Polymer Fibers 2002: Manchester 10-12 July

Highlights• 118 delegates, only 38 of whom were from the UK and 21 from the USA , attended this academic meeting dealing with the frontiers of fiber science.
• Data on the mechanical properties of single carbon nanotube molecules has been obtained by Raman spectroscopy. The molecules were manipulated using an atomic force microscope. The Youngs Modulus is put at 1000 Gpa.
• Atomic Force Microscopy can show the change of surface structure from spherulitic molecules through “shish-kebabs” to fibrils as unoriented PP fibers are drawn.
• X-ray diffraction linked to laser Raman spectroscopy can now give a full picture of molecular and crystal deformation as fibers come under load.
• Polyethylene or polypropylene can be polymerised on the surface of cellulose fibers after grafting on aluminium alkyls.
• TANDEC is studying the dissolution of cellulose from many sources as part of a project funded by the USDA. Melt blown cellulosic nonwoven are one objective.
• 3D shapes are being air-formed from 51mm fibers at UMIST. Applications in disposables are under development.
• Fibers can now be produced with 80% of the theoretical polymer chain strength.
• Work on the structure of the rigid-rod high performance fibers (Kevlar, PBO, M5) is relevant to the understanding of solvent-spun cellulose fiber structure.
• The Japanese project to develop super-strong fibers from commodity polymers is expected to breakthrough in the next year.
• Racemate PLA yields fibers with a 230 0 C melting point. However it will be costly to make this polymer commercially.
• Most fibers will creep-fail at about half their nominal breaking load given extended times under load.
• Computer modelling of polymer molecules to derive the physical properties of fibers made from them is still in its infancy, as is the modelling of fabrics based on fiber properties.

HIGH PERFORMANCE FIBERS

Past and future of high performance fibers E. Roerdink and J van Dingenen (DSM High Performance Fibers, The Netherlands )

High performance polymers are either rigid-rod types (as in Vectra, Zylon, Technora, Twaron, Kevlar and M5) made by spinning solutions of self-orienting liquid-crystals, or flexible chains (Dyneema, Spectra) where the solvent disentangles the long chains to allow crystals to form on gel-spinning.

The rigid-rods came first with Dupont famously spending $700million over 25 years before turning a profit on Kevlar.

DSM (Dutch State Mines) tried to dissolve ultra high molecular weight polyethylene in polar solvents and found fibers forming on a stirrer. Such “surface growing” of fibers was rapidly superseded by gel-spinning, the invention being licensed to Allied Signal for “Spectra”, commercialised in 1986. DSM/Toyobo followed with “Dyneema” in 1990.

Toyobo then developed their own rigid rod approach by reworking Dow's PBO technology to make “Zylon”.

With new super-fibers estimated to require 10 years and $500 million many other attempts were abandoned. Exceptions were Kuraray's KII based on PVOH, the plant being capable of making several other lower performance fibers as well, and M5, picked up by Magellan after Akzo abandoned it.

The current market for super fibers was put at 50,000 tonnes at prices around $30,000/tonne. Aramids had 55% of this, Carbon fiber about 35%.

For the future, watch

Nexia's development of Biosteel, based on milk from transgenic goats – their DNA having been modified with spider DNA to allow spider-silk protein production. (Interesting but unlikely to yield superstrong fibers).

Carbon Nanotubes (see later)

Progress in super fibers in Japan Kazuyuki Yabuki (Toyobo Research Center Co Ltd, Shiga , Japan )

Zylon (Toyobo) matches carbon fiber T800 for modulus and strength and now reaches 80% of the theoretical PBO crystal modulus. Light and chemical stability are being improved.

Technora (Teijin) is an aramid with superior chemical stability and light resistance.

Vecry (Kuraray) is a sheath/core monofilament with a sea-island sheath (PEN or PPS) on a Vectran core.

Kuralon KII (Kuraray) achieves superfiber strengths when the gel-spun fiber is coagulated in cold methanol and stretched near melting temperature to prevent work-hardening.

Dyneema (Toyobo/DSM) was introduced with a 2.9 Gpa strength 10 years ago. It is now 3.9 Gpa commercially and 7 Gpa in the laboratory. 5-6 Gpa looks possible industrially.

All these fibers suffer from relatively poor performance in compression due to weak interchain forces (c.f. the covalent longitudinal bonds). 3D polymers (Cross-linked polyamides mentioned) have therefore been modelled which exceed diamond modulii in all three directions.

Superfibers can be made from commodity polymers (e.g. PET – a semi-rigid-rod polymer). Japan 's Kikutani Project, started this year is expected to breakthough to low cost superfibers in the next year.

One small slide inset, not reproduced in the printed version and not described by the speaker showed a laser heating a very small area of a polyester fiber allowing rapid stretching.

Advances in M5 (PIPD) fiber properties and expectations from fiber theories Doetze J. Sikkema (Magellan Systems International, The Netherlands )

Carbon fiber, being held together covalently, breaks catastrophically, whereas fibers relying on hydrogen bonding fail in a less critical fashion. Aramid strengths have been exceeded by manipulating polymers with no conformational mobility at all – Toyobo's PBO (poly- p-phenylenebenzobisoxazole – “Zylon”) being the best example. However PBO composites fail too easily under compression.

“M5” (PIPD – a polypyridobisimidazole made from 2,3,5,6-tetraamino pyridine and 2,6-dihydroxy-terephthalic acid) developed by Akzo-Nobel corrects this problem by maintaining the rigid-rod structure while adding extra hydrogen bonding sites. The restructuring of Akzo Nobel (acquisition of Courtaulds and the formation of Acordis) led to this project being abandoned, Magellan Systems International being formed to commercialise it using the A-N equipment. Composites made from the fiber demonstrate much improved impact resistance, damage tolerance and wear resistance than those using carbon fiber. UV stability is also unusual, the effects of long exposure, having if anything a slight strengthening effect on the fiber. (The molecular similarity between PIPD monomer and UV stabilisers was invoked to explain this.)

Fiber theory: The strength of fibers Maurits Northolt (Acordis Industrial Fibers, Arnhem , The Netherlands )

Fiber breakage under load is the result of shear failure brought about by the imperfect orientation of the fibrils, crystals and polymer chains within the fiber. All fiber elongation is due to shear between fibrils and within crystals, chain stretching being negligible. Fibers of different strengths from the same polymer all fail when extension reaches the hyperbolic shear-failure curve. Cellulosic fibers have more in common with the aramids and other rigid-rod polymers than with the thermoplastics. The strongest fibers will have the lowest elongation and highest initial modulus. Other factors of importance are:

• Impurities and flaws in the fiber
• Cross sectional variations
• Creep (i.e. Time)

The time effect is much more important than generally understood. Given much longer loading times than used in tensile testing, most fibers will fail at about half their nominal breaking load. The latest high modulus fibers (Such as Magellan's M5) have 4 inter-chain hydrogen bonds where the aramids have only 2.

Mechanical analysis of high-performance polymer fibers and the consequences for end-use A. Schaap and J. van den Heuvel (Teijin/Twaron, The Netherlands )

Mean strength less 3 standard deviations is a better predictor of composite strength than the normally-used mean strength. Single filaments have the same strength whether twisted or untwisted unless the compression forces go above the critical point.

(no printed version)

Deformation mechanisms in single fibers R. J. Young, C. Riekel, M.M. Moran, R.J. Davies (UMIST, Manchester , UK )

Synchrotron X-Ray diffraction using the micro-focus beam line at ESRF has been used to study changes in the structure of PBO filaments as they come under load. A 3µ X-ray beam had been stepped across the 12µ diameter fibers in 2µ steps. Three types of PBO, the AS (as spun) the HM (higher modulus by heat treatment of AS) and HM+ (ultra high modulus from non-aqueous spinning) were used. When linked with parallel studies using 2µ laser Raman spectroscopy, a full picture of both crystal and molecular deformation of fibers was obtained. (No printed version)

Stress distribution in PBO fiber as viewed from vibrational spectroscopic measurements under tension T. Kitagawa, K. Tashiro, K. Yabuki ( Toyobo Research Center , Shiga , Japan )

Unlike Kevlar, PBO has a lower fiber modulus than expected from its crystal modulus. Raman spectroscopy of fibers under load fitted a hypothetical mechanical series/parallel arrangement of crystals and amorphous regions. It was concluded that PBO must have small amorphous regions between the crystals. These must be eliminated to get the maximum strength. (This appears to be achieved in the HM+ version mentioned above).

MECHANICAL PROPERTIES

Ex-situ and in-situ observation of polypropylene fibers using advanced microscopy techniques O.K. Risnes, R.R. Mather, A. Neville, J. Buckman ( Heriot-Watt University , UK )

Scanning Probe Microscopy (SPM) comprises Atomic Force Microscopy (AFM) which measures the vertical movement of the probe due to atoms at the surface, and Lateral Force Microscopy (LFM) which measures the lateral movement of the probe. The technique has been used to study the development of structure during the melt extrusion and drawing of PP. Spherical molecules on the surface of the undrawn fibers can be seen to change to “heavily deformed spherulites”, shish-kebab structures and fibrils on drawing.

PA 66 high performance fibers: Microstructural mechanisms responsible for their mechanical properties during loading and fracture A. Marcellan, A.R. Bunsell, R. Piques, Ph. Colomban (Ecole des Mines de Paris, Evry , France )

The use of µ-Raman spectroscopy showed that the PA66 fibers have a skin-core structure leading to the outer few microns experiencing different stresses to the core when the fiber is loaded. Wide-angle X-Ray diffraction shows that the orientation of the amorphous regions increases under load and makes an important contribution to the modulus below 5% strain.

Fiber transverse deformation and cut performance of protective apparel Warren F. Knoff (Du Pont Company, USA )

Cutting is very rapid transverse abrasion under very high pressure. Cut resistance of a fiber has nothing to do with fiber tenacity but is related to the work required to deform the fiber in the transverse direction (TDW – transverse direction wear). This can be assessed using the Kawabata compression test where TDW is defined as the area under the compression curve when the diameter is reduced by 30%. The TDW results for Kevlar correlate well with the cut resistance measured on an auto-cut tester.

• Continuous filaments are harder to cut than staple: a feature explained by crimper damage during staple manufacture.
• Drier fiber is harder to cut.
• Heat treatment improves cut resistance up to 250 0 C (Kevlar)
• Higher deniers are harder to cut: a feature explained by the less ordered structure of higher denier versions of Kevlar.

Numerical modelling of the tensile behaviour of fibers with geometrical and structural irregularities W. He, X. Wang ( Deakin University , Victoria , Australia )

Computer modelling of fibers with varying cross section and small cracks in the surface showed that fibers would break at their weakest point. The graphics were pretty though.

Progress towards first principles modelling of the mechanical properties of fibers G.R. Davies (IRC in Polymer Science & Technology, University of Leeds , UK )

Attempts to derive fiber properties from computer models of polymer molecules are still years away from delivering useful results. Some progress has been made in predicting the Raman shifts from a cellulose molecule under load.

The initial modulus of fibers - intrinsic or not? N. Pan ( University of California , Davis , USA )

Breaking load increases and elongation decreases as the length of fiber under test is reduced. Dr Pan's work showed that the modulus also changed with gauge length: shorter fibers becoming less stiff in extension. Despite the fact that during his talk he had addressed all the factors where errors might have led to this result, he was thoroughly put down by the moderator who insisted that modulus does not change with gauge length, and that his findings were due to fiber slippage in the clamps.

PROCESSING

Fiber structure development in high-speed melt spinning of polylactides Takeshi Kikutani (Tokyo Institute of Technology , Japan )

Racemate Polylactic Acid (r-PLA, made from equal parts of polymers produced from L- and D-lactides) crystallises well to give a fiber with a melting point of 230 0 C c.f. 170 0 C for the current PLA polymer based on mainly L-lactides (PLLA). The stereocomplex crystals formed from r-PLA were however shown by WAXS to be “contaminated” with a -crystals from the L-lactide. The a -form could have arisen in the cooling process after annealing above the melting point of the a -form. The r-PLA had nevertheless been spun into fiber at 7km/min demonstrating improved structure and shrinkage compared with the commercial form of PLA. Orientation-induced crystallisation occurred at 4km/min for the r-PLA c.f. 5-6km/min for the PLLA.

Asked if the presence of the a -form crystal was perhaps due to the polymer mixture having a slight surplus of the PLLA, Dr Kikutani had thought this may be the case but was prevented from analysing the sample from Cargill Dow by the terms of the sampling agreement. The r-PLA was thought to be very expensive. (It could not be made from a 50/50 mix of the monomers but required 100% PDLA to be mixed 50/50 with 100% PLLA)

A new concept for self-reinforced polypropylene composites J Loos, T. Schimanski, P.J. Lemstra, N.O. Cabrera, B.Alcock, T.Peijs ( Eindhoven University of Technology , The Netherlands )

Problems with recycling glass-reinforced PP composites led to this work to develop an “all PP” co-extruded tape composite of similar strength. A high modulus isotactic PP core polymer is covered with a lower-melting PP copolymer sheath, the whole being crushed at the copolymer melting temperature to form the composite.

Failure analysis on the composite shows that the bonds between the sheaths are stronger than the interfibrillar bonds in the homopolymer core. While the stiffness of the all PP composites was inferior to the glass reinforced controls, impact studies showed the all PP product to be superior. It showed less damage after a 30joule impact than the GRP showed after a 15 joule impact. Future work will involve other polymers than PP. Asked about compressive and flexural strengths, Dr Alcock said these had yet to be measured. The questioner pointed out that glass has the same modulus in all directions whereas any man-made polymer would always have poorer properties in the transverse direction.

Processing and biorelevant characterization of fibers from bioerodable, polymeric biomaterials Mike Jaffe ( Rutgers University , New Jersey , USA )

Bioerodable polymers degrade in-vivo, serving as a temporary scaffold to establish growing tissue. They are made in 20gm lots by the biomedical community, a group with no understanding of fiber science. Prof. Jaffe has been studying the 100+ “library” of polyarylates in fiber form to see how their structure could affect the polymer/biological interface. He concluded that the “library” is not simply a group of amorphous polymers with systematic Tg behaviour and surface properties. They showed complex melting behaviour and were “replete with nanostructure”. He was now searching for the biological impact of such properties.

Thermosetting of partially crystalline fibers: temperature-time effects and a predictive model D.R. Salem, N. Vasanthan (TRI/Princeton, New Jersey , USA )

Filaments of nylon 6, 66 and polyester were twisted, heated, cooled and then assessed for residual twist as a measure of heat set. The variables studied were heating time and temperature, the moisture content of the fibers and their microstructure. Time emerged as a major variable, equivalent to temperature: similar setting could be achieved at lower temperatures by holding the twist in for longer times. Equations have been derived which allow the prediction of the degree of heat setting for any combination of time and temperature.

Elongational rheology of fiber forming polymers J. Collier, S. Petrovan, P. Patil, B. Collier ( University of Tennessee , USA )

Elongational Viscosities of LD- and HD-PE, lyocell solutions from two different pulps and nylon 66 resins of different viscosities were measured at different Strain Rates. Graphs of EV versus SR showed a general decline of EV with increasing SR, the higher DP polymers giving higher EV curves.

Processing and properties of melt-spun and drawn 2-methyl-1,3-propanediol substituted poly(ethylene terephthalate) J.E. Spruiell and X. Ling ( University of Tennessee , USA )

Co-polymers of PET have been made with up to 25% of the ethylene glycol being substituted by MPDiol. The 25% level proved unspinnable due to an inability to crystallise, but monofils were obtained from 4, 7, and 10% of the MPDiol. Increasing MPDiol content reduced the crystallinity and molecular orientation obtainable at any given spinning speed and increased the fiber shrinkage. Higher than expected stable spinning speed was a possible advantage of adding up to 7% of the MPDiol, such speeds being necessary to obtain a shrink-free fiber.

The effect of coagulation conditions on the microfibrillar network of a rigid polymer Y. Tsabba, D.M. Rein, Y. Cohen (Technion, Haifa , Israel )

Dry-jet wet spinning of rigid rod polymers yields a microfibrillar structure, the size of the fibrils being important to the fiber's performance in composites. In this work ribbons spun from PBZT (poly(p-phenylene benzobisthiazole)) were coagulated quickly or slowly in water or phosphoric acid before drying with supercritical CO 2 and X-ray diffraction study. Slow coagulation yielded better aligned microfibrils, but of the same size as the fast-coagulated versions. Heat treatment did increase the size of the fibrils in water-coagulated fibers. Dr Tsabba proposed a diffusion controlled nucleation and growth mechanism for fibril formation as being more likely than the currently accepted spinodal decomposition mechanism.

(No print out available)

Melt spinning of fine and ultra-fine PEEK-filaments H. Brunig, R. Beyreuther, R. Vogel, B. Tandler ( Institute of Polymer Research Dresden , Germany )

1 dtex PEEK fibers have been spun to make better yarns when blended with carbon fibers. A questioner commented that with carbon fiber now being cheaper than PEEK, he couldn't see the point.

FIRE RETARDANCY OF FIBERS

Substantive intumescent flame retardants for fibers - Are they feasible? A.R. Horrocks and S. Zhang (Bolton Institute, UK )

Substantive intumescence can be introduced into conventional fibers by reacting them with a char-promoting polyol phosphoryl chloride, providing they have active hydrogen. (e.g. cellulose, wool, nylon). Proban treated cotton appeared to be the most promising substrate, being washable at the boil and surviving as a fibrous char through 600 0 C heating for 10 minutes.

Reaction to fire of ‘M5' rigid rod polymer fibers S. Bourbigot, X. Flambard, M. Ferreira, E. Devaux, F. Poutch (GEMTEX, Roubaix , France )

M5 has a limiting oxygen index of >50%, and compared with Kevlar releases much less heat and smoke when ignited. It's Radiant Heat Release peaks at 50 kW/m 2 compared with 300kW/min for Kevlar. Furthermore while similar to Kevlar in air, it degrades slowly between 450 and 600 0 C under pyrolyitic conditions to form a stable residue with 55% solids (c.f Kevlar which degrades quickly to 40% solids.)

Aramid protective clothing in first choice or recycled - mechanical and thermal behaviour in reaction to fire X. Flambard, S. Bourbigot, M. Ferreira, P.-Y. Quefelec, F. Poutch (GEMTEX, Roubaix , France )

Recycled Kevlar and Twaron show excellent cut resistance but poor abrasion and flame resistance. With the recycled fibers being half the price of the virgin products, and products containing some recycled fiber being hard to distinquish from the 100% virgin products, problems could result.

NATURAL FIBERS

Rheology and lyocell solutions from different cellulose sources B.Collier, J.Collier, S.Petrovan, M.Dever, Z.Li, X.Ling Wei ( University of Tennessee , USA )

14% Solutions of a variety of sources of cellulose had been made in NMMO:
• Unbleached and bleached softwood
• Unbleached and bleached hardwood
• Unbleached and bleached recycled newsprint (pre-consumer)
• Unbleached and bleached thermomechanical pulp
• Unbleached Kudzo pulp
• Unbleached Bagasse pulp
• Dissolving pulps at two DP's
• Cotton linters

Dynamic rheological measurements were performed on an ARES rheometer using parallel plate geometry.

At high deformation rates, lyocell from cotton shows the highest viscosity. Paper pulps were similar to dissolving pulps. The activation energy for the flow of lyocell solutions is slightly higher than for PE or PP melts.

Chemical modification of lignocellulosic fibers A. Gandini (EFPG, St Martin díHeres, France )

Natural fiber composites suffer problems of incompatibility between the fiber surface and the polymer matrix. Chemical modification of the fiber surface could help by:
• Grafting polymers to create non-polar “hairs, umbrellas or bridges” at the fiber surface.
• Using reagents capable of bonding to the cellulosic –OH and polymerising into macromolecules which could co-crystallise with the matrix. (e.g. free radical polymerisation of styrene on the surface of cellulose)
• Using stiff, planar molecules with identical reactive groups on both sides of the plane. (e.g phenylene 1,4 diisocyanate)

Mr Gandini also revealed that his latest studies involved reacting aluminium alkyl with cellulose to allow polyethylene or polypropylene to be polymerised on the surface.

Overview on structural mechanics of natural fibers John Hearle (UMIST, Manchester , UK )

Natural cellulose fibers are composed of crystalline microfibrils generated by the polymerisation of glucose at the surfaces of enzyme complexes. These microfibrils are laid down in helical arrays to form cell walls. In cotton the mechanical properties are dominated by the secondary wall and the small lumen which forms at maturity and collapses on drying.

Protein fibers are more complicated, silk being the simplest and comprising block polymers dry-spun from solution. Wool and hair are the most complex. Here keratin and keratin associated proteins are laid down to form crystalline microfibrils in an amorphous matrix. These are bunched into macrofibrils, assembled into cells (para-, meso-, and ortho-cortex) all within a cuticle of scale shaped cells.

Greater understanding of these structures was becoming more important now that genetic manipulation and computer modelling was possible.

Ultra-high surface fibrous membranes from natural proteins and enzymes Y.-L. Hsieh ( University of California , Davis , USA )

Fibrous membranes were made by electrospinning and stabilised by cross-linking to prevent dissolution in water. These membranes (~0.5 micron fibers) had higher catalytic activity than membranes cast from the same solutions.

The proteins could not be electrospun directly. Blends of casein with polyethylene oxide or polyvinyl acetate had to be used. PEO was best. 80/20 Casein/PEO could be spun as a 10% solution.

Surface analysis of softened paper by time-of-flight secondary ion mass spectrometry (ToF-SIMS) and the Kawabata Evaluation System (KES) M. Parfitt, J.C. Vickerman, C.M. Carr, R. Mitchell, N. Ince, P. Knight (UMIST, Manchester, UK)

The use of KES for bulk softness and ToF-SIMS for surface smoothness allows the factors affecting the perceived softness of toilet tissues treated with different softeners and debonders to be understood.

Conductive polypyrrole coated fibers and yarns A. Kaynak, L. Wang, R. Beltran, X. Wang ( Deakin University , Victoria , Australia )

The effects of monomer, dopant and oxidant concentrations, reaction time and temperature on the conductivity, surface morphology and tensile properties of polypyrrole-coated polyester fabrics were investigated. Optimum oxidant/monomer ratio was found to be 2.22 and the optimum dopant monomer ratio was 0.4. The polypyrrole coat did not affect the tactile properties significantly. The dopant used was anthraquinone-2-sulphonic acid sodium salt monohydrate (AQSA) and the oxidant was ferric chloride hexahydrate. The pyrrole was polymerised onto the fabric over 1-16 hours.

Fiber Assemblies

The effects of mould porosity on fibers distribution in 3D nonwovens R.H. Gong, N. Ravirala (UMIST, Manchester , UK )

Air-laying long fibers straight from a card onto 3D “moulds” gives thin areas where the surface is at an angle to the main direction of air flow. Computational fluid dynamic modelling (CFD) has allowed the porosity of these surfaces to be increased to allow uniform basis weights over the whole surface. The validity of the CFD technique is proved by the near perfect linear relationship between flow rate per unit area of mould and the resulting web thickness.

In private conversation Hugh Gong revealed that he is now working on finger covers for use in hospitals.

The failure behaviour of knitted polyester/urethane acrylate composites: effect of stitch length R. Day (UMIST, Manchester , UK )

A study of stitch length in knitted fabrics used to reinforce a flexible matrix. Longer lengths give weaker composites.

Multiscale modelling of fibrous networks in textile composites P. Potluri, J.W.S. Hearle, T.V. Sagar, P. Mandal (UMIST, Manchester , UK )

Computer modelling of the forces on two filaments twisted together. Once again we seem a long way off getting a useful model of fabric properties.

NANOTECHNOLOGY

Deformation of carbon nanotubes under hydrostatic pressure and in composites R.J. Young , C.A. Cooper, M. Montes, M.P. Halsall, J. Sandler, M.S.P. Shaffer, A.H. Windle (UMIST, Manchester , UK )

Single and multiwall carbon nanotubes (individual molecules with a diameter ~1nm) have been deformed under in a diamond anvil alone and in an epoxy matrix. Raman spectroscopy was used to follow the deformation. Above a critical pressure (~2Gpa) they take on the appearance of graphite, but revert to tubes as the pressure is released. In a polymer matrix, these tubes behave like high modulus carbon fiber. The effective Youngs modulus of the single walled nanotubes dispersed in a composite is estimated at around 1 Tpa (1000 Gpa).

The nanotubes were grown by vapour deposition on dioxide coated silicon containing iron catalyst particles. They grow from the catalyst particles without forming bundles. They can be manipulated with the probe of an atomic force microscope. Raman spectra can be obtained from a single molecule (~10 5 Carbon atoms), and individual molecules have their own unique “breathing mode” vibration. The nanotubes show characteristics of both molecules and fibers.

Keynote: Nanoscience and nanotechnology -The chemistry of the 21st century Sir Harry Kroto ( University of Sussex , Brighton , UK )

This talk by the joint-winner of the 1996 Nobel Prize for Chemistry (for the discoverey of fullerenes – C 60 etc.) was more entertainment than information. He concluded by predicting:

• Nanotube bundles being grown as continuous filaments, their use in composites revolutionising structural materials.
• Extrusion of nanotubes, including boron nitride nanotubes.
• Nanowires, where the carbon tube has insulating atoms on the surface.
• “Carpets” of nanotubes.

Dyeable Polypropylene via Nanotechnology Quingo Fan et al ( University of Massachusetts , Dartmouth ) and Yiqi Yang ( University of Nebraska , Lincoln)

A “PP nanocomposite” is made by dispersing nanoclay in a solution of PP in xylene. The clay (montmorillonite) had been doped with a quaternary ammonium compound to provide dye sites. Acid dyeing occured at the quat and proved stable to washing. Disperse dyeing occured in the “tortuous pathways created by the oriented nanoclay in the polymer system”. The latter gave the best shade depths. 2% and 4% of the clays were added to the PP which was cast into thin film for dyeing.

Asked how the clay content affected the moisture regain or absorbency of the fiber, Mr Fan said these properties had not been measured.

Preparation of nanocomposite fibers for permanent antibacterial effect S.Y. Yeo, H.J. Lee, S H. Jeong ( Hanyang University , Seoul , South Korea )

The use of 11.6nm silver particles in the sheath of a conventional PP bico to make an antimicrobial fiber. Nanointeresting.

FIBERS SURFACES

Effect of surface deposits on softening of fiber surfaces and their relevance to processing Y.K. Kamath, S.B. Ruetsch, E. Petrovichova (TRI/Princeton, USA )

The effects of synthetic finishes on the softness of nylon and polyester fibers was studied using the atomic force microscope in “nanoindentation” mode. Unexpectedly nylon dented less than PET.

Fiber friction measurements increased with time after finish application, the greatest increase being observed with nylon. This measure suggested nylon had a softer surface than PET after exposure to finish.

Surface characterization of fibrous webs using AFM I.A Ansari, T.K. Ghosh ( North Carolina State University , USA )

An attempt to scan the surface of a melt-blown PP fiber using the atomic force microscope raised many problems which prevented detailed information being obtained.

Surface chemical analysis of Tencel treated with a cationic fixing agent S. Rosunee, C.M. Carr, S. Hibbert (UMIST, Manchester , UK )

X-ray photoelectron spectroscopy was used to study the effect of washing on the non-reactive (formaldehyde-free) cationic fixing agents used to improve wash fastness of direct dyes on Tencel. Uncharged nitrogen was seen to be removed from the surface by leaving only the cationic species.

Calvin Woodings

17 th July 2002