Prof. Sayali Bhamare
Head, Dept. of Fashion Designing
K.V.N. Naik College, Nashik
Introduction
The name nanofibre or nano textile is derived from the nanometer. It is a scientific measurement unit which represents a billionth part of one meter, or two to four atoms wide. The NSF (National Science Foundation) defines nanofibres as having a diameter of less than one micron or less than that.
Nanofibres are a part of nonwoven industries. These textiles are an exciting new class of textile material. These nanofibres are used for several non apparel applications such as filtration, medical applications, wipes, insulation, energy storage, some part of Information Technology and others. Nanofibres carries special properties which make them suitable for an extensive application such as drug delivery system, transistors, aerospace, capacitors, battery separators and fuel cells.
There are 2 techniques of producing nanofibres. One is Electrospinning process and another is spinning bi-component fibres. Electrospinning process is known since 1934 when the petition was filed. It is a process that spins fibres of minimum diameter of 10 nanometer to hundreds of nanometer. Microscopic advancements such as scanning electron microscopy has allowed us to understand the structure and anatomy of nanofibres. Properties of nanofibres depend on polymer, viscosity, electric field strength, field uniformity anf DCD i.e., distance between nozzle and collectors. Today, the production rate of electrospinning process is low and measured in grams per hour.
The second technique of nanofibres production is spinning bi-component fibres. Island-in-a-sea and segmented pie structures are the bi component fibres mostly used. High forces of air jet or water jet are used to split bi-component fibres. The most often used fibres are polystyrene, polycarbonate, nylon, PEO and water soluble polymers. The ratio of polymers is commonly 80% islands and 20% sea. Nanofibres produced with this technique have a very narrow diameter range but are coarser in quality range.
Nanofibres composite construction :
Nanofibres were applied to 0.6 ounces per square yard nylon SB material and to 1.0 ounce per square yard nylon SB. Then these two layers were laminated together. Three different types of nanofibres composite fibres are designed by altering the thickness and weight of base cloth.
Two types of composite constructions are as follows :
- The nanofibre / SB layer between outer shell layer fabric and chemical filtration layer.
- Nanofibre / SB layer is infused over the shell fabruc and free floats against chemical filtration layer.
The performance and the durability of the composite structure depends on the finished fabric architecture. Polymeric nanofibre composites can provide enhanced protection against chemical agents such as radio active ducts, biological aerosols, micro droplets.
Properties of Nanofibres :
- Nanofibres have a special property as they have extremely high surface to weight ratio as compared to other conventional nonwoven.
- Properties like high pore volume, tight pore size, low density, large surface are to mass make the nonwoven nanofibres suitable for a large range of filtration applications.
- The size of nanofivres is smaller than human hair which is 50-150 µm. The elastic modulus of polymeric nanofibres of less than 350 nanometer is 1.0 ± 0.2 Gpa. These properties makes nanofibres suitable for medical and battery separator applications.
Applications of nanofibre :
Medical Application : Use of nanofibres in medical application is very important. In recent times, nanofibres are being used in drug and gene delivery, artificial organs, artificial blood vessels, medical facemasks, sanitary napkins, diapers etc. Nanofibres are smaller than human blood cells. So they posses a capacity to carry drugs directly into blood cells. Nanofibres can also be used to make bandages and sutures that can be easily dissolve into body. This minimizes the rate of infections, blood loss or any other injury. Nanofibres are also used to make artificial organs to replace original ones but costs much expensive. Johnson & Johnson and Genzyme corporation are already using nanofibres for anti adhesion materials.
Filtration Application : Electrospun nanofibres have diameters smaller than melt blown webs or conventional fibres. This leads to increase in surface area and decrease in basis weight. This property makes them suitable for many filtration uses. Nanofibres are suitable for filtering submission particles from air or water. These are also used in wide range of filtration applications such as facemasks, protective clothing, chemical resistant clothing, aerosol filters. Military clothing is currently under development for chemical and biological protection has been enhanced by laminating a layer of nanofibre between the inner side layer and carbon fibres. e-Spin technologies, Donaldson companies are producing and marketing filter media nanofibres.
Challenges in nanofibres :
Production of nanofibres is quite expensive compared to other fibres due to the usage of high cost of technology and low production rate. The process involves emission of vapors from electrospinning solution while forming the web. This needs to be controlled and disposed of in an ecofriendly manner. This again needs involvement of additional machinery and costings. These evaporated vapors also causes health hazards due to inhalation of vapors. Nanofibres’ packaging is challenging as compared ti conventional fibres. The packaging and handling is to be done under expert observation.
Thus the challenges can be summarized as economical, health hazard, environmental hazards, solvent vapor, packaging and handling.
Conclusion
Nano textiles provide many opportunities in new areas of application enhancing market potential. India will soon grow in manufacturing due to low cost of production. A slight reduction in quality leads to heavy loss. So there is no second sell. Innovation, successful application, selection of raw material and machinery will be the key to success. Quality production is the thrust by the production houses to remain competitive in upcoming years.
