UTTAR PRADESH TEXTILE TECHNOLOGY INSTITUTEKANPUR

SUBMITTED TO – PRESENTED BY -

SHIV KUMAR KANNAUJIYA

Dr. MUKESH KUMAR SINGH HIMANSHU JAISWAL

ARUN KUMAR

ABSTRACT

Currently, there are three techniques available for the synthesis of nanofibers

1. electro spinning, 2. self-assembly, and 3. phase separation.

Of these techniques, electro spinning is the most widely studied technique and

has also demonstrated the most promising results in terms of tissue engineering

applications .

The availability of a wide range of natural and synthetic biomaterials has

broadened the scope for development of nanofibres scaffolds, especially using the

electro spinning technique.

The three dimensional synthetic biodegradable scaffolds designed using

nanofibers serve as an excellent framework for cell adhesion, proliferation and

differentiation.

Keywords: electro spinning, phase separation, self-assembly, nanofiber,

biomaterial, tissue engineering, scaffold, drug delivery.

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INTRODUCTION

The nonwoven industry generally considers nanofibers as having a diameter of less than

one micron, although the National Science Foundation (NSF) defines nanofibers as

having at least one dimension of 100 nanometer (nm) or less. The name derives from the

nanometer, a scientific measurement unit representing a billionth of a meter, or three to

four atoms wide. Nanofibers are an exciting new class of material used for several value

added applications such as medical, filtration, barrier, wipes, personal care, composite,

garments, insulation, and energy storage. Special properties of nanofibers make them

suitable for a wide range of applications from medical to consumer products and

industrial to high-tech applications for aerospace, capacitors, transistors, drug delivery

systems, battery separators, energy storage, fuel cells, and information technology .

Generally, polymeric nanofibers are produced by an electro spinning process . Electro

spinning is a process that spins fibers of diameters ranging from 10nm to several hundred

nano meters . This method has been known since 1934 when the first patent on electros

pinning was filed. Fiber properties depend on field uniformity, polymer viscosity, electric

field strength and DCD (distance between nozzle and collector). Advancements in

microscopy such as scanning electron microscopy has enabled us to better understand the

structure and morphology of nanofibers.

At present the production rate of this process is low and measured in grams per hour.

HYSTRY OF NANOFIBRES

The first attempts at nanofiber production were carried out between 1934 and 1944.

Formhals published the first patent at this time describing the experimental production of nanofibers.

The next step was taken in 1966 by Professor Harold L. Simons, who patented an instrument for producing ultra-thin and ultra light nanofibersfabrics with various patterns.

In 1971 Professor Peter K Baumgartner made a device for the spinning of acrylic fibers with a diameter of 0.05 – 1.1 microns. The work of these inventors, and in particular their followers Professors Darrell.

The first technology enabling the production of nanofibers appeared on the global market in the 1980s. Donaldson, one of the leading companies in nanofibers based applications brought out the nanofibers first time for advanced commercial applications such as air filtration technology in 1981. The nanofibers presence showed apromise in reducing operating costs and improved efficiency.

ELECTROSPINNING PROCESS

The process makes use of electrostatic and mechanical force to spin fibers from the tip

of a fine orifice or spinneret. The spinneret is maintained at positive or negative charge

by a DC power supply. When the electrostatic repelling force overcomes the surface

tension force of the polymer solution, the liquid spills out of the spinneret and forms an

extremely fine continuous filament.

It has the misleading appearance of forming multiple filaments from one spinneret

nozzle, but current theory is that the filaments do not split.

These filaments are collected onto a rotating or stationary collector with an electrode

beneath of the opposite charge to that of the spinneret where they accumulate and bond

together to form nanofiber fabric.

The distance between the spinneret nozzle and the collector generally varies from 15–30

cm.

The process can be carried out at room temperature unless heat is required to keep the

polymer in liquid state.

The final fiber properties depend on polymer type and operating conditions. Fiber

fineness can be generally regulated from ten to a thousand nanometers in diameter .

POLYMER-SOLVENTS USED IN ELECTROSPINNING

The polymer is usually dissolved in suitable solvent and spun from solution.

Nanofibers in the range of 10-to 2000 nm diameter can be achieved by choosing the

appropriate polymer solvent system .

POLYMER SOLVENTS

Nylon 6 and nylon 66 Formic Acid

Polyacrylonitrile Dimethyl formaldehyde

PET Trifluoroacetic acid/Dimethyl chloride

PVA Water

Polystyrene DMF/Toluene

Nylon-6-co-polyamide Formic acid

Poly benzimidazole Dimethyl acetamide

Polyramide Sulfuric acid

Polyimides

Phenol

POLYMER SOLVENTS

Nylon 6 and nylon 66 Formic Acid

Poly acrylonitrile Dimethyl formaldehyde

PVA Water

Polystyrene DMF/Toluene

Nylon-6-co-polyamide Formic acid

Polyramide Sulfuric acid

Polyimides Phenol

NANOFIBERS FROM SPLITTING BICOMPONENT FIBERS

As described above, nanofibers are also manufactured by splitting of bicomponent fibers; most often bicomponent fibers are used in this technique are islands-in-a-sea, and segmented pie structures. Bicomponent fibers are split with the help of the high forces of air or water jets.

Figure shows the bicomponent nanofiber before and after splitting.

A pack of 198 filaments in single islands is divided into individual filaments of 0.9 μm. In this example, Hills Inc has succeeded in producing fibers with up to 1000 islands at normal spinning rates. Furthermore bi-component fibers of 600 islands have been divided into individual fibers of 300 nm .

PROPERTIES OF NANOFIBERS

Nanofibers exhibit special properties mainly due to extremely high surface to weight ratio

compared to conventional nonwovens.

Low density, large surface area to mass, high pore volume, and tight pore size make the

nanofiber nonwoven appropriate for a wide range of filtration applications

In Figure 1 shows how much smaller nanofibers are compared to a human hair, which is

50-150 μm.

Figure 2 shows the size of a pollen particle compared to nanofibers.

The elastic modulus of polymeric nanofibers of less than 350 nm is found to be 1.0±0.2

Gpa. figure1 figure 2

APPLICATIONS OF NANOFIBERS

1 FILTRATION-

Nanofibers have significant applications in the area of filtration since their surface area is

substantially greater and have smaller micro pores than melt blown (MB)webs.

High porous structure with high surface area makes them ideally suited for many

filtration applications.

Fibre type Fibre sizeIn micrometre

Fibre surface area per mass of fibre material m2/g

Nanofibers 0.05 80

Spunbond fiber 20 0.2

Melt blown fiber 2.0 2

2. MEDICAL APPLICATION

Nanofibers are also used in medical applications, which include, drug and gene delivery,

artificial blood vessels, artificial organs, and medical facemasks.

For example, carbon fiber hollow nano tubes, smaller than blood cells, have potential to

carry drugs in to blood cells.

Nanofibers and webs are capable of delivering medicines directly to internal tissues.

Anti-adhesion materials made of cellulose are already available from companies such as

Johnson & Johnson and Genzyme Corporation .

Researchers have spun a fiber from a compound naturally present in blood. This

nanofiber can be used as varieties of medical applications such as bandages or sutures

that ultimately dissolve in to body. This nanofiber minimizes infection rate, blood lose

and is also absorbed by the body.

Nanofibers and business

Nanofibers offer hope in finding solutions for fundamental problems in the development of human society – the cleaning and production of drinking water, mobile sources of energy, batteries enabling advanced energy storage.

These are problems which directly concern millions of people.

this huge potential demand represents a great business opportunity.

Demand for products containing nanofibers is expected to grow by as much as 40%.

The business potential of nanofibers is further enhanced by the fact that, unlike nanoparticles, nanofibers with dimensions over 100 nm are not regulated, even in the EU, and are potentially suitable for use in the food industry .

It play crucial part in industry economy….

Events Expert Services

Company Profiles Researchers Profiles

Liquid Filtration Environment

Energy Advanced Materials

Food and Packaging Health & Personal Care

CHALLENGES IN NANOFIBERS

The process of making nanofibers is quite expensive compared to conventional fibers due

to low production rate and high cost of technology.

In addition the vapors emitting from electro spinning solution while forming the web

need to be recovered or disposed of in an environmental friendly manner.

This involves additional equipment and cost.

The fineness of fiber and evaporated vapour also raises much concern over possible

health hazard due to inhalation of fibers.

Thus the challenges faced can be summarized

1 economics

2 health hazard

3 solvent vapour

4 packaging shipping handling

CONCLUSSION

Mimicking the architecture of ECM is one of the major challenges of tissue engineering.

Amongst all the approaches used to prepare ECM synthetically, the approach using

nanofibers has shown the most promising results.

Nanofibers can be formed using either one of the three prevailing techniques: electro

spinning, self assembly, or phase separation. Electro spinning is the most widely studied

technique and has also shown the most promising results.

The availability of a large range of natural and synthetic biomaterials has fueled the area

of nanofiber synthesis, especially using the electro spinning technique.

REFERENCES

1. Textile World “Nano Technology and Nonwoven”. P52, November 2003.

2. Gajanan Bhat and Youneung Lee, “Recent advancements in Electrospun nanofibers.”

Proceedings of the twelfth international symposium of Processing and Fabrication of

Advanced materials, Ed TS Srivatsan & RA Vain, TMS, 2003.

3. Electrostatic spinning of Nanofibers spin Technologies, Chattanooga, TN.

4. Www.nano21c.com, Nano Techniques Co., Ltd. “Mass production of Electro spun

Nanofibers for filtration

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