Polymeric nanofibers production

(except electrospinning)

Eva Košťáková

KNT, FT, TUL

Possibilities of polymeric nanofibers productions

- Drawing

- Template Synthesis

- Phase Separation

- Self-Assemby

- Melt-blown technology

- Production of bi-component fibers - Type "Islands-in-the-sea"

- Forcespinning

- Electrospinning

Drawing

A small drop from whose county is using a

micropipette and micromanipulator forced out of

nanofiber.

Speed extracting fibers must be about 10-4 ms-1

Discontinuous process.

Only laboratory technology

Unable to control the dimensions of the fibers.

Fiber diameter from 2-100nm up to several micrometers; length from 10m to several centimeters

Drawing

Appeared in Applied Physics Letters, vol. 89, no.18, pp. 183105-7, 2006

Drawing (TUL – Jana Bajáková)

Drawing – thread – TUL (Jana Bajáková)

Drawing - TUL (Jana Bajáková)

Drawing - TUL (Jana Bajáková and Lukáš Stanislav

micromanipulator - VIDEO

Template Synthesis

Use templates or membranes to obtain the nanofiber materials.

Only for laboratory production

Ability to manage fiber diameters

Membranes made from special materials - such as metal oxides (alumina).

Example PAN in DMF – diameter cca 100nm, fiber length cca 10m.

Self-Assembly

Building nanowires of smaller molecules such as in

the kit!

Usually concentric arrangement of "giant-molecule"

= nanofibers.

Only laboratory production

Inability to control dimensional nanowires (only

certain ranged between diameters and lengths)

Very fine fibers (7-100nm in diameter;

hundreds of nanometers in length - 20 micrometers

Phase Separation

The production process Creating a homogeneous solution.

A small amount (2 ml) solution poured into a

teflon container.

Achieving gelation temperature, which depends

on the concentration of polymer in solution.

The solvent was eluted with water.

Remove the gel from the container and dried

using the freeze-drying (freeze-drying).

Eg. it is possible to use polylactic

acid, and the solvent tetrahydrofuran

Not suitable polymers = non-fibrous structure

Phase Separation

Only laboratory production.

Inability to control dimensional nanowires (some

ranged between diameters and lengths).

DIRECTLY TO MAKE nanofiber layer.

It is possible to use only some of the polymers.

Less demanding for equipment.

50-500nm in diameter, porous structure with a

network of "endless" filaments.

Melt-blown Technology

http://www.hillsinc.net/nanomeltblownfabric.shtml

Only special types of polymers (eg high MFI polypropylene) - diameter about 250nm;

rather filaments

MFI is usually higher then for microfiber materials production by melt-blown

technology (more then 1000)

Industrial production

http://www.kasen.co.jp/english/product/line/work.html

http://www.engr.utk.edu/mse/Textiles/Melt%20Blown%20Technology_files/image009.jpg

Technologie Melt-blown

using high MFI (vysoký index toku) polypropylene

Meltblowing Another method that Hills, Inc. uses to produce nanofibers involves using a

meltblowing technique. Hills uses a proprietary design to make die with 100 holes

per inch that can be used At 1500 psi. The overall production rate per length of

the spin pack is the same as standard meltblowing. With this technology, the L/D of

the capillaries is increased to 30, and the resulting pressure drop increases from the

standard 40 psi to several hundred psi or greater. As a result, the average melt

blown fiber size is greatly reduced and the rangeof the fiber size is also reduced. In

this technique the spin hole diameters are in the range of 0.10 to 0.15 mm; therefore,

the polymer must have a MFI of 1000 or greater and be extremely clean.

http://www.hillsinc.net/

http://www.kasen.co.jp/english/product/line/work.html

Technologie Melt-blown Technologie Spun-bond

Production of bi-component fibers - type „island-in-the-sea“

cca 500 nm diameter (POP/PVA)

Production of bi-component fibers - type „island-in-the-sea“

Islands-In-The-Sea

One technique that Hills practices to produce nanofibers is done using the

Island-In-The-Sea (fibers within fibers) method. This method, developed

using Hills in-house pilot line, has the capability of making a large number

of fibers within a fiber. The Hills lab has been able to spin up to 1200 fibers

within a single fiber. The Hills’ Islands-In-The-Sea process has the potential

of producing over 4,000 fibers within a single fiber. Using the same

techniques, these filament can be produced as hollow tubes.

http://www.hillsinc.net/

http://www.engr.utk.edu/mse/Textiles/Nanofiber%20Nonwovens.htm

nanofibers are also manufactured by splitting of bicomponent fibers; most often bicomponent fibers 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

Forcespinnig – Cetrifugal spinning

Spinneret

First sell machine – 2010

http://www.youtube.com/watch?v=8Q-kydRdghI&feature=related

http://www.youtube.com/watch?feature=endscreen&NR=1&v=nr8cbpAt9oQ

Forcespinnig – Cetrifugal spinning

Process a broader range of materials Melt–spinning Solution spinning Organic Polymers, Inorganic Polymers, Metals, more Infusion of nanoparticles, carbon nanofibers/nanotubes Simple Parameters and Repeatable Results Rotational speed Orifice diameter Viscoelesticity of the material Distance to the collector Target/Uniform Diameter Average fiber diameters 400nm and below Homogeneity +/- 35% at 300nm average

DOI: 10.1021/nl101355x

| Nano Lett. 2010, 10,

2257-–2261

Combination of forcespinning and electrospinning

Image of PAN

nanofiber formation in

electrocentrifugal

spinning at rotational

speed of 6630 rpm and

polymer solution of

15% wt.

F. Dabirian et al. / Journal of

Electrostatics 69 (2011) 540e546

Combination of forcespinning and electrospinning

Scanning electron microscopy of nanofibers produced by electrocentrifugal spinning of (a)

15% and (b) 16% wt PAN in DMF at rotational speed of 6360 rpm and applied

voltage of 15 kV.

Combination of forcespinning and electrospinning

Overwiev

Drawing

Template - sythesis

Phase separation

solution gel

Fibrous

layer

Self-assembly

Melt-blown

„Islands-in-the

sea“

Forcespinning

Technology Type of

production

Typical fiber

diameter

Requirements for machinery

advantages

disadvantages

Drawing Laboratory 2-1000 nm small Very fine fibers Discontinuous process

small productivity

Template Synthesis Laboratory

cca 100nm Suitable templates Přesné rozměry vláken dle

šablony, další zpracování

special templates

Phase Separation Laboratory 50-500nm small Production of fibrous

layer

Only some polymers

Self-Assembly Laboratory

7-100nm

middle Very fine fibers Very difficult process

Melt-blown Industrial 250nm huge High productivity Only some polymers

expensive machinery

Islands-in-the-sea Industrial 500nm huge Control fiber diameter Only some polymers,

expensive machinery

Forcespinning Industrial 200nm Depending on the volume

of production

Lower outlay for

preparing solutions and

melts, the possibility of

process control.

Solvents may cause

corrosion,

poměrněvelký fiber

diameter

Electrospinning Industrial 50-500nm

(and more)

Depending on the volume

of production

Large quantities of

polymer production within

fibrous layer, endless

fibers

High voltage,

unstabilities

of process