber length and density without impacting the performance of goats and their offspring. Therefore, melatonin implantation during the cashmere non-growing period (late April and June) is an effective way to increase cashmere yield and improve cashmere characteristics of goats.

A Comprehensive Review on Carbon-Based Polymer Nanocomposite Foams as Electromagnetic Interference Shields and Piezoresistive Sensors

2020 ◽  
Vol 2 (8) ◽  
pp. 2318-2350 ◽  
Author(s):  
Mahyar Panahi-Sarmad ◽  
Mina Noroozi ◽  
Mahbod Abrisham ◽  
Siroos Eghbalinia ◽  
Fatemeh Teimoury ◽  
...  
Keyword(s):  
Electromagnetic Interference ◽  
Polymer Nanocomposite ◽  
Comprehensive Review ◽  
Piezoresistive Sensors ◽  
Nanocomposite Foams ◽  
Carbon Based

scholarly journals A New Empirical Model for Viscosity of Sulfonated Polyacrylamide Polymers

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 1046 ◽  
Author(s):  
Saeed Akbari ◽  
Syed Mohammad Mahmood ◽  
Hosein Ghaedi ◽  
Sameer Al-Hajri
Keyword(s):  
Polymer Solution ◽  
Oil Recovery ◽  
Empirical Model ◽  
Linear Regression Analysis ◽  
Polymer Concentration ◽  
Polymer Flooding ◽  
Solution Viscosity ◽  
Operational Variables ◽  
Reservoir Conditions ◽  
Sulfonated Polyacrylamide

Copolymers of acrylamide with the sodium salt of 2-acrylamido-2-methylpropane sulfonic acid—known as sulfonated polyacrylamide polymers—had been shown to produce very promising results in the enhancement of oil recovery, particularly in polymer flooding. The aim of this work is to develop an empirical model through the use of a design of experiments (DOE) approach for bulk viscosity of these copolymers as a function of polymer characteristics (i.e., sulfonation degree and molecular weight), oil reservoir conditions (i.e., temperature, formation brine salinity and hardness) and field operational variables (i.e., polymer concentration, shear rate and aging time). The data required for the non-linear regression analysis were generated from 120 planned experimental runs, which had used the Box-Behnken construct from the typical Response Surface Methodology (RSM) design. The data were collected during rheological experiments and the model that was constructed had been proven to be acceptable with the Adjusted R-Squared value of 0.9624. Apart from showing the polymer concentration as being the most important factor in the determination of polymer solution viscosity, the evaluation of the model terms as well as the Sobol sensitivity analysis had also shown a considerable interaction between the process parameters. As such, the proposed viscosity model can be suitably applied to the optimization of the polymer solution properties for the polymer flooding process and the prediction of the rheological data required for polymer flood simulators.

Measurements and mapping of 282,420 nerve fibers in the S1–5 nerve roots

2009 ◽  
Vol 11 (3) ◽  
pp. 255-263 ◽  
Author(s):  
Erik F. Hauck ◽  
Markus Schwefer ◽  
Werner Wittkowski ◽  
Hans W. Bothe
Keyword(s):  
Nerve Fiber ◽  
Cross Sections ◽  
Fiber Diameter ◽  
Inverse Correlation ◽  
Nerve Fibers ◽  
Fiber Types ◽  
Nerve Roots ◽  
Sacral Nerve ◽  
Dorsal Roots ◽  
Fiber Stimulation

Object The study aims to analyze nerve fiber types in the sacral nerve roots as a prerequisite for stimulation. Methods One-micrometer cross-sections of human ventral and dorsal S1–5 roots were stained with osmium and toluidine blue. The total fiber diameter and myelin sheath were measured in 282,420 nerve fibers. Results The analysis revealed the following 3 main nerve fiber types: Aα fibers (diameter 6–14 μm), Aγ fibers (diameter 2–4 μm), and B fibers (diameter < 2 μm). The B fibers were absent in S-1, present in some S-2 fascicles, and abundant from S-3 to S-5. The Aα fibers dominated the S-1 roots and most fascicles of S-2 roots. In the S3–5 roots, only a few Aα fibers were present. The relative occurrence of Aγ fibers increased from S-1 to S-5. In dorsal roots, Aγ fibers represented ~ 70% of all nerve fibers in every root and fascicle. Conclusions The B fibers represented efferent parasympathetic fibers. These fibers were concentrated in certain areas of the nerve roots, not randomly distributed. The Aα fibers innervate lower-extremity muscles and sphincters. The inverse correlation of Aα and Aγ fibers in the ventral roots from S-1 to S-5 is surprising. In dorsal roots, Aγ fibers may conduct pain, touch, and temperature signals. Highly selective fiber stimulation specific for type, location, and direction may improve sacral nerve stimulation for a spastic bladder in paraplegic individuals.

Genetic evaluation of fiber length and fiber diameter from Inner Mongolia White Cashmere goats at different ages

2015 ◽  
Vol 123 (1) ◽  
pp. 22-26 ◽  
Author(s):  
Zhiying Wang ◽  
Zhixin Wang ◽  
Yan Liu ◽  
RuiJun Wang ◽  
Yanjun Zhang ◽  
...  
Keyword(s):  
Inner Mongolia ◽  
Fiber Length ◽  
Fiber Diameter ◽  
Genetic Evaluation ◽  
Different Ages ◽  
Cashmere Goats

Optimization of Solvent System and Polymer Concentration for Synthesis of Polyvinyl Alcohol (PVA) Fiber Using Rotary Forcespinning Technique

2015 ◽  
Vol 1123 ◽  
pp. 20-23 ◽  
Author(s):  
Muhammad Miftahul Munir ◽  
Ahmad Fauzi ◽  
Ade Yeti Nuryantini ◽  
Nursuhud ◽  
Eri Sofiari ◽  
...  
Keyword(s):  
Polyvinyl Alcohol ◽  
Fiber Diameter ◽  
Polymer Concentration ◽  
Solvent System ◽  
Polymer Fiber ◽  
Fiber Morphology ◽  
Ethanol Content ◽  
Optimization Parameters ◽  
Pva Fiber

Rotary forcespinning is one of techniques used for fabrication of polymer fiber. In this paper optimization of several parameters for synthesis of Polyvinyl Alcohol (PVA) fiber using rotary forcespinning technique was described. In order to obtain PVA fiber with smallest diameter the optimization parameters of solvent system and polymer concentration were performed. The results show that PVA dissolved in water as a single solvent produced fiber with high wettability. A mixture of water and ethanol as a solvent system was developed with variation in ethanol content. The effects of ethanol content on fiber diameter were investigated. Rotary forcespinning using solvent with ethanol content below 30% resulted in PVA fiber with high wettability, while solvent ethanol content of more than 70% was unable to dissolve PVA completely. The effect of PVA concentration on the fiber morphology was investigated by adjusting PVA concentration in the range of 9 to 13 weight %. The diameter of the PVA fiber was uniform and could be controlled by adjusting the PVA concentration.

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