Nano-particles can help enhance the physical properties of conventional textiles in areas such as anti-microbial properties, water-repellency, soil-resistance, anti-static, anti-infrared and flame retardant properties, dyeability, and strength of textile materials, aver B H Patel and Dr D P Chattopadhyay.

These days, the word "nano" seems to be popping up everywhere. Wall Street, Hollywood, and major universities around the globe have all endeavored to associate their diverse enterprises with this word. "Nano" is a metric unit that means one billionth of a unit; as of late, it has been used most frequently in reference to nanotechnology. The term "nanotechnology" has never been used so broadly.

K Eric Drexler coined it in his 1986 book, Engines of Creation to refer to his theories for molecular manufacturing, following up on visionary ideas presented 27 years earlier by famed physicist, Richard Feynman. As the possibilities of molecular nanotechnology grew and excitement built in the scientific community many researchers began using the term for their own endeavors at the nanoscale, unrelated to molecular manufacturing.

Nanotechnology seeks to provide and apply knowledge of the behaviour of objects in the nanometre (nm) size range to the assembly of complex structures for use in a variety of practical applications. The tiniest substances promise to transform industry and create a huge market. In chemicals, cosmetics, pharmaceuticals, technology and textiles, businesses are researching and manufacturing products based on nanotechnology, which uses bits of matter measured in billionths of a metre.

The technology, utilising materials a thousand times smaller than the width of a human hair, is showing up in everything from auto parts to sunscreens and clothing ^(1,2). However, nanotechnology has been used to improve products that most of us use everyday. These include laundry detergent, 6-pack rings, and surgical tools. One of the most widespread applications of nanotechnology is in clothing. Nanotechnology is also called a "bottom up" technology owing to using such small-scale building units, in contrast to bulky material engineering that is considered a "top down" approach ⁽³⁾. Many textile industries and research organisation has already developed fabrics with distinguishing properties. Scratch-and-sniff clothing is one example. Pleasantly scented, tiny polymer beads are added to clothing, such as within a strawberry applied on a shirt. Then there are menthol pajamas, scented to open the nasal passages of people suffering from colds, ensuring a good night's sleep.

Some other type of clothing niche being explored on many fronts, with perhaps more staying power than scratch-and-sniff shirts, involves the nanoscale improvement of fabrics and fibres. Nanotechnology is adding its labels to popular clothing brands with various products: Resists Spills, Resists Static, Coolest Comfort, and Repels and Releases Stains. Researchers all around the world are looking at all sorts of metal additives and polymer additives, inorganic, organic materials to take them at nanoscale to impart lots of interesting properties to textiles.

Preparation of nano-sized materials

There are several physico-chemical methods for preparation of nano-sized material mentioned as below ⁽⁴⁾ :

• Vapour phase reaction.

• Chemical vapour deposition.

• Inert gas condensation.

• Laser ablation.

• Plasma spraying.

• Spray conversion.

• Sputtering.

Some commercially available nano-particles

Nano-particles may consist of various elements and compounds. The size of the molecules is the sole criterion for inclusion in the category of nano-particles. Nano-particles have a length of 1 to 100 nm. Conventional materials have grain sizes ranging from microns to several millimeters and contain several billions atoms each, nanometre sized grains contain only about 900 atoms, exhibit new and improved properties compared to the corresponding bulk material (Table1). Some nano-particles currently available are as follows ^(5-7):

1. Metals: Pd/Pt, Ag, Fe, etc.

2. Compounds: - Organic: Vitamins, DNA, Hydroxylapatite, Colour pigments.
                       - Inorganic: TiO2, ZnO, Fe2O3, MgO, SiO2 etc.

3. Polymer: - cellulose nano-whiskers
                 - carbon nano-whiskers.

Table 1 Nano-particles and potential textile applications

Metals and metal oxides nano-particles

Nano-size particles of Pd/Pt, Ag and Fe can be applied on textiles to impart antibacterial, conductive magnetic properties and remote heating properties. Silver has been used for the treatment of medical ailments for over 100 years due to its natural anti-bacterial and anti-fungal properties. Nano-silver particles are widely applied in socks to prohibit the growth of bacterial. In addition, nano-silver can be applied to a range of other healthcare products such as dressings for burns, scald, and skin donor and recipient sites.

Nano-silver particles can be applied on textiles by padding method with good laundering durability ⁽⁸⁾. Hoon Joo Lee and Song Hoon Jeong ⁽⁹⁾ have reported that nano-sized silver colloids and nano-silver treated polyester nonwovens have good bacteriostasis. Water based and ethanol based nano-silver colloids with spherical nano-particals of diameter 2-5 nm can be applied to polyester nonwoven fabric. It has been reported that the growth of bacteria colonies is absolutely inhibited with only 10 ppm colloidal silver nano-particles.

Nano-size particles of TiO₂, ZnO, Al₂O₃, and MgO are a group of metal oxide that possesses photo catalytic ability, electrical conductivity, UV absorption, and photo-oxidising capacity against chemical and biological species. Intensive research involving the nono-particles of metal oxides have been focusing on antimicrobial, self decontaminating, and UV blocking functions for both military protection gears and civilian health products. Nylon fibre filled with ZnO nano-particles can provide UV shielding function and reducing static electricity of nylon fibre. A composite fibre with nano-particles of TiO₂/MgO can provide self-sterilising function ⁽¹⁰⁾.

TiO₂ and MgO nano-particles can be entrapped into a textile fibres during the spinning process or incorporated into a textile material via normal textile finishing methods with a resultant material having chemical and biological protective performance ⁽¹¹⁾.Cellulose fibre filled with nano-particles of metal oxides (such as TiO₂) from in situ synthesis can be used as a catalyst in fuel cells ⁽¹²⁾.

Polymer and polymer nano-composites

It has been established in recent years that polymer-based composites reinforced with a small percentage of strong fillers can significantly improve the mechanical, thermal and barrier properties of the pure polymer matrix. Moreover, these improvements are achieved through conventional processing techniques without any detrimental effects on processability, appearance, density and aging performance of the matrix. Now-a-day's hybrid polymers (such as Organoallcoxy silanes), which are the hybrid structure of inorganic-organic nano-composite materials are being used to impart the combination of scatch resistance with dirt-repellent effect, high transparency, special barrier properties or antimicrobial function to the material ⁽¹³⁾.

Clay nano-particles: Clay basically consists of hydrous aluminosilicate and is low in density. Nanosize clay particles or flaks can impart excellent flame retardant functionality to the textile due to the heat resistant behaviour of the nanoclay ⁽¹⁴⁾. UV blocking power and outstanding barrier functionality are due to the internees of nanoclay to corrosive chemicals and its neatly layers configuration inside fibre ^(15,16). In terms of mechanical attributes, nylon6 clay composite with a clay mask fraction of 5% shows 40% higher tensile strength, 68% greater tensile modulus, 60% higher flexural strength, and 126% greater flexural modulus.

Such a significant improvements in composite strength even leads to application of nano clay filler as a protective insert in infantry helmets ^(15,16). Nano clay fillers modified with quaternary ammonium salt have been introduced into polypropylene fibre, the resultant fibre can be coloured by acid and disperse dyes to 1-4% colour shades for incorporation of less than 5% nano-dry fillers. The modified nano clay introduces dye attaching sites to the polypropylene fibre generates void space inside the fibre to entrap dyes without degrading the beneficial properties of polypropylene ⁽¹⁷⁾.

Carbon nano particles: Carbon nano black particles are extremely effective reinforcing material for composite fibres ⁽¹⁰⁾. With their high aspect ratio, carbon black nano particles can improve abrasion resistance and hence increase the durability of composite fibres. Carbon black nano particles can also result in high chemical resistance and electric conductivity after they are mixed with fibre polymer matrix. Polyester, nylon and polypropylene have been used as polymer matrix with weight percentage of nano size filler range from 5% to 20% ^(18,19).

Dapeng Li and Gang Sun ⁽²⁰⁾ have reported that carbon black nano-particles can directly be used in traditional dyeing processes to dye polyester and acrylic fabrics. Polyester and acrylic fabric were dyed with nano carbon black particles using a dip-pad, dry and cure technique. Effective colouration of these fabrics has been reported with 8 nm particles, using cationic dispersing agent, at 180⁰C treatment temperature.

Polymer nano-whiskers: Nano-whiskers, each of which is just 10 nanometres long (a grain of sand is 1 lakh nanometres in comparison). Basically, nano whiskers, 1/1000 the size of a typical cotton fibre are attached to the individual, constituent fibres of the fabric. The whiskers are hydrocarbons added by dipping in an aqueous solution 8. The whiskers modify water-resistance of fabric due to surface tension that causes water to form into drops or spheres. The spaces between the whiskers on the fabric are smaller than a typical drop of water while the whiskers are hydrophobic and do not absorb water. As a result, water remains on top of the whiskers and above the surface of the fabric.

Another similar product is nanosphere that makes fabric water and soil-resistant. In his work Soane ⁽²⁾ immersed the cotton fabric in a pool containing a mixture of water and billions of these nanowhiskers, then heated the pool in order to evaporate the water and cause the nanowhiskers to chemically bond to the cotton's cylindrical fibres, coating each thread entirely.

Cotton fibres, primarily composed of cellulose (Figure 1), owe their high degree of absorbency to the many The stain-repellent fabrics from Nano-Tex, incorporate billions of tiny fibres, each about to nanometres (that's 0.0000004 inches) long, that are embedded within traditional cotton or linen. The waterproof fibres, which Nano-Tex calls "nanowhiskers," make the fabric dense, increasing the surface tension so drops of liquid can't soak through-just like raindrops on a freshly waxed car.

The company says this Nano-Care treatment will withstand 50 home launderings before its effectiveness is lost. These may be due to the negatively charged, hydrophilic hydroxyl groups that lie along the naturally occurring polymer's carbohydrate structure. The outer-shell electrons of the carbon atoms from which the whiskers are constructed form nonpolar covalent bonds and therefore do not readily bind to polar water molecules.

Thus, the attachment of the carbon whiskers to the cotton fibres permanently alters the physical properties of the cotton by changing the fibres from hydrophilic to hydrophobic. Because the nanowhiskers are so small, they are able to permeate the cotton fabric and attach to each thread without modifying the appearance or feel of the pants. The ability to engineer effective nanostructures such as these owes its many promising applications to the enduring maturation of nanoscience.

In another study the cotton nanocomposites, fibre modified with organo clays, have been developed to improve the thermal properties of cotton with minimal impact on other desirable properties ⁽²¹⁾. A method of laboratory scale wet spinning and nonwoven production has been developed; regenerated cellulose nanocomposite fibres have been produced by a wet spinning technique that is a modification of the Lyocell method for producing regenerated cellulose commercially. The nanocomposite fibres were processed into nonwoven substrates using small-scale paper production equipment. Thermal analysis revealed that the nonwoven production process does not hinder the improvements in thermal behaviour seen in earlier tests on fibres. Moisture regains analysis showed that the water uptake of these materials is comparable to that of unprocessed cotton.

In another work, carbon nanowhiskers and carbon nanotubes were doped with two types of polymer precursors were used; linear low density polyethylene and nylon-6. The fillers in each case were carbon nanowhiskers and multi-walled carbon nanotubes. It has been reported that the improvement with carbon nanowhiskers was around 17% while it increased to 34% with MWCNT.

Out of the four systems (two fillers and two polymers) investigated, the system with Nylon-6 infused with MWCNT yielded the most promising results. Tension tests on individual filament of this system showed about 150-300% improvement in strength and stiffness with 1% MWCNT loading. TEM studies revealed that extrusion technique caused sufficient alignment of MWCNT along the length of the filament, which may have caused the gain in mechanical properties.

The former involves separation of nano-whiskers from cellulose fibres, proper treatment and embedment into polymers. It has been found that these nano-whiskers have twice the strength of conventional glass fibres. The embedment of graphene layers into polymers has its own advantages. Apart from high modulus, electrically conductive graphene layers enable proper orientation (by applying known voltage) of the graphene layers in the polymer during manufacturing thereby increasing the reinforcement effect and hence the enhancement of many properties.

Nano-whiskers are wonder molecules, which can impart various functional properties not only to the textiles but also contribute significantly in the field of electronics and medicine. Recently several works has been reported, where nano-whiskers have been synthesised from a variety of materials by using some new and improved techniques.

Nano-particles in functional textile finishing

In some typical textile finishing applications nano-particles can substantially alter surface properties and also confer different functions to the textile materials ^(22,23). The nano size particles offer a larger surface area compared to bigger particles. Being in the nanometre range, the particles are transparent, so they do not blur colour or alter brightness of textile substrates.

Nano-particles can be applied on textiles by two-stage process. Initially, there is the manufacture of new, stable nano-material, which must in the first instance be protected against properties defined by the size of the particles. The second step sees the creation of the foils, emulsions and dispersions that can be applied to the final textile product, in the most favourable case, by means of conventional finishing processes.

Nano particles are most commonly applied to textiles by coating using a composition of nano particles, a surfactant, ingredients and a carrier medium. Coating techniques, which modify the surface of the textile, include:

• Spraying: the coating composition is sprayed on to textiles, with control of the depth and targeting to specific areas.

• Dipping and soaking in an immersion container followed by a drying step.

• Transfer printing such as rotary, flexography and inkjet printing.

• Washing, accomplished by using a washing solution containing nano particles during wash or rinse cycles in a washing machine.

• Padding, where nano particles are attached to the fabrics with the use of padder applied under pressure.

Nano particles have large surface area to volume ratio, which makes it easy for them to attach to fibre or fabrics, and increase the durability of the functions imparted by the particles. In addition, the coating of nano particles does not affect the breathability, and hand feel of the textile. The commonest functions are wrinkle resistance, stain, soil and water repellency and anti static, anti bacterial and anti ultraviolet protection ⁽⁸⁾.

Wrinkle resistance: Wrinkling occurs when the fibre is severally creased. When fibre or fabric is bent, hydrogen bonds between the molecular chains in the amorphous regions break and allow the chains to slip past one another. The bonds, reform in new places and fibre or fabric is held in the creased configurations. The disadvantages of conventional resin applications include decrease in the strength of fibre and in abrasion resistance, water absorbency and dyeability, as well as in as in breathability.

Stain resistance: Staining of fabrics occurs from re-deposition of soil during laundering or dry cleaning, deposition of dry soil from the air or contact with foreign matter. Silicon chemicals and fluorochemical finishes can be used to confirm resistance to soil, water and even oily stains. The stain-repellent fabrics from Nano-Tex (Figure 2), incorporate billions of tiny fibres, each about to nanometres (that's 0.0000004 inches) long, that are embedded within traditional cotton or linen. The waterproof fibres, which Nano-Tex calls "nanowhiskers," make the fabric dense, increasing the surface tension so drops of liquid can't soak through-just like raindrops on a freshly waxed car. The company says this Nano-Care treatment will withstand 50 home launderings before its effectiveness is lost.

The most developed nanotechnology application for textiles is currently in the areas of stain, oil, and water repellency; stain release and wrinkle resistance. Stain resistance, stain repellent, and dual action repel and release finishes all can be applied by using nanotechnology.

Repellent products lower the critical surface tension of the fabric so the fabric does not attract stains or soil. Oil and water bead up and roll off the fabric. When a repellent finish is applied to fabrics, the invisible repellent finish provides superior water/oil repellency and protection against spills and stains.

Stain release products allow for stains and spills to soak into the fabric; oil and water may bead slightly and stains are applied, the fabric will be slightly oil/water repellent, but the invisible stain release finish allows for ground in stains to be easily removed during laundering. This finish with the addition of a water-loving component allows absorbed stains to wash out and easily removed with home laundering. When a stain release finish is Dual-action repel and release is the newest finish in the industry. The finish combines advantages of both stain release and repellent finishes into one. This twofold protection offers a unique balance of repellency that works in tandem with an advanced stain release, which helps to liberate the toughest stains including tough ground-in stains. With dual-action repel and release finishes, consumers get twice the stain protection in one easy-to-care-for fabric.

Water repellency: Water repellant finishes modify the surface of fibre and do not block the interstices. Hence fabric permits air and water vapour to pass through. Early water repellant coatings were easily removed dry cleaning or laundering. Nowadays, wax emulsions, pyridinium compounds, N-methylol compounds, silicons and fluoro chemicals are used to impart water repellency to various natural and synthetic fibres.

To improve the properties of wrinkle resistance, stain resistance and water repellency recently several products have been introduced. Nano Whisker introduced by Nano-tex is one of the best options. They are attached to the fabric permanently, unlike the topical coatings or bulky laminated fabrics that have traditionally been used for this purpose. The whiskers are hydrocarbons added to the fibres in an aqueous solution. The changes to the fibres do not affect the natural hand feel and breathability of the fabric. The fabric shows very good wrinkle resistance, the processing is undetectable and a " peach fuzz" effect has been reported. The finish can be applied onto textiles through a nanoscale emulsification process in a more thorough, even, and precise manner than traditional methods.

In the case of fabric, rolls of woven cotton fabric from textile mills are immersed in liquids containing trillions of nanowhiskers they are waterproof and increase the density of the fabric. Then this treated cotton, is dried in ovens binding the tiny fibres to the comparatively much larger cotton threads. This increases the surface tension on the outer layer of the fabric so liquid cannot soak through.

Though the final product looks unchanged, it provides a nearly solid barrier to liquid or wrinkles, for instance. Nanowhiskers provides an even application and does not change the surface properties unlike traditional finishes. Nano-particles are extremely tiny and therefore the addition of these particles on fabric is not detectable by hand.

Fig 3

Nano-particles added on textile materials cannot be detected by the naked eye; therefore the original colour of the products will not be altered. Nano-particles form a protective layer on the face of textile materials instead of changing their chemical properties; therefore they give no hazardous substances and have no side effects. Textile products, which have been processed with nano-particles, are more durable than the traditional finishes with repeated washing.

Nano-finishes can add additional functionality to fabrics such combination of wrinkle and stain repellency in one application. But on the other hand, Nano-tech garments could under perform if proper care is not taken. Proper care for these garments includes the use of delicate machine washes and drip dying, no dry-cleaning and avoiding the use of chlorine bleach and wringing of the clothes.

Anti static performance: Static usually builds up in synthetic fibres such as in nylon and polyester because they absorb little water. Conventionally surfactants are used to spread the small amount of moisture on the surface of fibre so as to pose the charge to leak away. One of the best electrically conductive nano particles is silver. Silver nano particle helps to dissipate the static charge effectively.

Anti bacterial effect: The commonly used anti bacterial agent was quaternary ammonium compounds. Many chlorinated organic compounds and organo metallic compounds containing copper, silver, iron, manganese or zinc also make fabrics resist growth of bacteria. The use of nano silver particle offers durable anti-bacterial finishing to the textile.

Ultra violet protection: To impart UV protection, several nano compounds or nano particles can be applied on textile material. The commonest nano compounds used are titanium dioxide and zinc oxide of nano size. They provide a protective benefit by reflecting, scattering or absorbing harmful UV.

At present several research organisations and industries are offering nanotechology and its application techniques for textiles. Some of them are as follows:

1. Nano-Tex, LLC, Greensbara, NC, USA.

2. Texcote Technology (International) Ltd, Sweden.

3. Schoeller Textiles AG, Switzerland.

4. Beiging Zhong-Shong Century Nanotechnology Co Ltd, China.

Testing and analysis of nano-materials The morphological features of nano material and structures need to be determined in various stages of production such as size distribution, porosity, pore size distribution, surface structure and composition, which are critical to ensure the materials and structures are in nano scale to archive special properties ^(24-26). Such structural feature can be characterised by a rang of techniques and instruments such as Particle Analyser, Atomic Force Microscopy (AFM), Scanning Tunneling Microscopy (STM), Scanning Electron Microscopy (SEM), High Resolution Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), Near Field Scanning Optical Microscopy (NSOM or SNOM), X-ray and Neutron Diffraction or other spectroscopic techniques.

The properties of nano materials and structures/composites also need to be measured to test whether specific and unique properties can be derived due to the nano scale structures. Properties characterisation should be carried out in various aspects in relation to specific functions to be achieved such as in physics, mechanical, electrochemical, optical and thermal properties. Examples of propertie's characterisation techniques: property to be characterised techniques; Dynamic Time Resolved Techniques; Magnetic Scanning Electron Microscopy with Polarisation Analysis (SEMPA); Surface Magnet - Optic Kert Effect (SMOKE) Spectroscopy; Spin-Polarised Low -Energy Electron Microscopy (SPLEEM); Magnetic Force Microscopy (MFM); Electrochemical Impedance Spectroscopy; Potential Sweep Method; Electrochemical Quartz Crystal Microbalance, Mechanical Electricity Method; Vibrating Reed Method; Thermal Diffractional Scanning Colorimeter(DSC).

Finally, functional performances of final products need to be characterised to test the roles and impact of nano materials and nano scale structures. Only when new and/or significantly enhanced properties are introduced, due to the nano scale sizes or structures, can nano-products be claimed, based on the definition of nanotechnolgy.

Economical and environmental aspects

The unique properties of nanomaterials have attracted not only scientists and research workers but also businesses, because of their huge economic potential. The national science foundation reports that nano-related goods and services will increase to a US$ 1 trillion market by 2015. This amount is larger than the combined businesses of the telecommunications and information technology industries. Several hundred billion Euros are forecast to be created by nanotechnology in the next decade ⁽²⁴⁾. The nano materials markets could expand to US$ 4 billion by 2007. It was believed that 2 million new employment opportunities would be created in order to meet the worldwide annual production demand of US$ 1 trillion in 10-15 years.

Nanotechnology may impart favourably on the environment as well. By using less resource without sacrificing performance, nanotechnology may save raw materials and also upgrade quality of life.

Conclusion

The development in the applications of nano-particles, nano-composites and nano-sphere has been very rapid in past years, particularly in the field of textile finishing. These nano-size materials are able to enhance the physical properties of conventional textiles in areas such as anti-microbial properties, water-repellency, soil-resistance, anti-static, anti-infrared and flam retardant properties, dyeability, and strength of textile materials. In future the application of these wonder nano-particles can be extended to produce textiles with health-care and wound healing functions as well as self-cleaning and repairing functions.

References

1. Information from http://www.dictionary.com

2. Information from http://www.nano-tex.com

3. E Menezes, K Singh: Colourage, LI, 8, 2004, 55.

4. P B Jhala, The Indian Textile Journal, CXIV, 8, 2004,13.

5. J Beringer, D Hofor: Melliand Textileberichte, 85,9, 2004,698.

6. L Zhu, and K H Narh: Journal of Polymer Science: B: 42, 2003, 2391.

7. Information from http://www.egr.msu.edu/cmsc/biomaterials/research.html

8. Y W Wang, C W M Yuen, M Y S Leung, S K A Kuand, H L I Lam: Textile Asia, XXXV, 5,2004,27.

9. H J Lee and S H Jeong: Textile Research Journal, 74,5,2004,442.

10. L Qian: AATCC Review, 4,5,2004,14.

11. Hartley, M Scott, A Holly: The Next Generation of Chemical and Biological Protective Material Utilising Reactive Nano-particles, Gentex corp, Carbondale, pa.

12. He, Junhui, T Kunitake and A Nakao: Chemical Materials, 15,23,2003,13.

13. Dr S Amberg-schwab, D Ulrikeweber: International Textile Bulletin, 50, 1, 2004,

14. Information from- http://www.egr.msu.edu/-tomanek/phy905/w-1-2-6.html

15. J W Gilman, et al: In Chemistry and Technology of Polymer additives, Edited by A K Malaika, S A Golovoy and C A Wilkie: Blackwell Science Inc, Malden, Mass., 1999, 249.

16. Information from- http;//www.ccmr.cornell.edu/-gianellis/research/silicates.html

17. F Qinguo, et al: AATCC Review, 3, 6, 2003,25.

18. Information from- http;//www.nanophase.com/applications/, 2002.

19. J Chen, and N Tsubokawa: Polymer Journal, 32,9, 2000, 729.

20. D Li and G Sun: AATCC Review, 3, 12, 2003.19.

21. Information from- http://www.egr.msu.edu/cmsc/biomaterials/index.html

22. Soane S David: US Patent, No.6, 607,994,2003.

23. A V Shivaprakash and M Mohankumar: Man-made Textiles in India, XLVII, 2,2005,75.

24. Li L Lokyuen and H Junyan: Textile Asia, XXXIV, 11,2003,26.

25. Information from- http://www.egr.msu.edu/cmsc/esem/index.html.

26. Information from- http://www.egr.msu.edu/cmsc/nano/index.html.

Note: For detailed version of this article please refer the print version of The Indian Textile Journal December 2007 issue.

B H Patel
Department of Textile Chemistry,
Faculty of Technology & Engineering,
The M S University of Baroda, Vadodara 390001.

Dr D P Chattopadhyay
Department of Textile Chemistry,
Faculty of Technology & Engineering,
The M S University of Baroda, Vadodara 390001.