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Electrospinning Technology:
Electrospinning technology has been known since twentieth century. Electrospinning is an old but yet immature process which is now used to form nanoscale polymer fibers. It is a relatively simple method to produce submicron fibers from solutions of different polymers and polymer blends. Electrospinning uses an electrical charge to draw very fine fibres from a liquid. Electrospinning shares characteristics of both electrospraying and conventional solution dry spinning of fibers. We can say electrospinning is an established method of producing nano-fibers from a wide variety of natural and synthetic polymers.
Because of the small pore size and high surface area inherent in electrospun textiles, these fabrics show promise for use in protective clothing for soldiers filtration applications, membranes, reinforcing fibers in composite materials, optical and electronic applications, biomedical devices (cosmetics, skin healing and skin cleansing, wound dressing, drug delivery and pharmaceuticals, supports for enzymes or catalysts, scaffolds for tissue engineering, and templates for the formation of hollow fibers with inner diameters in the nanometer range.
Properties of Electrospun Nanofibers:
Two forms of electrospun nano fibers were produced by normal and aligned electrospinning methods. The randomly aligned fiber mats were collected on a large, flat, grounded target, while the aligned fibers were created by parallel collecting electrodes. Electron microscopy was used to illustrate the morphology of the electrospun fibers. The results showed that higher concentration could produce larger fibers due to more polymer chains and chain entanglements.
It is difficult to measure mechanical properties of each electrospun single nanofiber with existing test techniques, because of their very small diameters. Therefore, mechanical tests were performed instead on nano-scale nonwoven webs with conventional testing methods. Mechanical properties of electrospun PU nanowebs were investigated by Pedicini and Farris.
Among the many electrospun polymers reported in the literature are poly (p-phenylene terephthalamide), tri-block copolymers, polyethylene oxide and DNA from solution; and polyethylene and polypropylene from the melt. Nylon was the first commercialized synthetic fiber and is used throughout the world in many applications. It has been widely used as an important engineering plastic and synthetic fiber because of its good mechanical properties. It has been produced by traditional methods such as melt, wet and dry spinning and is available in staple, tow, monofilament and multifilament forms. Fiber diameters produced by these methods range from 10 to 500 µm.
Nylon-6,6 (N6,6), polybenzimidazole (PBI) and poly (tetrafluoroethylene) membranes produced from electrospun fibers as protective layers. Properties of these electrospun membranes, including structural effects upon moisture transport, air convection, aerosol filtration, porosity and tensile strength. N6, the polymer crystalline structure was altered from α to γ form when electrospun.
The ability of the electrospinning process to produce the γ form implies that the fibers are under high stress when they are being formed. Nylon-12 has only one preferred conformation, and the chain conformation is conserved after processing.
Mechanical properties of two widely different molecular weight electrospun N6,6 nanowebs are compared by using conventional test methods. The main objective of this part of the study was to determine whether the use of high molecular weight N6,6 is a viable approach to improve the mechanical properties of electrospun nylon filaments.
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| Schematic diagram of eletrospinning set-up |
Conventional fiber spinning techniques such as wet spinning, dry spinning, melt spinning and gel spinning usually produce polymer fibers with diameters down to the micrometer range. If the fiber diameter is reduced from micrometers to nanometers, very large surface area to volume ratios are obtained and flexibility in surface functionalities and better mechanical performance may be achieved.
Because of the small pore size and high surface area inherent in electrospun textiles, these fabrics show promise for use in protective clothing for soldiers filtration applications, membranes, reinforcing fibers in composite materials, optical and electronic applications, biomedical devices (cosmetics, skin healing and skin cleansing, wound dressing, drug delivery and pharmaceuticals, supports for enzymes or catalysts, scaffolds for tissue engineering, and templates for the formation of hollow fibers with inner diameters in the nanometer range.
Properties of Electrospun Nanofibers:
Two forms of electrospun nano fibers were produced by normal and aligned electrospinning methods. The randomly aligned fiber mats were collected on a large, flat, grounded target, while the aligned fibers were created by parallel collecting electrodes. Electron microscopy was used to illustrate the morphology of the electrospun fibers. The results showed that higher concentration could produce larger fibers due to more polymer chains and chain entanglements.
It is difficult to measure mechanical properties of each electrospun single nanofiber with existing test techniques, because of their very small diameters. Therefore, mechanical tests were performed instead on nano-scale nonwoven webs with conventional testing methods. Mechanical properties of electrospun PU nanowebs were investigated by Pedicini and Farris.
Among the many electrospun polymers reported in the literature are poly (p-phenylene terephthalamide), tri-block copolymers, polyethylene oxide and DNA from solution; and polyethylene and polypropylene from the melt. Nylon was the first commercialized synthetic fiber and is used throughout the world in many applications. It has been widely used as an important engineering plastic and synthetic fiber because of its good mechanical properties. It has been produced by traditional methods such as melt, wet and dry spinning and is available in staple, tow, monofilament and multifilament forms. Fiber diameters produced by these methods range from 10 to 500 µm.
Nylon-6,6 (N6,6), polybenzimidazole (PBI) and poly (tetrafluoroethylene) membranes produced from electrospun fibers as protective layers. Properties of these electrospun membranes, including structural effects upon moisture transport, air convection, aerosol filtration, porosity and tensile strength. N6, the polymer crystalline structure was altered from α to γ form when electrospun.
The ability of the electrospinning process to produce the γ form implies that the fibers are under high stress when they are being formed. Nylon-12 has only one preferred conformation, and the chain conformation is conserved after processing.
Mechanical properties of two widely different molecular weight electrospun N6,6 nanowebs are compared by using conventional test methods. The main objective of this part of the study was to determine whether the use of high molecular weight N6,6 is a viable approach to improve the mechanical properties of electrospun nylon filaments.
Reference:
- Nanofibers and nanotechnology in textiles Edited by P. J. Brown and K. Stevens
- Filtration Properties of Electrospinning Nanofibers, Xiao-Hong Qin, Shan-Yuan Wang
- Mechanical and Physical Properties of Electrospun Nanofibers, ZHANG SHU.
- Functional Applications of Electrospun Nanofibers
- Jian Fang, Xungai Wang, and Tong Lin
- www.en.wikipedia.org/wiki/Electrospinning
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