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Development of functionalized nano-structured textile materials

Programme: EUREKA
Acronym: NANOTEX
Contract number: 173-E
EUREKA project number: E! 3776- NANOTEX

Priority field no.: 7
S/T field no.: 014 LIGHT INDUSTRY
S/T subfield title: Machines and machinery for the light industry; Products and technologies in the light industry

Duration: october 2008 – october 2011

Project description:

The main objective of this project is constituted by novel knowledge acquiring on photoactive nano-materials and by the development of new products with anti-bacterial effects for self-sterilizing and self-cleaning purposes, with high protection against UV radiations.
The project proposes the achievement of photoactive textile fabrics with the following characteristics:
1. natural aspect preservation of the textile fabrics
2. high anti-bacterial efficiency
3. unpleasant smells removal
4. self-sterilizing and self-cleaning effects kept even after 50 washing cycles
5. VOC (volatile organic compounds) reduction and the prevention of close space (indoor) syndrome determined by VOC presence

Project specific objectives meant to achieve the scope proposed are:
• Development of new photo-catalytic nano-materials with activity and high resistance to UV and to visible light
• Development of techniques for these materials deposition on various textile substrates
• Characterization of the physical and chemical properties for the photo-catalytic nano-materials and for the coatings performed

Project activities:
To reach the objectives proposed, the following activities execution is considered:

Stage I: Elaboration of the manufacturing technology for the photo-catalytic textile materials / 01.10.2008 – 28.02.2009
Activity I.1 Technical-scientific study
Activity I.2: Design of the laboratory technology
Objective: leading efforts will be focused on the selection of compounds and of technologies for their deposition on the textile materials, with applications of high industrial relevance, such as the materials providing self-cleaning, anti-microbial, and purifying capacity, as well as the hygiene applications.

Stage II: Elaboration of photo-catalytic nano-structured materials with enhanced properties to visible light, meant for indoor articles or items/1.03.2009 - 10.12.2009
Activity II.1 Experimental tests for the photo-catalytic compounds deposition on treated textile substrates
Activity II.1.3 Assessment of the self-cleaning characteristics. Dissemination of results
II.2 Testing of materials with photo-catalytic coatings
The main objective of the stage is constituted by the deposition of the active photo-catalytic nano-materials with increased sensibility in the visible region/interval of the solar spectrum, with high adaptability and stability to environment, on textile substrates having different fibrous compositions (i.e. polyester and polyester/cotton blends etc.) applicable for indoor articles (curtains, shadings, covers).

Stage III: Elaboration of the photo-catalytic nano-structured materials with enhanced properties to visible light, meant for medical articles / 11.12.2009 - 10.12. 2010
III.1 Laboratory experimental tests for the achievement of textile fabrics with self-sterilizing and self-cleaning properties
III.2 Investigation of the photo-catalytic effect provided by the materials achieved
To reach this objective, there are considered – the deposition of titanium dioxide nano-clusters of different sizes, the surface, the crystallographic compositions on textile materials – for the achievement of fabrics with self-cleaning and anti-bacterial effects, meant for medical articles and for indoor textiles (bathrobes, masks, bedcovers or sheets). In order to improve the TiO2 bactericide effect, there will be also considered the inclusion of other metal oxides, such as Ag2O, CuO, ZnO, and TixZnyOz.
The determination of the physical and chemical properties for the substrates on which the photo-catalytic nano-materials were deposited and the testing on their photo-catalytic and super-hydrophilic activity will allow the selection of treatment technologies among the ones experimentally checked.

Stage IV. Optimization of the photo-catalytic textile structures
/ 11.12. 2010 – 30. 09. 2011
IV.1 Determination of stability and lifespan for the nano-structured multi-functional textile materials
IV.2 Selection of the photo-catalytic textile structures, of the technological methods and the analysis methods, considering the long-lasting physical, comfort, aesthetic and anti-bacterial properties, superior to the conventional ones already traded on the international market. Dissemination of results
The main objective of this stage is constituted by the determination of antibacterial and self-sterilizing properties displayed by the substrates on which the photo-catalytic nano-materials were deposited.
There are also taken into consideration:
- lifespan assessment of the textile fabrics treated with photo-catalytic compounds in various environmental conditions and different employment conditions
- elaboration of the technical materials referring to the research results
- dissemination of information.

Project objectives:
- development of new photo-catalytic materials active to visible light, based on titanium doped with different metals
- nano-structured compositions applicable in the textile industry: indoor textile articles, medical articles
- textile materials with self-cleaning, self-sterilizing, and anti-bacterial capacity.

ELKEDE Thechnology and design Center S.A. – Athens, Greece - EUREKA Project Manager
Tel +30 210 285 5580; Fax +30 210 284 6471; www.elkede.gr
Contact Mr. Theodoros Giakoumakis tgiak@elkede.gr

S.C. OPTICOAT S.A. - Romania Project Manager
telefon: 0722237127; fax: 3444035, e-mail: office@opticoat.ro
Contact: fiz. Arcadie Sobetkii, arcadie@opticoat.ro

INCDTP - Institutul National de Cercetare Dezvoltare pentru Textile si Pielarie (RO)
Tel: 0213404200; fax: 021 3405515; www.certex.ro;
Contact: Dr. Ing. Iuliana Dumitrescu; certex@ns.certex.ro

S.C. Prodconfarm S.A. (RO)
telefon: 0248206136, fax:0248206137
Contact: ing. Minulescu Alin

Aitex - Asociacion De Ivnestigacion De La Industria Textil Spain
Tel +34 96 554 22 00; Fax +34 96 554 34 94 www.aitex.es
Contact: Ms. Rosa Lopez; rlopez@aitex.es

Univ. Of Maribor / Faculty Of Mechanical Engineering /Department Of Textile Materials And Design Slovenia
Tel +386 2220 79500; Fax +386 2220 7990; www.fs.uni-mb.si
Contact: Ass. Prof. Bojana Voncina, bojana.vocina@uni-mb.si

Pascual Y Bernabeu S.A. , Spain
Tel +34 96 55 90 152; Fax +34 96 65 00 532; www.pascualybernabeu.com
Contact: Mr. Javier Frances, javier@frances.ws

Iw Textile Research Institute, Poland
Tel +48 42 6163 110; Fax +48 42 6792 638; www.iw.lodz.pl
Contact: Phd Eng. Jadwiga Sojka-Ledakowicz, ledakowicz@mail.iw.lodz.pl
Konus Konex Ltd. , Slovenia
Tel +386 375 73100; Fax +386 357 53140; WWW.konuskonex.com
Contact: B. Sc. Ales Grilj, ales.grilj@konuskonex.com

The main objective of the 1st stage, unfolded in the period lapsing from 01.10.2008 to 28.02.2009, consisted in the selection of the photo-catalytic compounds and of their depositing technologies on the textile materials.

For this purpose, there have been conducted a technical-scientific study which highlighted the following aspects:
- The photo-catalysis mechanism: semi-conductive materials activation by solar or artificial light and generation of (HO-) radicals of the water molecules adsorbed from the semi-conductor surface, namely O2. - and HO2, formed by capturing the photo-generated electrons;
- The photo-catalysts operating principle: TiO2, with a relatively wide [range] of the forbidden energy band, by 3.0 - 3.2 eV, generates strong oxido-reductive reactions, in the presence of UV radiations and humidity in the surrounding environment;
- Types of photo-catalysts: the most important photo-catalyst used at present is TiO2, due to its increased photo-oxidizing power, its chemical stability, to the corrosion resistance, to its simple post-processing, the low cost, to the operation in mild conditions and to its safety regarding human health. TiO2, with a 3.2 eV band, can only absorb light with wavelength shorter than 385 nm. As the solar light contains just an extremely narrow domain of these radiations of high energy and, in this case, there is a small quantity of the kind of energy needed for the oxidation reactions to take place, the problem arose concerning speed improvement for the photoreactions and for the efficient use of solar radiations, by adjusting the TiO2 band structure. Considering this, there were synthesized plenty of other compounds with enhanced photo-catalytic properties, such as: ZnO, WO3, SnO2, CaTiO3, Fe2 O3, MoO3, Nb2 O5, TiX Zr(1-x) O2, SiC, SrTiO3, CdS, GaP, InP, GaAs, BaTiO3, KNbO3, Ta2 O5, Bi2 O3, NiO, Cu2 O, SiO2, MoS2, InPb, RuO2, CeO2, Ti(OH)4; or either combinations of these with metals or metal oxides, such as: Pt, Pd, Au, Os, Rh, RuO2, Nb, Cu, Sn, Ni, and Fe.
- Functions of the photo-catalysts:
- the self-cleaning effects: the UV radiations generate active oxygen and radicals able to de-compose the organic contaminants into carbon dioxide, thus allowing the substrate surface remain clean;
- the antibacterial effects: TiO2 photo-catalytic reaction determines the reaction for the lipid peroxidation of the cells membrane, leading to the destruction of bacteria, fungi, tumor cells and even cancer cells. Due to the reduced selectivity against bacteria species and to their ability to decompose toxins produced by these (bacteria), the TiO2 based photo-catalysts have been intensively used for finishing hospital indoor materials and medical equipments;
- air purification: deodorizing filters found in air purifiers, meant to remove the aldehydes or other volatile organic compounds possibly encountered in the indoor air;
- air pollutants removal: NO oxidation into NO2 to NO3;
- water cleaning and soil decontamination: the cleaning of wastewaters from enterprises, the underground water and rivers. Titanium oxide can decompose endocrine disruptors like the bisphenol;
- anti-fog effects: applicability for street mirrors and automobile windows;

- Study on the technologies to be employed for the application of photo-catalytic compounds on the textile fabrics:
A. Techniques for the cover with dry particles
A1. In situ cover with dry particles
A2. Post treatment cover with particles
A3. Electrostatic deposition
A4. Mechanical dry covering
A5. Melting processes (Melt blowing)
A6. Bi-component fibers forming
Out of all these techniques, remarkable photo-catalytic effects were achieved by incorporating some special titanium oxide nano-particles into the acrylic fibers used for clothing, sports articles, uniforms, bet sheets, carpets or coverlets, and, generally, commodities. Because titanium oxide is found inside t he fiber, the yarns provide excellent self-cleaning, deodorizing, antibiotic, and anti-soiling functions, as well as an excellent functional stability.

B. Wet covering methods: spraying, impregnation, self-assembly, sol-gel, and transfer printing. Covering compositions are formed of photo-catalysts nano-particles, one tension activator, solvents, and other ingredients.
B1. Molecular self-assembly: there can be performed 10 - 30nm covers of the monofilaments forming a woven or a knitted fabric. Once with achieving an even covering, high, long-lasting and stable functionality is conferred, without losing the fabric texture, and cutting problems are solved, like de-lamination and shading caused by clothing contraction and folding in wearing. By strict control of molecular arrangements, it is possible to combine functions with antagonic properties, such as the antistatic function requiring the absorption of a certain water quantity and water repelling function supposing high waterproofing, respectively water removal from the material.
B2. Sol-gel method: the sol-gel solutions can be applied on the textile fabrics at ambient temperature and at temperatures ranging around 400C, thus achieving nano-crystalline films of titanium dioxide, anatas. Materials thus treated show photo-catalytic self-cleaning properties, bactericide activity, color [dye] stains de-composing, degradation of red wine and coffee stains.
B3. Impregnation / exhaustion methods: are the simplest methods frequently used in the textile industry, on the common installations. To achieve the photo-catalytic layers by these methods, the metal nano-particles are included in different compositions or can be either incorporated in micro-gels, micro- and nano-capsules.

C. Physical methods
C1. Cold vapor deposition method (CVD): less applicable to textile fabrics due to high temperatures needed to transfer the molecular precursors under the form of vapors
C2. Chemical vapors deposition in plasma: applicable for textile fabrics in temperatures below 1500C. Plasma treatments do not modify weight, thickness, bulkiness, air permeability, breaking elongation and breaking resistance. Fabrics treated in plasma become waterproofed and show an increased resistance to blood and water [penetration], as compared to other treatments, inhibit bacteria growth, but also Staphylococcus aureus, being a true barrier against microorganisms. Plasma treatments are increasingly applied in the textile industry, because of their numerous advantages against the classical treatments: cost-efficient, environmentally-friendly, even, applicable to many types of materials, they are at the same time capable to preserve unchanged the basic properties of the substrate. Nonwoven fabrics used for the surgical gowns are treated in plasma containing fluorine-carbide, but also with antimicrobial finishes.
C3. Sputtering in radiofrequency: generates high purity homogeneous layers with well-controlled composition, according to different substrates. Films are transparent in the visible domain, conductive and either crystalline or porous, depending on the deposition parameters (the argon and oxygen content, the sputtering power, the bias voltage).
C4. Organometallic vapors deposition at atmospheric pressure: TiO2 particles are deposited on surfaces with high porosity at 4230K temperature, under the form of a thin layer containing 10 - 50 nm in size particles.

Study on the methods of characterization for the compounds and the textile fabrics treated with the photo-catalytic compounds

I.1.2.1 Characterization of the photo-catalytic materials
Mechanical properties
The effects of photo-catalysts particles present on the textile fabrics noted over the physical-mechanical resistances can be assessed by means of:

- determining the tear and breaking, according to standards ISO 13937-1:2000-04; EN ISO 13937-1:2000; EN ISO 13937-1:2002-03, on specific testing equipments;

- characterizing the bending behavior of fibers and of treated, respectively untreated fabrics, possible by using the cantilever method (ASTM D5732).

- determining the abrasion resistance for the surface of materials achieved;

- determining the quantity of photo-catalyst deposited on the fabric, evaluated by weighing methods, according to standard ISO 3801 / 1977-09, by material thickness measurements (ISO 5084: 1996) and by yarns diameter measurements, conducted before and after deposition;

- evaluating the performances and their lifetime, by means of an accelerated aging test, using some adequate laboratory equipments (i.e. weatherometer Xenon 3-1, Apollo, Xenotest):

Thermal characterization
Thermal-gravimetric analyses and differential thermal analyses (TGA/DTA) under airflow allow the determination of temperatures in which de-composing phenomena take place, as well as for phase changes, reactions, and emissions of volatile compounds.
Differential scanning calorimetry, performed on Diamond DSC (Perkin Elmer), consisting in the mediation of two scans per sample type, in a temperature range varying from 2500C to 21000C, and a 200C/min speed, will allow the analysis of changes in the photo-catalysts crystallinity.

Surface characterization
The determination of load degree for particles and their distribution on the textile fabrics surface is achievable by means of various techniques, such as atomic force microscopy, scanning electron microscopy (SEM) and the EDX elemental analysis (Energy Dispersive X-ray), as well as with surface analysis techniques (Brunauer, Emmet, Teller (BET)), optical microscopy, confocal laser scanning microscopy, fluorescence microscopy, refractive index based optical microscopy etc. Apparatuses existent in INCDTP laboratory equipping will allow the proper determination of particles distribution, by means of optical microscopy, scanning electron microscopy, EDX elemental analysis (Energy Dispersive X-ray) with SEM.

Optical microscopy
Fibers microscope images performed on Projectina, 10 - 1000x amplified, will enable the macro and micro visualization of particles distribution. Surfaces unevenness and particles clustering in certain areas hamper the achievement of real images for the particles distribution on fibers surface, even when immersing in solvents with refractive index similar to fibers is employed.

Scanning electron microscopy (SEM)
Nevertheless, SEM images (Quanta 200, FEI, The Netherlands) enable particle visualization at nano-metric scale. Yet, the method presents certain limitations, such as particles included into fibers hiding by TiO2 large particles, and significant variations for the same sample depending on the loading percent and on particles uneven distribution.

Photo-catalytic tests
The photo-catalytic effects of the various metal oxides can be highlighted by:
- dyestuff de-composition under UV irradiation (methyl orange, Neolan Blue 2G,)
- organic substances degradation: acetaldehyde, benzene, toluene etc.

The tests assess the photo-catalysts capacity to remove/clean the stains produced by sweat greases, wine, make-up, coffee, ketch-up, mustard; the deodorizing effect (cigarette smoke),

The hydrophilic/hydrophobic features characterizing the textile fabrics treated with photo-catalysts can be assessed by determining water absorption and the contact angle, by performing FT-IR and XPS analyses, capable of showing if TiO2 generated the C-O and C=O groups on the polyester surface.

Study on the risks presented by the photo-catalytic compounds for the human health

The nano-particles can pass through skin, lungs and the intestinal duct with effects still to be understood over human health. Relevant characteristics of nano-particles referring to their action over the human health are:
- size: the nano-particles are generally more toxic than the larger particles, because they have the possibility to get through the cell membranes, and thus be ingested into blood and further on into different organs;
- chemical composition and surface characteristics: the nano-particles toxicity mainly depends on the chemical composition, as well as on the chemicals absorbed on their surface;
- shape: recent studies showed an increased toxicity for the carbon nano-tubes (CNTs), as compared to the other shapes.
TiO2 used as photo-catalyst is considered to be physically and chemically safe, being certified as food additive in countries like USA and Japan. Titanium dioxide is non-inflammatory (non-combustible) and odorless, being used for numerous industrial applications, such as coloring agent in food industry, important additive in pharmaceutics, cosmetics and also for other commodities. TiO2 was used as reference non-toxic powder within many toxicology studies on particles. TiO2 was considered biologically inert until the arise of studies related to ultrafine particles, which demonstrated that the ultrafine titanium dioxide particles (20 nm in diameter) trigger an inflammatory reaction of the rats kidneys, higher than the one determined by the particles that are larger in diameter (250 nm). TiO2 nano-particles show a preferential placement along the cell membrane in the inter-cellular areas. TiO2 nano-particles present the highest level of toxicity followed by the oxides of Ni, Al, Fe, Zr and Zn.
Designing of laboratory technology
The processes supposed by the photo-catalytic substrates achievement involve the deposition of the photo-catalytic compounds on the textile support.
For this purpose, there can be used as textile supports knits, woven, or non-woven fabrics made of either natural or synthetic fibers, but also blends of these. Due to the destructive effect of the photo-catalysts, the use of synthetic fibers is preferred, such as polyester, polyamides, polypropylene, polyurethanes, aramids, glass fibers, especially in case of using the materials for home/indoor textile applications.
In case of using the photo-catalytic textile materials for medical applications, there should be also taken into consideration the comfort properties they should provide the wearer. In the design stage of these types of textile materials, the physical and mechanical properties are to be accounted, due to their influence on the clothing comfort: fabric mass, thickness, volume (bulkiness), porosity, and its nature alike.
For the medical articles, woven and non-woven types of textile fabrics will be tested:
- polypropylene of micro-fine waterproofed (hydrophobic) fibers, which are 10 microns in fiber diameter, 12 – 40g/m2 in mass, 200 - 380 mm H2O resistance to liquids and 100 - 400l/sec/m2 air porosity;
- polyester, polyethylene or nylon, 2 - 7 microns in fiber diameter and 15 g/m2 - 25 g/m2 in weight.
- 15 - 50 % polyester/ 85-50% cotton woven fabrics, 175 - 320 g/m² in mass;

N.B.: - woven fabrics will have a flat structure, being made of round-cross-section yarns;

For the indoor textiles, woven and non-woven textile fabrics will be selected, of yarns given bellow:
-polynitrilacrylic: bulkiness, thermal-isolation capacity, thermal-plasticity, reduced mass per m2, good dimensional stability, showing no felting phenomena.

- polyolefinic: reduced specific mass, high air and vapor permeability, due to structural porosity, creaselessness, reduced thermal conductibility, rotting resistance, low cost;

- polyesteric: high resistance to the action of light radiations, especially the UV ones.

Fabrics type of construction: it is considered the manufacture of some flat woven fabrics, because this way the warp yarns are overlaid (some over the other), fact that leads to a lower porosity, adequate to even depositions of the photo-catalytic substrates.

Selection of the deposition technologies for the photo-catalytic compounds
Among the techniques available for thick films deposition, there will be experimented:
1. the exhaustion treatment of fabrics (made of cotton, polyester), by the help of finishing agents containing TiO2 nano-crystals, TiO2 doped with Ag, particles of Ag covered in TiO2 (Ag/TiO2), in order to simultaneously obtain the photo-catalytic and the anti-microbial properties. Finishing auxiliaries will be employed with 0.05 - 2% concentrations of the photo-catalytic materials, as reported to the substrate total weight. The photo-catalytic finishes will be fixed on the substrate by the help of a binder. As binders, organic or inorganic compounds will be used of the poly-acrylates, vinyl esters, polyurethanes, polyethylene-vinyl acetates, polyolefins, polyesters, polyamides, polyethers, poly(styrene-co-butadiene), poly-isoprene, and polycloroprene type and combinations of these. The ratio between the photo-catalytic finishing and the binder is generally 1:0.1 - 1:5. The photo-catalytic coating composition can be prepared with any of the methods. The preparation method generally consists in the photo-catalytic particles dispersion or suspension in liquid medium, whose binder addition is followed. To ease the path of a stable dispersion or suspension forming for the photo-catalytic material, dispersants are added, yet compatible with the photo-catalytic material and the binder as well, such as phosphate esters, ammonia, ammonium hydroxide.
2. the photo-catalytic coating by spraying: there will be used sprays capable of providing the substrates thin films, strongly bind to these, with semi-permanent deodorizing, anti-bacterial, and self-sterilizing actions. These can be used on such textile products like curtains, pillows, garments, footwear, bed sheets, sofas, artificial flowers and plants.

In case of the photo-catalyzing materials fixed on active organic substrates, textile materials included, the photo-catalysts oxidative power will lead to a decrease in resistance, to exfoliation, and to substrate de-composition.
In order to prevent these, photo-catalysts mixed with organic materials will be used, for which the photo-catalyst particles are included in the core/sheath structures, prepared by the help of some inert particles (TiO2 particles produced by TiO2 covering with porous inert silica, hydroxyapatites, acrylic resins), which prevent the contact with the substrate.

Among the techniques available for the deposition of thin films for TiO2, such as spray pyrolysis, sol-gel method, sputtering, solvothermal method, pulsed laser deposition, atomic layer deposition, chemical vapor deposition (CVD) and photo-assisted CVD, pulsed DC reactive magnetron sputtering, there will be used:

1. Deposition of TiO2 photo-catalytic layers using RF magnetron sputtering

This technique will be used for the deposition of TiO2 thin, transparent, photo-catalytic films on cotton and polyester fabrics, at room temperature. Ar and O2 will be used as work gases. In order to improve the photo-catalytic activity of films, doping with Ag and Zn will be subjected to trial.
TiO2/Ag/TiO2 multi-layers formation on the polyester, nylon, and acrylic fibers by means of RF magnetron sputtering will be achieved by using Ti and Ag oxide as target materials, to be found in an oxygen, nitrogen and argon atmosphere.
2. Plasma assisted deposition of TiO2 photo-catalytic layers