nanotechnology in the textil industry

Beatriz Vinuesa Mora

ET1039- Nanotechnology

Nanotechnology

In the Textil Industry

Nanotechnology in the Textile Industry / 1

INDEX

1. Introduction .............................................................................................................. 2

2. Nanotechnology in Textiles ...................................................................................... 3

3. Nanotechnology Based Finishes and Coatings for Advanced Technical Textiles

(Applications) ............................................................................................................ 4

4. Future Trends and conclusions ............................................................................... 18

5. Bibliography ............................................................................................................ 19


1. Introduction

Nano-science and nanotechnology combined, have revitalized material science and led

to the development and evolution of a new range of improved materials including

polymers and textiles through nanostructuring and nanoengineering. Nanotechnology

is an emerging interdisciplinary area that is expected to have wide ranging implications

in all fields of science and technology such as material science, mechanics, electronics,

optics, medicine, energy and aerospace, plastics and textiles.

Although Nanotechnology is still in its infancy, it is already proving to be a useful tool

in improving the performance of textiles and generating worldwide interest. An

overview on impact of nanotechnology on textiles indicates a clear shift to

nanomaterials as a new tool to improve properties and gain multi functionalities.

Organized nanostructures as exhibited by either fibers, nanocoatings, nanofinishing,

nanofibers and nanocomposites seem to have immense potential to revolutionize the

textile industry with new functionality such as self-cleaning surfaces, conducting

textiles, antimicrobial properties, controlled hydrophilicity or hydrophobicity,

protection against fire, UV radiation etc. without affecting the bulk properties of fibers

and fabrics.


2. Nanotechnology in Textiles

The use of nanomaterials and nanotechnology based processes is growing at a

tremendous rate in all fields of science and technology. Textile industry is also

experiencing the benefits of nanotechnology in its diverse field of applications.

Textile based nanoproducts starting from nanocomposite fibers, nanofibers to

intelligent high performance polymeric nanocoatings are getting their way not only in

high performance advanced applications, but nanoparticles are also successfully being

used in conventional textiles to impart new functionality and improved performance.

Greater repeatability, reliability and robustness are the main advantages of

nanotechnological advancements in textiles.

Nanoparticle application during conventional textile processing techniques like

finishing, coating and dyeing enhances the product performance manifold and imparts

hitherto unachieved functionality. New coating techniques like sol-gel, layer-by-layer,

plasma polymerization, etc. can develop multi-functionality, intelligence, excellent

durability and weather resistance to fabrics.

The present essay focuses on the development and potential applications of

nanotechnology in developing multifunctional and smart nanocomposite fibers,

nanofibers and other new nanofinished and nanocoated textiles.

The influence of nanomaterials in textile finishing and processing to enhance product

performance is discussed. Nanocoating is relatively a new technique in the textile field

and currently under research and development. Polymeric nanocomposite coatings

where nanoparticles are dispersed in polymeric media and used for coating

applications is a promising route to develop multifunctional and intelligent high

performance textiles. The most researched area to produce multifunctional, smart

fibers is the preparation of nanocomposite fibers where the exceptional properties of

nanoparticles have been utilized to enhance and to impart several functionality on

conventional textile grade fibers.

Nanofibers which are sub-micron size in diameter are gaining popularity in some

specialized technical applications such as filter fabric, antibacterial patches, tissue

engineering and chemical protective suits.


3. Nanotechnology Based Finishes and Coatings for Advanced

Technical Textiles (Applications)

Nanotechnology has opened immense possibilities in textile finishing area resulting

into innovative new finishes as well as new application techniques. Particular emphasis

is on making chemical finishing more controllable, durable and significantly enhance

the functionality by incorporating various nanoparticles or creating nanostructured

surfaces. The unprecedented level of textile performances claimed for these

nanofinishes such as stain resistance, antimicrobial, controlled hydrophilicity /

hydrophobicity, antistatic, UV protective , wrinkle resistant and shrink proof abilities

can be exploited for a range of technical textile applications such protective clothing,

medical textiles, sportswear, automotive textiles etc.

Nanofinishes are generally applied in nanoemulsion form, which enables a more

thorough, even and precise application on textile surfaces. They are generally

emulsified into either nanomicelles, made into nanosols or wrapped in nanocapsules

that can adhere to textile substrates easily and more uniformly. Since nanoparticles

have a large surface area to volume ratio and high surface energy, they have better

affinity for fabrics. Therefore these finishes are more durable, effective and do not

adversely affect the original handle and breathability of the fabric. A range of different

textile products and finishes based on nanotechnology has already been launched in

the market. The recent developments in nanofinishing on textiles have been briefly

described below.

Water and Oil Repellent (Hydrophobic) Nanofinishes

The premier range of Nano Care and NanoPel nanofinishes marketed by NanoTex Inc.

USA are the next generation easy care finishes based on nanotechnology. These

finishes which come under Resist spills TM Category protect the fabric against both

water and oil based liquid stains / soils. Tiny whiskers aligned by proprietary “spines”

are designed to repel liquids and are attached to the fibers utilizing molecular "hooks”.

These whiskers and hooks are very-very small in fact no more than 1/1000th the size of

cotton fiber. These whiskers cause the liquids or semisolids to roll off the fabric thus

cause minimal staining, which can be removed with simple washing. Since the attached

whiskers are of nanoscale size, they do not affect the hand, breathability of fabric and

can withstand 50 home launderings.


Super Hydrophobic: Self Cleaning Nano Finishes

Many plants in nature including the Lotus leaf exhibit unusual wetting characteristic of

super hydrophobicity (Fig. 2). A super hydrophobic surface is the one that can bead off

water droplets completely; such surfaces exhibit water droplet advancing angles of

150o degree or higher. A self-cleaning surface thus results since the rolling water

droplets across the surface can easily pick up the dirt particles to leave behind a clean

surface. Taking the inspiration from the nature there have been several approaches

researched to create super hydrophobic surfaces on textiles, which mimic the

nanostructured Lotus leaf and therefore exhibit self-cleaning properties.

Nano Sphere, a Lotus effect based textile finish has been developed, patented and

commercialized by Schoeller Texil AG of Switzerland. Super hydrophobic silica coating

film on cotton substrates, which are transparent and durable have been reported by

W.A.Daud and coworkers of the Hong Kong Polytechnique University using low

temperature sol-gel coating based on a low temperature process. This nanocomposite

coating has new applications in daily use material and such as plastics or textiles and is

an eco-friendly substitute for fluorocarbon based water repellant finish. There is less

than 5% decrease in textile strength and tearing strength. The air permeability of the

fabric remains unchanged. The washing durability of the coatings is also good.

Fig.1. Lotus leaf effect and a SEM image of its surface [1,2]


Photocatalytic Self Cleaning Finishes

Dr. John Xin and Dr. Walid Daoud of the Hong Kong Polytechnic University’s

Nanotechnology Centre for Functional and Intelligent Textiles and Apparel developed a

process for the sol gel coating on textile substrates at low temperature. They also

claimed that photocatalytic self-cleaning properties could be imparted to the coated

fabric on coating cotton with TiO2 nanoparticles that are about 20 nm in size (Fig. 3).

The nanotitania coated fabrics maintain their antibacterial property up to 55 washes /

home launderings and UV protection characteristics up to 22 washes.

Fig. 2. SEM images of (a) uncoated cotton fiber, (b) titania coated cotton fiber showing the morphological change in

the surface structure, (c) higher magnification image of titania coated cotton fiber showing the shape and size of the

titania particles, and (d) higher magnification image of a titania film coated on glass [1,2]

Hydrophilic Nano Finishes

The poor moisture absorption property of synthetic fabrics such as polyester and

polyamides limits its applications in the apparel sector. The new range of hydrophilic

nanofinishes 'Cotton Touch’ TM and ‘Coolest Comfort’ TM commercialized by

NanoTex, USA makes the synthetic fabric look and feel like cotton.

“Nanotouch gives durable cellulose wrapping over synthetic fibers such as polyester

and polyamides. Cellulosic sheath and synthetic core together form a concentric

structure to bring overall solutions to the drawbacks of synthetics such as static

discharge, harsh handle and glaring luster. It can also last 50 launderings and expected

to eliminate the decline in demand of synthetic microfiber and broaden the use of

synthetics to new applications. ‘Nano Dry’. Finish provides break through moisture

wicking to draw moisture away from body while drying quickly. It improves the


moisture absorption of polyamides and polyesters making them hydrophilic and

comfortable. The main applications are in sportswear and close to body garments that

require perspiration absorbency. The finish lasts 50 launderings.

Antibacterial Nanofinishes based on Nanosilver

A range of antimicrobial textile finishes and products have been reported and quite a

few have been commercialized, which are based on much superior antimicrobial

properties of silver in nanoform. Nano silver particles containing antimicrobial

dressings have been incorporated in wound care and have gained wide acceptance in

medical industry, as a safe and effective means of controlling microbial growth in the

wound, often resulting in improved healing. A range of nano silver based medical

textiles for health and hygiene has been developed and commercialized.

UV Protective Nanofinishes

Semiconductor oxides such as TiO2, ZnO, SiO2 and Al2O3 are known to have UV

blocking property29-30. It is also known that nanosized TiO2 and ZnO particles are

more efficient at absorbing and scattering UV radiation than the conventional size

particles and thus were better able to block UV radiation as have much larger surface

area to volume ratio. A lot of efforts have been made on the application UV bulking

treatment to fabrics using nanotechnology. UV blocking treatments for cotton fabric

has been developed using sol-gel method by Xin and coworkers. A thin layer of TiO2

nanoparticle is formed, on the surface of treated cotton fabric, which provides

excellent UV protection, the finish is durable up to 50 home launderings. Apart from

TiO2, ZnO nanorods of 10 to 50 nm in length were also applied to cotton fabric to

provide UV protection. The rods exhibited excellent UV protection.

Antistatic Nanofinishes

Synthetic fibers such as Nylon and polyester are prone to static charge accumulation as

they absorb less water. It has been reported that nanosized TiO2, ZnO whiskers,

nanoantimony-doped tin oxide (ATO) and silane nanosol could impart antistatic

properties to synthetic fibers. TiO2, ZnO and TiO2 nanoparticles are electrically

conductive materials and help dissipate the static charge in these fibers.


Nano Matrix: Self Assembly based nanocoatings

Toray Industries, Inc. have succeeded in developing a “nanoscale processing

technology” that allows the formation of molecular arrangement and molecular

assembly necessary to bring out further advanced functionalities in textile processing.

This “nano-scale processing technology” named “NanoMATRIX” forms the functional

material coating (10-30 nm) consisting of nano-scale molecular assembly on each of

the monofilament that forms the fabric (woven / knitted fabric) (Fig. 4). “Nano-matrix”

is based on the concept of “self-organization” by controlling the conditions like

temperature, pressure, magnetic field, electrical field, humidity, additives etc. The

application of this technology is expected to lead to development of new

functionalities as well as remarkable improvements in the existing functions (quality,

durability, feel etc) without losing the fabric’s texture.

Fig 3. Nanomatrix Technology from Toray for nanocoatings on textiles through self -Assembly [1,2]


Nanocoatings

Nanostructured surfaces are of great interest, due to their large surface area, which

might yield high functionality. Nanocoating refers to the covering of materials with a

layer on the nanometer scale (10 - 100 nm in thickness) or covering of a nanoscale

entity to form nanocomposite and structured materials. Nanocoatings on Textiles have

recently been explored using mainly processes such as plasma-assisted polymerization,

self-assembly, sol-gel nanocoating and electrochemical depsition.

Plasma assisted nanocoatings

Plasma polymerization enables deposition of very thin nanostructured coatings (<

100nm) via gas phase activation and plasma substrate interactions. This dry and

ecofriendly technology offers an attractive alternative to replace wet chemical process

steps for surface modification (finishing) of textiles. Plasma polymerization can impart

a wide range of functionalities such as water repellency, hydrophilicity, dyeability,

conductivity and biocompatibility due to the nanoscaled modification of textiles and

fibers. The advantages over conventional wet chemical processing is that it needs a

very low material and low energy input, hence is environmental friendly, it does not

affect the bulk properties of textiles and fibers such as feel (touch), handle, optical

properties and mechanical strength. Moreover, these plasma-assisted coatings are

more durable as compared to other surface modification techniques such as wet

processes, radiation or simple plasma activation because nanoscaled plasma polymer

coatings get covalently attached or bonded to textile surfaces.

Low-pressure plasma polymerization of unsaturated fluorohydrocarbons i.e. C3F6,

C4F8 on selected textiles has been industrially performed using a semi continuous

process to impart stain repellant properties on fabrics. Oil repellency grades of 4-5

were achievable in short treatment times (30-60 sec), which are superior to Scotch–

Guard finished samples. The softness, feel, color, permeability, abrasion resistance,

water performance and friction coefficient properties of original fabric were unaltered

by these nanoscaled ultrathin (<100 nm) plasma coatings. The up scaling of plasma

technology to industrial scale for textile applications is the major challenge faced by

the researchers and technologists. Low-pressure plasma processes are still the state of

the art technology, as effects produced by atmospheric plasma are comparatively

weak and non-uniform. The other issues of concern are the efficiency of plasma

polymerization process in terms of deposition rates and the right process speeds, so

that they can be integrated with the current textile production lines. High investment

cost and requirement of vacuum technology further limits the present application of

this technology at industrial scale to only niche textile products. M/s EMPA, a Swiss


based company, specializing in this area have mainly developed low-pressure plasma

reactor for plasma-polymerized coatings.

Polymer Nanocomposites

Polymer nanocomposites are the advanced new class of materials with an ultrafine

dispersion of nanofillers or nanoparticles in a polymeric matrix, where at least one

dimension of nanofillers is smaller than about 10nm. The volume and influence of the

interfacial interactions increases exponentially with decreasing filler /reinforcement

size and thus forms an additional separate phase known as interphase, which is

distinct from the dispersed and continuous phases and hence influences the composite

properties to a much greater extent even at low nanofiller loading (< 5%). Therefore,

their properties are much superior to conventional composites. The interest in

polymer nanocomposites further arises from the fact that, they are light weight as

compared to conventional composites because of the low filler loadings, are usually

transparent as scattering is minimized because of the nanoscale dimension involved

and are still processable in many different ways including production of fibers with

nanoscale fillers embedded in the polymer matrix. With these improved set of

properties, they show promising applications in developing advanced textile materials

such as- Nanocomposite fibers, nanofibers and other nanomaterial incorporated fibers

and coated textiles for applications in medical, defense, aerospace and other technical

textile applications such as filtration, protective clothing besides a range of smart and

intelligent textiles.

Polymers nanocomposites thus offer tremendous potential when produced in fiber

form and offer properties that leapfrog those of currently known commodity synthetic

fibres.

Nanocomposite fibres that contain nanoscale embedded rigid particles as

reinforcements show improved high temperature mechanical property, thermal

stability, useful optical, electrical, barrier or other functionality such as improved

dyeability, flame retardance, antimicrobial property etc. These novel biphasic

nanocomposites fibres in which dispersed phase is of nanoscale dimension, will make a

major impact in tire reinforcement, electro optical devices and other applications such

as medical textiles, protective clothing etc.

The work on spinning of nanocomposites started about seven years ago and several

research groups across the world are exploring the synthesis, fiber processing,

structureproperty characterization and correlation and molecular modeling of these

unique new composites fibers. Polymeric nanocomposite fibres have been mostly spun


through three basic methods of fiber spinning -Melt spinning, Solution spinning and

Electrospinning.

Although, most of the research reports on polymeric nanocomposites is where it has

been studied in form of films or moulded specimens and very few reports on their

spinning into Nanocomposite fiber form. However, there are some reports on

composite fibers based on all the three major types of nanofillers viz layered silicate

nanoclays (MMT), carbon nanotubes (CNT) and nanofibers, metal oxide nanoparticles

(TiO2, ZnO, SiO2 etc.) and hybrid nanostructured materials such as POSS have been

reported in literature.

Polymeric Nanofibers

Recently, there has been an increased interest in producing nanofibers that are

submicron size in diameter. Typically conventional melt blown ultrafine fiber diameter

ranges from 2000 to 5000 nm, whereas polymeric nanofibres ranges from 50 to 500

nm. Nanofibers are characterized by extra ordinary high surface area per unit mass (for

instance nanofibres with 100nm in diameter have a specific surface of 1000 m2/g) high

porosity and lightweight.

These unique properties of nanofibres make them potential candidates for a wide

range of application such as filtration, barrier fabrics, protective clothing, wipes and

biomedical applications such as scaffolds for tissue engineering. Electrospinning is a

process that produces continuous polymeric nanofibres (diameter in submicron range)

through an action of an external electric field imposed on a polymer solution or melt.

Recently, electrospinning has also been extended to making nanofibres from polymer

nanocomposites, incorporating nanoclays, CNTs and other nanoparticles and adding a

new dimension to nanofibres. These nanocomposite fibers when deposited over textile

substrates can be further used to manufacturer fabrics, antistatic materials,

electromagnetic shielding materials, high performance separation medium, reinforcing

materials, electrical and thermal conductivity materials, wave absorbing materials etc.


Fig. 4. Electrospun nanofibrous web under SEM [1,2]

Fig. 5. Schematic diagram of electrospinning set up [1,2]


Nanocomposite Fibers

At Textile Deptt IIT Delhi, we have investigated nanocomposite fibers based on all the

three major types of nanofillers viz layered silicate nanoclays (MMT), carbon

nanotubes (CNT) and nanofibers, and hybrid nanostructured materials such as POSS.

Compatibilized polypropylene/nanoclay composite filaments were produced by melt

intercalation route using twin screw compunder coupled to a fiber take up device and

drawing machine and characterized to study the effect of the compatibilizer and the

role of nanoclay in improving the properties. The compatibilizer used was Maleic

anhydride grafted Polypropylene (PP-g-MA).

Clay loadings of up to 1 wt % with up to 3-wt % of the compatibilizer were studied. The

dyeability properties of these filaments showed that nanocomposite filaments took up

disperse dyes unlike the neat PP filaments which have to be dope dyed.

There was a significant improvement in tensile, thermal, dynamic mechanical and

creep resistance properties of PP/nanoclay composite filaments over neat PP

filaments4.

Another development was making high performance fibers based on polymeric

nanocomposites based on a novel class of hybrid nanostructured filler, Polyhedral

Oligomeric Silsesquioxane (POSS). The system chosen for the study is the simple

‘octamethyl POSS’, a molecular silica as the nanofiller and HDPE as the polymeric

matrix. At comparatively very low loadings (0.25-0.5 wt %), POSS actually gives a

lubricating effect and facilitates the drawing of filaments, which results in higher

tensile strength and modulus.

With increase in POSS concentration beyond 1 wt %, POSS existing as

nanocrystals/aggregates starts hindering the orientation of HDPE chains leading to a

gradual fall in tensile strength and modulus. Incorporation of POSS also modifies the

thermal degradation behaviour of HDPE and broadens the temperature range of

thermal degradation. The HDPE-POSS nanocomposite filaments also exhibit better UV

resistance than neat HDPE filaments, which may be attributed to the

scattering/reflective action of POSS5-8.

An attempt to explore the feasibility of producing filaments from polyurethane (PU)

/clay nanocomposites and compare their structure and properties vis-a-vis neat PU

filaments has been carried out as a part of doctoral thesis by our research group. This

work reports the production of filaments from neat polyurethane and

polyurethane/clay nanocomposite by dry-jet-wet spinning; a technique being used for

the first time for this system. An organomodified nanoclay was used as a filler and

thermoplastic polyurethane as the matrix. Dispersed nanoclay in PU matrix has

induced both external morphological changes as well as internal micromorphology.


Nanoclay dispersion reduces the stretchability by enhancing the void content of the

nanocomposite filaments.

Modulus and tenacity are enhanced significantly in the presence of nanoclay at low

concentrations; nevertheless elongation and elastic recovery are marginally affected.

Thermal studies suggest that a significant improvement in thermal stability of PU/clay

nanocomposites filaments is due to hybridization with inorganic nanoclay. High

thermal shrinkage at low clay concentration indicated high orientation due to good

dispersion and exfoliation of clay in filaments. Boiling water shrinkage and water

swelling also indicated high orientation and reduced swelling due to incorporation of

clay. Fire retardant properties studied by cone calorimetry shows excellent fire

retardant properties at low clay content (0.25 wt %). Dyeability properties of

nanocomposite fibres also get significantly enhanced in the presence of nanoclay.

Weatherability resistance of PU/clay filaments are significant only at higher clay

concentration (~ 1 wt %).

Polyamide or nylon 6/clay nanocomposites have been widely investigated due to their

much superior tensile strength and modulus, improved heat resistance (heat distortion

temperature increases from 65°C to 120°C) as well as excellent gas and water barrier

propertie over their neat nylon 6 counterparts. In a study by our research group

nylon/clay nanocomposite fibers were prepared by melt intercalation route and spun

into filaments which were converted into cords and tested for tire cord related

properties such as tensile strength, rubber to cord adhesion and fatigue resistance.

The nylon/clay nanocomposite cords exhibited improved tensile strength (21%) as well

as improved reubber to cord adhesion (35%) but slightly reduced fatigue resistance as

compared to neat nylon filaments9.

Nanocomposite Coatings

A glance at the literature available shows interesting applications of polymer

nanocomposites as coatings with attractive combinations of properties not achievable

by neat polymeric conventional coatings. Novel Polyurethane/ MMT (clay) based

nanocomposites as coatings for inflatables has been explored in an ongoing research

project at Department of Textile Technology, Indian Institute of Technology, Delhi by

M Joshi et.al. The coated fabrics showed improved gas barrier property without

affecting the transparency and tear strength. Clays are believed to increase the barrier

properties by creating a tortuous path that retards the progress of gas molecules i.e.

gas diffusion through the matrix resin10.


A significant achievement of our group has been the work where novel hybrid

nanographite particles have been synthesized via co-deposition of iron and nickel on

nanographite particles using fluidized bed electrolysis, a simple and eco-friendly

technique11. These metal coated nanographite particles were dispersed in

polyurethane matrix and showed a significant enhancement in microwave absorption

as a thin coating and at relatively low loadings (<10 wt %). The microwave absorption

frequency range further widened to X (8 – 12 GHz) and Ku (12 – 18 GHz) bands. These

nanocomposite coatings were truly multifunctional as they also enhanced the gas

barrier, UV resistance and conducting property of the coatings. The flexibility of such

nanocomposite coatings is almost retained at 10 wt% loading and the durability is

found to be excellent under accelerated weathering conditions. These excellent results

have been reported for the first time using novel hybrid nanographite particles in

polyurethane matrix and there are no similar literature reports for other RAM

coatings12-13. This work has got us the “National Award (2011-2012)” from Ministry

of Chemicals and fertilizers”, Govt. of India for Innovation in Downstream

Petrochemical Industry in the Category of Academic Research and Development.

Fig. 6 : FeNiNG dispersed polyurethane film under tapping mode of AFM: at low magnification (a) Height image and

(b) Phase Image; at high magnification (c) Height image and (d) Phase Image [12, 13]


The developed Polyurethane/hybrid nanographite based nanocomposite in coating or film form have the potential

defence applications as camouflage coatings, covering or envelop on army vehicles, naval ships, military

establishments, etc. for an effective microwave shielding effect. These flexible polymer nano composites also offer

the possibility of many other industrial applications in microsystem technologies, as microwave or radar absorbent

material; in astronautics and for anticorrosive coatings.

Nanocoatings

Layer-by-layer assembly (L-b-L) is a unique technique for the fabrication of composite

films and deposition of coatings with nanometer precision. Since the introduction of

polyelectrolyte multilayer architectures formed by the alternate deposition (layerby-

layer self-assembly) of polycations and polyanions from solution to a solid support by

Decher et al. in 1991, numerous papers have been published using this very simple yet

versatile technique to modify organic or inorganic solid surfaces.

Application of L-b-L process to modify the surfaces of textile substrates i.e fiber or

fabrics has not been either extensively studied or understood. Recently there have

been only few reports on depositing nanolayers of polyelectrolytes on cotton, silk and

nylon fibres which seem to be a promising technique for future applications.

In our work on nanocoatings on textiles using L-b-L technique we report nanocoating

of cotton substrate using L-b-L process, to impart various functional properties on

cotton textiles such as antimicrobial , self-cleaning, hydrophilicity / hydrophobicity

etc.14.

Cotton fibers offer unique challenges to the deposition of nanolayers because of a

unique cross-section as well as chemical and physical heterogeneity of its surfaces.

Cationic cotton surface has been successfully coated with alternate layers of anionic

and cationic polyelectrolytes, i.e. poly (sodium 4-styrene sulphonate) and poly

(allylamine hydrochloride) using L-B-L technique. A study by M. Joshi, Wazed Ali, S.

Rajendran reports that the multilayer formation of polyelectrolytes on cotton surface

is sensitive to different process parameters such as pH, temperature, concentration of

polyelectrolyte solution, dipping time and addition of salt15. Layer by layer technique

can also be utilized to create multifunctional textile surface as antifouling, self-cleaning

and water resistant coatings for micro-fluids channels and bio sensors. A stable lotus

leaf structure has been mimicked to create super hydrophobic surfaces using silica

nanoparticles and a low surface energy finish on cotton substrate14.

Antimicrobial silver nanoparticles can be immobilized on nylon and silk fibers by this

method. The sequential dipping of nylon or silk fibers in dilute solutions of poly

(diallyldimethylammonium chloride) and silver nanoparticles capped with poly

(methacrylic acid) lead to the formation of a colored thin film possessing antimicrobial

properties. The amount of deposition on both silk and nylon fibers increases as a


function of the number of deposited layers though the L-B-L coating on the nylon

fibers is not as uniform as on the silk fibers. The deposition of bilayers onto the fibers

results in significant bacteria reduction for the silk and the nylon fiber. New

antimicrobial synthetic or natural fibers can be designed through this technique.

In a study by M. Joshi et al, L-B-L nanocoating has been carried out on cotton fabric

using chitosan as the cationic polyelectrolyte and poly sodium-4-styrene sulfonate as

the anionic polyelectrolyte. The process is assisted with ultrasonic treatment for

uniform very thin (few nm) deposition of the bi-layers. Thus produced fabric has good

antimicrobial property; however, the feel, flexibility and breathability of the fabric are

not affected16.

Further chitosan nanoparticles and silver modified chitosan nanparticles have been

synthesized and the effect of surface charge, size and shape has been studied to

optimize the antibacterial property17,18 and then these have been applied on cotton

as well as polyester surface using L-b-L self-assembly approach19,20.


4. Future Trends and conclusions

Nanotechnology has thus emerged as the ‘key’ technology, which has revitalized the

material science and has the potential for development and evolution of a new range

of improved materials including polymers and textiles. However there are many

challenges in the development of these products, which need to be intensively

researched so that the wide range of application envisaged can become a commercial

reality. An excellent dispersion and stabilization of the nanoparticles in the polymer

matrix is crucial to achieving the desired nano effects. The tendency to agglomerate

due to extremely high surface area is the major problem facing the effective

incorporation of nanoadditives in coatings/finishing as well as in nanocomposite

preparation.

Surface engineering of nanoparticles and combining them with functional surface-

active polymers can bring the nanoparticles onto fibers/textiles without losing their

superb, nanoscopic properties.

To conclude nano-technology, definitely has the potential to being revolution in the

field of technical textiles. There is however a word of caution because industrial

commercialization of the nanotechnology products can become a commercial reality.

The issues are:

a) Large scale production of nano particles and their cost.

b) Impact of uncontrolled release of nanoparticles in the environments and their

effect on human health and ecology widely covered under the domain

‘nanotoxicology’.

c) Practical philosophy and ethics on the wide spread use of nanotechnology

based products.


5. Bibliography

M. Joshi and A. Bhattacharyya (2011) Nanotechnology.

M. Joshi and B. S. Butola (2007) Isothermal crystallisation of HDPE/POSS

Nanocomposite.

Sachin Kumar, B S Butola and M Joshi (2010) Preparation of hybrid

Polypropylene/POSS nanocomposite monofilaments.

B. S. Butola, M.Joshi, and S. Kumar (2010) Hybrid Organic-Inorganic POSS.

nanotechnology in the textil industry

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