Nanotubes, flushable wipes and PLA/PHBV blends

Analysis of Nanoparticles in Meltspun Filaments

Johannes Wulfhorst of the Institut für Textiltechnik (ITA) der RWTH Aachen, Aachen (Germany) reported on the ways of checking the orientation of carbon nanotubes in polymers used to make electroconductive fibres.  An FEI Tecnai F20 electron microscope is used to create a series of 2D views as the sample is tilted through 120 degrees.  Tomographic imaging software compiles these into a 3D model to allow exact nanotube orientation analysis to be carried out.  The work shows that nanotubes do indeed get oriented in the axial direction during fibre extrusion.  ITA has also observed that carbon nanotube inclusion alters the bimodal melting character of polyester.

Improved Dispersibility of Wet Wipes

Roland Scholz of Kelheim Fibres GmbH, Kelheim (Germany) reviewed fibre types and their effect on the dispersibility of wet wipes made by carding and hydroentanglement.  0.9 and 1.7 dtex round fibres were compared with 1.7 dtex “gel-surface” fibre, solid flat fibres with a 5:1 aspect ratio, inflated-collapsed fibres with a 20:1 aspect ratio and a new fibre of undisclosed dimensions in lengths of  12, 16 and 20mm.  The shorter the fibre the easier was the dispersion in the tube test, similar results being obtained from the Netherlands sewer pump test.  The round fibres and the “new shape” fibres dispersed best at these lengths.  Standard 40mm fibres formed ropes.

Fully Bio-Based and Degradable PHBV / PLA Fibers

Peng Chen of the Ningbo Institute of Materials Technology and Engineering, Ningbo (China) has discovered that polyhydroxy butyrate valerate fibres (PHBV) are too brittle and rigid to make good nonwovens.  Surprisingly blends of PHBV with PLA – which is also brittle and rigid – are soft and give nonwovens with reduced shrinkage.  The mixture of polymers is extruded with additives to promote “reactive blending”, at speeds up to 3000m/min.  The resulting yarn can be stretched up to 3 times off-line to make the final soft but glossy yarn.  The unexpected softness is thought to arise from the oriented fine lamellae structure induced by extensional flow during spinning and drawing.  It feels like rayon or silk but is naturally hydrophobic.

Denkendorf at Dornbirn

Harvesting and Storing of Solar Energy

Thomas Stegmaier of the Institut für Textil- und Verfahrenstechnik (ITV), Denkendorf (Germany) described a 3-layer textile roofing fabric engineered to allow air to be pumped through the middle layer.  This air reached 150-160^oC on a hot day and was used to dry out a silica-gel “energy store”.  This stores the energy “without loss” and yields warm dry air months later when humid air is pumped through it.

Asked about the efficiency of heat recovery, Mr Stegamaier said this had yet to be calculated.

Micro Fibers Based on Cellulose and its Acetate

Frank Hermanutz of the Institut für Textilchemie und Chemiefasern (ITCF) Denkendorf, Denkendorf (Germany) has used spinnerets made by new laser hole drilling technology for the direct spinning of cellulose and cellulose acetate fibres.  The holes are drilled with an ultra-short pulsed laser using a highly focussed beam circulating helically around the circumference of the required hole.  The system was developed at IFSW in Stuttgart. The resulting holes have a naturally conical inlet and a precise outlet down to 25 microns in diameter.  Half-inch thimbles with 2000x25 micron holes in gold/platinum looked excellent for wet spinning and for air-gap, a 250 hole stainless steel version had been made.  Cellulose microfibers down to 0.2 dtex have been wet-spun from a solution of cotton linters in an ionic liquid (8% to 16% in 1-ethyl-3-methylimidazolium acetate) and from cellulose acetate in acetone.  The latter had a very rough non-circular cross section.

Finer, Stronger Melt Blown

Christoph Rieger of the Institut für Textil- und Verfahrenstechnik (ITV), Denkendorf (Germany) promoted ITV’s recently developed ability to produce melt blown PP down to 0.4 microns and stabilised melt blown PET webs of high strength and thermal stability to 200^oC.  They are also capable of hydroentangling melt blowns and their laminates with other fabrics to get the best combinations of strength and fineness.

Bicomponent Fibers by overjacketing extrusion and electrospinning

Felix A. Reifler of EMPA Laboratory for Advanced Fibers, St. Gallen (Switzerland) was using overjacketing extrusion to add a sheath or sheaths to a monofil core. The technology was essentially that used to apply insulation to fine copper wires.  The main application appears to be applying an insulating sheath to silver-coated yarns for use in conductive textiles.  An 80 micron polyester is plasma-sputter coated with silver and overcoated with 8 microns of thermoplastic PA12-based elastomer at 25 m/min.  Dip-coating can also be used.  PLA and PVA sheaths have also been tried.  Adhesion of the sheath needs improving and the work continues.

Juan Esteban Diaz Gómez of NanoMyP Nanomateriales y Polímeros S.L., Armilla (Spain) has been spinning bicomponent nanofibres from annular nozzles where the core polymer solution can be a non-electrospinnable polymer.  Hollow nanofibres, and liquid filled nanofibres (hydrophobic liquid inside a hydrophilic polymer) are also possible.  They are now working on scaling up the process and further improving it with air-jets (“electroblowing”) or rotation (“Forcespinning™).  “Smart materials with physicochemical properties tailored to customer needs” is now the subject of a new department.  P&G, Unilever and Henkel were among the companies listed as customers of NanoMyP.

Liquid Crystal Nonwoven from Kuraray

Yasuhiro Shirotani of Kuraray Co., Ltd., Saijo (Japan) said Vecrus™ was a melt-blown nonwoven made from the Vectran™ liquid crystal polymer.  The nonwoven withstood temperatures of 330C and shrunk less than 1% at 260C. Vectran™ is a wholly aromatic polyester made from 4-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid.  It is used for printed circuit boards, electromagnetic shielding and electric motor insulation.  It’s moisture regain is only 0.002%.  A new version of the melt blown is now being developed with half the standard fibre diameter (3 microns: down from 7) The melt-blown webs will be made in the 3.5 to 20 gsm range and will have a breaking length of over 10 km, double that of the standard Vecrus™

Applications will include fibre reinforced plastics for phones and laptops, Li-ion battery separators, heat resistant wipes in copy machines and heat resistant filters.  In the copy machines the new wiping roll uses a 6gsm 20 micron thick Vecrus™ which gives 3 times the usual length of wiper in the cartridge.

Kelheim Viscose for Dry and Wet Nonwovens

Philip Wimmer of Kelheim Fibres GmbH, Kelheim (Germany) reviewed the changes in absorbency through Kelheim’s range of Italian fibres to illustrate that pure cellulose fibre can give from 1:1 to 4:1 water retention compared with cotton’s 0.5:1.  He then moved on to consider the possibilities of less absorbent, more hydrophobic types.  More crystalline fibres are less accessible to water and stronger, but this approach can do no more than halve the retention.  Adding non-absorbent fillers can do the same, but these more than halve the strength.  Chemical modification works, e.g. acetylation but the result is not pure cellulose.  Hydrophobic agents can be applied as finishes or added to the viscose, the latter approach giving a more permanent change in hydrophobicity which can resist washing and dry cleaning.  Kelheim have now developed such a product using an additive made from renewable, biodegradable raw materials which is also FDA approved for hygiene and food contact applications.


Ingo Bernt of Kelheim Fibres GmbH, Kelheim (Germany) ran through the properties of the Italian fibres again, the new additions this time being a 4dtex Leonardo smooth flat fibre and “Umberto”, a variable cross-section fibre giving an alphabet soup of shapes.  Umberto was not included in the written paper.  The finer Leonardo gives papers of higher strength and folding endurance than the 9dtex, but slightly lower transparency.  Anionic treatment as used to make the Verdi fibre boosts strength and folding endurance further.

Cellulose Acetate Nanofibres from Agricultural Waste

Roberto Frassine of the Politecnico di Milano Polymer Engineering  Lab., Milano (Italy) has been using corn-cobs and straw, wheat straw and even seaweed as a source of cellulose for acetylation – a process which normally requires the highest quality dissolving pulp.  The cellulose extraction and purification process involves Toluene/Ethanol extraction of waxes followed by bleaching first with alkaline peroxide and then with an acetic/formic acid/hydrogen peroxide mixture. 

A final peroxide extract yields a pure cellulose with a DP rather lower than that obtained from wood.  This was acetylated  and dissolved in dichloromethane/methanol for electrospinning to nonwovens.  At acetate concentrations of 7% and 10% the nonwovens were of good quality.  A lab. scale batch reactor has now been built to allow 1.5kg batches of acetate to made for future experimentation.

Tencel for Battery Applications

Marco Gallo of Lenzing AG, Lenzing (Austria) described the development of separators for alkaline batteries using Tencel.  Tencel can be refined in disc refiners and beaters to give a hgher proportion of microfibers and fewer cut fibres than pulps.  This leads to lighter, thinner papers with smaller pores and hence better insulation and conductivity than alternatives.  Cellulosics are normally blended with PVA fibres and bonded with PVA latex.  Tencel can be used in blend with pulp or viscose in the cellulosic portion according to the cost/benefits required.
New varieties of Tencel are under development which will allow further reductions in the weight of the separator required per battery.  These also improve the dimensional stability and durability of the paper in the strong alkalis used.  There were numerous questions:

•         Can Tencel be used to obtain nanofibres?  Yes but at a cost which only works for some applications.
•          What operating temperatures must the separator be designed for? -30 to +50C
•          Is the whole furnish refined together?  No Tencel is refined separately.
•          Is Tencel paper used in double-layer electrolytic capacitors?  Yes.
•          Are fibrils lost through the wire?  Yes this is an issue which necessitates careful tuning of the refiner.
•          Would Tencel be used in electric car batteries?  Yes – this is under development.

          See also Innovation:  Product development with Tencel 1988

Carbon Footprint of Garments

Jürgen Ströhle of Benninger AG, Uzwil (Switzerland) said the carbon footprint of garments depends crucially on the country of manufacture.  

• Brazil is best by far because most energy generation is from biomass.  India and China are worst because they use most coal.  
• For fibres, PET appeared worst followed Asian viscose and US and Chinese cotton.  
• Austrian viscose had the lowest carbon and water footprint, while US cotton had the highest water footprint.  
• Studies of T-shirt finishing methods revealed that 100% viscose shirts had least impact, 100% cotton most, with 100% PET in between.  
• For dress shirts, cotton was worst with Tencel and PET equally good.  

Asked if organic cotton would be better, Mr Ströhle thought it would make no difference to the finishing impact but would be better at the raw material stage.  On a cradle-grave basis, half the impact of a T shirt is at the production stage and half in washing/drying.

Tencel Gel

Martina Opietnik of Lenzing AG, Lenzing (Austria) reviewed the development of Micro Fibre Cellulose from Turbak’s development of a nanocellulose gel in 1983, through their use in biocomposites in the 90’s and in transparent cellulose nanofibre paper in the 00’s, to their current applications in flexible organic light emitting diode displays.  Traditionally pulp is acid-degraded, beaten and homogenised to make MFC but now the lyocell process can be used to make either fibres or beads which require much less energy to convert into MFC. 

Tencel fibre gives a fibrous gel but the Tencel beads give a 3-D structure and a perfectly smooth gel.  They are both white viscous suspensions which are stable over a range of pH’s and temperature, but show thixotropic behaviour.  They also form films on drying, and can be used as coatings for films, textiles, papers and tablets.  Applications in packaging, cosmetics, food thickening, and medicines are envisaged.  In food it could also be a calorie-free fat substitute.

Asked if the coatings would be stable on polyesters, Ms Opietnik thought the gel would stick well to the surfaces of films or fibres but would have to cross-linked for durability.  Application could be by spraying.  Is the gel regarded as a fibre under the REACH regulations?  Maybe a new directive was needed to clarify this aspect.

Cellulose: from biogenic polymer to novel functions and innovative applications

This was the title of the paper given to approximately 280 attendees at the third Cooperation Forum Biopolymers in Straubing by Dr. Haio Harms, CEO of Kelheim Fibres GmbH. The paper illustrated impressively the versatility of viscose fibres made in Kelheim and presented future-oriented applications possibilities for their use. “Cellulose- and lignocellulose-based materials and composites” was one of the main topics of the Forum organized by Bayern Innovativ in collaboration with the Centre of Excellence for Renewable Resources in Straubing – and Kelheim’s viscose fibres are a prime example of such materials. 

Speciality fibres from Kelheim are high-performance materials which can substitute oil based synthetic materials in certain applications and deliver equal or even better performance; filters and speciality papers are examples of end products which can benefit from Kelheim’s fibres – and even carbon fibres are made from viscose fibre precursors. In addition to this, viscose fibres are made from 100% renewable cellulose as a raw material and are therefore completely biodegradable. 

As a result, the field trip to the speciality fibre manufacturer’s headquarters at Kelheim, which was offered as part of the additional programme of the cooperation forum, was met with great interest. Around 50 visitors were given the opportunity to see the production plant and Kelheim’s R&D pilot plants.