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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
Nanotechnology in the Textile Industry / 2
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.
Nanotechnology in the Textile Industry / 3
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.
Nanotechnology in the Textile Industry / 4
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.
Nanotechnology in the Textile Industry / 5
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]
Nanotechnology in the Textile Industry / 6
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
Nanotechnology in the Textile Industry / 7
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.
Nanotechnology in the Textile Industry / 8
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]
Nanotechnology in the Textile Industry / 9
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
Nanotechnology in the Textile Industry / 10
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
Nanotechnology in the Textile Industry / 11
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.
Nanotechnology in the Textile Industry / 12
Fig. 4. Electrospun nanofibrous web under SEM [1,2]
Fig. 5. Schematic diagram of electrospinning set up [1,2]
Nanotechnology in the Textile Industry / 13
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.
Nanotechnology in the Textile Industry / 14
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.
Nanotechnology in the Textile Industry / 15
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]
Nanotechnology in the Textile Industry / 16
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
Nanotechnology in the Textile Industry / 17
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.
Nanotechnology in the Textile Industry / 18
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.
Nanotechnology in the Textile Industry / 19
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.