Nanotechnology is an emerging interdisciplinary technology that has been booming in many areas during the recent decade, including materials science, mechanics, electronics, optics, medicine, plastics, energy, electronics, and aerospace. The wave has shown huge potential in the textile industry. Research activities on using nanotechnology to improve existing material performances and developing extraordinary functions are flourishing. Future developments of nanotechnology in textiles will have a twofold focus: 1) upgrading existing functions in performances of textile materials; 2) developing smart and intelligent textiles with unprecedented functions. The latter is more urgent from the standpoint of homeland security and advancement of technology.
2.0 Current status
The nano technology is expanding in all the disciplines. About 1500 patterns were registered in the year 2004 alone. The nano technology is growing in development of fibres, composites and novel finishing methods. Some of the innovations are focused here.
In the Table.1, the world level nano technology scenario in various disciplines is shown. In the field of chemistry, energy and environment the innovation and development were found to be aggressive. This statistics may change the future due to new insights by the young budding engineers.
2.1 Application to fibers
Some Japanese manufacturers of synthetic fibers are currently developing Nano fibres. Kanebo Spinning Corp, Japan has developed a 20 layer polyester fiber for high water and oil absorption properties. Teijin Fibers Ltd, Japan has been with a trial production of luminescent Core fibre. The core is covered with approximately 60 layers of nylon and polyester nano fibres with different refractive indices. This creates a mythical hue that changes according to the angle of light incidence with the fabric and the angle from which the fabric is viewed. Toray Industries, Inc. Japan has developed a fabric with effective moisture absorption properties though a structure containing bundles of nano nylon threads. Research is in line with the use of nanotechnology in Textiles for improving hand, dimensional stability, ultraviolet resistance, flame resistance, anti-static, anti-bacterial, moisture-absorption, and odder prevention.
2.2.0 In Composite Fibers
Nano sized composite fibers generated through fillers and form forming process. Nano Composite is shown in the figure2. The fillers are from clay, metal oxides, Graphite Nanofibers (GNF) and Carbon Nanotubes (CNT). The main function of nanosize fillers is to increase the mechanical strength and improve the physical properties such as conductivity and antistatic behaviors. Due to their large surface area, these nanofillers have a better interaction with polymer matrices. Being in the nanometer range, the fillers might interfere with polymer chain movement and thus reduce the chain mobility. Carbon nanotubes (CNT) are the most promising building blocks existing. CNT consists of tiny shell(s) of graphite rolled up into a cylinder. CNTs are classified into single-walled carbon nanotubes (SWNT) and multi-walled carbon nanotubes (MWNT). They are usually made by carbon-arc discharge, laser ablation, and Chemical vapor deposition. The potential applications include conductive, energy storage, energy conversion devices, sensors and field emission displays. Carbon nanofibers can effectively increase the tensile strength of composite fibers due to its high aspect ratio, while carbon black nanoparticles can improve their abrasion resistance and toughness. Both of them have high chemical resistance and electric conductivity.
Being evenly distributed in polymer matrices, Nanoparticles can carry load and increase the toughness and abrasion resistance; nanofibers can transfer stress away from polymer matrices and enhance tensile strength of composite fibers.
Clay nanoparticles or nanoflakes are composed of several types of hydrous alumino silicates. Each type differs in chemical composition and crystal structure. Clay nanoparticles possess electrical, heat and chemical resistance and an ability of blocking UV light. The mechanical properties with a nanoclay mass fraction of 5 % exhibit about 40% higher tensile strength, 68% greater tensile modulus, 60% higher flexural strength, and 126% increased flexural modulus. In addition, the heat distortion temperature (HDT) increased from 65C to 152C.
Clay nanoparticles is to introduce dye-attracting sites and creating dye- holding space in polypropylene fibers. These nanoparticles are introduced to the polypropylene matrix in a melting or dissolving process with the help and/or organic solvent and/or mechanical blending including the use of sonic and/or electric field. The nanoparticles are supposed to provide chemical, mechanical, physical linkages and thermal stability.
3.0 In Textile finishing
The impact of nanotechnology in the textile finishing area has brought up innovative finishes as well as new application techniques. Particular attention has been paid in making chemical finishing more controllable and more thorough. Ideally, discrete molecules or nanoparticles of finishes can be brought individually to designated sites on textile materials in a specific orientation and trajectory through thermodynamic, electrostatic or other technical approaches. One of the trends in synthesis process is to pursue a nanoscale emulsification, through which finishes can be applied to textile material in a more thorough, even and precise manner. Finishes can be emulsified into nano-micelles, made into nano-sols or wrapped in nanocapsules, which can adhere to textile substrates more evenly. These advanced finishes set up an unprecedented level of textile performances of stain-resistant, moisture content, anti-static& wrinkle resistant and shrink proof abilities. Nanoparticles such as metal oxides and ceramics are also used in textile finishing to alter surface properties and impart textile functions. Nanosize particles have a larger surface area and hence higher efficiency than larger size particles. Besides, nanosize particles are transparent, and do not blur color and brightness of the textile substrates. However, preventing nanoparticles from aggregation is the key to achieve a desired performance. Finishing with nanoparticles can convert fabrics into sensor-based materials. If nanocrystalline piezoceramic particles are incorporated into fabrics, the finished fabric can convert exerted mechanical forces into electrical signals enabling the monitoring of bodily functions such as heart rhythm and pulse if they are worn next to skin.
4.0 Utilization of Metal oxide in Textile application
Nanosize particles of Ti02, Al2O3, ZnO, and MgO are a group of metal oxides that possess photo catalytic ability, electrical conductivity, UV absorption and photo-oxidizing capacity against chemical and biological species. Intensive researches involving the Nanoparticles of metal oxides have been focusing on antimicrobial, self-decontaminating and UV blocking functions for both military protection gears and civilian health products. Nylon fiber filled with ZnO Nanoparticles can provide UV shielding function and reducing static electricity of nylon fiber. A composite fiber with Nanoparticles of Ti02/ MgO can provide self-sterilizing function
5.0 Electro spinning of Nanofibers
Electro spinning involves dissolving cellulose in a solvent and squeezing the liquid polymer solution through a tiny pinhole and applying a high voltage to the pinhole. The technique relies on electrical rather than mechanical forces to form fibers. Thus, special properties are required of polymer solutions for electro spinning, including the ability to carry electrical charges. The charge pulls the polymer solutions through the air into a tiny fiber, which is collected on an electrical ground. The fiber produced is less than 100 nanometers in diameter, which is 1,000 times smaller than conventional spinning. Thus, this technique of electro spinning of spin nanofibers from cellulose soon is able to produce a low cost, high-value, high-strength fiber from a biodegradable and renewable waste product for air filtration.
6.0 Smart Materials via Nanotechnology
While synthesis of defect-free materials will lead to substantial improvements in performance, molecular nanotechnology will make changes that are more radical by integrating computers, sensors, and micro- and nanomachines with materials. Micro pumps and flexible micro tubes could transport coolant or a heated medium to needed parts of clothing. Semi-permeable membrane to allow only particular kinds of molecules (Water) through, to keep one side of a fabric dry or another side wet. On the wet side, the water could be transported away to an evaporator, or stored. An active, programmable material made up of small cellular units that could connect to each others with screws. Computers would direct the cells, powered with small electrostatic motors, to adjust their relative spacing with the screws. By tightening and loosening the screws, the shape of an item could change to conform to the needs of the user. (i.e. a solid, rigid object could be made to behave like a fabric.)
Fabrics could be of self-cleaning by robotic devices similar to mites could periodically scour the fabric surfaces and integral conveyors could transport the dirt to a collection site, or the previously mentioned molecule-selective membrane could transport water to one side or the other for a cleaning rinse. Nano sensing objects embedded in a fabric is shown in the figure3. Fabrics could be of self-repairing with sensors to detect discontinuities in the material via loss of signal or a reported strain overload and send robotic crews to repair damages. The virtual environment for the nano robot is shown in the figure 4.
Undoubtedly, Nanotechnology holds an enormously promising future for textiles. It was estimated that nanotechnology will bring about hundreds of billions dollars of market impact on new materials within a decade; textile certainly has an important share in his material market. We expect to see a new horizon of textile materials under this irresistible technology wave. Nano tex, California based Inc. has recently launched several products that involved in fabric development.
The Nano pel is a product, which can repel strains and offer good comfort and breath ability. Nano dry enhanced fabrics provide superior wicking properties to move perspiration away from the body while drying quickly the three dimensional nano dry material shown in the figure 6. Nano care is a wrinkle free and strain resistant and water repellent fabric shown in the figure 7. Nano touch is of durable cellulose wrapping over synthetic fiber.
7.0 Indian scenario
Department of Science and Technology, UGC have already started many programme in the nano technology area. Indian Premier research and academic institutions are working towards the development and innovation related to MEMS, Nano structures, Synthesis and characterization, Nano electronics, CNT and Nano-composites. Some of the Bangalore based private companies Biomix,Q-tex, Velbionano and Yashnano- also in the development and application of Nano technology. Nano- Tex, the US based nano technology company has planed to set up a research centre in Bangalore. Our Indian Government is phase in with the Nano technology mission.
Working at a billionth of a nanometer scale is a continuous source of new opportunities for the textile industry. Nanotechnology will not only help the marketing of fabric and fashion because of its unique and incompatible properties but it is also a revolution for human beings like the Internet. Nanotech can surely opens up an interesting new playing field for the textile industry in future.
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- USPTO20050101209-Moisture management properties.
- USTPO20030060547-Polypropelene nano composites.
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- http://www.salsgiver.com/pcople/for rest/IFAl text.html