NANOTECHNOLOGY IN TEXTILES

INTRODUCTION•nanos (greek) means dwarf•technologies dealing with structures less than 100 nm•1 nm is a trillionth of 1 m (10-9 m)•surface properties play a more important role compared to•the volume properties - therefore:•Richard Phillips Feynman “There is plenty of room at the•Bottom” is considered to be the “father” of nanotechnolgy•interdisciplinary interaction of sciences (physics, chemistry)•therefore nanotechnology is called a convergent technology•nano materials are already of significance today

Nano Products Available in the Market

•pigments (most important)•up-to-date computer chips (nano lithography)•surface functionalisation with nano layers or composites“self-cleaning” surfaces (“lotus-leaf effect”)•optically functional surfaces for antireflective coatings of displays (“moth-eye effect”)•chemical nano-products already exist for a long time:

like TiO2 or ZnO nanoparticles in sunscreens•textile research focuses on new functional properties:

soil-repellence, UV-protection, abrasion resistance, drug delivery...

SOME APPLICATIONS OF NANOTECHNOLOGY IN TEXTILES

1) Ag (antimicrobial activity)

2) SiO2 (sol-gel, ceramic layers)

3) TiO2 (UV-protection, photocatalysis)

4) bionics: shark-skin effect, self-cleaning surfaces

FUNCTIONAL/INTELLIGENT MATERIALS

functional materials(on the market)

• waterproof, wind-tight, breathable,humidity transportetc.

• optimized materialpropertiese.g. color fastness,tensile and abrasionresistance, heat-proof, cold-resistant

smart materials(in the market)

• smell release orodor control

• advanced wearingcomfort and heatinsulation

• individuallyadjustable heatinsulation

• microcapsules withphase changematerials (PCM)

• reflection materials• EM field protection• UV protection

intelligent materials(under development)

• developments withnew raw materials

• development withadditional electronicfunctions

Antimicrobial Fiber Modification(biochemical effect with nano silver)

antimicrobial body wear

• caused by increasing customerawareness of hygiene

• odor control• medical applications

• silver nanoparticles in the fiber• silver nano coating• high washing fastness• done by electrospinning microfiber

cross section

braced silvercoating on thefiber surface

silver coating

Micro fiber

Ceramic Coating (Sol-Gel-Process)

• matrix-precursor (SiO2 nanoparticles with cross-linking silicium organic compounds)

• functional additives

LyogelSol

Properties:

mechanical: reinforcing, scratch-resistant, antistatic, anti-adhesiveoptical: interference colors, UV protection, IR absorptionbiological: antimicrobial, medical applications

Xerogel

textile

- solvent Temp.

How to improve the UPF of Textiles(ultraviolet protection factor)

+ fabric design+ tighter weaving or knitting+ higher weight

+ textile finishing+ organic dyes absorbing UV light+ optical brighteners (in detergents)+ dark coloration

+ fiber modification+ TiO2, ZnO nano pigments for dulling of chemical fibers+ coating is essential to prevent photocatalytic reactions

+ terephthalic acid absorbs in the spectral UV range

+ protection is increased by additional dulling (µ/n-TiO2)+ best protection possible

Polyester (PET, PPT, PBT)

Fiber Raw Materials and UV Protection

Polyamide (PA 6, PA 6,6) - nylon

natural fibers (cotton, wool, linen)) & regen. cellulose fibers (CV, CLY)

+ only „full dull“ types provide good protection

+ little to no protection at all (especially when wet)

+ full dull viscose (TiO2) was available a few years ago

Application of nano TiO2 on Fibers

PA uncoated PA 2 % nano-TiO2 coating

UPF

UPF after nano TiO2 Coating

UPF Rating according to AS/NZS 4399:1996

60

5050

4035

3030

25

20

1010

5

0CO (100 %) 142 g/m2 PES/CO (50/50) 125 g/m2 PA (100 %) 97 g/m2

UPF (uncoated)

UPF (2 % Nano-TiO2)

Photocatalytic Degradation of Matterwith TiO2 (Anatase Crystal-Modification)

+ photocatalytic TiO2 nanoparticles in anatase crystalmodification in presence with UV-radiation, water andoxygen generate free radicals

+ radicals destroy organic substances

+ catalytic process, therefore large and free accessiblesurface area (e.g. nano) is required

PhotocatalysisWhen a semiconductor material is illuminated with ultra band gap light it becomes a powerful redox catalyst capable of killing bacteria, cleaning water, and even splitting water to give hydrogen and oxygen.

When photocatalyst titanium dioxide (TiO2) absorbs Ultraviolet (UV)* radiation from sunlight or illuminated light source (fluorescent lamps), it will produce pairs of electrons and holes. The electron of the valence band of titanium dioxide becomes excited when illuminated by light. The excess energy of this excited electron promoted the electron to the conduction band of titanium dioxide therefore creating the negative-electron (e-) and positive-hole (h+) pair. This stage is referred as the semiconductor's 'photo-excitation' state. The energy difference between the valence band and the conduction band is known as the 'Band Gap'. Wavelength of the light necessary for photo-excitation is: 1240 (Planck's constant, h) / 3.2 ev (band gap energy) = 388 nm

The positive-hole of titanium dioxide breaks apart the water molecule to form hydrogen gas and hydroxyl radical. The negative-electron reacts with oxygen molecule to form super oxide anion. This cycle continues when light is available.

Fiber Degradation (SEM Image of Polyamide)

Nature as the Role Model:Shark Skin with minimized Flow Resistance

source:

Bionics: Swimmsuits with Shark-Skin-Effect

+ different frictioncoefficients on the fabric(knitted or printed)

+ creation of micro vortices

Soil Repellence (Lotus Effect®)

+ nature as the role model (“bionics”)+ combination of micro- and nanostructures with low

surface energy generated by wax crystals+ such high performance is not achieved by common

fluorocarbon finish+ water, oil and dirt simply roll off+ but: structures are sensitive to mechanical stress

(scratching, abrasion, washing)+ effect is lost if structures are damaged+ nature can re-grow these structures - but textiles not (yet)

Self-Cleaning Process in Nature (1)

hydrophobic surfacehydrophilic surface

nanostructurefor small particles

microstructurefor larger particles

Self-Cleaning Process in Nature (2)

Self-Cleaning on Plants (Spiraea)

species 2species 1

Self-Cleaning on Insects (Rose Beetle)

Self-Cleaning on Insects (Housefly)

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self-cleaning textile coatingwith nanostructured surface

SEM image (top) andAFM surface topography of a lotus leaf

Self-Cleaning on Plants (Lotus Leaf)

source: Schoeller Textiles

Other Advancements

Other Applications

Woven opticalfibers ( screen )

Woven orprinted Bus

Woven or PrintedElectrodes

Silk Organza( Silk + Gold )

EmbroidedNRIKeypad

Circuit onOrganza

SMART TEXTILES

References Beringer, Dr. Jan (2005). Nanotechnology in

Textile Finishing. State of the Art and future Prospects. Hohenstein Insitutes.

McLaughlin, James (2004). Nanotechnology & Its Applications in Textiles. University of Ulster.

Sawhney, P.,Singh, K., Codon, B., Sachinvala, N., and David Hui. Nanotochnology in Modern Textiles

http://www.mchnanosolutions.com/mechanism.html