Tech Textil Conference and Exhibition: June 2009 Frankfurt

Introduction

Three overlapping conferences and a large exhibition meant that only a selection of the available presentations could be covered.  Themes included Materials and Technology, Medical Applications, Natural Fibres, Textiles in Construction, Sports and Outdoor Clothing, Fashion and Design, Wearable Electronics, Protective Textiles, and in Vehicles and Buildings. The numerous European technical institutes and universities provided the majority of the papers.

Points from the Exhibition

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. 

 Tencel fibre is finding increasing application in filtration and advanced electrical papers for high output batteries and condensers.  The fibre is also being used to make carbon fibre for high temperature insulation.  Wolfgang Plasser has replaced Robert Gregan as the VP Nonwovens Fibres.

 Tencelweb® 100% cellulose spunlaid nonwovens will be prototyped on a pilot line  at Lenzing in collaboration with Weyerhaeuser.  The line will also allow the key questions related to productivity and costs of such production to be ascertained. At present it appears that high-value specialities and niche products will be the targets: attempts to produce commodity, high volume products being unlikely unless technological breakthoughs are made.

 Asahi (Japan) has been making Bemliese^TM 100% spunlaid cellulose nonwovens commercially since 1973.  Their cuprammonium production route remains at 4000 tonnes/year capacity, and they report steady business in lint-free, ultra-pure products for the electronic and medical markets.  Their new Bemliese^TM MF fabrics are made from direct spun 3-4 micron diameter fibres on old machines using new spinnerettes with "very tiny holes".  Other details of this remarkable achievement were not forthcoming. The one microfibre fabric on display (TA30B) appeared whiter and more papery than regular Bemliese perhaps due to the self-bonding nature of wet-spun cellulosic fibres at this diameter.

 Hyosung (Korea) still produce lyocell filament yarns using the List Discotherm dissolver, and their main market remains industrial yarn, mainly for run-flat radial tyres.  Their capacity is 700 tonnes/year, and the plant operates at about half this rate.  They say the fibre is too expensive compared with viscose tyre yarn, but expect a new customer to require their remaining capacity later this year.

 Pegas is now offering 8gsm SSMMMS fabrics from their new line.  The stated application is diaper core wrap.

 SAPPI dissolving pulp used in viscose and Tencel production was in short supply in the EU apparently because a revival in demand in Asia had resulted in some shipments being diverted to that region.

 Technoplants (Italy) introduced Fiberfoam®, made from small (~5mm) balls of thermoplastic fibre arranged in a batt and thermally bonded.  Wadding thicknesses can vary from 10 to 100mms and densities from 15 to 120 kgs/m³.  Technoplants will produce the machinery and are building the first demonstration line which will be ready for customer trials in September.  The wadding on display was made from 80% polyester with 20% PET/CoPET bico as a binder and was intended as a replacement for urethane foam.  It felt significantly more substantial than the usual homogenous high loft waddings.

 Waxman's (UK)  “So” range of functionalised speciality viscose fibres was still on display and despite bullish claims, a spokesman admitted that these Japanese specialities were attracting minimal interest because of their high prices.  Several types are about to be withdrawn.

 Dounor (France)showed an impressively soft and uniform polyethylene spunbond at 20 gsm.  This had been made on an R2 line no longer economic for PP diaper components.  It was about 20% more expensive than the equivalent PP fabric.

 Smartfiber AG (Germany), the company formed around the lyocell pilot plant and Seacell lyocell/alginate alloy fibre developed by TITK/Zimmer showed Smartcel® Hygienic, a cellulose fibre with a copper “overlay”, apparently bonded to the surface with sodium polyacrylate.  Applications targeted include air filters for air-conditioning systems. 

This fibre complements the other intelligent fibres:

 l  Smartcel Clima (with paraffin based phase change material),

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.

 Shandong Helon Co Ltd (China), the company that introduced the bamboo fibre that was in fact viscose rayon made from bamboo pulp were showing a 1.5denier/38mm supersoft Jutecell^TM fibre,  a viscose made from Jute pulp.

They are pulping the jute themselves, whereas they had to buy in the bamboo pulp.  I asked why they didn't sell their regular rayon (made from cotton linters) as cotton but didn't get a sensible reply. Jutecell^TM maintained the antibacterial and antifungal properties of jute thanks to their special production process – which presumably allows some of the non-cellulosics in the plant to contaminate the viscose fibre.  They also make flame retardant rayon.

 They claim a viscose staple capacity of 120,000 tonnes/year and a cotton pulping mill with a capacity of 130,000 tonnes/year making the dissolving pulp for the viscose plant.

 Greenfiber (Rumania) started production of PET staple from bottles in 2006 and now have 4 lines producing about 50,000 tonnes/year of fibre, mainly for nonwoven wipes and home furnishings.  They claim to be very competitively priced.

 Reskin were showing knitted nylon adhesive backed pads intended to protect the posteriors of cyclists from chafing. Interestingly these were to be attached to the perineum, not to the shorts, and the adhesive had been carefully formulated to stay in place yet be removed without the pain of depilation.  (It works!)

 IREMA were showing samples of the integrated nanofibre filter made using two meltblown heads angled to intermingle the nanofibres from one head with regular meltblown from the other.  The product was clearly very two-sided (very soft on one side only) despite being heavily thermally bonded to a carbboard-like texture.  

 Arkema has developed a "biosourced" range of polymers.  The include Rilsan PA11, a high performance nylon for industrial textiles "100% biodourced" from caster beans, Platamid Rnew, a 100% biosourced hot-melt adhesive, and Pebax Rnew, a thermoplastic elastomer with "20 to 90% renewable carbon content".  As a 200gsm waistband, the latter offers total recovery from 100% extension, and a breaking extension of 600%.

Medical applications of Tencel™

Tom Burrow of Lenzing (Austria) 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.

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

 A Tencel/Chitosan fibre (“Tencel C”) has been evaluated in wound healing, where standard Tencel has appeared to do well compared with cotton.  A porcine ex-vivo method was used. Here small discs of tissue punched from live pig’s ears are wounded and the regrowth of the epidermis is monitored in contact with the different dressings.  Tencel was compared with Tencel C (two different varieties, one with low and the other with high chitosan content), bleached cotton and Tergal polyester, with PBS and Untreated controls.  All three Tencels were significantly better than bleached cotton, giving positive effects on wound healing and morphology.  In addition Tencel C gave improved cell proliferation at the  wound margin, with the low level of chitosan being the best.

 In response to questions, Mr Burrow added:

 ·        Tencel C is not commercial yet

·        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.

Integrated Nanofibres

Wolfgang Rupertseder, Plant Manager of Irema Filter (Germany) 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.

 The Irema method of integrating nanofibres into a filter uses two melt-blow heads angled inwards to allow intermingling of the fibres before laying.  One head is set up to produce regular meltblown and the other to produce fibres in the 200nm to 600nm range.  The resulting filter has a gradient of nanofibres which reduces the pressure drop and increases the dust-holding capacity.  Irema claim to have a 30% share of the German cabin air filter market, 30% of this now using their integrated nanofibre products. 

 In response to questions, Mr Rupertseder said their products are currently all PP based but they had PET versions under development.  Cellulosic filters could not be produced.

Plasma Functionalisation of Fabrics

Dirk Hegemann of EMPA St Gallen (Switzerland)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:

 l  Highly conductive filament yarns could be made with nanolayers of silver or copper.

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 Hegemann has combined plasma copolymerisation with sputtering and claims durably hydrophilic and hydrophobic treatments.  His process is air-to-air with both filaments and fabrics, the plasma treatments being carried out in a closed tank.  Tersuisse Multifils is the first company to scale up the process.

Novel Technology for Smart Materials

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:

 l  Multicomponent (i.e. tricomponent and above) fibres and films

  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 4^th 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.

 Among the myriad of potential applications were solid state batteries and capacitors made by printing, and super-hydrophilic or super-hydrophobic materials.

Intelligent Textiles

Luca Mezzo of Nanocyl (Belgium) 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.

 When added to a fibre-forming polymer the nanotubes give good conductivity until the fibre is stretched after spinning when conductivity drops to zero.  However after annealing at 160C, good conductivity returns.  These fibres can be added to a composite and their conductivity monitored during use, a significant reduction predicting imminent tensile failure when the composite is under stress.  In vapour sensing applications the conductivity alters according to the solvent type and its concentration. In temperature sensing the conductivity falls as the orientation is lost, and in water sensing, the swelling of the hydrophilic polymer fibre in a pipe lagging can be used to give a once-only indication of pipe leakage.

 The conductive fibres can also be heated when a current is passed through them.

Odour-reducing textiles

Harmut Finger of the Institute for Energy and the Environment (IUTA - Germany) 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.

 The tests showed the fabrics containing 60 gsm of 0.3mm diameter active carbon giving a specific surface area of 1800m2/gm would be effective for leisure use, the example being hunting apparel.  They could be laundered 3 times without loss of efficacy.

 IUTA are also working with carbon nanotubes to get thinner fabrics with no compromise on their textile performance.

Opportunities in Bionics

Thomas Stegemaier of ITV Denkendorf (Germany)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.

 In nature, hairy surfaces provide many unique properties, and natures hairs are fibre reinforced composites.  As well as fur and feathers, hairs occur on leaves, on the feet of insects,  and in spider webs.  So, fibre-based man-made materials must provide the best basis for bionic developments.

 Self-cleaning textiles based on the lotus-effect is one objective:

·        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.

 Microbubbles emitted from the skin of penquins allow them to move fast under water and nonwettable fabrics capable of emitting microbubbles are being developed for ships hulls.

 The desert beetle drinks water harvested from fog, and this is being copied to harvest drinking water in remote areas.  A non-wettable textile net with an area of 70m2 is now collecting up to 4000 litres/day of potable water in the Namibian desert.  From the slide the construction appeared to be a layer of loopy monofilaments supported on a knitted net.

Electrospun silk fibroin tubes

Prof Giuliano Freddi of the Silk Experimental Station (SSS - Italy) 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.

 Degumming of silk removes the sericin and leaves fibroin which dissolves readily in formic acid allowing conversion into films, fibres and hydrogels.  Fibroin has a long history of use in surgery as sutures and is well tolerated when implanted into living tissue. 

 SSS has now electrospun tubular fibroin matrices, the objective being to use them in surgery as by-pass grafts for small blood vessels.  The 7.5% solution of fibroin in formic acid is electosprayed onto a 6mm diameter mandrel rotating at 3000 rpm for 2 hours to produce a 150mm long tube of nanofibres with a wall thickness of around 180 microns.  The fibres are about 750nm in diameter and have a smooth circular cross section.  Removal from the mandrel causes the wall to crimp, and the whole matrix is microporous enough to allow colonization with 3T3 fibroblasts in 7 days of cell culture.

 Tube burst strengths are 4 times the upper physiological pressure of 120mm Hg so the silk fibroin electrospun tubes appear to be a promising graft for vascular replacement.

Ecological Hospital Textiles

Kathrin Pietsch of the Technical University of Dresden(Germany) 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.

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.

Body Modelling

Sybille Krzywinski of Dresden Technical University(Germany) 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.

Hyper-flax

Michael Scheffer of Saxion Textile College (Holland)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:

·        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.