Innovative Textile Applications of Nanotechnology, Rarely has a technology attracted as much publicity in a short period of time as nanotechnology. It has been hailed as the biggest innovation since computer chips. The fundamentals of nanotechnology lie in the fact that the properties of material change drastically when either of its dimensions is reduced to the nanometer range for example gold changes its color to red and its melting point decreases whereas copper reduces its conductivity in the presence of a magnetic field when reduces to nanometer size. There is also an increase in reactivity due to an increase in the surface-to-volume ratio. Properties at this stage are described by quantum mechanics rather than classical mechanics.
Nanotechnology is increasingly attracting worldwide attention, federal funding, and research activity due to its wide range of uses. Moreover, a small amount of nanosize particle can interfere with matrix polymer, bringing up the resultant material to unprecedented level.
The textile industry has already been impacted (Innovative Textile Applications of Nanotechnology) by nanotechnology. Research involving nanotechnology to improve performances is flourishing. There are two concepts in molecular nanotechnology:
(a) Positional assembly: Positional assembly is a technique that has been suggested as a means to build objects, devices, and systems on a molecular scale using automated processes. It is frequently used in normal macroscopic manufacturing.
(b) Massive parallelism (self-replication): Self-replication is a process in which devices whose diameters are of atomic scale, on the order of nanometers, create copies of themselves.
In Manufacturing Textiles (Innovative Textile Applications of Nanotechnology)
Large changes can be made in the properties of fabric (Innovative Textile Applications of Nanotechnology) by making a small change in its constituent material. Here comes nanotechnology in manufacturing textiles. Fabric using nanofibres, nanocomposites, etc are getting appreciation from the whole world. Their demand has increased by many folds due to their unique properties.
Nanofibres: Nanofibers are defined as fibers having diameters in the range of nanometers. They can be produced by interfacial polymerisation and electro-spinning. Some nanofibers are given below:
(i) Electro spun cellulose: It is a high performance material obtained from reclaimed cellulose by using electrospinning method.
(ii) Luminescent Polyester: The polyester core is covered with approximately 60 layers of nylon and polyester. This creates a mystical hue that changes according to (i) how light strikes the fabric and
(ii) The angle from which the fabric is viewed. Only reflecting light of a specific wavelength, this structure effectively brings out color.
Carbon Nanofibres: These are the ordered array of carbon atoms that have high tensile strength due to high aspect ratio. They also have high chemical resistance and electrical conductivity.
Composite fibers: Fibers that are employed by filler materials such as nanoparticles to get desired properties are called composite fibers. Carbon nanoparticles are added to fiber to enhance their tensile strength, resistivity to chemicals, and electrical conductivity. Composite fibers are also employed by clay nanoparticles for flame retardant, anti-UV and anti-corrosive behavior for example nanoparticles of Montmorillonite have been applied as UV-blocker in nylon composite fibers. The mechanical properties with clay mass fraction of 5 per cent exhibits a 40 per cent higher tensile strength, 68 per cent greater tensile modulus, 60 per cent higher flexural strength and a 126 per cent increased flexural modulus. Also, the heat distortion temperature raised from 65°C to 152°C. Clay nanoparticles are also used to introduce dye-attracting sites and create dye holding space in polyproprene fibers. Some metal oxide nanoparticles are also used to impart unique properties in fabric such as ZnO nanoparticles are used for UV shielding function and reduction in static electricity in synthetic fibers, and TiO₂/MgO nanoparticles for self sterilising property.
Carbon Nanotubes: Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure. Nanotubes are members of the fullerene structural family, which also nanotubes may be capped with a hemisphere of the buckyball structure. CNT has tensile strength 100 times that of steel at 1/6th weight. Generally, CNT are classified into single walled carbon nanotube (SWNTs) and multi walled carbon nanotube (MWNTs). One of the best examples of the CNT composite fiber is SWCT-polyvinyl alcohol fiber with fiber diameters in the macro meter range produced by using a coagulation-based spinning process. The fiber exhibits high stiffness and strength, moreover, toughness is 20 times higher than steel wire of the same length and mass. Therefore this type of fiber has potential applications in safety harnesses, explosion-proof blankets, and electromagnetic shielding
In Finishing Textiles
Nanoparticles when employed in a fabric impart their properties to the fabric. Here comes nanotechnology in (Innovative Textile Applications of Nanotechnology) finishing textiles. In this field, particular attention has been paid to making chemical finishing more controllable and 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. The nanotechnology finishes create carefree fabrics that minimise stains, offer superior liquid repellency and provide additional wrinkle resistance.
(a) Water Repellent Finish
There is a great demand for water-repellant garments in this new emerging world e.g. dresses for divers, and swimmers, waterproof coverings for tents, waterproof bags, shoes, raincoats, etc. Wetting of fabric (Innovative Textile Applications of Nanotechnology) depends upon difference in surface tension of solid fabric and liquid. If the critical surface tension of solid fabric is greater or equal to the surface tension of liquid then the liquid will wet the fabric. Thus, water repellency can be attained when the critical surface tension of the solid is smaller than the surface tension of the liquid. This is done by using fluorocarbons, which are organic compounds consisting of perfluorinated carbon chains.
Fluorocarbons generally lower the surface tensions by forming a thin film of coating around the fiber. Some useful fluorocarbons are perflouroalkyl acrylate polymers. Fluorocarbons can be added in a number of ways like by spraying, foam, or exhaust. Researchers at Clemson University developed a high water repellent coating made of silver nanoparticles. The patented coating-a polymer film (polyglycidyl methacrylate) mixed with silver nanoparticles can be permanently integrated into any common fabric like cotton, polyester, silk, etc.
Nano-tex enhances the water repellent property by creating nano-whiskers, which are made of hydrocarbons and are 1/1000th size of typical cotton fiber. They are added to create a peach fuzz effect without lowering the strength of cotton. They create a surface through which water molecules can pass while water droplets cannot, thus maintaining breathability. Schoeller improves water repellence by nanospheres. Nanosphere impregnation involves a 3-D surface structure with gel-forming additives which repel water and prevent dirt particles from attaching themselves. The mechanism is similar to the lotus effect occurring in nature.
(b) Self Cleaning Effect
With the help of nanotechnology self-cleaning fabric surface are produced by the following methods. In the first place, create extremely water repellent microscopically rough surfaces on which dirt particles can hardly get a hold and therefore, can be simply rinsed off water. The second example is given by photocatalytic layers. When layer of nanocrystalline titanium oxide is exposed to sunlight, it can remove dust, dirt and bacteria by itself. Coating of mixture of polyglycidyl methacrylate and silver nanoparticles is also used due to their resistance to dirt and water.
(c) Anti-Microbial Finish
Self Cleaning Effect Nano-sized silver coating is used to provide anti microbial properties. Metallic ions convert free oxygen into active oxygen, which destroys the organic substance to create the sterilising effect. Nano silver is also very reactive with proteins. When contacting bacteria and fungi, it will adversely effect cellular metabolism and inhibit cell growth. Photocatalytic effect of TiO and ZnO are also used for anti microbial finish.
(d) Wrinkle Resistance
To improve wrinkle resistance of cotton and silk, fabrics are employed with nano-titanium dioxide and nano silica. Nano-titanium dioxide was employed with carboxylic acid as a catalyst under UV radiation to catalyse the cross linking reaction between the cellulose molecules and the acid. On the other hand, nano-silica was applied with maleic anhydride as a catalyst. This process improved the wrinkle resistance of silk.
(e) Flame Retardant Finish
For flame retardant finish in garments is achieved by using colloidal antimony pentoxide which is supplied by Nycol nano Technologies, Inc. Nano antimony pentaoxide used with Halogenated flame retardants for a flame retardant finishes. The ratio of halogen to antimony is 5:1 to 2:1.
(f) Odour Fights Finish
Odours are formed as a result of bacterial growth. Thus these can be prevented by antimicrobial finish. Cyclodextrins can be incorporated into a fabric finish to prevent odour. Greensheild, a nanotech firm in Taiwan, has applied nanotechnology to create underwear’s that can fight odour. The underwear fiber release undetectable negative ions and infrared rays that destroy odour causing bacteria. Similarly, microcapsules containing fragrances can also be implanted in fabric for slow release overtime to neutralize foul odour.
(g) UV Protection
For protecting material from UV radiation, we add semiconductor oxides of TiO₂, ZnO, SiO₂, and Al₂O₃. Among these TiO₂ and ZnO are commonly used. The nanoparticles have large surface area per unit mass and volume, thus more effective in scattering and absorbing UV radiation. Apart from TiO₂, ZnO nanorods of 10 to 50 nm length also show excellent results in blocking UV rays.
In Protective Textiles
Protective textiles demand the balance of very different properties of drape, thermal resistance, barrier to liquids, water permeability, reduction in weight and cost, antistatic and stretch properties etc. with conflicting requirements against heat, cold, chemical and bacteria. Nanotechnology with its latest developments is helping in providing these properties to protective textiles. Electro-spun nanofibre-based membrane are used for making the material light weight.
Nanomaterials such as nanotubes developed either from silicon or carbon would be very useful for producing highly functional protective clothing. Carbon nanotubes provides fibres of ultra high strength and performance. Further enhancement of fibre strength and conductivity is achieved by heat treatment. Electrospun polypropylene nanofibre and polyurethane nanofibres are used as barrier to liquid penetration in protective clothing.
Polymer clay nanocomposites have emerged as a new class of materials that have superior properties such as higher tensile strength, heat resistance, and less permeability to gas compared with traditional composites. Thus it is conceivable that nanotechnology developments in long term will play a key role in protective systems.
In Medical Textiles
Nanotechnology also have widespread applications in medical textiles such as imparting antimicrobial properties to clothing, development of wound closing nanofibre systems, in drug delivery systems, in blood filtration etc. A new medical technology to clean blood affected by radiological, chemical and biological attacks is being developed jointly by Argonne National Laboratory and The University of Chicago Hospitals.
In addition to cleaning biological and radiological toxins from blood, the technology shows promise for delivering therapeutic drugs to targeted cells and organs. This technology uses a novel approach to magnetic filtration. The key is biodegradable polynanospheres 100 to 5000 nm in diameter, which are injected into the patients blood stream and are small enough to pass through the smallest blood vessels, yet too large to be filtered from the blood stream into the kidneys. Textile fibers on the nano order level produced by ultrafine processing nanotechnology can be used to enhance drug delivery in biomedical applications.
The objective of drug delivery system is to deliver a defined amount of drug efficiently, precisely and for a defined period of time. Drug delivery for polymer nanofibres is based on the principle that dissolution rate of a drug particulate increases with increased surface area of both the drug and corresponding carrier.
Nanotechnology has an enormously promising future for textiles. The recent developments in finishing and manufacturing textiles based on nanotechnology have endless possibilities and at present the application of nanotechnology in textile merely reached a straight line. These nano finished textiles have wider applications in protecting material, drug delivery in medicines, space suit designs, etc. Our surrounded world is full of textile applications which can be innovated by using nanotechnology. It has also opened new opportunities for research and development work. Though there are some security concerns regarding use of nanotechnology but we hope that it will make our future better and bring hundreds of billion dollars to textile industry.
By Manoj Kumar Gupta
The author is with Mechanical Engineering Department, HNB Garhwal University, Srinagar (Uttarakhand)
Further Reading
[1] Rathinamoorthy R and Senthil Kumar P, “Synthesis of nanoparticles and their applications in textiles.” Milliand International, 2009, may, 110-111.
[2] Nivedita S and Roy S,” Nanotechnology and its potentials in sericulture”, Indian Silk, 2011, March, 21-33.
[3] Moghe AK and Gupta BS, “Hybrid nanofibre structures for tissue engineering”, AATCC Review, 2009, October,
3-47.
[4] Wilson A, “Advanced nonwoven media for liquid filtration: A Growth Area”, Technical Textiles International, 2010, December, 11-16.
[5] Viswanath C S and Ramachandran T, “Comfort characteristics of cotton fabrics finished with fluoro-alkyl nano lotus finish”, Indian Journal of Fabre and Textile Research, 2010, December, 342-348.
[6] Rathinamoorthy R and Sumothy M, “Nanofinish adds value to functional textiles”, Textile Asia, 2010, July, 41-44.
[7] Rathinamoorthy R, “Textile nano fibers for drug delivery”, Textile Asia, 2010, April, 29-31.
[8] Shanmugasundaran OL, “Application of nanotechnology in textile finishing- A Review”, Textile Review, 2009, November, 135-139.
[9] Chinchole YD and Saraskan RU, “Application of nanotechnology in textiles and other fields”, Textile Review, 2009, December, 19-29.
[10] Buiyle G, “Nanoscale finishing of textiles via plasma treatment”, New Cloth Market, 2009, December, 39-46.
[11]Sivakumar GS and Prince PA, “Nanofinishing: The next wave in nano finishing”, Textile Review, 2009, December, 14-18.
[12] Kathirvelu S, D Souza L and Dhurai B, “Study of stain eliminating textiles using ZnO nano particles”, Journal of Textile Institute, 2010, June, 520-526.
[13] Mangat MM, “Health safety and environment aspect of nanotechnology a technical textiles”, 2010, April, 17-20.
[14]Priya SS and Selva kumar N “Basics on synthesis of nano metal oxide sols and nano TiO₂ and its uses on textile materials”, Colourage, 2009, November, 77-83.
[15]Chaudhary SN, Krishna A and Borkan SP, “Developments in protective textiles”, Asian Textile Journal, 2009, December, 37-43.
[16] Paul R, “Nano Cotton Fabrics with high ultraviolet protection”, Textile Research Journal, 2010, March, 454-462.
[17]Raut SB, Vasavada DA and Chaudhary SB, “Nano-particles-application in textile finishing”, Manmade Textiles in India, 2010, December, 432-437.
[18] Ibrahim NA, Refaic R and Ahmed AF, “Novel approach for attaining cotton fabric with Multifunctional properties”, Journal of Industrial Textiles, 2010, July, 65-83.
[19]Applications of nano technology in textiles by Dr Poonam G Bhagchandani.
[20] Lei Qian and Juan P Hinestroza, “Application of nanotechnology for high performance textiles”, JTATM, summer 2004.
[21] www.Whatis.com
[22] www.nanotechobservers.com
[23] www.wikipedia.com
[24]www.nanowerks.com
[25] www.technical-textiles.com
