Nano-fiber spinning

Advances in filament yarn spinning of textiles and polymers 

Synthetic fibers, beginning with rayon in apparel, have expanded into multiple fiber types and products found throughout our lives. The processes and techniques used to produce these fibers have also changed dramatically during the past 70 years. Fiber manufacturing equipment and processes continue to change to both reduce the cost of fibers and to introduce newer fibers with specialized properties. 

Andreas Desch, F. R. (February 2011). Dienes and rieter OFT Develop new nanofiber spinning installations. International Fiber Journaly2S l)y 38-39. 

(2011). Nonwovens Industry. (Online) Available at www.nonwovens-industry. com. 

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Medeiros ES, et al. Solution blow spinning a new method to produce micro- and nano-fibers from polymer solutions. J Appl Polym Sci 2(X)9 113(4) 2322—30. 

Liu Y, He JH, Yu JY, Xu L, Liu LF. Jet type electrostatic spinning equipment capable of producing nano fiber in bulk. CN101003916. 2007. 

In general, when discussing polymer/CNT composites, two major classes come to mind. First, the CNT nano-fillers are dispersed within a polymer at a specified concentration, and the entire mixture is fabricated into a composite. Secondly, as grown CNT are processed into fibers or films, and this macroscopic CNT material is then embedded into a polymer matrix [65]. The four major fiber-spinning methods (Fig. 11.15) used for polymer/CNT composites from both the solution and melt include dry-spiiming [66], wet-spinning [67],... 

Neves, N.M., Campos, R., Pedro, A., Cunha, J., Macedo, F., Reis, R.L., 2007. Patterning of polymer nano fiber meshes by electro spinning for biomedical applications. International Journal of Nanomedicine 2, 433 148. 

Hu J, Wang X, Ding B, Lin J, Yu J, Sun G (2011) One-step electro-spinning/netting technique for controUably preparing polyurethane nano-fiber/net. Macromol Rapid Commun 32(21) 1729-1734. doi 10.1002/marc.201100343... 

There are many ways to implement nano-scale controlled properties into textiles. One is to give the fiber itself a nano-scale by fiber spinning. With novel fiber spinning technologies it is possible to spin fibers with diameters between 20 and 500 nm 10-500 times thinner than fibers spiimable by traditional fiber spinning techniques. An aim is to make the production of fibers with diameters below lOOnm highly productive and state-of-the-art. 

As with the polymers, a high polarity of the solvent improves the electrostatic process. Further a high electrical conductivity of the solvent is required for the production of nano-fibers. PVA and PEO are favorites for experiments as they can be processed from aqueous solutions and no special safety considerations have to be made regarding toxicity or explosivity. In addition, water is highly polar and most suitable for electrostatic spinning. (Their use for filters is limited, of course.) These are the main requirements on the solvents. In practice these ideal conditions will rarely be found. The use of chlorinated organic solvents is accepted when only small amounts are processed (e.g. for medical applications). It is difficult to obtain an operation permit for... 

Dauner, M., Production of nano fiber nonwovens using electrostatic spinning 7th Symposium Textile Filter , Chemnitz, 2-3 March, 2004... 

J. Hn, X. Wang, B. Ding, J. Lin, J. Yn, G. Snn, One-step electro-spinning/netting tech-niqne for controllably preparing polyurethane nano-fiber/net, Macromolecular Rapid Communications, 32 (2011) 1729-1734. 

Dzenis Y (2004) Material science. Spinning continuous fibers for nano technology. S cience 304 1917—1919. 

Sun D, Chang C, Li S, Lin L. Near-field elecUrospinning. Nano Lett 2006 6(4) 839 2. Fuh YK, Chen S Y, Ye JC. Massively parallel aligned microfibers-based harvester deposited via in situ, oriented poled near-field electro spinning. Appl Phys Lett 2013 103(3) 033114. Pu J, Yan X, Jiang Y, Chang C, Lin L. Piezoelectric actuation of direct-write electrospun fibers. Sensor Actuat A- Phys 2010 164(l) 131-6. 

When solution of a polymer with some inoiganic ions is electrospun, the polymer fibrils will be elongated within the spinning direction and those ions are held in the inter-fibril spaces. When those electrospun fibers are calcined, ceramic fibers wiH be obtained. The present study has attempted to employ such spaces formed in poIy(vinyl alcohol) (PVA) as nano- or micro-reactor spaces for precipitation of nano-crystaUine particles. Exposing the spun PVA mats to ammonia vapor fixed metal ions in the form of hydroxide and, induced apatitic calcium phosphate crystallites when the precursor solution involved calcium and hydrogen orthophosphate ions. 

A liquid phase, as opposed to a vapor or solid phase, includes dispersions, solutions and melts. Several processes, which yield continuous inorganic fibers directly from the melt, have been discussed in Chapter 4. Only one generic process, dry spinning, is known to yield one specific amorphous oxide fiber directly from a liquid phase other than that of a melt. All other processes which start with a liquid phase (see Chapters 8-12) yield first a solid, non-functional precursor or green fiber, and then a functional, nano- or polycrystailine ceramic fiber. Such refractory ceramic fibers are therefore directly derived from a solid phase, a precursor or a green fiber, and only indirectly from a liquid phase. 

Various techniques have been reported in the literature to produce nano-fibrous structures. These include self-assembly, phase separation, melt spinning involving islands in the sea (INS) and splittable fibers, and electrospinning. Each of these methods produces fibers of different diameter range (see Fig. 2.1) and has advantages and disadvantages. 

The results presented indicate that uniform sheath-core fibers of nano dimensions can be produced from two polymers by carefully adjusting the spinning conditions, in particular the applied voltage. As it is generally known, the polymer solution flow rates and concentrations directly controlled the core-sheath fractions and, therefore, the overall fiber size. 

The preparation of MFCs is quite different from that of the conventional composites, insofar as the reinforcing micro- or nanofibrils are created in situ during processing, as is the relaxed, isotropic thermoplastic matrix. The MFC technology can, therefore, be contrasted with the electro-spinning methods used to produce nano-sized materials mainly in the form of nonwoven fibers with colloidal length scales, i.e., diameters mostly of tens to hundreds of nanometers [57]. 

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