Embedded Files
NEW GENERATION FIBER
Faster, stronger, lighter, safer ... these demands are constantly being pushed upon today's researchers and manufacturers, including protective clothing - routine or specialized. High performance fibers aid enormously in allowing products to meet these challenges. High performance fibers are driven by special technical functions that require specific physical properties unique to these fibers.
Some of the most prominent of these properties are: tensile strength, operating temperature, limiting oxygen index and chemical resistance. Each fiber has a unique combination of the above properties which allows it to fill a niche in the high performance fiber spectrum. High-performance fibers, used in fabric applications ranging from bulletproof vests to trampolines, must have a sufficient number of chemical and physical bonds for transferring the stress along the fiber. The fibers should possess high stiffness and strength to limit their deformation.
NANO FIBER
Nanofibres are fibres measured in nanometres—one billionth of a meter. Their size is just 3-4 atoms thick with diameters of 50-500nm and their characteristics include low density, lightweight with large surface area to mass, high pore volume, and tight pore size. Generally, polymeric nanofibres are produced by an electrospinning process and bi-component spinning technique. Electrospinning is a process that spins of diameters ranging from 10nm to several hundred nanometres. This method has been known since 1934 when the first patent on electrospinning was filed. Electrospinning can be carried out from polymer melt or solution.
ELECTROSPINNING PROCESS.
Definition: electric field used to draw polymer stream out of solution. The process makes use of electrostatic and mechanical force to spin fibers from the tip of a fine orifice or spinneret. The spinneret is maintained at positive or negative charge by a DC power supply.
When the electrostatic repelling force overcomes the surface tension force of the polymer solution, the liquid spills out of the spinneret and forms an extremely fine continuous filament. These filaments are collected onto a rotating or stationary collector with an electrode beneath of the opposite charge to that of the spinneret where they accumulate and bond together to form nanofiber fabric.
D- electric field overcomes solution surface tension; polymer stream generated
E- fibers 1) collected and 2) patterned on plate
PROPERTIES OF NANOFIBERS
Nanofibers exhibit special properties mainly due to extremely high surface to weight ratio compared to conventional nonwovens. Low density, large surface area to mass, high pore volume, and tight pore size make the nanofiber nonwoven appropriate for a wide range of filtration applications.
The elastic modulus of polymeric nanofibers of less than 350 nm is found to be 1.0±0.2 Gpa. Nanofibers are an exciting new class of material used for several value added applications such as medical, filtration, barrier, wipes, personal care, composite, garments, insulation, and energy storage. Special properties of nanofibers make them suitable for a wide range of applications from medical to consumer products and industrial to high-tech applications for aerospace, capacitors, transistors, drug delivery systems, battery separators, energy storage, fuel cells, and information technology.
Challenges in Nanofibres
Ø The process of making nanofibres is quite expensive compared to conventional fibres due to low production rate and high cost of technology.
Ø In addition the vapours emitting from electro spinning solution while forming the web need to be recovered or disposed of in an environmental – friendly manner. This involves additional equipment and cost.
Ø The fineness of fibre and evaporated vapour also raises much concern over possible health hazard due to inhalation of fibres.
Thus the challenges faced can be summarized as :
ü Economics
ü Health hazards
ü Solvent vapor
ü Packaging shipping
Google Sites
Report abuse