53rd Man-Made Fibers Congress, - Kelheim Fibres · 53rd Man-Made Fibers Congress, ... Image left:...

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53rd Man-Made Fibers Congress, Dornbirn 2014

Dr. Nina Köhne - Kelheim Fibres GmbH

Absorbency

filtration

Surfacemodification

Reactivemodification

Intrinsic

modification

Electrical Conductive Viscose Fibres and their Applications

- Dr. Nina Köhne

Overview

• Design of Viscose Fibres

• Electrical Conductive Additives

• Production of Electrical Conductive Viscose Fibres– Characteristics of Electrical Conductive Additives– Characteristics of Intrinsically Modified Viscose Fibres

• Application of Electrical Conductive Materials

• Summary

Design of Viscose Fibres – Modifications

Cutting

Removal of CS2 & Sx

Stretching

Spinning

Bleaching, Washing, Finishing

Baling

CS2-Recovery

SpinbathRecovery

Additives

Spinning conditions

Cellulose

Design of Viscose Fibres – Fibre Modification

Standard

round Danufil®

Variation of Cross Sectiontrilobal Galaxy® hollow flat Bramante flat Leonardo

Tailor made solutions

Modification:Surface Chemical Intrinsic

Electrical Conductive Additives

modifications of carbon conductive polymersmetals

10-9 10-6 10-3 100 10+3 10+6 10+9 10+12 10+15 [Ω • cm]

copper

silver

polyaniline (undoped)

polyaniline (doped)

polypyrrole (doped)

polypyrrole(undoped)

graphite

CNT carbon black

conductor semiconductor isolator

spec. resistivity

Challenge: Transfer of electrical conductivity of additive to fibre Achievement of percolation threshold, formation of current paths

Electrical Conductive Additives

carbon fibre (Toho Tenax)

modifications of carbon conductive polymersmetals fibres

steel fibre (Bekaert)

silver plated polyamide fibre (Statex)

10-9 10-6 10-3 100 10+3 10+6 10+9 10+12 10+15 [Ω • cm]

copper

silver

polyaniline (undoped)

polyaniline (doped)

polypyrrole (doped)

polypyrrole(undoped)

graphite

CNT carbon black

conductor semiconductor isolator

spec. resistivity

standard viscose fibre

Motivation for the Development

• Although many electrically conductive products are already available onthe market, further developments in the following areas are desirable

– Wearing comfort

– Washability– Processability– Manufacturing costs

• After intrinsic modification of standard viscose fibres above mentionedrequirements should be achieved

Approach: Production of viscose fibres with different conductiveadditives and characterisation of fibre properties and electric resistance

Production of Electrical Conductive Viscose Fibres

Carbon nanotubeGraphiteAmorphous carbon

Carbon black

not testedpoorgoodSpinnability

tube-shaped

length: µm-scale

diameter: nm-scale

µm-scale

nm-scale

poor, expensivevery good, good valuevery good, good valueAvailability

10-4 – 10-5 Ω•cm8,0 • 10-4 Ω•cm1,0 • 10-1 Ω•cmResistivity

Images: „Eight Allotropes of Carbon“ von Created by Michael Ströck (mstroeck) - Created by Michael Ströck (mstroeck).

Lizenziert unter Creative Commons Attribution-Share Alike 3.0 über Wikimedia Commons –

http://commons.wikimedia.org/wiki/File:Eight_Allotropes_of_Carbon.png#mediaviewer/Datei:Eight_Allotropes_of_Carbon.png

Additive: Characteristics of Carbon Black

• Primary particle size, structure and surface area are essential for propertiesof carbon black

• Highest electrical conductive properties are available with carbon black withsmall primary particle sizes, high structure and high surface area

structure

lowest viscositylowest electrical conductivity

highest viscosityhighest electrical conductivity

most difficult dispersibilitymost intensive colour strength

easiest dispersibilitylowest colour strength

Additive – Characteristics of Carbon Black

• Primary particle is globular

• In dispersions primary particlesform branched, chain-likeaggregates and agglomerates

• Effective, stable dispersionsfor spinning process have to be prepared no standardproduct

primary particlesize: 10 – 60 nm

aggregatesize: < 1 µm

agglomeratesize: >> 1 µm

primary particle

structure

outer surface

total surface

chemical surface

Images: Product information of carbon black, Co. Harold Scholz

Additive: Percolation Threshold

• Electrical conductivity has to betransferred from additive to fibre

• Contact of conductive particles

– critical content of particlesmust be achieved

– current paths are formed

• If threshold is passed, an increaseof conductive particles causes no significant reduction in resistivity

content of conductive additive [%]

thresholdinsulating conducting

Additive: Percolation Threshold

• Percolation threshold and specific

resistivity of fibres are dependenton

– Manufacturing method of

carbon black

– Specific surface/structure of carbon black

– Content of carbon black

– Dispersant

– Spinning conditions

5 10 15 20 25

extra conductive carbon blackconductive carbon blackcolour carbon black

content of conductive additive [%]

Images: Product information of carbon black, Co. Harold Scholz

Characterisation of Intrinsically Modified Viscose Fibres

Determination of volume resistivitywith annular electrode

Determination of sheet resistance

with ʹfour point methodʹ

• Measurement of sheet resistance of thin layers with four point method(mainly used in semiconductor industry)

• Measurement of surface or volume resistivity with annular electrode (e.g. EN1149 for protective clothing)

Image left: Wikipedia, „Fourpointprobe GMR“ von Maciej UMacieju - Eigenes Werk. Lizenziert unter Public domain über Wikimedia

Commons - http://commons.wikimedia.org/wiki/File:Fourpointprobe_GMR.png#mediaviewer/Datei:Fourpointprobe_GMR.png

• Carbon black is distributed equally all-over viscose fibre matrix, currentpaths are formed

• Additivs like graphite and graphene were tested spinning of fibres was not possible

• Additivs like CNTs and conductive polymers were not tested rawmaterials and resulting fibre are too expensive

2 µm2 µm

SEM image of standard viscose fibre SEM images of carbon black loaded viscose fibre

0% 5% 10% 15% 20%

• Experimental results confirm that fibre tenacity decrease with higher content and with type of carbon black in fibre matrix

• After passing of percolation threshold fibre resistivity decrease significantly

• Challenge: achievement of favoured fibre resistivity with good processibility/adequate fibre tenacity

tivity

[ ΩΩ ΩΩ•

Carbon black content [%]

5 10 15 20

12 106

101020

18Image left: „Static slide“ von Ken Bosma from Green Valley, Arizona, USA - Electric SlideUploaded by Pieter Kuiper.

Lizenziert unter Creative Commons Attribution 2.0 über Wikimedia Commons –

http://commons.wikimedia.org/wiki/File:Static_slide.jpg#mediaviewer/Datei:Static_slide.jpg

Application of Electrical Conductive Materials

conductive propertiessmart textiles: heatable or luminescent fibres and textiles, sensors

< 1low specific resistance

anti-static propertiesshielding textiles: e.g. clean room fabrics, protective apparel and work-wear

103 – 106middle specific resistance

anti-static propertiesstatic dissipative textiles: e.g. protective clothingagainst electrical shocks, filter materials

106 – 109high specific resistance

Field of application[Ω Ω Ω Ω • cm]Resistance range

Wearing comfort

Washability

Processibility

Fibre tenacity

Conductivity

Conductive viscose fibresMetal fibres

Conclusion:• Both materials have pros and cons• No fibre could be used for several applications further developments

are inevitable

• Advantages of modified viscose fibres are washability and comfort

• Application needed where absolute value of resistivity is not crucial, only a

change of resistivity must be detected humidity sensor

• Electrical resistivity of carbon black loaded viscose fibre is dependent on humidity reversible effect

Summary

• Carbon black is suitable for the production of

electrical conductive viscose fibres

• Challenging parameters in the production of

conductive viscose fibres are

– Manufacturing method of carbon black

– Specific surface/structure of carbon black

– Stability of dispersions for spinning process

– Conductivity transfer from additive to fibre

• Application of electrical conductive fibres

competes with metallic wires

– Advantage of fibres are washability and comfort

– Electrical resistivity of fibres is dependent on

humidity (absolute value is not crucial)

For what application may you need electrical conductive viscose fibres?

Image above: Product information of carbon black, Co. Harold Scholz

Thank you for your attention

Please visit our stand in the exhibition area

in the foyer at the Dornbirn MFC 2014!

nina.koehne@kelheim-fibres.com

53rd Man-Made Fibers Congress, - Kelheim Fibres · 53rd Man-Made Fibers Congress, ... Image left:...

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