Nano fiber manufacturing

Little is yet known about the effects of nanomaterials and exposures for humans and that creates problems for safety and health. There are no estabUshed occupational exposure limits in the United States, but some are emerging from manufacturers of nanomaterials and by other countries. NIOSH has developed RELs for titanium dioxide and carbon nanotubes and carbon nano fibers. 

Fibers are the basic element of nonwovens world consumption of fibers in nonwoven production is 63% polypropylene, 23% polyester, 8% viscose rayon, 2% acrylic, 1.5% polyamide and 3% other high performance fibers [8]. The data in Fig. 10.4 shows the market share of important polymers and fibers in the nonwovens market. Manufacturers of nonwoven products can make use of almost any kind of fibers. These include traditional textile fibers, as well as recently developed hi-tech fibers. Future advancements will be in bicomponent fibers, micro-fibers (split bicomponent fibers or meltblown nonwovens), nano-fibers, biodegradable fibers, super-absorbent fibers and high performance fibers. The selection of raw fibers, to a considerable degree, determines the properties of the final nonwoven products. The selection of fibers also depends on customer requirement, cost, processability, changes of properties because of web formation and consolidation. The fibers can be in the form of filament, staple fiber or even yam. 

Hong, Y. T, et al.. Filament Bundle Type Nano Fiber and Manufacturing Method Thereof, 2010, Google Patents. 

Foume F (1999) Synthetic fibers machines and equipment, manufacture, properties handbook for plan engineering, machine design and operatiOTi. Hanser Publishers, Munich Friedrich K, Fakirov S, Zhang Z (2005) Polymer composites from Nano- to macro-scale. Springer, Berlin... 

Silt density index (SDl) is a sensitive method for determining the ability of a filter to remove colloidal particles 14). SDl (in min ) is used extensively as a criterion in minimizing fouling of reverse osmosis membranes. The lower the SDl value, the cleaner is the stream. Manufacturers of reverse osmosis membranes recommend that the stream be prefiltered so that it has an SDl factor less than 3.0. Typically 1 pm absolnte 6) filters have an SDl of about 4-5. Manufacturers of hallow fiber membrane filters claim SDI s in the range of 1.75 to 2.25. SDl measurements of effluents from the nano alumina media range from 0.5-1.0. The SDl of 32% PAC media was measured and found to be about 1.0. Turbidity as well as SDl tests have confirmed that the extent of shedding of PAC particles into effluent streams is minimal. 

Structures made from fibers with diameters ranging from the nano- to the microscale are predestined to meet those requirements due to the extraordinary ratio between surface and volume. Via textile processing technologies, fibers can be manufactured into complex, load-adapted stmctures with interconnected pore spaces. 

Zinc electrodes can also be manufactured by the plastic-bonded method, similar to that of the nickel electrode described above. The zinc oxide dry powder, PTFE binder and other additives are blended with an organic solvent and then the mixture is passed through a calendaring process similar to that in Fig. 31.1. The PTFE fibriUates into a nano-structured three-dimensional fiber matrix. This electrode structure for the calcium zincate electrode is shown in Fig. 31.3 for a freshly prepared electrode. The active materials are locked into the electrode structural matrix which helps to reduce the tendency towards shape change and dendritic growth. 

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