Thursday, 13 July 2000

Polypropylene in Textiles World Congress Huddersfield UK:

Over 260 delegates from 24 countries gathered at the University of Huddersfield to listen to papers presented by 32 speakers from 14 countries. This was the last of a series of conferences organised by Dr Kim Ghandi who retires this year. It was probably the most successful and the series will be a sad loss to the conference circuit. Summaries of the papers grouped according to areas of interest follow:

Increasing Polypropylene Fibres Versatility Through Novel Effect Additives
Jean Roch Pauquet & Patricia Schrijver - Rzymelka, Ciba Specialty Chemicals Inc, Switzerland
Ciba’s new phenol-free stabiliser Fiberstab L112 is based on the HP 136 lactone, the Irgafos 168 phosphite and the hindered amine, Tinuvin 622.
It is as effective as the phenolic/phosphite system during processing but dramatically reduces the potential for gas fading.
The hindered amine component provides the long-term thermal and UV stability compared with a phenolic.
Their latest high molecular weight oligomer hindered amine light stabiliser system, Chimassorb 2020. This gives superior light stability against automotive specifications, high extraction resistance, low volatility and better colour yield (with pigments) than the current state-of-the-art stabilisers.
Their revolutionary new n-alkoxy hindered amine, halogen-free flame-retardant (Flamestab NOR 116) provides protection to PP fibres at unexpectedly low concentrations, while controlling both thermal and light degradation. It can also be mixed with conventional FR compounds such as deca-bromo diphenyl oxide to reduce the concentrations required and improve fibre properties.
Permanent antistatic behaviour can be achieved by blending 4 - 10% of a hydrophilic copolymer into the polypropylene. Irgastat P22 does this by forming a network of conductive polymer chains within the fibre. Surface resistance of the polypropylene is thereby reduced from 1015 ohms to around 1010 ohms at 10% add-on.
Antimicrobial activity can be achieved by adding an additive that has been used in cosmetics for more than 30 years. 0.1% of Irgaguard B1000 allows the fibres to inhibit the growth of gram-positive and gram-negative bacteria.
CIBA were working on an additive to make PP permanently hydrophilic, but did not expect it to be commercial for about 3 years.
None of the compounds were approved for food use yet, but Chimassorb 2020 will be.

Surface Control in Polypropylene Fibres and Fabrics

Dr. Tom W. Theyson, Goulston Technologies Inc, USA
Most topically applied materials had some effect on the strength of any thermal-bond between fibres, the greatest effect arising from silicones. 0.6% of can reduce the thermal bond strength by 55%.
Maybe specialised materials could be developed to enhance bond strengths.
Strike-through times of 2-2.5 seconds were easily achieved with almost any topically applied surfactant, but migration of the chemical into the fluid prevented the achievement of good wicking rates and good multiple-insult strike-through times.
Durable hydrophilicity requires the use of surfactants that can penetrate or be bonded to the fibre surface, and such surfactants must be both oil- (to penetrate the PP) and water-loving.
Goulston has developed such materials that at 0.5% add-on enable PP fibres give 2.5 second strike-through times after 10 wettings: an approach which is now looking capable of being durable enough for textile use.
Other properties achievable from durable topical applications were soft handle, antimicrobial activity from self-polymerising materials and active care properties from baby-oil, aloe etc. In this latter case, only “advertising” levels of activity were possible in fibre production: functional levels of activity needed the materials to be applied on the finished product.
Plasma, sulphur dioxide, fluorine and other high energy surface modification techniques all had potential, especially in conjunction with topical treatments. The first examples of such combinations were just becoming commercially available.

"MOPLEN ULTRA" Innovative Polypropylene Resins Family for Spunbond and Melt-Blown Nonwovens
Giancarlo Braca, Franco Sartori, Technology Business Support, Montell Europe /Ferrara - Italy

Moplen Ultra 817HOXP is a more stereo-regular polymer with a narrower molecular weight distribution and a higher crystallinity arising from a higher crystallisation temperature and shorter crystallisation time.
When spinning the 25 MFR resin to 0.72 dtex filaments in yarn form, take up speeds of 4500m/min can be achieved compared with 3900m/min for the “benchmark” polymer against which all comparisons were made.
When spun to give the same elongation as the control, the 817HOXP gives a 20% increase in filament tensiles and higher birefringence, confirming the higher level of molecular orientation achieved.
Plant trials on the Lurgi-Docan, the NVT®, and on Reicofil II and III machines all confirmed the laboratory results and showed the 817HOXP to be a very forgiving resin with a wide operating window.
The meltblowing version also has a narrow molecular weight distribution, and a Melt Flow Rate of 1,800 achieved directly in polymerisation and without recourse to peroxide degradation (“Moplen Ultra 810HOXS”).
In the laboratory this can be processed at lower melt temperatures to give meltblown fabrics with finer, more uniform fibre sizes and hence more uniform pore sizes and better barrier properties.
The lower operating temperature should lead to reduced fuming (better working conditions) and lower operating costs.
Industrial scale meltblowing trials are about to take place and the resin is expected to be on the market this autumn.

Hydroentangled - Spunbonded Nonwovens from Polypropylene - High Product Quality for Technical ApplicationDipl-lng. H Erth, Dipl-lng. D Blechschmidt,, Dipl-lng. (FH) M Brodtka, Dipl-lng. (FH) Rainer. Linder Saxon Textile Research Institute, Chemnitz, Germany
Webs of PP from two catalyst systems with filaments from 0.8 to 2 dtex, at 35-300 gsm, made at speeds from 2 to 18 metres/min were first pre-bonded in a calender prior to Fleissner hydroentanglement.
He concluded the metallocene PP gave the best results, and that hydroentanglement generally gave bulkier, softer and more absorbent products than either needled or thermally bonded spunlaid materials.
Surprisingly, nonwoven thickness after hydroentanglement up to 190 bar was always higher, often twice as thick, as the lightly pre-bonded starting webs.
This was the result of fibres being reoriented in the Z-direction.
Asked whether the bulking effect could be achieved on fully-thermally-bonded spunlaids, he said the trials remained to be done.

Production possibilities of Polypropylene Microfibres
Dipl-lng. Christine Harder- Swiss Federal Institute of Tech., Zurich, Switzerland
A review of PP yarn spinning and texturizing processes considering the problems of making pigmented microfibres.
Agglomeration of pigment in the masterbatch was still preventing pigmented microfibres from being commercially attractive.

PP - Fabrics - Your Partner ST

Jurg L Wildhaber- Sulzer Textil Ltd, Switzerland
14%, or 30 billion m2 of World fabric production is now used in the technical textiles sector.
Of this, 32% is “simple” e.g. cotton, fabrics, and 16% is “complicated” e.g. air-bag or aramid fabrics. 14% is glass, and the remaining 38% is based on polypropylene.
Slit-film, multifil and monofil yarns can all be woven on Sulzer projectile looms, typically at widths of 5.4 metres for carpet backing, flexible intermediate bulk containers, geotextiles and agrotextiles.
In the latter category, shades for tobacco plantations were now being woven 6.5 metres wide, and machines to weave up to 8.5 metres wide could now be ordered.
Fibrillated PP tapes could be woven to make geotextiles to outperform nonwovens.

Smart Fibres( Synthetic)
Simon Senior, Drake Extrusion Ltd, UK
A review of the gloomier recent predictions related to population growth and global warming.
He concluded that the pressure on agriculture to feed the world’s population by the year 2050 would leave little scope for growing cotton or trees, or in fact any natural fibres or fibre forming polymers.
Natural fibres would be “squeezed out”, leaving synthetics in general and polypropylene in particular to respond to the textile needs of the expected 11 billion people.
Dreams of smart fibres and textiles would come true:
o T-shirts would have built in Global Positioning Systems so that parents could always know the whereaouts of their children.
o Charged fibres and fabrics would repel dirt into collecting “magnets”.
o Body odour control would be achieved using antimicrobial fibres such as Acordis’ Amicor™ or Drake’s Permafresh™.
o Body temperature would be controlled using phase-change materials.
o Telephone key-pads would be built into shirt-cuffs.
o Strain gauges built into skin-tight undergarments would allow computer analysis of sporting activities (e.g. golf swing).
o Sound systems would be built into carpets (vibrating fibres)
o Over-floor heating systems would be built into carpets.
o Smart rugs would provide therapy for foot ailments.
o Security systems would be built into carpets (footprint recognition).
o Emergency lighting would be built into carpets (fibres that glow in the dark and direct you to an emergency exit)
Drake’s Permafresh™ fibre used a polymer additive enabling 20% of the resulting antimicrobial polypropylene fibre to protect 80% of untreated PP in a blend fabric.
Applications expected in carpet pile and underlay, bedding fabrics, and upholstery, major themes being fungal growth and dust-mite control.

Three interesting Developments which could Boost the image of PP
Francis A Woodruff, Web Processing, UK
Foam coating, in addition its well known advantages, allows the coat to stay on one side even when the fabric has 2mm apertures. The foam collapses in the oven.
Coating growth in the UK is being driven by the Fire Regulations but similarly tight regulations will be adopted by other countries.
Land-fill waste disposal may well be banned: the problems of incineration of latex-backed carpets would increase the emphasis on recycling.
If carpets used PP pile and recycled-PP needlefelt backings fixed to the facing by powder bonding, the whole structure could be melted and recycled to make the needlefelt backing.
Corona and plasma treatments would allow the reactivity of the PP surface to be increased. Reduced pressure plasma treatment was now commercial and atmospheric pressure treatment had been developed.
Wettability and dyeability were improved by these treatments, but the PP film surface energy increase from 33 to 50 dynes/cm2 was still not enough to allow adhesive bonding.
Plasma treatment required banks of electrodes to achieve treatment times of a few seconds.
The improvement in surface activity did decay with time, and any fabric treatment depending on this effect had to be done immediately.
Other successes of plasma treatment trials were:
Increased moisture absorbency of wool.
6-fold increase in peel-bond strength of a polyurethane coating.
Doubling the wet strength of a PET fabric
Quadrupling the wet-strength of a PP/Cellulose nonwoven.
Improved uptake of reactive dyes on cotton.

Quantification of Antioxidants in Polypropylene Using SFE / HPLC

Maria Thilen & Prof. Roshan Shishoo, IFP Research AB, Sweden
Extraction of ground polymer with supercritical fluid followed by HPLC allowed the antioxidant levels in PP to be monitored.
In order to get the best extraction yields, 2% of methanol was added to the liquid carbon dioxide which was pumped at 4 mls/min through the sample at 384 bar and 120oC.
10 minutes extraction was normally adequate but 1 hour used to be absolutely sure.
1 hour of SCFE extraction was shown to be equivalent to 96 hours cyclohexane extraction.
Whatever the method, 70% of the antioxidant was the maximum extractable.
Results from PP thermally aged at 70oC showed that antioxidant level fell sharply after 240 hours.
A knowledge of the antioxidant level in used PP was important in deciding how to recycle.

Asota M40 - A New Generation Polypropylene Hollow Fibre
H Linsbauer - Asota Gmbh, Linz, Austria
The fibre has 3 small holes arranged to create an internal trilobal section, this giving the fibre higher resilience and rigidity than either a single larger hole or the equivalent unenclosed trilobal section.
At 20% blend with wool in carpet yarns dyeing of the PP component is not necessary.
Polypropylene, being higher in the triboelectric series than either nylon or polyester also had a lower tendency to generate static.
Recovery levels from a carpet-pile compression test were quoted as 92.1% from the hollow fibre, 88.5% from the equivalent tri-lobal fibre and 86% from the round section fibre.
Asota also have the technology to add Actigard™ to the polymer to make their fibres antimicrobial.

Polypropylene Industry in Turkey
Dr. Hale Canbaz Karakas, Textile Eng Dept. Istanbul Technical University,Turkey
After China, Turkey is the world’s second largest exporter of IBC’s (big-bags) but is relatively new in PP-containing carpets.
In response to customer demand Turkey plans to develop rapidly to supply PP carpets into the EU.

Electrically Conductive Fibres from Polyaniline-Polypropylene Blends

Prof. P Nousiainen, M Rissanen, A Puolakka, Tampere University of Technology, M Jussila, J Laakso - Panipol Ltd, Porvoo, I Pykko - Tamfibres Ltd, Tampere, Finland
Blends of PP with 10 to 20% of a polyaniline doped with a sulphonic acid could be converted into electro-conductive chips for textile filament manufacture.
Getting the polyaniline to mix properly with the PP was a problem that had been tackled by Neste Oy but the process was secret.
Spinning trials on their compounds showed that the conductive additive had a minor deleterious effect on spinnability. This, coupled with the blend effect, reduced the fibre tenacity by between 14 and 43%.
Extrusion temperatures of 210oC gave uneven blends: 240oC being needed for best results.
In nonwovens, 5% of the PP-PANI fibre in blend with cotton gave improved carding and cross-lapping, and reduced the surface resistivity of the nonwoven from 1011 ohms to 1010 ohms.
In blend with polypropylene the effects were more impressive, surface resistivity falling from around 1012 ohms to nearly 109 ohms at the 5% level of PP-PANI. Increasing the PP-PANI level to 30% did not affect the resistance further.

Dendritic Polymers : A New Concept for Dyeable Polypropylene Fibres
Peter E Froehling, DSM Research, Geleen - Netherlands
Stephen M. Burkinshaw - University of Leeds UK.
Dendritic polymers are “grown” tree-like in 3 dimensions becoming very large, approximately spherical macro-molecules with numerous branches and spaces between the branches that can trap other molecules.
If the ends of the branches are terminated by groups receptive to acid or disperse dyes, the molecules will confer this property to whatever they can be blended with.
4% of a fatty amide polyamine dendrimer allowed acid-dyeable PP fibres to be produced.
At 80oC and somewhat lower pH’s than normal for nylon dyeing, brightly coloured fibres were obtained with a wide range of acid dyes. Unfortunately, the dyes did not penetrate into the middle of the fibre (ring-dyeing) due to their highly polar nature, and wash fastness was poor.
Disperse dyeing PP containing 3% of a fatty amide modified polypropylene-imine dendrimer at 80-120oC gave intensely coloured through-dyed materials with good to excellent wash and rub fastness.
The additives are currently very expensive, dye-baths are slow to exhaust and there are questions over UV stability.
The development continues with, amongst other approaches, attempts to modify the disperse dyes (which have after all been optimised for polyester) to better suit both polypropylene and the dendrimer additives.
CRW Comments: dendrimers terminated with hydoxyl groups should allow the production of permanently hydrophilic fibres, or increase the absorbency of already hydrophilic materials.

Bicomponent PP I PE Matrix Fibril Filament Yarns Spun with the Addition Of Paraffin Oil
Andrej Demsar, Franci Sluga, University of Ljubljana, Faculty of Natural
Science and Engineering, Dept. of Textiles, Snezniska, Slovenia
Polypropylene and polyethylene are largely immiscible in the molten state so the extrusion of a blend of these polymers results in a bicomponency due to fibrils of one polymer being dispersed in a matrix of the other.
Addition of 2% paraffin oil (a plasticiser and compatibiliser) to the extruder generally lowered the viscosity, thereby lowering the dye-head pressure and improving the spinnability.
The resulting yarns were more uniform (reduced C.V. of yarn properties), higher in density with lower spontaneous relaxation, lower in ductility, higher in strength and with a lower melting temperature than those spun without the addition of paraffin oil.

Polypropylene in Staple Fibres with a view to Advanced Process Technologies for One-step Staple fibre Production
Dipl. Ing. Hendrik Tiemeir - Neumag Process Engineering Germany

A comparison of Neumag’s spinning lines for polypropylene.
The low speed inline machine is an economical way of making up to 50 tpd staple.
The compact high speed inline machine makes better fibre up to 10 tpd.

PP Textiles: Into the Future
Colin M. Purvis - Director General EATP, Brussels, Belgium
Worldwide production of PP fibre, slit film, spunlaid and tapes has grown at 6-7% per year on average, is now approaching 5 million tonnes/year and accounts for 26% of the total PP resin usage.
Almost 2 million tonnes is produced in Europe, where it now accounts for 35% of the man-made fibre market.

Market Perspectives of the European Polyolefin Textile Industry
Dr. Jean - Pierre Peckstadt, Senior Adviser EATP, Brussels, Belgium
1.63 million tonnes of resin were used to make textile products, of which 500,000 tonnes were staple fibre and 271,000 tonnes were spunlaid. (1998 figures for Europe)
Medical and hygiene uses accounted for 228,000 tonnes of this (122,000 tonnes being spunlaid/meltblown). Geotextiles used 41,000 tonnes of spunlaid and 15,000 tonnes of staple fibre, 30,000 tonnes of slit film and 20,000 tonnes of mono or multifil yarns.
475,000 tonnes of PP went into floor coverings of which 100,000 tonnes were needlepunched carpet “pile”. (Tufted and woven pile accounted for 145,000 and 125,000 tonnes respectively. The remainder was used for backings.)
The automotive sector is still dominated by polyester, but 20,000 tonnes of virgin PP needlefelt finds its way into car carpets, trunk liners, package trays etc.
Further aggressive growth at the expense of other synthetics is expected as the technology improves and new varieties are developed.

Structure and Properties of Spunbonded Nonwovens Produced from Polypropylene Polymers.
Dr. Gajanan S. Bhat & Rammohan Nanjundappa, The University of Tennessee, Knoxville, USA
TANDEC is working on spunbonds but no interesting conclusions drawn yet.

Polymer Additives for Future Demands and Improvements in Man-Made Fibres
Joachim Bayer - Clariant GmbH, Germany
For melt stability after 5 extrusions (i.e. recycled 4 times), the standard phosphite-based stabilisers were outperformed by a lactone-based multicomponent stabiliser which in turn proved inferior to the two diphosphonite-based stabilisers especially at the lower extrusion temperature (230oC c.f. 270oC).
For colour stability, one of the diphosphonite based compounds (the non-cyclic one) was superior to all other types. This stabiliser also improved the UV stability of a weathered PP geotextile (as measured in the Xenotest 1200).
In further evaluations of accelerated exposure stability against the automotive industry’s hot colour fastness and ageing standards, three different PP types were stabilised with two well-known HALS (hindered amine light stabiliser) compounds.
The number of exposure cycles required to halve the PP’s tensile strength was significantly greater for one of the polymers combined with one of the HALS additives (the Hostavin® N 30).
Polymer and stabiliser choices had to be carefully optimised for best performance against specification.
The Introduction of a New Stabilizing System for Textile Products - Fiberstab L - from the View of a PP ProducerDI. Bernd Schutz - Targor GmbH, Germany
The first grades to use Fibrestab L were commercialised and approved between April 98 and September 99. They now make 4 different PP-grades (Novelin 1101 M,N,R & S) using three different stabiliser systems.
This amounts to 120,000 tonnes/year of filament, staple and nonwoven types.
They are now working on a 6 melt flow rate (MFR) grade for geotextiles using the new stabiliser.
The new stabilizer gave better spinning, better yarn properties, reduced discoloration and good thermal stability.
It also allowed levels of HALS stabiliser to be reduced, and gave the advantages of a phenol-free system to their customers.

The Markets for PP in Textiles Worldwide
G Mackie, Geerdes international Inc, Virginia, USA
European PP textile consumption is only 25% of the worldwide level of 5.7 million tonnes.
Of this 1.35 million tonnes were staple fibre and 750,000 tonnes were spunlaid/meltblown.
Nonwoven uses amounted to 520,000 tonnes in the USA, and 410,000 tonnes in Western Europe.
World resin production of about 23 million tonnes in 1999 could be expected to almost double by 2010.
PP homopolymer resin prices, having fallen to almost $500/ton a couple of years ago, could be expected to rise to $750/ton by 2010.

Spin Finishes for Polypropylene Staple Fibres used in the Spunlace Process

Christine Wild, Cognis Deutschland GmbH

Christine Wild, Cognis Deutschland GmbH, Germany
Compared with viscose or polyester finishes, PP needed more antistatic protection, better lubrication and better wettability, and therefore more finish than the other fibres.
This has to be achieved without creating foam in the HE process and without adding to the filtration load.
The finishes had to be emulsion rather than dispersions and the liquid particle size had to be below 1 micron. They also have to be chemically suitable for hygiene applications and ideally FDA approved.
Stantex S6397: a semi-permanent hydrophilic, low foam finish with improved hard-water stability achieved without the use of complexing agents such as EDTA which might soon be banned on textiles in Germany.
The data presented to support this claim showed the new finish on PP to be superior to a conventionally finished PES fibre in foaming tests with waters of differing hardness, and in sink-time testing.
The new finish was applicable to viscose and polyester also.
Hydroentangled disposable products would continue to be made from viscose for the foreseeable future, but blends with PP, or even PP alone, could be used for more durable products where higher wet strength was needed.
Blends with PP were to be preferred over blends with PES because PP was antimony-free, lower in cost and had a softer handle.

Antimicrobials in Polypropylene - Their Promise and Environmental Impact
Dr. W Curtis White, Robert A.Monticello , James W.Krueger, AEGIS Environments, Michigan, USA, Patrice Vandendaele, Devan Chemicals N V, Renaix- Belgium
Conventional antimicrobials leach from PP fibres to form, in efficacy testing on agar culture plates, a “zone of inhibition” on which the organisms cannot grow.
At the boundary of this ZOI most organisms are killed, but the few that survive are those with enhanced resistance to the biocide.
If cultures are taken of these survivors, and the tests are successively repeated, it has been shown that bacteria can develop complete resistance to the biocide in just three generations.
The Dow-Corning organofunctional silane compounds (as used in medical nonwovens and consumer textiles since 1976) to create an antimicrobial that bonds to PP with excellent durability. (non-leaching)
It’s a 3-trimethoxy silyl propyl dimethyl octadecyl ammonium chloride on a lipophilic aliphatic chain, also known as AEM 5772 or Aegis Microbe Shield.
It bonds to the PP through the silyl group and kills bacteria - without being destroyed itself - by physically penetrating the cell membrane with the aliphatic chain “sword” before “electrocuting” it with the charged nitrogen atom on the quaternary ammonium group.
The compound can be added to the PP spin-finish or padded onto the nonwoven.
It is already in use on Drypers™ diaper topsheets and can safely be used on filters for fish tanks because it is completely non-leaching.
Socks, underwear, bedsheets, waddings and carpets are among the other applications.
On carpets, it destroys the symbiotic fungi on which the dust-mite depends, and so prevents dust-mite colonies from developing.
Its presence on a fabric can be highlighted with bromo-phenol blue indicator.

Availability of Fabrics with PP Fibres for Clothing Purpose
G. Dziworska , Prof I Frydrych., Institute of Textile Architecture, Poland
Comprehensive trials comparing cotton, viscose, polyester, nylon and lyocell with PP in yarns and woven fabrics.

New Technologies for PP - Nonwoven-Production Require Modified Spin Finishes
Dr. Jurgen Peschel - Dr. Alfred Schulberger,- Dr. Th. Bohme K G Chem. Fabrik GmbH & Co. Germany
New spin-finishes for both staple fibre and spun-laid hygienic nonwovens targetting higher production speeds, more efficient processes, and lower production costs while meeting the most stringent dermatological and toxicological requirements of the most demanding consumer products companies such as Procter and Gamble and Kimberly-Clark.
Their Synthesin 7292 is also good on short-cut fibre for air-lay, wet-lay, flock and concrete reinforcement.

Effect of Proportional Blending of Recycled Polyethylene on the Properties of Polypropylene Fibres Intended for Geotextile Applications
S. M. Gillon, A. R. Horrocks, M Miraftab, P Davies, Bolton Institute, UK

They took Novolen 1101R polypropylene and added recycled HDPE (injection moulding grade Linpac H-750 recovered from trays and crates).
Virgin HDPE (Rigidex HD 5211) was used as a control.
Up to around 10% of either HDPE was thought to give acceptably small reductions in tensile properties but the recycled HDPE gave poor results in accelerated oven ageing tests.
Work continues to try to find out why this is occurring.

Modelling the Drawing of Polypropylene Fibres : Control Factors and their Interactions
R. Yang , A . F. Fotheringham, R R Mather, & G. Allan, School of Textiles,
Heriot - Watt University, Netherdale, Galashiels, UK
The factorial experimental design used to develop a computer model of PP spinning and drawing was described.
It will ultimately be capable of printing out the process conditions needed to make a fibre with whatever tenacity and elongation is required.
The effects and interactions of spinning temperature, winding speed, metering pump speed and drawing conditions on tenacity, modulus, elongation and crystallinity were presented.
Two-stage drawing emerged as clearly superior to one-stage drawing for all outcomes.

Effect of Resin Properties on the Crystallisation Point of Polypropylene During Spinning
Olivier Merle, TOTALFINA, Fina Research S A, Belgium
Also considered the effect of calendar bonding on the properties of a point-bonded nonwoven fabric.
Thermal bondability, like the tensile properties of a PP fibre, depends crucially on the morphology created during manufacture.
Stress-induced crystallisation, resulting in an epitaxial or “shish-kebab” morphology where lateral crystals form after the main axial crystallisation (which carries most of the load), gives best results.
Cold drawing on the other hand leads to a fibrillar structure that gives nonwovens with lower mechanical properties.
The onset of crystallisation can be determined by observing the spinning filaments with an infra-red camera because crystallisation is an exothermic process.
Molecular weight distribution was found to have the strongest influence on the position of crystallisation, narrower distributions delaying its onset and reducing the bondability of the resulting fibre.
Increases in molecular weight were beneficial to both bondability and fibre tenacity.
Spinning speed has no effect on the crystallisation point.
Nucleating agents have no effect on the crystallisation point.
Fibres are in the nip of a thermal bonding calender for less than 15 milliseconds.
The extreme pressures in the nip increase the melting temperature of the polymer.
The temperature at the centre of the fabric is raised by deformation induced heating as well as conduction.
Sections of bonding points contain fibres that have stayed round, suggesting that melting is not a prerequisite of bonding.

Highly Efficient UV Stabilizers for Polypropylene Fibres
Jerry M. Eng - Cytech lndustries Rotterdam, Netherlands- Leonard H.Davis -Cytec Industries Inc,Stamford, USA, Ivan Vulic -Cytec Industries, Rotterdam, Netherlands
A comparison of the stabilisation performance of four hindered amine light stabilisers for PP.
1)A low molecular weight ester (Tinuvin 770) 2) a high molecular weight polyester (Tinuvin 622) 3) an “optimised” high molecular weight triazine (Cyasorb® UV-3346) and 4) a high molecular weight triazine (Chimassorb 944).
Product 3 from Cytec Industries unsurprisingly proved best in xenon arc weathering tests and Florida weathering.
Meltblown: The Increasing Meltflow Rate and its Benefits
Nancy Noynaert, Borealis Polymers N. V. Beringem, Belgium
Their HL512B (1200 MFR) was recommended.

Innovative Process in BCF Yam Production
Gunter Klambauer, SML, Lenzing, Austria
The new compact spinning plant is flexible and allows fast colour changes.
The texturizer gives very high and uniform crimp contraction over a wide range of deniers.
The resulting yarn gives Texturmat contractions of up to 21% and a thermal shrinkage of less than 0.8%.

Evaluation of Fibre Heatsetting by MDSC
Myriam Vanneste, Valja Everaert - Centexbel - Garren Engineering, Gent Els
Verdonck TA Instruments - Brussels, Belgium
An estimate of heat-setting temperature is traditionally given by the pre-melting endothermic peak (PEP) in a thermogram from a Differential Scanning Calorimeter.
Modulated-temperature differential scanning calorimetry (MDSC) improves on this by splitting the heat flow signal into Reversing and Non-Reversing components with respect to the heat capacity.
Correlation of the onset of NR heat-flow with heat-setting temperature was perfectly linear, and it was concluded that MDSC provided an efficient way of determining the heat-setting conditions for an unknown PP sample.

Thursday, 6 July 2000

Nonwoven Network Meeting

PLA Fibres
Jim Lunt of Cargill-Dow Polymers gave the presentation on Poly Lactic Acid fibres. Most of the information had already been published, the following points being worth noting:
- PLA USP: "The only melt-spinnable natural-based fibre."
- CDP think they will need an FTC classification other than Natural, Synthetic or Regenerated. (It’s a synthetic polymer, the monomers for which are obtained from a renewable resource.)
- They are not allowed to claim biodegradation in the USA because the composting infrastructure needed to deal with it does not exist.
- The current 4000 tonnes capacity is being stretched to 8000 tpy ahead of the Blair plant coming on stream.
- They claim to be able to use any carbohydrate and foresee future plants installed in developing countries to use any biomass.

Mr Lunt was wearing a PLA/Wool blend jacket with PLA buttons. PLA golf shirts from Kanebo were passed round along with some knits that looked and felt like microfibre filament polyester.
He admitted PLA (M.Pt. 175oC) could not be ironed successfully: a serious disadvantage in textiles. In mitigation, the fibre, like polyester, was essentially non-iron.
They were developing a 210oC M.Pt version based on a polymer with alternating D and L units - "A stereo complex with interlocking D and L structure." This would be available in 2 years.
PLA does not support bacterial growth and only degraded in composting after hydrolysis at temperatures above 60oC.
Yoghurt pots branded "Danone - Jahreszeit" had been test marketed in Germany: they disappear in 47 days in an composter.
100% PLA teabags are on sale in Japan: from the slide they looked exceptionally uniform. (maybe they were very the woven filament bags used for premium tea-bags.)
PLA has the lowest refractive index of all fibres and hence dyes to very brilliant colours.
With a limiting oxygen index of 26% it is essentially non-flam.
It is unaffected by UV exposure.
Interface, the carpet company were said to have made a great success of PLA in carpets.
He said price would be 50 to 100c/lb with the lower figure being possible but unlikely until cheaper biomass sources become usable - i.e. not from Blair. He confirmed the existence of an exclusive users club with the available fibre rationed between the club members who pay to have access to samples. Blair would be expected to produce 140,000 tonnes of resin and would supply 10 club members each having access to 15,000 tonnes. The paper is on the website.

Oasis Update
Bill Brunskill of Acordis’s Technical Absorbents (JV with Ciba) reviewed progress with the “Oasis” superabsorbent fibre. The main applications were listed as: cable-wrap yarns, ink-jet pads, Tatami mats, secondary medical dressings, meat and fish tray liners, femcare, cooling bandages and coffin liners.
Products said to contain “Oasis” were circulated for inspection. They included panty-liners with two-part topsheet (a prettily patterned dri-weave target area with soft thermal bond - maybe hydrophobic - at the sides: maybe from P&G).
A detailed comparison with Lanseal (Toyobo) and Fibersorb (Camelot) showed Oasis™ to have the best balance of Free Swell, Retention, AUL, Centrifuge Retention, and Gel Retention results.
Companies mentioned either on slides or on the sample labels were Geca-Tapes for cable wrap, Zorba PLC for meat packs, Dyecor Ltd, and Conveen (inco pads). A written paper was not available.

Wet Laid Specialities
Nigel Walker of Technical Fibre Products reviewed the wet-laid nonwoven niches where they currently have thriving business:
Fibres laid: Ceramic, Zirconia, Microglass, Rockwool, Basalt, Pitch and PAN Carbon, Carbon whiskers, Nickel, Copper, Silicon carbide, Aramids, PVOH.
They produce 500mm to 1700mm widths, 5 to 2000 gsm and down to 5kgs in batch size.
They design and construct their own formers. (Thermal Ceramics Inc. in the USA has one.)
The main applications mentioned were:
battery separators for lithium and silver-zinc batteries.
8 gsm cryogenic tissues free from all organic matter and suitable for use in high vacuum (negligible outgassing at the molecule level)
High temperature insulation (up to 1600oC with alumina papers)
Fire-protection with intumescent papers (Expands 20x - “Thin ‘til Hot”). Fitted to doors, ventilators and pipes, they seal them up in the event of a fire.
Composite manufacture: they make the mouldable sheets for the IBM “Think-Pad” computers, EMI/RFI shielding & “Signature management” mouldings (Stealth)
They recently signed a JV with Johnson-Matthey to make membrane electrode assemblies for the polymer electrolyte fuel cells said to be capable of replacing petrol engines.

Resilient Waddings
Terry Saunders, MD of GTM Georgia USA, sells a system for making high loft waddings by pleating card webs prior to through-air bonding. The resulting fibre orientation is largely Z-direction, the products being 15 to 40mm thick. After bonding, they can be sliced down to as little as 3mm thick. (this seems to be the old Corweb process used to make the superabsorbent cores of the original J&J “Serenity” inco-pad.)
They claim fourteen of their machines are either running or on order. A 3.2 metre line is being constructed in the UK. Eight m/c’s were sold in the USA last year.
The pleater and bonding oven cost $360,000 but a full line would cost $1.3M. The main products seemed to based on waste fibres mixed with 20% bico to allow through-air bonding.
Waddings illustrated were made from textile waste, shoddy, PES, cotton, and waste coverstock. Weights were from 100 to 1600 gsm.
Applications claimed were: Liquid and air filters (very low pressure drop arising from the axial fibre orientation as in a cigarette filter), mattress pads, automotive waddings - insulation, foam replacement, trunk liners - “GM love it”, sleeping bags - “Doesn’t bottom out on compression”.

Tissue Culture
Dr R J Minns, a consultant clinical scientist in the Department of Medical Physics at Dryburn Hospital Durham, has been using textile implants to encourage the growth of new tissue in vivo. Rough hydrophilic, electronegative surfaces appear to be preferred by the fibroblasts responsible for new tissue growth: carbon fibre being better than polyester or PTFE. Hernia reinforcement, pressure sore repair and articular cartilage resurfacing have all been successfully demonstrated using carbon fibre woven/nonwoven composites. He foresees the use of carbon fibre pads to encourage new cartilage growth in joints taking over from hip-replacement operations.

Needle Design
The Foster Needle (George Swarbrick) paper on needle design reviewed the field. Points of interest were:
Needles generally have 9 barbs but in most operations only the bottom 6 ever contact the fibre. 6-barb designs would be shorter, stronger, cheaper and less likely to break. Customers were however resistant to changing from the traditional 9 barb design.
Different designs needed for different fibres. (Glass, Kevlar, Ceramic mentioned).
Rapid growth in felt/clay/woven PP composites for landfill liners. The clay is wetted before needling. Some producers now use 21-barbed needles for these products.
Jute/grass-seed/jute composites were now being needled.
Woven upholstery fabrics are being needled to raise a fuzz on one side to get better adhesion of a subsequent coating.

Landfill Liners
Dave Walmsley of the Environment Agency described the QC procedures required to allow landfill liners to be qualified. Landfill management is a comparatively recent phenomena in the UK, commencing about 15 years ago when problems with leachate began to be understood. If there is no natural clay layer at a prospective land-fill site a liner must be fitted, and this must contain the leachate for very long periods under pressures of some 20-30 tonnes/m2. He expected UK landfilling to be phased out over the next 20 years in favour of recycling, with householders being expected to sort waste into numerous categories prior to collection. Once the recycling infrastructure was in place he saw old landfill’s being mined for reusable waste.

DTI Grants
Dave Groffman of the Department of Trade and Industry listed the numerous grants currently available to small businesses. They included grants as low as £2500 to allow companies with fewer than 10 employees to use consultants to help write the feasibility studies needed to apply for larger grants!

Recycled PET Spunbonds
Mechanniche Moderna’s paper on spunbonds from recycled PET was in fact an advertisement for their entire PET spinning machine range. Recycled PET has to be dried to below 30ppm water to avoid degradation. Intrinsic viscosity of the resin falls by 0.01% for every 16ppm water. (The written paper was a collection of slides on an apparently unrelated subject.)