ABSTRACT:
Textiles
have function of second skin enabling human to living extreme conditions. At
the same time consumers have increasingly aware of risk the garments make cause to human health. The consciousness
on the health among mankind increased urge for the developments of an antimicrobial
finished textiles and infection free clothing. This articles has dealt with the
impotence of silver based anti microbial finish, how it is done presently
and merits & future scope of silver
based antimicrobial finish.
WHAT ARE MICROBES?
Microbes are
the tiniest creatures not seen by the naked eye. They include a variety of
micro-organisms like Bacteria, Fungi, Algae and viruses. Bacteria are
uni-cellular organisms which grow very rapidly under warmth and moisture.
ANTI-MICROBIAL FOR GARMENTS:
The
main reason for treating garments with antimicrobial control of perspiration odours. As the bacteria reproduced
they give off gases which are familiar perspiration odour. Treating fabric with
anti microbial means, that bacteria which have been transferred from the skin
or the environment do not reproduce in the fabric. The reduction in bacteria
means the volume of gas given off will be much smaller than an odour will not
develop.
NECESSITY OF ANTIMICROBIAL FINISHES:
Antimicrobial treatment for textile
materials is necessary to fulfil the following objectives:
Ø To avoid cross infection by pathogenic
micro organisms;
Ø To control the infestation by microbes;
Ø To arrest metabolism in microbes in
order to reduce the formation odour; and
Ø To safeguard the textile products from
staining, discolouration and quality deterioration.
SILVER BASED ANTI
MICROBIAL:
Among the various antimicrobial
agents used for the finishing of textile substrates, silver or silver ions have
long been known to have strong inhibitory and bacterial effects as well as a
broad spectrum of antimicrobial activities. The inhibitory effect of silver
ion/ silver metal on bacteria has been attributed to the interaction of silver
ion with thiol groups in bacteria as well as to the oxidative destruction of
micro organism in aqueous medium. Silver ion based antimicrobial finishes have
been developed by the interaction of a silver salt such as silver nitrate with
anionic co polymer of styrene, ethyl acrylate , acrylic acid and divinyl
benzene having at least support about 0.008 meter equal of carboxylic group per
gram of polymer and ≥ 0.0009 mol of
silver per gram of the polymer. The films of such polymeric finishes release
anti bacterial and anti fungal silver ions slowly over a very long period of
time.
In
another patent, it is disclosed that a silver containing anti microbial agent
that has affinity for textile fibres can be produced by treating cross- linked
carboxyl methyl cellulose having greater than 0.4 carboxyl methyl group with
silver nitrate. The anti microbial finishing agent may have 0.01 to 1 % silver bound to the water resistant cross
linked CMC (Ag.)
Milliken
& company have developed a silver antimicrobial agent. That name is Alphasan™
by forming a complex of silver with zirconium phosphate. Other silver
containing antimicrobial are silver substituted zeolite available from sinanen
under the trade name Zeomic™ AJ, and silver subsisted
glass available from the Ishizuka glass under
the trade name Ionpore™. This compound can be applied on the fabrics by exhaustion
with a dye solution. The antimicrobial fabric thus produced on finishing with
and acrylic co polymer makes the antimicrobial finish more durable.
Another method of producing durable silver
containing antimicrobial finish is to encapsulate a silver compound is nano
particle with a fibre reactive polymer. The resulting micro nano capsules when
applied to a fabric, reactive with it and thus provide durable silver based
anti microbial finish. The micro encapsulation of the nano particles may be
carried out in different ways. For instance, for producing micro capsules of
water soluble products, the product may first be dissolved in water and
subsequently emulsified after adding an emulsifier and oil soluble
encapsulating monomers or oligomer or polymers. On polymerization and
cross-linking, the resulting shell encapsulate the water soluble product. One of
the fibre reactive polymers used for this purpose is poly (styrene co –maliec anhydride).
Yang
has patented the a process for preparing a
silver nanoparticles containing functional microcapsule having the intrinsic
antimicrobial and therapeutic functions of silver as well as additional
functional of the products contained in the inner core of the capsule. Such
microcapsule can be prepared by a two-step process. In the first step an
emulsified solution of a perfume is encapsulated with melanin precondensate.
The microcapsule so produced is treated with silver nanoparticle dispersed in water-soluble
styrene maleic anhydride polymer solution before it fully dries. Thus
microcapsules with duel function are produced. In these microcapsules, the
silver nanoparticles are on the surface of the capsule (Fig. 1), Instead of a
perfume, one can have a thermo
sensitive pigment, thermal storage material or pharmaceutical preparation
in the inner core.
Fig: 1 Structural view of a
Silver nano particle containing functional microcapsule
(a). Microcapsule (b). Inner core contains functional substance such as perfume, a thermo
sensitive pigment, thermal storage material or pharmaceutical preparation and
(c). Inner shell.
In
a chemical reduction method of producing highly concentrated stable dispersions
of nano sized silver particles; silver nitrate is reduced with ascorbic acid to
precipitate metallic silver in acidic solutions according to following
reaction:
2Ag+
+ C6H8O6 ¨ 2Ag0 + C6H6O6
+ 2H+
Anti
microbial fabrics made from cotton, linen, silk, wool, polyester, nylon, or
their blends having nano silver particles can be produced by immersing them in
nano silver particle- containing solution producing by reducing silver nitrate
with glucose and drying at 120 0 to 1600C for about 40 – 60 min. The
treated fabrics were yellow orange colour. Electron microscopic studies of the
antimicrobial fabric indicate that the fabric samples contained nano silver
particles which were evenly distributed and contained particles that were
mostly bellow or about 10 nm size. Chemical testing indicated that the silver
content in the fabrics was about 0.4-0.9 % by weight. The treated fabrics
showed effect anti microbial activity against various bacteria, fungi,
Chlamydia, that included.
Silver-containing
antimicrobials have been incorporated into wound care devices and are rapidly
gaining acceptance in the medical industry as a safe and effective means of
controlling microbial growth in the wound bed, often resulting in improved
healing. It is known that placing surface- available silver in contact with a
wound allows the silver to enter the wound and become absorbed by undesirable
bacteria and fungi that grow and prosper in the warm moist environment of the
wound site. Once absorbed, the silver ions kill microbes , resulting in
treatment of infected wounds or the prevention of infection in at risk wounds.
Some of the commercial silver antimicrobial wound care products are Acticoat™,
Actisorb™ And Silverlon™.
ADVANTAGE OF SILVER CONTAINING ANTI MICROBIAL
Generally
silver based antimicrobial have more advantages compare to other antimicrobial
agents, there are given bellow. Control of a wide range of bacteria
perspiration by consumer as very safe able to withstand temperature of 400 to
5000 C for polymer
applications;
Silver based antimicrobials works in three ways and
a bacterial cell
i.
Reaction with thiol groups on proteins and enzyme
ii.
Interference with DNA
& RNA functionality
iii.
Modification of the plasma membrane of the cell
Because
there are three separate modes of activity, it is difficult for a bacterial cell
to develop resistance to silver based antimicrobials. It is almost impossible
for a cell to adapt to all three methods of attack.
CONCLUSION:
Generally
silver based antimicrobial agents have more cost compare to other antimicrobial
agents but it have more desirable properties like durability, very good control of a wide range of bacteria
perspiration and etc, so now people are
more considering about the quality rather than any other things like cost ,etc
of the products, so these silver based anti-microbial finished materials will
going to take very good place in future days.
REFERENCE:
- http://www.japoncorp.net/article.asp?art_ID=11589
- ML
Gulrajani / nano finishing /IJF&TR/ Pp197-199
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