Nano-Finishing Of Textiles (TT-03)

ABSTRACT

The benefits to science and society from Nanotechnology are substantial. If the criterion is to produce very minute particle size fibers and materials the nano technology is the only way to achieve the same. This article elucidates about the nano finishing in textile. Techno-science recently introduced some nano finishes for textile substrateshas been reviewed here. The logic of using low molecular weight fiber-reactive fluorocarbons that from the basics of Nano-Care finish durable hydrophobic characteristic to fabrics. And mechanisms proposed to explain the photo-catalytic self-cleaning effect of TiO2 have been described.

Developments in the production and evaluation of nano silver and wound care devices based on anti microbial activity of silver have been covered in detail. Anti pollen finish by using the polymer which have antistatic or electro conductive composition, flame retardant finish by using colloidal antimony pentoxide, Odour fight finish by using tourmaline, UV protection finish by using nano clay particles, Self cleaning suits by using film polymer mixed with silver nano particles and characteristics of nano finishing in Garments have been described.

CONTENTS

♦INTRODUCTION

♦NANO TECHNOLOGY

♦SYNTHESIS OF NANOPHASE MATERIALS

♦INTRODUCTION OF NANO-FINISHES

♦FUNCTIONAL FINISHING

♦APPLICATION OF NANO-FINISHES

♦EASY CARE HYDROPHOBIC FINISH

.ANTI-MICROBIAL FINISH
.PHOTO CATALYTIC SELF-CLEANING FINISH
.ANTI-POLLEN FINISH
.FLAME RETARDANT FINISH
.ODOUR FIGHTS FINISH
.UV PROTECTION FINISH
.SELF CLEANING SUITS

♦CHARACTERISTICS OF NANO FINISHING IN GARMENTS

♦CONCLUSION

INTRODUCTION

The term Nano in Nano technology comes from a Greek word "Nanos" which means 'dwarf'. The dictionary meaning of dwarf is abnormally small.

One nanometer is one billionth of a meter or 10-9 meters. One Nano meters is about 100000 times smaller than the diameter of the human hair.

Unique properties of Nano materials have attracted not only scientist and research workers but also the businessmen, especially the textile, because of their high economical potential.

NANO TECHNOLOGY

In 1974, Prof.Nario Taniguchi states that "Nano tech mainly consists of the processing of Separation, consolidation and deformation of materials by one atom or one molecule.

Nano tech is the design characterization production and application structures, devices and system by controlling shape & size at the nano scale.

This technology that can work at the Molecular level, atom by atom to create large structures with improved molecular organization.

Nanotech research efforts in textile have focused on 2 main areas

1. Upgrading existing functions and performance of textile materials

2. Developing intelligent textiles with completely new characteristics and functions

SYNTHESIS OF NANOPHASE MATERIALS

There are 2 ways in synthesis of Nano phase materials they are:

. Top down approach

. Bottom up approach

Top down approach involving breaking down the bulk materials to nano sizes (Eg. Mechanical alloying)

Bottom up approach the nano particles also made by building atom by atom
(Eg. Inert gas condensation)

One of the trends in synthesis process is to pursure nano scale emulsification through which finishes can be applied to textile materials in more through, even and precise manner. Finishes can be emulsified into nano-micielles made into nano sols (or) wrapped in nano capsules, that can be adhere to textile substrates more evenly.

INTRODUCTION OF NANO-FINISHES

The first commercial application of Nano tech in textile and clothing industry is found in the form of Nano particle (some times called nano bead) through a finishing process, which is generally known as nano finishing.

The impact of nano technology in the textile finishing area has brought up innovative finishing as well as new application technique. Particular attention has been paid in making chemical finishing more controllable and more thorough, ideally discrete molecules or nano particles of finishes can be brought individually to designated sites on textile materials in a specific orientation and trajectory through thermodynamic, electrostatic or others technical approaches.

It is known that atoms & molecules posses totally different behaviour than those of bulk materials. While this properties are formerly described by quantum mechanics and latter governed by classic mechanics.

FUNCTIONAL FINISHING

The application of ultra fine particles, produced using nano technology, in textile finishing is fast growing. These application, are aimed at imparting multi functional properties such as ultra violet resistant, anti bacterial, moisture control to apparel products, made from natural fibres including, cotton, wool, silk and also synthetic fibres such as polyester and nylon. These multifunctional properties are achieved through changing fabric at molecular level by nano technology process.

Unstainable apparels based on nano technology are becoming widely popular. The nano technology finish creates care free fabrics that minimize stains, superior liquid repellency and provide wrinkle resistance. These enhanced fabric allow water and oil spills to easily bead and roll of the fabric without penetrating the fibres and maintain in the fabric throughout the life of the garment.

EASY CARE HYDROPHOBIC NANO FINISH

Hydrophobic surface can be produced mainly in 2 ways.

1. By creating rough structure on a hydrophobic surface.

2. By modifying a rough surface using materials with low surface free energy.

Both these approaches have been used to give a hydrophobic finish to textile substrates.

Fluorocarbon finishes constitute an important class of hydrophobic finishes. These finishes first applied to textile in the 1965 to impart water and oil repellency.

Fluorocarbons are a class of organic chemicals that contain a perfluoroalkyl residue in which all the hydrogen atoms have been replaced by Fluorine. These chemicals have very high thermal stability and low reactivity. They considerably reduce the surface tension.

Fluorocarbon finishes are dispersions of perfluorinated acrylates having co-monomers.

In the fluorocarbon finishes, the critical surface tension depends on the chain length of fluorinated side chain and is minimum for chain length of n=9. The effect of the chain length on the oil and water repellency is shown in table bellow.

ANTI MICROBIAL FINISH

"Silver" has been used in jewellery and for food utensils. It is a well known fact that the growth of bacteria and microorganisms in food or water is prevented when stored in silver vessels due to its antibacterial properties. The anti-bacterial properties of silver are now scientifically recognised. Silver ions have broad spectrum of anti microbial activities.

The method of producing durable silver containing antimicrobial finish is to encapsulate a silver compound or nano particle with a fibre reactive polymer like poly (styrene co-maleic anhydride)

. Prof. Yang has patented a process for preparing a silver nano particle containing functional microcapsule having the intrinsic anti-microbial and therapeutic functions of silver as well as additional functions of the products contained in the inner core of the capsule.

. These microcapsules can be prepared by a twostep process. In the first step an emulsified solution of a perfume is encapsulated with melanin pre-condensate. In 2nd step microcapsule so produce is treated with silver nano particle dispersed in water soluble styrene maleic anhydride polymer solution before it fully dies. Thus the microcapsules with duel function are produced.

. In these microcapsules, the silver nanoparticles are on the surface of the capsule.

. Instead of perfume, we may use thermo sensitive pigment, thermal storage materials or pharmaceutical preparation in the inner core.

. The treated yarns showed effective anti-microbial activity against various bacteria, fungi and chlamydia that included escherichia coli, citrobacter, bacillus subtilis etc.,

. This finished goods is used in medical industry as a safe & effective means of controlling medical growth in the wound bed.

PHOTO CATALYTIC SELF-CLEANING

During the last two decades, advanced orientation processes that are combination of powerful oxidizing agents (catalytic initiators) with UV or near - UV light have been applied for the removal of organic pollutants and xenobiotics from textile effluents among them, TiO2 has been proved to be an excellent catalyst in the photo degradation of colorants and other organic pollutants.

Photo catalytic propensity of semi conductors such as TiO₂ has been attributed the valence band to the conduction band brought above by the absorption of a photon of ultra-band gap light.

In the coating composition developed by XIN and Daoud, a sol mixture may be prepared at Room temp by mixing titanium tetraisopropoxide, ethanol and acetic acid in a molar ratio of 1:100:0.05 respectively.

The fabric to be coated was dried at 1000C for 30 min, dipped in the above mentioned nanosol for 30sec and then pressed at a nip pressure of 2.75 kg/cm2 .The pressed substrates were then dried then at 800C for 10 min in a pre-heated oven to drive off ethanol and finally cured at 1000C for 5 min in a pre-heated curing oven.

Nano sized TiO2 particles show high photo catalytic activities because they have a large surface area per unit mass and volume as well as diffusion of the electron/ holes before recombination.

This finish also have anti bacterial properties after having been subject to 55 washes through home laundry machine & UV protection characteristics for 20 washes.

ANTI-POLLEN FINISH

. Miyuki keori Co of Japan is marketing anti-pollen fabrics and garments. It is claimed that particles of 30nm sizes are attached to the surface of yarns.

. The smoothness of the finish on the surface and the anti-static effect does not let pollen or dust come close.

. This is achieved by using the polymer which have antistatic or electro conductive composition. (Eg. Fluoroalkyl - (meth) acrylate polymers)

. It is used in coats, blousons, hats, gloves, arm covers, bedding covers, etc.,

FLAME RETARDANT FINISH

. Nyacol nano technologies, Inc has been the world's leading supplier of colloidal antimony pentoxide which is used for flame retardant finish in textile.

. It offers colloidal antimony pentoxide us fine particle dispension for use as a flame retardant synergist with halogenated flame-retardants. (The ratio of halogen to antimony are 5:1 to 2:1)

. Nano antimony pentoxide used with Halogenated flame-retardants for a flame retardant finishes.

. 10 parts of nycal in 1550 parts of aqueous dispersion, with pH 7 and add 40 parts of H2O and sufficient ammonia add for bring out pH 9, mix this with 50 parts of rubber latex and spray to the Non-woven material.

ODOUR FIGHTS FINISH

. A Taiwanesse nanotech firm Greensheild has created underwear that fights odour. This is achieved through nanotechnolgy.

. The underwear fibers release undetectable negative ions and infrared rays that destroy odour-causing bacteria.

. The negative ions create a magnetic field that inhibits the reproduction of bacteria, thus eliminating odour and lowering the risk of skin infection or irritation.

. Far infrared rays are absorbed by cells not just in the skin but throughout the body - causing all the individual atoms being vibrated at a higher frequency, which speeds up the metabolism and the elimination of wastes.

. Tourmaline a natural mineral limits a low-level radiation which in contact with oxygen, carbon di oxide and water molecules in the air promotes electrolytic dissociation and emits negative ions.

. This Nano finish can eliminate upto 99.99% of bacteria, 90% of odour and 75% sticky moisture within the cloth as well as contributing to the overall health of wearer.

UV PROTECTION

Clay nanoparticles or nano flakes are composed of several types of hydrous aluminoosilicates, each type differ in chemical composition and crystal structure. Clay nano particles posses electrical, heat, chemical resistance and an ability of locking UV light.

Nano clay particles of montmoriblonite being one of most commonly used UV blocker. It also increases 40% tensile strength, 60% flexural strength.

SELF CLEANING SUITS

Sending your favorite suit to dry cleaning for one day become very infrequent practice. Silver nano particles are used in a patented coating. A film polymer (poly glycidyl acrylate) mixed with silver nano particles can be permanently integrated into any common fabric including cotton, silk, polyester or blends; in the long run it can save time and money by reducing dry-cleaning expenses. It is also eco-friendly and contains no fluorine compounds.

The research team is also trying to engineer anti-microbial particles / odour free agents in to the coating, which could help to repel strong odours such as body odours & cigarette odours.

The coating would be flow essential also permanent for wear, without by dry cleaning

CHARACTERISTICS OF NANO FINISHING IN GARMENTS

1. Nano - processed garments have protective coating, which is water and beverage repellent.

2. Their protective layer is difficult to detect with the naked eye.

3. When a substance is manipulated at sizes of approximately 100 nm, the structure of the processed clothing becoming more compressed. This makes clothing stain and dirt resistant.

4. Saving time and laundering cost.

5. This technology embraces environmental friendly properties.

6. Nano-materials allows good ventilation and reduces moisture absorption, resulting in enhanced breathability while maintaining the good hand feel of ordinary material.

7. The crease resistant feature keeps clothing neat

8. Nano processed products are toxic free

9. Garments stay bright, fresh looking and are more durable than ordinary materials.

10. Manufacturing cost is low, adding value to the products.

CONCLUSION

Nano finishes being developed for textile substrates are at their infantile stage .The basic mechanisms and the logic of some of this finishes has been explained by the inventors. The probability of the type of commercial finishing applications covered in this article occurring within the next few years is quite high. Nano finishing can replaced traditional finishing technique of textile products and readymade clothing with products of superior quality and lower production costs. In feature, one can expect to see many more developments in textiles based on Nano Technology.

REFERENCES

1. M. J Wadia & U.M Mimkas, nano technology: A boon to textile Auxillary industries. Colorage Jan 2006 pp-51-56

2. PB Jhala - Nano technology in textiles ITJ- may 2004 pp- 13-18

3. M. Subramanian & Senthilkannan , Nano technology part2 ATJ- 2004 nov pp 117-121

4. ATJ team Nano technology creating innovations oct 2005 ATJ p- 95

5. K. A Aravindan & D. Gopalakrishan- A big future for small science : Nano technology in textiles MMTI Apr 2006 pp- 128-130

6. http:/www.ntcresearch.org

7. http:/www.nanostatics.com

8. P. Dhanapal &R. Anita-Nana technology-ITJ May 2006 pp 13-17

9. www.nanovip.com

10. www.nanocor.com

11. Prof. M.L Gulrajani - Nano finishes- Indian journal of fibers & textile research Vol 31, March 2006 pp 187-201

12. Ritu Jain & Saurabh Agarwal - Recent innovation in textiles part1 Nano technology ATJ Sep 2005 pp 55-59

13. Edward Menezes, Will Nano technology be commercially viable- Clothesline Aug 2004 pp 79-84

14. Technology of textile finishing by Dr. G. Nalangilli

About the author:

Aravin Prince .P & Raja .P are Final Year students in Department Of Textile Technology, RVS College Of ENGG. & TECH. DINDIGUL-624005
E-mail : aravinprince@gmail.com & rajastex@gmail.com