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SELFCLEANINGGARMENTS
BY,
S.PARTHIBAN
PSGCOLLEGEOFTECHNOLOGY
ABSTRACT
Water and soil repellency has been one of the major targets for
fiber and textile scientists and
manufacturers for centuries. Nano science is employed for this
type of problems. From the nano
science self cleaning is the wonderful technology for dirt free
with other functional finishes. So,
through this paper we deals with various mechanisms of
self-cleaning and the coatings,
manufacturing methods, and also various functional finishes like
antimicrobial; UV ray finishes
which can be imparted with the major advantages than the other
conventional finishes and
application area of this technique. Connection to this
limitation, problems with this technique
and recommendations for the purpose of bringing out new ideas
which is incorporated in the self
cleaning garments.
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CONTENTS INTRODUCTION...4
NANO LIFT UP THE SELF CLEANING FINISHES....4
SELF-CLEANING MECHANISM...4
MANUFACTURING METHOD...5
1. HYDROPHOBICCOATINGSTHELOTUS-EFFECT...5 2. HYDROPHILIC PHOTO
CATALYTIC COATINGS....6 3. USING SILVER NANOPARTICLES...7 4. EASY
TO CLEAN FINISHES...8
OTHER FUCTIONAL FINISHES...9
1. ANTIMICROBIAL FINISH....9 2. UV PROTECTIVE FINISH..10
INNOVATION IN SELF CLEANING FINISHES.....11
1. SELF-CLEANING WOOL AND SILK....11 2. PHOTO CATALYTIC
DEGRADATION OF ODORS COMPOUND.....12
CHARACTERISTICS OF SELF CLEANING GARMENTS...12
FUTURE WITH SELF-CLEANING GARMENTS ...13
AREAS OF APPLICATION..13
PROBLEMS WITH SELF-CLEANING FABRICS....14
RECOMMENDATION...14
CONCLUSION.14
REFERENCES.14
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INTRODUCTION:
Nature has already developed an elegant approach that combines
chemistry and physics to create
super repellant surfaces as well as self cleaning surfaces.
Lotus leaves is the best example of
self cleaning surfaces. The technology of self-cleaning coatings
has developed rapidly in recent
years. As a commercial product, their potential is huge and
their market truly global. Because of
the wide range of possible applications. The concept of self
cleaning textiles is based on the lotus
plant whose leaves are well-known for their ability to
self-clean by repelling water and dirt.
Now days peoples are very busy in their work that they do not
have time for clean their daily
wear cloths also people who are working in kitchens having
headache to wash their garments.
Also military peoples have to survive in such drastic condition
that they cannot wash their cloths.
Nano technology provides a new concept self cleaning textiles
which gives self cleaning as well
as fresh cloths every day, this not only technically benefited
but techno economically also
benefited. The field of self-cleaning coatings is divided into
two categories: hydrophobic and
hydrophilic. These two types of coating both clean themselves
through the action of water, the
former by rolling droplets and the latter by sheeting water that
carries away dirt. Hydrophilic
coatings, however, have an additional property: they can
chemically break down adsorbed dirt in
sunlight.
NANO IS BASICS FOR SELF CLEANING GARMENTS:
Nanotechnology is regarded as a key technology, which will not
only influence technological
development in the near future, but will also have economic,
social and ecological implications.
Nanotechnology deals with the science and technology at
dimensions of roughly 1 to 100
nanometers (1 Billion Nanometers = 1 Meter), although 100
nanometers presently is the
practically attainable dimension for textile products and
applications. Conventional methods used
to impart different properties to Fabrics often do not lead to
permanent effects, and will lose their
functions after Laundering or wearing. Nanotechnology can
provide high durability for fabrics,
because nano-particles have a large surface area-to-volume ratio
and high surface energy.
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SELF-CLEANING MECHANISM:
Nanocare fabrics are created by modifying the cylindrical
structure of the cotton fibres making
the fabric. At the nanoscale, cotton fibres like tree trunks.
Using nanotechniques, these tree
trunks are covered in a fuzz of minute whiskers which creates a
cushion of air around the fibre.
When water hits the fabric, it beads on the points of the
whiskers, the beads compress the air in
the cavities between the whiskers creating extra buoyancy. In
technical terms, the fabric has been
rendered super-non wettable or super-hydrophobic.
The whiskers also create fewer points of contact for dirt. When
water is applied to soiled fabric,
the droplet on an inclined super hydrophobic surface does not
slide off; it rolls off. When the
droplet rolls over a contamination, the particle is removed from
the surface if the force of
absorption of the particle is higher than the static friction
force between the particle and the
surface. Usually the force needed to remove a particle is very
low due to the minimized contact
area between the particle and the surface. As a result, the
droplet cleans the leaf by rolling off the
surface.
Diagram showing a droplet cleaning a super hydrophobic surface
by rolling off
Due to their high surface tension water droplets tend to
minimize their surface trying to achieve a
spherical shape. On contact with a surface, adhesion forces
result in wetting of the surface: either
complete or incomplete wetting may occur depending on the
structure of the surface and the
fluid tension of the droplet. The cause of self-cleaning
properties is the hydrophobic water-4
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repellent double structure of the surface. This enables the
contact area and the adhesion force
between surface and droplet to be significantly reduced
resulting in a self-cleaning process.
MANUFACTURING METHOD:
The manufacturing of self-cleaning textiles using
nanotechnology:-
Using hydrophobic coatingsthe lotus-effect
Using hydrophilic photo catalytic coatings
Using silver nanoparticles
Using easy to clean finishing
1. HYDROPHOBICCOATINGSTHELOTUS-EFFECT:
THE PHYSICAL BASIS:
Forces acting on a liquid droplet on a solid surface
To understand the physics behind the Lotus-Effect, the roughness
of a surface improves the wet
ability for hydrophilic surfaces Y (< 90). The drop will seem
to sink into the hydrophilic surface. The Y wet ability decreases
for hydrophobic surfaces (> 90). It gets energetically too
expensive to wet a rough hydrophobic surface. The result is an
increased water-repellency.
A droplet on a hydrophilic rough surface seems to sink into the
gaps
A droplet on a rough hydrophobic surface sitting on the
spikes
Theory as to how this hysteresis varies with the chemical and
topological properties of the
surface is still being developed, but ideally hysteresis should
be as close as possible to zero if
drops are to roll easily, at low surface inclination angles.
Because droplets tend to roll only on
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surfaces with very high static contact angles, the requirements
for a self-cleaning hydrophobic
surface, therefore, are a very high static water contact angle,
(< 90) , and a very low roll-off angle, i.e. the minimum
inclination angle necessary for a droplet to roll off the surface.
If the
wetted surface is more energetically favorable than the dry
surface, the static contact angle will
be less than 90 and the surface is termed hydrophilic. If the
dry surface is more favorable, then
the surface is hydrophobic, and its static contact angle will be
greater than 90.
2. HYDROPHILIC PHOTO CATALYTIC COATINGS:
These hydrophilic photo catalytic coatings chemically break down
dirt when exposed to light, a
process known as photo catalysis, although of course it is the
coating not the incident light that
acts as a catalyst.
TITANIUM DIOXIDE: THE ACTIVE PHOTOCATALYST:
TiO2 has been proved to be an excellent catalyst in the photo
degradation of colorants and other
organic pollutants. The fabric is coated with a thin layer of
titanium dioxide particles heaving 20
nanometers diameter. Titanium dioxide is a photo catalyst; when
it is illuminated by light of
energy higher than its band gap, electrons in TiO2 will jump
from the valence band to the
conduction band, and the electron (e) and electric hole (h+)
pairs will form on the surface of the
photo catalyst. The negative electrons and oxygen will combine
to form O2 , radical ions,
whereas the positive electric holes and water will generate
hydroxyl radicals OH. Since both
products are unstable chemical entities, when the organic
compound i.e. dirt, pollutants, and
micro organisms falls on the surface of the photo catalyst it
will combine with O2 - and OH- and
turn into carbon dioxide (CO2) and water (H2O).Since the
titanium dioxide acts as a catalyst, so
it is never used up.
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This coating will react through two distinct properties: photo
catalysis causes the coating to
chemically break down organic dirt adsorbed onto the fabric,
while hydrophilicity causes water
to form sheets rather than droplets contact angles are reduced
to very low values in sunlight
(the coating becomes super-hydrophilic), and dirt is washed
away. Super-hydrophilic state, it is
also non-toxic, chemically inert in the absence of light,
inexpensive, relatively easy to handle and
deposit into thin films Metallic gold or platinum nanoparticles
can assist photo-catalysis in TiO2
by acting as charge separators.
This finish also have anti bacterial properties after having
been subject to 55 washes through
home laundry machine & UV protection characteristics for 20
washes.
OTHER MATERIALS:
Several metal oxides and sulfides, including WO3, ZrO2, ZnO and
CdS, and polyoxometallates.
3. USING SILVER NANOPARTICLES:
A highly water-repellant coating made of silver nanoparticles
that can be used to produce suits
and other clothing items that offer superior resistance to dirt
as well as water and require much
less cleaning than conventional fabrics. Nano-Tex improves the
water-repellent property of
fabrics by creating nanowhiskers, which are made of hydrocarbons
and have about 1/1000 of the
size of a typical cotton fiber. They are added to the fabric to
create a peach fuzz effect without
lowering the strength of cotton.
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While treated textile surface do not adheres the dust particles
hence when water particles rolls
over it dust get washed off.
4. EASY TO CLEAN FINISHES:
ETC-Easy to clean surfaces was water repellent accordingly are
often confused with other self-
cleaning functions such as LOTUS EFFECT. Unlike the latter,
easy- to- clean surfaces are
smooth rather than rough. Surfaces have a lower force of surface
attraction due to a decrease in
their surface energy, resulting in reduced surface adhesion.
This causes water to be repelled,
forming water droplets and running off. Easy-to-clean surfaces
are therefore hydrophobic i.e.
water-repellent and often also oleo phobic i.e. oil repellent,
making them suitable for use in
bathroom.
MECHANISM:
The primary difference here is that easy to clean surface
coatings do not require uv light to function and their hydrophobic
surface properties-as opposed to hydrophilic-cause water to run of
in droplets rather than forming a thin film of water. Water that
runs off inclined ETC surfaces forms droplets, washing away surface
grime in the process.
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ADVANTAGES:
Generally speaking easy to clean surfaces are less susceptible
to dirt accumulation.
The benefit: stress free and easy cleaning, saves time and
cost
LIMITATIONS:
The disadvantage is that droplets dry individually, leaving
behind dirt residues although
these are easy to remove.
When only a small amount of water is involved, droplets of run
off water can form
runaways.
It is therefore necessary to consider where and how the
easy-to-clean function should best
be employed.
As a rule, suitable surfaces should be inclined and exposed to
sufficient quantities of water.
Abrasive detergents and brute force application by cleaning
personnel-in the worst case
both together and not uncommon and with time will damage
OTHER FUCTIONAL FINISHES:
ANTIMICROBIAL FINISH: Silver ions have broad spectrum of anti
microbial activities. 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 two step process.
1. In the first step an emulsified solution of a perfume is
encapsulated with melanin pre-
condensate.
2. 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.
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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 method of producing durable
silver containing antimicrobial
finish is to encapsulate silver compound or nano particle with a
fibre reactive polymer like poly
(styrene co-maleic anhydride).
The treated yarns showed effective anti-microbial activity
against various bacteria, fungi and
Chlamydia that included escherichia coli, citrobacter, and
bacillus subtilis. These finished goods
are used in medical industry as a safe & effective means of
controlling medical growth in the
wound bed.
UV PROTECTIVE FINISH:
The most important functions performed by the garment are to
protect the wearer from the
weather. However it is also to protect the wearer from harmful
rays of the sun. The UV-blocking
property of a fabric is enhanced when a dye, pigment,
delustrant, or ultraviolet absorber finish is
present that absorbs ultraviolet radiation and blocks its
transmission through a fabric to the skin
Metal oxides like ZnO as UV-blocker are more stable when
compared to organic UV-blocking 10
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agents. Hence, nano ZnO will really enhance the UV-blocking
property due to their increase surface
area and intense absorption in the UV region. For antibacterial
finishing, ZnO nanoparticles scores
over nano-silver in cost-effectiveness, whiteness, and
UV-blocking property.
INNOVATION IN SELF CLEANING FINISHES
SELF-CLEANING WOOL AND SILK:
Soon garments made of wool and silk may need no dry cleaning or
other special treatment in
order to remove marks and stains just expose them to sunlight.
It is all due to a nano particle
coating. For that, nano titanium dioxide that are four to five
nanometers in size. These fibers are
made of a protein called keratin, which does not have any
reactive chemical groups on its surface
to bind with titanium dioxide. So it is more difficult to
process. The researches chemically
modify the surface of wool fibers, adding chemical groups called
carboxylic groups, which
strongly attract titanium dioxide. Then they dip the fibers in a
titanium dioxide nanocrystal
solution. Titanium-dioxide-coated wool shows almost no sign of
the red stain after 20 hours of
exposure to simulated sunlight. Other stains disappear faster:
coffee stains fade away in two
hours, while blue-ink stains disappear in seventeen hours.
PHOTO CATALYTIC DEGRADATION OF ODORS COMPOUND:
A photo catalytic acrylic fiber SELFCLEAR yarn with
higher-dimensional self-cleaning
properties which had been exclusive with conventional photo
catalytic fibers, and started
recently sailing their product for manufacture of clothing,
sportswear, uniforms, bedding,
carpets, and daily goods. Because titanium oxide is applied into
SELFCLEAR yarn, it has a
higher self-cleaning activity with deodorant, antibiotic, and
anti-soiling properties as well as
excellent functional stability, as compared to fabrics using a
conventional photo catalytic
reaction.
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CHARACTERISTICS OF SELF CLEANING GARMENTS:
1. Another plus is that they can be permanently attached to the
garments fibers without
altering its texture or feel.
2. The self-cleaning clothes can also help conserve a
considerable amount of water and
energy that is normally utilized during the cleaning
process.
3. Self-cleaning property will become a standard feature of
future textiles and other
commonly used materials to maintain hygiene and prevent the
spread of pathogenic
infection.
4. The lotus leaf nanostructure and nano titanium dioxide
coating built on fabric can defend
and decompose stains, dirt, odours, bacteria, harmful gases, and
highly water and oil
repellent.
5. Self-cleaning garment can effectively reduce the laundering
process so as to protect the
environment.
6. The self-cleaning garment also possesses excellent UV
protection property. The
treatment has excellent durability towards washing and normal
usage without sacrifices
the soft hand and breathability of textile fabrics.
7. A polymer film mixed with silver nanoparticles -- can be
permanently integrated into any
common fabric, including silk, polyester and cotton.
8. In the long run, it can save time and money by reducing
expensive dry cleaning bills. It is
also environmentally friendly
9. Saving time and laundering cost.
10. This technology embraces environmental friendly
properties.
11. The crease resistant feature keeps clothing neat.
12. Garments stay bright, fresh looking and are more durable
than ordinary materials.
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The economic significance of the self cleaning textiles can be
outlined as follows:
1. Ease of maintenance and environmental protection because of
reduced cleaning efforts
2. Time, material, energy reduction and consequently
cost-efficiency during production
3. Makes textiles longer-lasting
4. People need not to suffer from heavy laundry bills.
5. Improved ageing behavior by extended surface purity
effect.
FUTURE WITH SELF-CLEANING GARMENTS:
The ultimate consequence in developing these self-cleaning
fabrics is that we can really limit our
use of things like chemicals, energy and water. That offer
superior resistance to dirt as well as
water and require much less cleaning than conventional fabrics.
Currently, industrial testing and
mill trials of this patent-pending technology are being
conducted. It is anticipated that as soon as
the technology receives the approval technically and
economically, self-cleaning property will
become a standard feature of future textile and other commonly
used materials to maintain
hygiene and prevent the spreading of pathogenic infection. The
coating could be applied to suits,
hospital garments, sportswear, military uniforms and outdoor
fabrics. It could appear in
consumer products within five years.
AREAS OF APPLICATION:
Medical textiles e.g. Hospital garments Sport tech e.g. Athletic
wear Defense textile e.g. Military uniforms Smart textiles
Upholstery under garments
PROBLEMS WITH SELF-CLEANING FABRIC:
The main reasons that self-cleaning fabrics require a lot of
time to break down stains is because
Titanium dioxide is very inefficient at using energy from
sunlight. Excitation of electrons to the
conduction band is only the beginning of the cleaning process.
These electrons must then react
with oxygen atoms, which then react with the dirt particles. All
of these reactions are limited by
access to and the amount of freed electrons in the titanium
dioxide. So for a large stain, a lot of
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light energy is needed before the fabric can fully break it
down. And also batch processing of a
hydrophobic material is a costly and time consuming
technique.
RECOMENDATION:
Super hydrophobic materials, which repel water, are typically
good at removing dirt particles but
don't deal with oils well. Materials that repel oil might not
work with certain types of oil. The
titanium-dioxide-coated materials, on the other hand, will not
work unless they are exposed to
sunlight for hours. Prices of clothing and other products
treated with the new coating will
initially be a bit more expensive than other water-repellant
garments; researches are currently
working on ways to make the coating cheaper. Further research
would be required to test ways of
applying titanium dioxide nanofilms to other textiles.
CONCLUSION:
The realization of self-cleaning properties on textile surfaces
by using the nanotechnology
includes a vast potential for the development of new materials
or new products and applications
for known materials. The opening of new application fields for
textiles will lead to a new growth
stage. For the growing market of technical textiles a further
increase in production volume, sales
and application fields can be expected by successful transfer of
the self cleaning effect on textile
materials. Structure based soil and water-repellent properties
lead to an efficient use of materials
and are therefore in agreement with the principles of
sustainable development. The use of a self-
cleaning coating is attractive as they are labor saving and
effectively improve the appearance of
the environment. In the long run, it can save time and money by
reducing expensive dry cleaning
bills. It could take about five years for the retail market for
self-cleaning clothes and linens to
launch as the technology still needs refining.
REFERRENCES:
www.fibre2fashion.com\technical textile\self cleaning finishing
www.proquest.com\selfcleaningofcotton
http://textileinfo.com/en/tech/nanotex www.textileinfo.com
www.iir-germany.com/nanotrends/ http://www.lotusan.de/ (in German).
http://www.activglass.com/index_eng.htm. http://www.ppg.com/. A.
Marmur, Langmuir, 2004, 20, 3517.
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W. Extrand, Langmuir, 2002, 18, 7991. Neinhaus and W. Barthlott,
An. Bot., 1997, 79, 667. Eur. Pat., EP 0772514, 1998. S. R.
Coulson, I. Woodward, J. P. S. Badyal, S. A. Brewer and C. Willis,
J. Phys. Chem. B, 2000, 104, 8836. A. B. D. Cassie and S. Baxter,
Trans. Faraday Soc., 1944, 40, 546. J. Bico, C. Marzolin and D.
Quere, Europhys. Lett., 1999, 47, 220. S. Shibuichi, T. Onda, N.
Satoh and K. Tsujii, J. Phys. Chem.