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CONFERENCE REPORT: The potential of nanotech in textiles
Lado Benisek summarises some of the contributions at the Aachen-Dresden Conference 2011.
The Aachen International Textile Conference attracted almost 500 participants from 25 countries, with the main topics: Health Care, Membranes and Filters, Novel Concepts in Textile Chemistry, and Efficiency in Textile Technology. Australia and New Zealand were participating countries at this annual event.
Nanotechnology in Textile Applications
According to Dr Martin Moeller, director of the German Wool Research Institute (DWI) and organiser of this year’s Aachen-Dresden Conference, the potential of nanotechnology has not yet been exploited. By the intelligent use of nanoparticles on textiles, a broad range of new properties can be generated on technical textiles and apparel.
This view was supported by Dr Harald Lutz (CHT, Germany), who summarised a range of nanotechnologies developed by CHT for textiles. Nanosilver antimicrobial properties for incorporation into synthetic fibres before fibre spinning can be achieved with iSys MB 11. iSys AG is suitable for application to cotton and PET, all approved by the Hohenstein Institute as being biologically harmless as a nanotechnology. iSys Sun, based on titanium dioxide nanoparticles, when bound to the textile, offers protection against UVA and UVB radiation, particularly for sportswear and leisure wear. Use of carbon nanotubes (CNT) to impart conductivity to textiles is three times as effective as the use of carbon black. Presently, CHT is researching the use of suitable nanoparticles to enhance the effectiveness of phosphorus-based flame-retardants. All these developments follow strict assessment of risk exposure and toxicity for nanocompounds.
Dyeing of Wool/PET Blends
Plasma treatment, followed by coating with polyelectrolytes, has allowed the fuctionalisation of the PET fibre surface by introducing amino groups that facilitate dyeing with acid dyes – thus allowing one-bath dyeing of wool/PET blends, according to PhD work by Tarek Salem (Leibnitz Institute of Polymer Research, Dresden).
Silver and Zinc Oxide as Enhanced Antimicrobials
Dr Elisabeth Heine, German Wool Research Institute (DWI), introduced the combination of the well-known antimicrobial silver and zinc oxide as an anti-septic and wound-healing agent. This combination offers enhanced antimicrobial properties, particularly when both agents are at nanoscale size. The challenge is to jointly attach both nanoparticles to textiles that would be of particular interest to biomedical applications.
Novel Atmospheric-Pressure, Ambient-Air Plasma Treatment
Dr Nial Finn, CSIRO, AUS, explained that the key to the efficacy of this plasma treatment for textiles is the air-flow through the plasma and the textile. The correct air flow allows plasma-power densities of around 10 kW/m2, without damaging the fabric and providing a high, uniform increase in surface energy, without the need for expensive noble gases.
The machine can treat, by fibre-surface modification, permeable textiles of all types from wool slivers to Kevlar fabric, for enhanced adhesion, reactivity and wetability. It can treat textiles adequately at speeds of up to 40 m/min at 1.4m machine length (2 sec residence time) and the speed can be simply increased by increasing the machine length.
Industrial trials with wool before spinning – with polymer applied at garment stage to bond yarns at crossways, allowing softer yarns with lower twists – resulted in excellent shrink-resistance and low pill propensity, including Optim wool fibre at 12 micron, thus avoiding chlorination. Plasma treatment also enhanced wool-yarn elongation and tenacity. Similar effects can be imparted to synthetic-fibre textiles: increased fibre-surface energy, enhanced bonding, wettability and reactivity, without reduction in yarn strength.
Antimicrobials for Health Protection
The medical industry is challenged by the presence of microorganisms and the health hazards they cause. Textiles in hospitals act as a microbial harbour and offer ideal conditions for their proliferation. Nosocomial infections are a serious issue for healthcare facilities. In Europe, more than 2 million patients/year are diagnosed with hospital-acquired infections, bed linen being responsible for 17% of all nosocomial infections.
Alain Langerock (Devan, Belgium) explained the mædical™ technology for the durable antimicrobial treatment of hospital textiles, requiring high durability to at least 50 industrial laundry cycles. This involves the fixation of a non-migrating permanent antimicrobial, based on a trihydroxysilyl derivative, on the fibres. This does not interfere with the skin flora of the users of treated textiles.
In Europe, 50,000 deaths/year occur from nosocomial infections and the costs in the USA for health-care systems are US$35-45 billion/year, according to Heinz Katzenmeier (Sanitized AG, Switzerland). Sanitized T99-19, a quat with trimethoxysilyl functionality, is recommended for healthcare-textile antimicrobial treatment, including against bacteria MRSA, NDM1 and viruses.
New Effective Coatings for Protective Clothing
Layered silicates, also known as nanoclays, are inexpensive and non-toxic minerals used as fillers in, for example, pharmaceuticals and as adsorption and decolourising agents for industrial wastewater treatment. In a research project by three German research institutes (FTB, Niederrhein University and DWI) a new coating system, based on modified nanoclays with high scavenger capacity from air for organic contaminants and environmental toxicants, was developed. Such coatings can be used on textiles for protective clothing, to avoid contact of human skin with toxic and other harmful substances.
Nanogold Merino Wool AULANA
Professor James H. Johnston, Victoria University of Wellington, New Zealand, presented an exciting lecture based on incorporating gold, a premier high-value metal, into a high-quality merino-wool fibre. Like metallic gold, the nanogold colourants incorporated into the wool fibre have a very high fastness to light, when compared with organic dyes. Additionally, the nanogold imparts antimicrobial, moth-resist and antistatic properties to the wool fibre.
Nanogold particles of specific sizes, and hence colour shades, have been deposited on to the surface and within the merino wool fibre by the proprietary reduction of gold chloride to gold nanosize particles associated with sulphur in the wool fibre, suggesting the formation of AuS bonds to the cystine amino acids in wool. This novel technology has been successfully developed to pilot-scale operation and is now being commercialised on fabrics and carpets.
The new gold product is called Aulana. This links the high value and premier position of gold with the high quality of NZ wool, according to Marcus Scollege, Consul General and Trade Commissioner, NZ Trade & Enterprise.
Magnetic Nanoparticles for Functional Textiles
Magnetic textiles are used in health care. The main approach for the preparation of magnetic textiles is to use magnetic fibres, which are spun from a polymer solution containing magnetic powders. However, it is difficult to achieve a homogenous distribution of the magnetic particles in the fibres.
Professor Kelu Yan (Donghua University, Shanghai, China) introduced an alternative method for the preparation of magnetic fabrics by coating the latter with magnetic nanoparticles. To improve the adhesion and the durability of the coating, a fibre-surface modification is required – irradiation by KrCl or Xe2 excilamps (Heraeus Nobelight, Germany) – which causes etching and photo-oxidation of the surface of the fibre – followed by dipping into a freshly prepared ferrofluid of Fe3O4 nanoparticles with a particle size of 10 to 20nm.
Meta-aramid, wool and polyester were modified with excilamps, followed by ferric oxide nanoparticle treatment. The magnetic textile fabrics were supermagnetic after a 10-hour wash.
Reproducible Uneven Dyeing
The fashion market today is increasingly demanding a ‘used look’, particularly for jeans, which can involve up to twenty different batch processes, such as washing, dyeing, bleaching, coating, baking, etching, sandblasting, etc. Kurt van Wersch (Monforts GmbH, Germany) presented the Matex Eco Applicator for continuous dyeing/treatment that can achieve similar effects continuously.
This Applicator contains two add-on rollers with troughs that allow one side of the fabric to be dyed/treated with one recipe, or two sides with one recipe, or two sides with two recipes. Dye application can be regulated to different levels, resulting in a variety of shades and hues. Mechanical manipulation of the fabric-guidance system can result in uneven dye application, simulating uneven wear.
Pigment, reactive or both dye applications is another available variable; over-feeding/hydro-extraction can produce longitudinal and transverse reproducible orientations. These variable options of this Applicator allow continuous, reproducible, uneven dyeing to obtain ‘used-look’ effects, thus saving considerable processing time and energy, compared with the present multitude of individual batch processes.
The next Aachen-Dresden International Textile Conference will take place in Dresden, from November 29-30, 2012, with emphasis on composites, membranes and buildings, protective textiles and chemistry for composites, membranes and protective textiles.
