Micro Encapsulation of Nanoparticles in Textiles

Micro encapsulation of nano particles may be defined as the process of surrounding or enveloping one substance within another substance on a very small scale, yielding capsules ranging from less than one nanometer to hundred nanometers in size. All three states of matter (solids, liquids, and gases) may be microencapsulated. This allows liquid and gas phase materials to be handled more easily as solids, and can offered some measure of protection to those handling hazardous materials.

The encapsulated particles produce their required effect when their core material is released. The nano capsules which are encapsulated can be used for producing special properties such as anti-microbial finishes, flame retardant finishes, fragrance finishes, PCM's (Phase Change Materials), stain resistant finishes and the very latest nano based process of yarn formation. Although it was known long back from the 1940's, its application in textiles did not gain much prominence since the 1980's. Gone are the days when textiles were limited to just a clothing. Today, it's just a clothing no more than a piece of properly entangled fibres.

The trend is towards smarter textiles. Imagine your cloth actually speaking to the environment and adjusts it according to the environmental conditions. The future holds ample opportunities for such type of innovations.
The advantage in using nano technology is that when the particles (for example, TiO2) are synthesized to a nano level, their property gets enhanced to a bigger extent than when they are used at the surface level. So, the micro encapsulation of these nano particles give a pronounced effect which is incomparable to the extent that the fabrics meant for this purpose is useless without the effect of both microencapsulation and nanotechnology.

INTRODUCTION

Microencapsulation of particles (en general), is used to give pronounced effect to the fabric. The properties imparted to the fabric by the encapsulation cannot be found in normal fabrics. Micro encapsulation may be achieved by a myriad of techniques, with several purposes in mind. Micro encapsulation processes are classified as mechanical might involve or even rely upon a chemical reaction, and some chemical techniques rely solely on physical events.

Microencapsulation can achieve several effects:

Antimicrobial fabrics: what these do is destroy micro-organisms penetrating the fabric;

Fresh fabrics: the purpose of these is to create a fresher effect and be more pleasant to the touch;

Cosmeto-textiles: these share the same objectives as cosmetics? To protect the skin from external agents;

Photo chromic textile: these are textiles that change color when exposed to certain light sources;

Thermo chromic textiles: these change color when the outside temperature changes.

The recently developed microencapsulation technology allows active compounds to be isolated by means of a spherical natural membrane. The small size of the microcapsules (between 5 and 20 microns in diameter) means that they can be applied to fabrics through ennobling processes, which in turn means that the microcapsules are able to release the active components encapsulated in them gradually and appropriately.

Micro encapsulation of nano particles can be broadly classified into 2 types

The various applications of microencapsulation of nano particles are discussed in the following paper.

YARN FORMING TECHNIQUES:

This is one the latest ventures among the advances in nano technology. Apart from the traditional and the modern spinning processes, nano technology is primarily used for the production of fancy yarns.

The principle of encapsulating the nano particles is most prominent in the electro spinning process (producing nanofibres from conducting and non conducting polymers).

The electro spun fiber can be fed in an air vortex spinning apparatus developed to form a linear fibrous assembly. The vortex of air provides a gentle means to convert a mixture of the fibril fed directly or indirectly into an integral assembly with proper level of orientation. The resulting linear assembly of fiber or yarn will be a hybrid of nano and micro fibers with a strong core filament, thus combing texture surface and strength in one assembly.

FINISHING OF FABRICS:

The technique has made considerable progress in the fields

Of phase-change materials for thermoregulation,

In aromatherapy,

And in the controlled release of fragrances.

A new field is opening up for cosmeto-textiles which are capable of imparting skin care benefits, combating ageing, and promoting a feeling of wellness or well-being.

Anti-microbial finish offer great potential for freshness retention during wear for intimate apparel, and for garments worn during periods of strenuous activity.

The controlled release of active substrates also offers opportunities in the medical textiles field. Insect-repellent and insect-resist treatments demonstrate higher levels of performance if microencapsulated.

PROCESS OF MICROENCAPSULATION:

Microencapsulation is a technique by micro packaging the active material and protecting from external environment till required, to affect the controlled release at the right time to facilitate the special finish. microcapsules are prepared by using the agent1 as core material and agent2 as wall material at different ratios by various techniques. The core material and the microcapsule is held together by means of binders which are welded to the fabric at specific conditions (depending upon the type of and nature of usage of the fabric)

It involves depositing microcapsules onto a yarn or fabric containing a slow-release
active agent. For these active agents to make a mark on the fabric, certain conditions are to be met (again depending upon the nature and type of end usage). Some active agents can be activated by washing the fabric, heating it a little above room conditions and by repeated usage of the fabric. The resulting micro encapsulated yarn or fabric using nano particles is shown in the following figure.

Figure (A) shows the nano particles on the surface of the fabric or yarn when it is in the first stage of encapsulation. Figure (B) shows the fabric or yarn after the treatments (washing, heating), which clearly indicates a significant change in appearance. The nano particle is welded onto the fabric more deeply and has started to produce the required finish.

APPLICATIONS

Micro encapsulation of Phase Change Materials(PCM's):

Broadly speaking, micro encapsulation may be defined as a micro packaging technique, wherein an active core material is encapsulated in a polymer shell of limited permeability. This technology enables us PCM's to be incorporated in textiles. These waxes are enclosed in a protective envelope in tiny microcapsules of a few nanometers diameter. During encapsulation PCM is put into particulate form and then coated with reactive monomer such as ethylene diammine. There the monomer-coated particulates of PCM are reacted with polymers, to form electrometric condensation polymeric shell. This prevents leakage during the fluid phase and garment remains resistant to laundering. Cleaning and exposure to the element. These microcapsules of PCM's can be incorporated in fibers, coatings and in foam.

In order to produce a microencapsulated PCM some of the following criteria had to be met:

1.Particle size

2.Uniformity of particles

3.Stability to mechanical action and chemicals

4.Core-to-shell ratio, with PCM content as high as possible

Anti microbial finish:

There are 2 types of anti microbial finishes commercially viable

Aloe Vera

Silver
Aloe Vera:

One of natures most effective skin treatments

Aloe Vera contains 75 nutrients, 200 active compounds, including 20 minerals, 18 amino acids, and 12 vitamins.

Benefits of using micro encapsulated Aloe Vera:

Stimulates cell growth and enhances the restoration of damaged skin

Moisturizes skin because of its water-holding capacity

Cools the skin

Primitive unicellular micro-organisms

Multiply very fast - as fast as double every 20 minutes

Cause odours and staining

Gram positive and negative

In its natural form, your clothes can actually promote microbe growth (humid, moist areas) resulting in infections ranging from the minor such as odor-causing and stain-causing to painful infections (foot fungus from socks) to the really harmful disease causing microbes.

Microbes can grow on the inside (the textile surface in contact with skin) and on the outside (microbes from external surroundings)

Health and hygiene conscious We don't have time to fall sick

Silver:

Most biocides only impact one cellular function

Silver can disrupt cell growth by multiple means

Modification of Plasma Membrane

Interferes with DNA and RNA functionality

Blocking of thiol groups on proteins and enzymes

Ag acts as efficient Biocide.

Why silver?

Need for Antimicrobial Finish:

Important for general textiles and high performance applications where the chance of microbial growth is high.

Antimicrobials fabrics gained significant importance due to its wide acceptance as surgical apparels, baby clothing and undergarment

Need for Herbal Antimicrobial Finish:

There are number of commercial antimicrobial agents, but their compliance with the regulation imposed by international bodies like EPU is Critical issue.

There is significant development in investigation of Eco-friendly, Natural Antimicrobial finish for application on textile substrate.

Anti bacterial activity of herbal micro encapsulated fabric:

Stain resistant:

Using nanotechnology, unique and permanent stain resistant finishes are being developed. Nanotechnology is defined as the precise manipulation of individual atoms and molecules to create layered structures. Nanosize particles can exhibit unexpected properties different from those of the bulk material. The basic premise is that properties can dramatically change when a substance's size is reduced to the nanometer range. For example, ceramics which are normally brittle can be deformable when their size is reduced. In bulk form, gold is inert; however, once it is encapsulated into small clusters of atoms it becomes highly reactive.

The lotus concept:

Scientists have looked to nature for inspiration. Studying the surface of lotus leaves, which have an incredible ability to repel water, scientists have developed a finish that has superior stain resistant qualities.

The surface of the lotus leaf appears smooth but is actually rough and naturally dirt and water repellent. The rough surface reduces the ability of water to spread out. Tiny crevices in the leaf's surface trap air, preventing the water droplets from adhering to the service. As droplets roll off the surface they pick up particles of dirt lying in their path. Using this same concept, scientists have developed a finish that forms a similar structure on the fibers surface. Fabrics can be cleaned by simply rinsing with water.

Companies have developed a treatment called Resists Spills. After the treatment is applied the fabric becomes both liquid repellent and stain resistant. Without ever penetrating the fabric, liquids such as coffee, wine, water and salad oil bead up and roll off the fabric.

Fragrance fabrics:

This microencapsulation process has led to the emergence of fragranced fabrics, with miniscule capsules of perfume

To protect the active core material from the environment

To affect controlled release of the active core

To deliver durability of the effect

Clothes that provide

Care

Freshness

Comfort

Protection

Micro-encapsulation involves depositing nanocapsules onto a yarn or fabric containing a slow-release active agent. This process has led to the emergence of fragranced fabrics, with nanocapsules of perfume

To protect the active core material from the environment

To affect controlled release of the active core

To deliver durability of the effect

CONCLUSION

The applications discussed are just a pin example of the activities taking place in the nanotechnology era. Apart from the discussed, in the medical field, the use of microencapsulated insulin which is slowly injected into the body through bandages is prepared by the principle of microencapsulation of nanoparticles. The fragrance fabrics are used to improve the freshness of the wearer and such type of fabrics are often preferred by the married couple on their wedding day. Stain resistant dhotis were common a long back even during the 90s. The main objective of using the nano particles is their overwhelming surface characteristics. In short,

a nanotextile is smart, short and sweet!!!!!!!!

References

1.http://www.tex.in/

2.http://www.nano-tex.com/faqs/faqs.html/

3.http://www.csiro.au/csiro/content/standard/ps6c.html

4.www.fibrelink.com

5.Havenith, G. (2001) -Temperature Regulation In The Elderly- Improving Comfort And Reducing Morbidity And Mortality Using Modern Technology. Gerontechnology, 1, sept 2001 pp 41-49

6.Shim H and McCullough AE: The effectiveness of phase change materials in outdoor clothing; Arbete och Hlsa 2000, 8: 90-94

7.Comfort properties and Human performance of textiles, Y.LI.., Textile Institute

8.Nanofinishing, Advances in Textiles Technology, NOV, 4-5, 2002

9.The features of nano fabric, ATA Journal, 15(5), 40, 2004

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About the author:

V. Anush Gurunath & S. Padagalingam are in the Department of Textile Technology, PSG College of Technology, Coimbatore-641004

Gopalkrishnan - I am doing PG Diploma in Home Textile Management. I did my Diploma in Textile Technology & B. Tech in Textile Technology from PSG College of Technology & Polytechnic College. After my diploma I worked as a Production & maintenance Supervisor in Cambodia Mills (NTC) Coimbatore, after three years of experience I came back to my B. Tech. I did 17 paper presented in various technical symposiums, national & international conferences in all over India and i participated in various technical workshops & innovative project works. I published several articles in journals, magazines.

Area of Interest: innovative textiles, Technical textiles
Coimbatore - 641 004, Email: dgk_psgtech@yahoo.co.in