Correlation of Morphology of Electrospun Fibers with Rheology of Linear Polyacrylamide Solution (original) (raw)
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The Journal of Engineering and Exact Sciences
The technique of electrospinning polymeric nanofibers has been emerging in the academic environment due to its well-parias and low operational, but the production of these nanofibers finds challenges regarding homogeneity and reproduction of obtained results. As properties of polymeric solutions are important for the determination of electrospinning parameters, such as the applied electrical voltage and injection rate. Seeking rheological behavior of polymeric solutions; which may be affected by the concentration of the polymeric solution and the preparation temperature of these solutions. This way this work studied the effect of the production temperature of polyacrylonitrile and methyl acrylate copolymer solutions and related them to the nanofibers produced at the same injection rates and electrical stresses. It was observed the inversely proportional behavior between the temperature of preparation of the solutions and the viscosity of the solutions at room temperature, which refl...
Micro & Nano Letters, 2012
This study focuses on using curve fitting methodology and power law equation to analyse polyacrylonitrile (PAN) nanofibres morphology synthesised by electrospinning. The effects of polymer solution properties (i.e. polymer concentration, viscosity and Berry number) on electrospinnability of the PAN/DMF (N,N-dimethylformamide) solutions are investigated. For the polymer electrospun from concentrated solution (3.5 , Be , 7.5), the nanofibres form without beads. The relationship between solution viscosity and its concentration is in the form: h ¼ 0.0205C 4.16 , the relation between the diameter of electrospun the PAN nanofibres and solution concentration is in the form: d ¼ 0.0326C 3.45 , and the relationship between the nanofibres diameter and solution viscosity is in the form: d ¼ 0.834h 0.827 .
Industrial & Engineering Chemistry Research, 2015
This study aims at investigating the effect of solution elasticity on fiber diameter of electrospun nanofibers using viscoelastic Boger fluids of poly(vinyl alcohol) having varying degrees of elasticity (expressed in terms of relaxation time (λ) and Deborah number (De)) and similar viscosity. On electrospinning, the solutions with higher elasticity formed fibers with larger diameter, thereby, experiencing lower extension (on the order of 10 4), compared to the solutions of lower elasticity, which underwent higher extensions (up to 10 6), resulting in finer fibers. The diameter of the spun nanofibers was found to have a strong dependence on λ of the solutions. Effect of elasticity was also evident when the fiber diameter increased slightly with the increase in flow rate for solutions with higher elasticity. However, the effect of distance was negligible on the fiber diameter. The results suggest that the elasticity of the solution has an important role in governing the final diameter of electrospun fibers.
A Novel Study of Electrospun Nanofibers Morphology as a Function of Polymer Solution Properties
Electrospinning is a process of production fibers with diameters ranging from the submicron down to the nanometer size by applying a high voltage to a polymer solution. The important parameters in the morphology of electrospun polymer fibers are polymer structure, polymer solution properties, processing conditions, and ambient parameters. In the present work electrospinning of polyacrylonitrile (PAN) has been attempted to generate uniform nanofibers without beads. Electrospinning was performed at various concentrations ranging from 4 to 18 w/v%. The effects of polymer solution properties on electrospinnability of the PAN/DMF solutions have investigated. Fiber morphology was observed under a scanning electron microscopy (SEM). For the polymer electrospun from low concentration (Be<2), polymer droplets have formed. For the polymer electrospun from semi-dilute solution concentration (2<Be<3.5), the formation of nanofiber with beads. Uniform fiber formation was observed at Be>4. The relationship between solution viscosity and its concentration is in the form: η 0.0205C 4.16 and relation between the diameter of electrospun the PAN nanofiber and solution concentration is in the form: d 0.0326C 3.45 .
Viscosity of Polyacrylonitrile Solutions: The Effect of the Molecular Weight
Polymer Science Series A, 2015
The copolymer of acrylonitrile with methyl acrylate and itaconic acid (93 : 5.7 : 1.3) is synthesized via free radical copolymerization. For solutions of the initial copolymer and its 12 fractions in dimethyl sulfoxide, viscosities are measured in a wide shear stress range. The viscosity behavior of 10% solutions is examined in more detail, and the rheological studies of several fractions are performed in the concentration interval from 5 to 20%. All solutions exhibit weak non Newtonian behavior. This makes it possible to determine the zero shear viscosity. The dependences of this viscosity on the number average and weight average molecular masses for the equiconcentrated solutions obey an exponential law with the same exponent, equal to 2.3. The macromolecules of copolymers are inclined toward association. For low molecular mass fractions, this effect is the most pronounced.
Characterization of electrospun poly(N-isopropyl acrylamide) fibers
Polymer, 2008
Poly(N-isopropyl acrylamide) (pNIPAM) is an interesting material in that it shows a thermoresponsive behavior around 32 C in aqueous solutions. This behavior mimics that of many proteins in solution and as a result, many researchers have studied pNIPAM as a model for protein behavior. Yet, little is known about the processability of pNIPAM into three-dimensional matrices and whether such processing affects polymer conformation. In this work, 3D fibrous mats of pNIPAM were prepared by electrospinning from three different solvents and the resulting morphologies evaluated. Additionally, electrospun pNIPAM was evaluated with polarized Raman and infrared spectroscopies and compared against the spectra of the bulk material. It was found that the electrospinning process did not alter the polymer structure or morphology.
Macroscopic Viscosity of Polymer Solutions from the Nanoscale Analysis
ACS Applied Polymer Materials
The effective viscosity in polymer solutions probed by diffusion of nanoparticles depends on their size. It is a welldefined function of the probe size, the radius of gyration, mesh size (correlation length), activation energy, and its parameters. As the nanoparticle's size exceeds the radius of gyration of polymer coils, the effective viscosity approaches its macroscopic limiting value. Here, we apply the equation for effective viscosity in the macroscopic limit to the following polymer solutions: hydroxypropyl cellulose (HPC) in water, polymethylmethacrylate (PMMA) in toluene, and polyacrylonitrile (PAN) in dimethyl sulfoxide (DMSO). We compare them with previous data for PEG/PEO in water and PDMS in ethyl acetate. We determine polymer parameters from the measurements of the macroscopic viscosity in a wide range of average polymer molecular weights (24−300 kg/mol), temperatures (283−303 K), and concentrations (0.005−1.000 g/cm 3). In addition, the polydispersity of polymers is taken into account in the appropriate molecular weight averaging functions. We provide the model applicable for the study of nanoscale probe diffusion in polymer solutions and macroscopic characterization of different polymer materials via rheological measurements.
AIP Conference Proceedings, 2011
Polyvinyl acetate (PVAc) nanofibers were prepared by technology of electrospinning with help of multi-jets electrospinning machine from acetic acid/water solvent system. The stability of the process was tested in a broad concentration region from 5 to 40 wt. % of PVAc. The main attention was carried out to study the effect of polyvinyl acetate solution concentration/viscosity onto mean diameter of prepared nanofibers. It was found that increased solution viscosity leads to increase of fibers diameters from appox. 60 nm at viscosity ~ 0.04 Pa.s to appox. 1000 nm at viscosity ~ 6-7 Pa.s. The PVAc nanofibres can be considered as a potential precursor for preparation of inorganic fibrous nanoparticles. Their dimensions can be effectively controlled by PVAc nanofibers diameter by easy diameter-concentration/viscosity optimalization.
Influence of Salts on Electrospinning of Aqueous and Nonaqueous Polymer Solutions
A roller electrospinning system was used to produce nanofibres by using different solution systems. Although the process of electrospinning has been known for over half a century, knowledge about spinning behaviour is still lacking. In this work, we investigated the effects of salt for two solution systems on spinning performance, fibre diameter, and web structure. Polyurethane (PU) and polyethylene oxide (PEO) were used as polymer, and tetraethylammonium bromide and lithium chloride were used as salt. Both polymer and salt concentrations had a noteworthy influence on the spinning performance, morphology, and diameter of the nanofibres. Results indicated that adding salt increased the spinnability of PU. Salt created complex bonding with dimethylformamide solvent and PU polymer. Salt added to PEO solution decreased the spinning performance of fibres while creating thin nanofibres, as explained by the leaky dielectric model.
Electrospun Polyamide-6 Nanofibers: Effects of Solvent Systems
2004
In this work, polyamide-6 (PA-6) solutions were prepared in various single solvent and mixed solvent systems. The concentration of PA-6 in the solutions was fixed at 32% (w/v). Some of the solution properties, i.e. shear viscosity, surface tension, and conductivity, were measured. For single solvent systems, only the solution of PA-6 in 85 wt.% formic acid gave a uniform electrospun fibers, with the average diameters being about 83.5 nm, while the solutions of PA-6 in m-cresol and 20 and 40 wt.% sulfuric acid did not form uniform fibers. For mixed solvent systems, the solvent mixtures were prepared by mixing 85 wt.% formic acid with m-cresol, 20 and 40 wt.% sulfuric acid, acetic acid, ethanol, dimethyl formamide (DMF), and dimethyl sulfoxide (DMSO) in the compositional ratios of 10 to 40% (v/v). In general, the average diameters of the as-spun fibers were found to increase with increasing content of the second solvent. In mixed solvents of high compositional ratios of m-cresol and s...