electrospinning of nanofibers from polymer solutions and melts - Spingenix


Solution Electrospinning

Solution Electrospinning. Low surface tension solvents such as ethanol can be added to the electrospinning solution to aid in the formation of smooth nanofibers. Another way to reduce surface tension is to add a surfactant to the solution. More homogeneous fibers can be obtained by adding surfactant. Fiber morphology is improved even when a thin, insoluble surfactant is added to the solution

Electrospinning solution

During electrospinning, the solution is stretched by repelling the charges on its surface. If the conductivity of the solution is increased, more charge can be transported to the electrospin beam. The conductivity of the solution can be increased by adding ions. Also, many drugs and proteins ionize when dissolved in water. If the solution is not completely drawn off, peeling will occur. Therefore, if a very small amount of salt or polyelectrode is added to the solution, the charges carried by the solution will increase and raise the voltage of the solution. As a result, smooth fibers are formed. Increasing the tensile strength of the solution makes it possible to obtain fibers with a smaller diameter. However, there are limits to reducing the fiber diameter. When the solution is stretched, a large viscoelastic force is generated against the force of the rod column.

Electrospinning fundamentals optimizing solution and apparatus parameters

As the conductivity of the solution increases with the presence of ions, the critical voltage required for electrospinning also decreases. Another effect of increased loading is greater instability of the whip. As a result, the degree of fiber accumulation increases. In this case, by increasing the beam path, smaller fibers are obtained.

The process parameters affecting the electrospinning process are the second most important group of parameters affecting the properties of the solution. Process parameters include applied voltage, solution feed rate, solution temperature, manifold type, nozzle diameter, and nozzle-to-manifold spacing.

Electrospinning of nanofibers from polymer solutions and melts

When a voltage is applied, the resulting electric field affects the drag and acceleration of the jet. When a higher voltage is applied, the solution has greater drag due to greater columnar forces in the jet. This not only reduces fiber diameter, but also causes the solvent to evaporate more quickly, resulting in drier fibers. When using low-viscosity solutions, the application of high voltage during electrospinning can lead to secondary jet formation. This reduces the diameter of the fiber. Another factor that can affect fiber diameter is the flight time of the electrospindle. The long flight time gives the fibers time to stretch and stretch before reaching the collector.

Acetic acid electrospinning solution

The feed rate determines the amount of solution available for electrospinning. There is some tension and feed rate to keep the Taylor cone stable. As the feed rate increases, the fiber diameter or bead size increases as the volume of solution drawn from the nozzle increases. However, there are limits to increasing the fiber diameter due to the high draw-in speed.

Solution electrospinning process

The temperature of the solution is effective to both increase the rate of evaporation and decrease the viscosity of the solution. At low viscosities, column forces create greater drag forces on the solution jet, resulting in smoother and finer fibers. By increasing the mobility of polymer molecules with increasing solution temperature, the attractive effect of the column forces on the solution jet also increases. Demir et al (2002), in their study on electrospinning PU nanofibers, found that the fibers obtained at high solution temperature are more uniform and homogeneous than the fibers obtained at room temperature.

They also indicated that the electrospinning process is faster at high solution temperatures, which could be beneficial for industrial applications. However, applying high temperatures to electrospinning solutions of biological materials such as enzymes and proteins can result in a loss of performance of these materials.

Both the shape and the material of the collector affect the electrospinning and the structure of the formed nanofibers. Many different collector designs, both movable and fixed, have been used in studies. The most commonly used collectors are aluminum plates. In addition, metal mesh, rotating drum, rotating disk, conveyor belt, triangular frame, parallel ring, and liquid bath are some of the materials used to collect electrospun nanofibers.

Electrospinning Polymers

Electrospinning Polymers. First, the spun polymer must be converted to a liquid state. A polymeric thermoplastic can then simply be melted, otherwise dissolved or dissolved in a solvent, or chemically treated to form thermoplastic derivatives. The molten polymer is then passed through a mold, then cooled to a rubbery state and then to a solid state.[1] When using a polymer solution, the solvent exits after passing through the nozzle.

Wet spinning is the oldest of the five processes. This method is used for polymers that need to be dissolved in a solvent for spinning. The spray nozzle causes the fiber to be immersed in a chemical bath. fall out and solidify after leaving. This process takes its name from this “wet” bath. Acrylic, viscose, aramid, medacryl and tights are produced with this process.[1] A type of wet spinning: dry jet wet spinning, the solution is extruded and sucked into the air, and then immersed in a liquid bath. In this process, lyocell cellulose is dissolved during spinning.

Electrospinning jets and polymer nanofibers

A solution of a fibrogenic material and a solvent is extruded through a nozzle. A stream of hot air hits the nozzles of the solution emerging from the mold, the solvent evaporates and solid filaments remain. Solution Blowing Spinning is a similar technique where the polymer solution is sprayed directly onto a target. fleece mats. Melt spinning is used for fusible polymers. When the polymer is extruded through a spray nozzle, it solidifies on cooling. Nylon, olefin, polyester, saran and sulfur are produced from this process. Solid polymer pellets or granules, an extruder. Pellets are compressed, heated and melted by an extruder and then fed to a rotating pump and die.

Electrospinning of nanofibers from polymer solutions and melts

Direct spinning avoids the solid polymer pellet stage. Molten polymer is made from raw materials and then pumped from the polymer finisher directly to the spinning mill. Direct spinning is mainly used in the production of polyester fibers and filaments and is intended for high production capacity (> 100 tons per day).

Electrospinning of polymer nanofibers

Gel spinning, also known as wet-dry spinning, is used to achieve high strength or other special properties in fibers. The polymer is in a “gel” state, which somehow holds the polymer chains together, and is only partially liquid. These bonds create strong chain forces that increase the tensile strength of the fibers. Polymer chains in fibers also have a high degree of orientation, which increases strength. The fibers are first air dried and then cooled in a liquid bath. This process produces low tenacity polyethylene and aramid fibers.

Nanometre diameter fibres of polymer produced by electrospinning

Electrospinning uses an electrical charge (usually at the micro or nano scale) to extract very fine fibers from a liquid, polymer solution or molten polymer. Electrospinning has the properties of both electrospray and traditional dry solution spinning[3] of fibers. This process does not require the use of coagulation or high temperature chemistry to produce strong yarns from solution. This makes the process particularly suitable for the production of fibers from large and complex molecules. Electrospinning fusion is also applied. This process ensures that no solvent is transferred to the final product.

Polymer nanofibers assembled by electrospinning

In recent years, various methods for the production and application of nanostructures, especially polymer nanofibers, in the field of bioengineering and tissue regeneration have been developed: nanoscale imaging of nanosystems and polymer nanofibers, polymer phase separation, photolithography and electron beam, chemical. Vapor Deposition, Centrifugal Firing (Spun) is formed by various manufacturing processes such as Electrogravity (E-Spun). The electrospinning process is one of the most important processes among other processes and is used as a simple, inexpensive and efficient technological process in the production of polymer nanofibers. Light weight, nanoscale and diameter of nanoscale fibers are widely preferred in medical applications because of their important features like morphology and surface structure. Composites, filter, protective, electronic and optical materials reinforced with sensors and nanofibers are widely used for biomedical applications of polymer nanofibers obtained by this method.

Electrospinning nanofibers

Electrospinning nanofibers. Chitosan [poly(b-1/4)-2-amino-2-deoxy-D-glucopyranose] is a polycationic property that has a partial or total effect by incorporating chitin into the cell wall of oysters and some fungi will. Deacetylation in alkaline medium is a biopolymer. Many researchers have found that chitosan is often preferred in biomedical applications due to its biocompatibility, biodegradability, non-toxicity, potential for cell adhesion and proliferation, antimicrobial activity, and its aid in rapid wound healing. However, chitosan can be produced in the form of powder, gel, foam, film, fiber and thread and used in many different forms in many fields (Tikhonov et al., 2006; Peter, 1996; Rao and Sharma, 1994; Rinaudo, 2006) . It is one of the synthetic polymers with mechanical and physical properties, biocompatible and biodegradable.

Electrospinning nanofibers

It is generally obtained by ring-opening polymerization of “ε-caprolactam”. It has a very wide range of uses, especially in the textile industry. Electrospinning can be briefly defined as the production of submicron fineness fibers by the application of electrostatic forces to a polymer solution or melt. This method includes operational steps such as (i) charging the solution with electric charges (ii) Taylor coning (iii) diluting the polymer jet by instability (whiplash instability) in the electric field (iv) diluting, collecting and solidifying. The polymer jet is converted into fibers on the collection mechanism.

Diameter and morphology of fibers obtained by electrospinning processes, solution properties (viscosity, conductivity, molecular weight and polymer concentration, surface tension, type of solvent), process parameters (electric field strength, distance between feeder and collector, feed amount of solution) and environmental conditions (temperature, humidity) (Chong et al., 2007; Lee et al., 2004). It can be seen that the academic and industry interest in the electrospinning method has increased in recent years as it allows the use of simple and efficient nanofibers. Production of natural and synthetic polymers

Nanofiber-based structures are considered as potential materials, due to their high surface-to-volume ratio, high porosity, and very small pore size (Li and Xia, 2004) As the surface tension increases sharply, electrostatic attraction is said to cause various problems. To overcome this problem, smooth nanofibers can be obtained by blending various polymers.

The chitosan (CS) produced at 2% by weight was dissolved homogeneously in 90% strength acetic acid with stirring for 24 h at room temperature. For 7 hours, homogeneous solution, electrogravity tests were performed. The solutions were mixed using a magnetic stirrer (Stuart, SB 162) for two hours at room temperature. The pH of the prepared solutions was determined using indicator cards (indicator strips, Merck) and their viscosity values. Their conductivity was determined using a Brookfield viscometer (DV-E viscometer). It was measured with a WTW brand device (Cond 3110). A spindle of the type S21 with a rotation of 30 rpm was used for viscometer measurements.

The electrospinning process was performed using a laboratory machine (NanoFMG, NS24) designed on the principle of vertical work. Each solution was transferred to syringes with a volume of 10 ml and introduced into an aluminum foil-covered cylindrical manifold using a 20-gauge delivery unit (nozzle), and the amount of the feed solutions was measured in an electric field of 0.50 ml/hour definitely. And the distance was adjusted to 15 cm. A voltage of 34 kV was applied in electrogravity experiments. Alternating current (AC) was used to create the electric field. The experiments were carried out at a relative humidity of 35-42% and at variable temperatures between 26-31 degrees Celsius.

The polycationic nature of chitosan and the strong intramolecular and intermolecular interactions in its chemical structure create significant problems in the electrospinning process. Strong hydrogen bonds prevent the free movement of polymer chain blocks in the electric field and lead to nozzle cracking during the electrospinning process [Li and Hsieh, 2006; Desai and Keith, 2008). In addition, the repulsive forces between the ionic groups in the polymer chain sufficiently prevent entanglement (entanglement) of the polymer chains. This prevents the formation of sufficient and continuous fibers during stretching, bending and impact instability of the polymer jet. These problems result in the formation of globules or irregular beaded fibers during the elongation of the polymer stream rather than the formation of regular fibers as a result of the electrospinning process.