Lenzing launched Tencel Powder in three forms: milled fibre, fibrids and spherical beads made from dope. Apparently the Heiligenkreuz lyocell plant still has surplus dissolving capacity and something like 1000 tonnes/year of cellulose in dope form cannot be converted into fibre because of bottlenecks in the fibre production process. Some of this surplus dope can be regenerated via “granulation”, washed and dried to give spherical particles down to 6 micron diameter. At the coarse end of the range 200 micron spherical particles are possible, and granules in sizes from 1 to 10mm are available at 75% moisture content. Fibrids, similar to the fibrils which make Tencel self-bonding after refining, are made from dope with diameters around 100 nm and lengths around 1 micron. The powders have water imbibitions of around 300% and the current main application is in polyurethane foam production to improve the absorbency and hence comfort of foam mattresses. Eurofoam is the main customer and Cellpur® is the brand of foam containing the powder. Another application is as a thickener in coatings and food products.
This fibre complements the other intelligent fibres:
l SeaCell Fiber Active Plus (with silver antibacterial),
l Smartcel Bioactive (5% silver in lyocell),
l Smartcel Ceramic (sintered from a heavily ceramic-loaded lyocell to make vibration dampers, ultrasound generators and medical products). Versions with silicon carbide and diamond powder are also available.
l Smartcel Energy (Conductive lyocell using 50% carbon loading to make electrically heatable fabrics.)
l All this from a 500 tonne/year pilot plant. Clearly none of these have taken off, so they keep adding new varieties.
Kuraray (Japan) were showing a textured multi-fil polyester yarn coated with multiwall carbon nanotubes to achieve electrical resistances down to 100 ohms/cm. At these very low resistances, electrically heatable fabrics were the target market. At 100,000 ohms/cm a wide range of durably antistatic textiles were possible.
Tom Burrow of Lenzing (
) promoted the advantages of Tencel over other fibres in general and then focused on recent comparisons of cotton with Tencel designed to show the improved comfort arising from Tencel use in a hospital. Austria
At Cleveland University Hospitals, 12 sufferers from dermatitis and 15 control patients each tried complete sets of bedding and garments made from both 100% Tencel and 100% cotton. In a randomized single-blind test protocol the Tencel was preferred for softness, thermal, humidity, odour, wrinkle and staining characteristics. Most significantly (according to Lenzing) Tencel proved less itchy, scoring 2 on a scale of 1 to 5 compared with cotton’s 2.6
· The low level of chitosan in Tencel C was obtained by adding chitosan as a finish to never dried fibre. The high level was applied after drying.
· The chitosan stays on the surface of the fibre and can survive 3 washes
· He didn’t know why standard Tencel was better for wound healing than bleached cotton, but it could be due to the higher water imbibition or different crystallinity or morphology.
· Wovens were used in preference to nonwovens in these trials because the fabrics were more readily available
· Tencel resists bacteria in challenge testing – again it’s ability to immobilize more of the challenge fluid probably being important here.
Wolfgang Rupertseder, Plant Manager of Irema Filter (
) reviewed the mechanisms of particle capture in filtration, pointing out that diffusion is key to capturing the small particles which are subject to Brownian motion. Ideally, filter fibres should have similar diameters to the particles they have to filter, and this means developing filters with nanoscale fibres to remove the smallest nuisance particles in air. For micron sized fibres, the air velocity at the fibre surface is zero, but with fibres below 0.5 microns diameter, “slip-flow” occurs allowing air velocities above zero. This coupled with the great increase in fibres/gram results in greater probability of particles colliding with fibres and being captured. Germany
Dirk Hegemann of EMPA St Gallen (
)commenced by pointing out that the nanomaterials market has been growing very much more slowly than predicted in 2006 and is currently at about a tenth of the expected value. Nanocoating with metals using plasma sputtering techniques was however looking promising: Switzerland
l These filaments look metallic but the low coating levels have no effect on their texture or textile properties.
l Durable antimicrobial properties are a useful side benefit, although silver is toxic and is released from the surface.
The silvered yarns kill microorganisms on contact with an efficiency related to the rate of loss of silver from the surface:
l 1 microgram loss per square centimetre per day isCytotoxic
l 0.1 microgram loss per square centimetre per day isBacteriocidal
l 0.001 microgram loss per square centimetre per day isBacteriostatic
l 5 micrograms loss per square centimetre per day stains the skin blue!
In solution the situation is different:
l 100ppm Ag occur under silver-containing wound dressings.
l 10ppm is the maximum concentration allowed into a sewage works.
l 0.1ppm is the maximum allowed in the effluent from laundering silver-containing textiles
l 0.01ppm is the concentration used in silver-containing textiles
However silver shows very low eco-toxicity because it is readily precipitated and passivated by traces of sulphur, chlorine and organic matter.
Dr Joao Gomes of the Centre for Nanotechnology and Smart Materials (CENTI- Portugal) is offering contract R&D services to industry managed under full confidentiality. Their aim is to deliver fully tested pilot production facilities for new technologies. They started in 2007 with an initial investment of €5 million to allow advanced fibre development, surface coating development, and smart materials development. This year they have 25 permanent R&D staff working on 40 industry driven projects and a turnover of €1million. Their projects include:
fibres with conductive cores in a dielectric matrix
different fillers in different layers
tricomponent piezoelectric fibres for sensor-actuator uses. (Piezoelectric layer between two conductive layers, with the possibility of adding a 4th layer as a coat)
Developing “fibre microstructures with controlled porosity”
Hollow fibres with 2-layer walls.
l Integration of electroactive materials directly with polymer surfaces (Ink jet technology)
l Development of RFID systems on polymeric substrates
l Development of new printable formulations for ink-jet application to unconventional substrates e.g. nonwovens
Metallic nanoparticle suspensions with low curing temperatures.
Printing of silver and copper nanoparticles on polymers
Patterning of metallic foil for printed circuits
Printing semiconductive, conductive and UV curable polymers onto polymeric substrates.
l Electro-spinning nanofibres in yarn form rather than as random sheets.
l Multifunctional coating technology including atmospheric plasma coating, ultrasonic deposition, nano-film formation and curing/drying with UV and/or IR.
l Thermo-sweating mannekins to allow the evaluation of the insulation and breathability of products during simulated use.
One slide illustrated a pilot line with DC Dual Magnetron sputtering, low pressure chemical vapour deposition, wire-feed metal evaporation and e-beam polymer deposition.
Luca Mezzo of Nanocyl (
) introduced the INTELTEX project, an EU funded partnership of 8 universities and 15 industrial companies (mainly small and medium sized enterprises – SMEs) targetting the use of nanofiller-based conductive polymer fibres in intelligent textiles. These fibres are meant to be the sensors for temperature, humidity and strain changes in textiles for use in medicine, building construction and personal protective garments. They become sensors through the incorporation of, for instance, carbon nanotubes (CNTs), which at a certain concentration give an electrical conductivity which varies according to strain and swelling caused by solvents or water. These CNTs are the high aspect ratio single wall variety with a diameter of a nanometre and length of a micron. Belgium
Harmut Finger of the Institute for Energy and the Environment (IUTA -
) described textiles containing layers of activated carbon spheres sandwiched between porous films and fabrics which had been designed to absorb body odour. The resulting laminates were 1-2mm thick, and were being tested for absorbtion of hexanal, a C6 aldehyde used as a water and oil soluble sweat substitute. Testing was by DIN 1327 – where gas bags of hexanal at various dilutions are sniffed by a panel before and after the absorbent fabric has been added. Germany
Thomas Stegemaier of ITV Denkendorf (
)defined bionics as the integration of biology with technology. Biomimetics is a related field and both are being dealt with by the Biokon Network, an association of the most important bionics R&D centres funded by the German government. Germany
· Lotusan™, a self-cleaning paint developed by Sto, provides one basis for wovens or nonwovens with a surface texture which rolls up water and dirt. This works better than any fluorocarbon finish.
· Self cleaning permanent fabric roofs based on PVC/glass fibre laminates are now ready to be commercialised.
· A new logo and certification system “Self Cleaning inspired by Nature” is now being given to companies and products meeting the desired standard, one example being Schmitz Werke who make self-cleaning awnings using the biomimetic technology.
Fabrics which stay dry under water have been inspired by the water hunt beetle and are being used to make swimwear which stays dry and warm both in and out of the water.
Prof Giuliano Freddi of the Silk Experimental Station (SSS -
) pointed out that natural silk is classed as non-biodegradable because it takes around 1 year to lose its tensile strength. Regenerated silk materials on the other hand are degradable in days and are rapidly absorbed by the body after implantation. Italy
Kathrin Pietsch of the
Technical University of Dresden( ) has concluded a major study of reusable and disposable drapes and gowns in German hospitals, the reusables being processed in 3 different treatment plants. Two types of reusables, silicone treated woven polyester filament and a 3 layer laminate with microporous PU film sandwiched between layers of woven PET filament were tested. 1650 Hip replacement operations were studied and the reusables checked after 35 cycles for the laminate and 70 use cycles for the silicone treated fabric. Microbiological assessment of barrier performance, wound healing rates, and life cycle analysis were also performed. Germany
The simultaneous translation was patchy, but the conclusions appeared to be that since cotton had been removed from reusable drapes and gowns, there were no real differences in performance between the disposables and the laminated reusables up to the 70 cycles of use level. However the simpler silicone treated materials failed to meet the hydrohead standards after only 5 uses and the trials with these were discontinued.
Sybille Krzywinski of
Dresden Technical University( ) has been addressing the problem of sports wear designers who need to construct garments not just to a particular size, but also to a posture appropriate for the particular sport. Cyclists, runners and skiers adopt different postures and while they can hold these postures for a short-time, they can not maintain them for long enough to conduct the whole body scanning on which garment designs could be based. So, DTU now scans bodies in a relaxed posture and uses this to create a “synthetic avatar” of great accuracy. Software then bends the avatar into the postures most appropriate for various garment, adds a grid to the surface, and generates the patterns from which the garments can be made. Germany
Michael Scheffer of
Saxion Textile College ( )used the old argument that as world fibre consumption was expected to reach 100 million tons by 2020, the delivery of an additional 35 million tons of fibre capacity in the next 10 years provides opportunities for natural fibres other than cotton. He believes linen from flax can recover its once important position in textiles: Holland
· If the remaining flax industry can be defragmented
· If the EU supports rotational agriculture for flax production
· If the current 3 euro/kg cost can be halved.
· If the current 200,000 ton global production can be increased dramatically
· If the variability of flax quality can be reduced – i.e. if flax types can be aligned with end-uses rather than agricultural economics.
He sees the need to develop new fine fibre varieties, a better fibre extraction process using enzymes, and an improved understanding of the importance of lignin catalysis. Enhancing the bio-medical properties of the lignan component of the plant which is host to a wide range of valuable medical compounds, would allow high value materials to be extracted along with the fibres.