Electrospinning surface tension

The surface tension seems more likely to be a function of solvent compositions, but is negligibly dependent on the solution concentration. Different solvents may contribute different surface tensions. However, not necessarily a lower surface tension of a solvent will always be more suitable for electrospinning. Generally, surface tension determines the upper and lower boundaries of electrospinning window if all other variables are held constant. The formation of droplets, bead and fibers can be driven by the surface tension of solution and lower surface tension of the spinning solution helps electrospinning to occur at lower electric field [57],... 

As a major component of the natural extracellular matrix, HA has also attracted considerable attention in electrospinning. However, it is very difficult to electrospin an aqueous HA solution because its unusual high viscosity and surface tension both hinder the electrospinning process. In addition, the... 

The following parameters and processing variables affect the electrospinning process (i) system parameters such as molecular weight, molecular weight distribution and architecture (branched, linear, etc.) of the polymer, and polymer solution properties (viscosity, conductivity, dielectric constant, and surface tension, charge carried by the spinning jet) and (ii) process parameters such as electric potential, flow rate and concentration, distance between the capillary and collection screen, ambient parameters... 

Figure 4.2 Schematic illustration of the conventional set-up for electrospinning. The insets show a drawing of the electrified Taylor cone, bending instability, and a typical SEM Image of the nonwoven mat of PET nanofibers deposited on the collector. The bending Instability Is a transversal vibration of the electrospinning jet. It is enhanced by electrostatic repulsion and suppressed by surface tension...

Other studies in 2000 by Drew et al. reported that it is very difficult to spin fibers of PANI complexed to sulfonated polystyrene (PANFSPS), even when solutions containing sodium chloride and dodecyl benzene sulfonic acid sodium salt were used to lower the surface tension and thereby enhance electrospinning [16,17]. However, PANFSPS nanofibers can be produced by adding a carrier polymer such as PEO, polyacrylonitrile, or polyurethane. Also reported was the use of electrostatically layered sulfonated polystyrene as a template for the surface polymerization of conjugated polymers in their conducting form. Enzymatic synthesis of PANI and a copolymer of pyrrole and PEDOT was done on electrospun nanofiber... 

Electrospinning uses a high-voltage electrical field (typically 10-20 kV) to form micro- and even nanoscale fibres from a suspended droplet of polymer melt or solution [118]. When the repulsive electrostatic interactions overcome the droplet s surface tension, a Taylor cone is formed and a polymer jet is ejected from the tip of this Taylor cone [119]. The polymer jet is then accelerated towards a grounded collector screen. As the jet moves through the air, a stretching process occurs and the solvent evaporates which results in a non-woven polymer fabric or polymer mat [120]. Electrospinning has already been applied for both synthetic as well... 

A detailed theory of the bending instability of the electrified polymer jets in electrospinning was given in [9, 10] (see also the reviews [11, 23, 24] and references therein). Recasting the inequality (2.22) for the onset of the aerodynamic bending reveals that the destabilizing electric force overcomes the stabilizing effect of the surface tension if... 

The morphology and the diameter of the electrospun nano Hers can be affected by many electrospinning parameters including solution properties (the concentration, liqnid viscosity, surface tension, and dielectric properties of the polymer solution), processing conditions (apphed voltage, volume Cbw rate, tip to collector distance, and the strength of the apphed electric Hid), and ambient conditions (temperature, atmospheric pressure and humidity) [17-20]. 

For the electrospinning process to be initiated, the solution must gain sufficient charges such that the repulsive forces within the solution are able to overcome the surface tension of the solution. Subsequent stretching or drawing of the electrospinning jet is also dependent on the ability of the solution to carry charges. 

Solvent volatility is an important factor in electrospinning. Since electrospinning requires a quick evaporation rate and phase separation, vapor pressure of the solvent affects the dr5dng time and evaporation rate. Other parameters affecting evaporation rate are boiling point, specific heat, enthalpy and heat of vaporization, rate of heat supply, interaction between solvent molecules, surface tension of the liquid, and air movement above the liquid surface. 

Basically, electrospinning process parameters can be classified into three differenttypes solution, process, and ambientparameters. Viscosity, conductivity, and surface tension which affect instantly dimensions and morphology of fiber. Viscosity is one of the most important solution parameters. 

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