Introduction
About 100 delegates, mainly staff and students from Europe’s
technical institutes and universities attended this now bi-annual conference. Two
thirds of the papers presented were from technical institutes and universities
and provided interesting updates on progress made on numerous EU-funded
initiatives in nonwovens.
PLA Meltblown
Ryan
McEneany, Research Scientist, Kimberly Clark, USA described the
outcome of a 10 year development programme on biopolymers. This was part of a strategy to cease being
the world’s largest single user of polypropylene and become a major user of
sustainable materials. Their PP use was
mainly in SMS processes and while PLA worked well in spunbond, it was difficult
in melt-blown due to the non-availability of the right Melt-Flow Rate.
Commencing with Natureworks 6201D PLA resin (MFR = 80g/10min
at 210oC), quite apart from the viscosity problem, they experienced
slow crystallization due to its high Tg (~60oC), high fibre
shrinkage, biased orientation in the web and poor thermal bonding when draw
ratios were high. They looked at flow
modifiers, higher process temperatures and lower molecular weight polymers and
it was the latter, obtained by processing undried resin, which showed the most
promise...
They therefore bought a Custom
Humidification Unit from AEC to allow the PLA’s moisture content to be raised
to 1000ppm in a controlled manner without risk of condensation. They processed it through a 40:1 L/D twin
screw extruder at shear rates in excess of 1000 per second to maximise chain
scission, vented the extruder prior to repelletising and finally dried the
resin ready for melt-blowing. The final
MFR ranged from 10 when sheared at 87ppm moisture to 116 at 1226 ppm
moisture. This still proved too viscous
in MB, but when 10% of an 8000 molecular weight polyethylene glycol was added a
final satisfactory MFR of 310 was obtained.
As received, the PLA 6201D had a molecular weight of
107,800. After the high-scission
processing and 10% PEG addition this had dropped to 58,400, sufficiently above
the 40,000 danger level where Natureworks report PLA to be too brittle to use.
A further benefit of adding PEG is that it acts as a nucleus
allowing PLA to crystallise more like PP.
Furthermore by using PEG-PPG block copolymer additives they could tailor
the crystallisation to suit their needs and reduce the hygroscopicity of the
final MB web. Quench and draw
temperatures could be adjusted to maximise crystallisation rate and to obtain
higher crystallisation levels at lower draw force. The final MB process used a single screw
extruder with limited blend capability running at 190-210oC to feed
a single die tip at 90 degrees to the web direction, 8-12” above the web
conveyor.
Fibre formation was good, and while the PLA fibres are
tackier than PP there were no wire-release issues. Throughputs could be raised into the
commercial range, but was still limited by high die-tip pressure. Using the best PEG-PPG random copolymer additive,
stronger webs with much higher extensibility were obtained than possible with
PP. Without the additive, both MD and CD
strengths of the PLA webs were slightly lower, but the extensibilities were
halved in the MD and quartered in the CD.
Remaining challenges were listed as:
·
Ageing of the webs further dropping the
molecular weight towards the brittle zone.
·
Phase separation from PEG crystallization
·
Improving the tensiles and crystallization
further
·
Web shrinkage
·
Increased hydrophilicity.
There were more questions than time available:
·
Were the monomers created in the hydrolytic
degradation removed? No, but the fabrics smelled OK. (no burnt sugar smell)
·
Why not source low molecular weight PLA? It would be a special product requiring very
large orders and it would be more expensive.
·
Does the more hygroscopic degraded PLA still
need a spin finish? Yes, but not for
rewet.
·
Have any ageing studies been done? Yes:
the PEG crystallises out and the brittleness increases so the meltblown
webs have a reduced shelf-life. New
formulations are being evaluated to overcome this.
·
Is biodegradation rate affected? No: PEG is
fully biodegradable.
Ahlstrom's PLA Nonwovens
Claudio
Ermondi, Senior VP, Ahlstrom, Italy was replaced by Ray Volpe, Food &
Medical Business, USA. He gave a somewhat
different paper to the one advertised, preferring to major on a general
introduction to the Ahlstrom Group and its successes in reducing its
environmental impact.
With
regard to the new PLA spunbond production, Mr Volpe thought the process needed
more work to remove the “black art”.
·
Standard PP spunbond machinery had had to be adapted to suit
PLA.
·
Temperature control had to be tightened throughout the
process, especially in calendering.
The
resulting BioWeb™ nonwovens were nevertheless being used in ultrasonically
sealed teabags, diaper leg-cuffs, topsheets and backsheets, plant root wrap and
soft-furnishing constructions.
In
response to questions about capacity and bottlenecks, he said progress had been
slowed by the recession during the last two years, but should pick up in the
next year or two. They hoped to be using
2x to 3x more PLA by 2015, and needed another nonwoven producer to “take the
jump” into PLA spunbonds.
Cellulose Spheres
Dr Josef
Innerlohinger, Project Manager, New Applications, Lenzing (Austria)
described various ways of making cellulose particles commencing with the
well-established micro-crystalline cellulose made from pulp by dissolution of
the amorphous cellulose in acid.
·
Tencel®FCP was made by grinding short-cut Tencel tow and
therefore could have diameters down to 0.9 micron and lengths of around around
0.4 mm. They were intended as fibrous
fillers for plastics reinforcement but may also find uses in paper, board and
construction materials.
·
Tencel® CP appeared to be 5-250 micron particles made by
precipitation of the NMMO solution of cellulose in a high-shear mixer, followed
by grinding. It has found an application
as filler in PU foam mattresses where the absorbency of the Tencel particles
provides a drier sleeping environment than is usual on foam.
·
Tencel® Fibrids are made by fibrillating short-cut Tencel®
in a refiner until nothing but the fibrils remain. These are a few microns long and sub-micron
in diameter. They have high absorbency
(WI = 600%) arising from their high surface area (200m2/gm if
solvent dried) and make film-like paper when sheeted.
·
Additional functionality can be achieved using dope
additives and a myriad of possible uses emerges. Lenzing are looking for partners to help
develop applications.
Mineral-Filled Fibres
Annabelle
Legrix of Imerys Minerals (UK) described their experience with film
production using resins loaded with calcium carbonate. Plastic bags made with 15% CaCO3
content required 10% less production energy, due to a more homogeneous melt
arising from faster heating (10x increase in melt thermal conductivity), lower
die-tip pressure, and faster cooling.
The latter gives better bubble stability for blown film and faster cycle
times in bottle moulding. (10% CaCO3
addition gives an 8% output increase for PE film. 40% CaCO3 addition gives a 40%
reduction in bottle production cycle time.)
For
fibre production, CaCO3 with finer particles, no particles near the
jet hole size, and easy dispersion without agglomeration is needed. Fiberlink™ 101S is such a filler, and has
been successfully added directly to PP for meltblowing and to masterbatches for
spunbond production. In these spunlaid
processes, the energy savings arising from faster heating and lower bonding
temperatures have been observed and the increase in density means area output
can be increased to maintain constant basis weight.
While
40% filler levels have been processed into meltblown, 20% is the maximum
recommended level in both meltblown and spunbond. In spunbond, deniers down to 1.5 have been
processed without fibre breakage.
Environmental
effects are being evaluated. So far the
carbon-footprint has been shown to be reduced c.f 100% PP at the same basis
weight. Other environmental impacts and process energy impacts are being
studied, as are the possible spin-offs from substantial increases in opacity
arising from the filler. (Opacity of a 25gsm web goes from 28% to 33% for a 0
to 20% filler increase.)
Oil
absorbency of filled MB PP is higher than 100% PP on a fabric volume basis, and
filtration efficiency rises from 86% to 89% as 10% filler is added. This is thought to be due to the higher
surface area and surface roughness of the filled fibres.
Testing
of filled and unfilled PP in a wipe blend with rayon showed that the filler
increased opacity and strength while panel testing of the same wipes showed
consumers preferred the wet texture of the CaCO3 filled wipes.
In
response to questions
·
the particle size for fibre production was 1.4 micron with
98% below 8 microns,
·
no trials with waste recycling had been done,
·
Filler did reduce fibre strength but this had been made up
by alterations of other process conditions.
·
Different finishes would be needed, and these would also
depend on polymer (PP, PET, PLA etc)
Comparing Woodpulps
Jean Ruiz
of the Paper Technical Center (CTP - France) described an experiment with 13 market
pulps, refined at 3 different intensities and converted into 20gsm handsheets
for evaluation of bulk and surface softness by expert panels. 5 panels were used each with 7 women and 8
men, 1 being from CTP the others being from the companies supporting the
project.
·
Softwood and deinked pulps
were harshest
·
Softness decreased with refining intensity
·
Hardwood pulps, especially eucalyptus, were the softest
However
the comparisons were made at similar refining conditions whereas in reality the
optimisation of refining for each pulp could alter its softness potential
relative to the others.
Mathematical
modelling of the results showed excellent agreement (r2=0.86)
between actual and predicted softness levels.
The model was based on MorFi analysis of pulp fibre characteristics such
as mean kink angle, mean curl index, broken fibre content, and fines content,
both by length and area. It also showed
that 60% of the perceived softness was due to the fibres used, and 34% was due
to the effect of process conditions on the paper surface state.
On-line
assessment of softness was attempted by using the output of an on-line fibre analyser
fed through the mathematical model to predict the “softness potential” of the
tissue in something close to real-time.
The model was validated during one week of industrial trials, where 189
reels of tissue were produced.
SCA,
Ahlstrom, Scott Paper, Botnia, BTG, and Fibria were listed as partners.
Nonwoven Scaffolds for Tissue Culture
Dr Elaine
Durham, Research Fellow, Nonwovens Research Group, Leeds University (UK)
listed the requirements for nonwovens in tissue culture:
·
The nonwoven scaffold should provide a template
to allow the 3D organisation of the cells being cultured.
·
It’s shape and strength will be tissue specific
(ligaments need very different scaffolds to bone)
·
It should be highly porous with a pore size to
suit the cells and to allow transport of nutrients, oxygen and waste products.
·
It has to appeal to the surgeon and appear
strong enough for implantation.
·
It should be biocompatible, biodegradable and
non-toxic, because...
·
...it must be absorbed by the body as the
tissues regrow.
Scaffolds could be made from synthetic sponges
(“porogen-fused scaffolds”), electrospun webs, hydrogels and nonwovens. They could also be made by 3D printing and
laser-sintering.
The internal architecture of the nonwoven is thought to be
key to its success. Cell growth tends to
occur at the surfaces and the resulting films prevent further growth in the
deeper pores. So, Leeds have adapted
their hydroentanglement process to make nonwovens with fine capillaries running
down the MD by hydroentangling two pre-needled 60gsm PLA webs together either
side of 0.2mm diameter high tenacity filaments spaced 0.4mm apart. These filaments can be pulled out leaving
capillaries down which cells can travel into the interior. X-ray micro tomography has been used to show
where the cells are within the scaffold after 14 weeks of culture. They still appear to be concentrated at the
surface of the scaffold, and on the internal surfaces of the micro capillaries.
Dr Durham concluded that the scaffolds with microchannels
have the potential to improve cell distribution and infiltration. In response to questions:
·
The microchannel scaffolds were 2.5mm thick
·
Dynamic cell culture had been tried and did give more
penetration.
·
The cells were only growing on the surface of the
capillaries
·
The cell-broth had been pipetted into each microchannel.
One
questioner observed that other labs don’t have this problem and can grow cells
throughout standard nonwoven webs.
Nonwovens for Tissue Culture
Annahit
Arshi of the Institute for Technical
Textiles, RWTH, Aachen (Germany) reviewed RWTH’s development of a
medical grade, quality assured production line for nonwovens for tissue
culture.
She observed that the change from supplier to client
dominated health care would result in the need for a whole spectrum of
artificial organs and tissues to extend the lives of tomorrows old people. Nonwovens provide excellent scaffolds for
cell growth, having a porous structure similar to collagen, while being strong,
absorbent, drapable, and capable of being made from a wide variety of fibres
with different surface structures.
At the microstructure level, fibre shape and surface texture
are adjustable: at the meso-structure level crimp and texturing of fibres or
filaments is important, and at the macro level, pore size and shape along with
wettability and absorbency are key. All
these factors could affect the adhesion, proliferation and differentiation of
the cells to be grown on them.
With funding from the EU and support from Freudenberg, RWTH
were therefore examining design and development concepts for the production of
medical grade nonwovens and Ms Arshi was focussing on Failure Mode Effect
Analysis to get a cumulative risk value for all possible failure-in-use
mechanisms. This RPZ value ought to be
below 125, but on the current machinery it was running at over 1000 due to high
levels of contamination, including metals, from the fibre preparation and needleloom
in the new line. So, RWTH is developing
a new needleloom with complete mass-force compensation (no vibration), totally
encapsulated lubricants, and clean-room quality bearings. They are also developing a new staple fibre
cutter with novel tow-traction system and new blade geometry, and a new carding
system.
Asked about the importance of fibre orientation in the web,
Ms Arshi said it depends on the cells to be cultured. Adipose tissue needs random laid to give
roundish pores and muscle tissue needs parallel-laid to give tubular
pores. Wouldn’t other nonwoven process
which gave less metal contamination than card/needle be better? Maybe.
Toxicology of Nanomaterials
Dr Karen
Wiensch, Head of Regulatory Toxicology, BASF (Germany) defined
nanotechnology as the intentional generation of structures smaller than 100nm
where properties (mechanical, optical, chemical, biological etc) differ from
those at a larger scale. Nanomaterials
in powder form are easily dispersed as aerosols and can penetrate the skin or
be deposited in the lungs and intestines where they can be further distributed
around the body causing inflammation, catalysing the formation of reactive
compounds and directly interacting with cells.
Recent
studies include:
·
The effects of titanium and zinc nanoparticles used in
sunscreens on UVB-damaged skin.
·
The distribution of nano-TiO2 in tissues
following intravenous introduction into rats.
·
The development of a test for assessing the effects of
inhalation of nano-TiO2 by rats.
·
Effects of nano-TiO2 and nano-ZnO on the mobility
and reproduction of fresh water Daphnia
magna
·
The effects of inhaling carbon nanotubes.
In
the latter study, during a 5 day exposure study, all the carbon nanotube
samples induced inflammation in the lungs of the animals, and granulomas formed
at high concentrations. The “no observed
adverse effect concentration” (NOAEC) was less than 3mg nanotubes per cubic
metre of air. In the 90 day exposure
study, 0.5 and 2.5mg/m3 of nanotubes in air caused absolute and
relative increases in lung weight, mild to severe inflammation, multifocal
granulomas and lipoproteinosis in all animals, with a severity clearly related
to nanotube concentration. Here 0.1 mg/m3
was regarded as the Low Observed Adverse Effect Concentration (LOAEC)
Finest Fibre Webs
Dr Martin
Dauner of ITW Denkendorf (Germany) reported on the breakthrough arising
from the collaboration of ITV with Rieter OFT GmbH to develop centrifugal
spinning for nanofibre production. ITV
now has a 1m wide pilot line which can use the same polymers and solvents as
nozzle electrospinning but at levels of productivity approaching that of melt
blowing.
At
the same time, progress to produce submicron fibres from meltblowing was made
by Hills Inc (USA), Irema (Germany) and Hollingsworth and Vose (Germany), and
all these had to address the problem of how to handle the fragile webs and
control their performance in filtration.
There are now several other projects underway:
·
“Nablo” is a joint
project between Freudenberg Filtration Technologies, Neumag Oerlikon Textiles
GmbH, ITWM and ITV which targets developing melt blow technology to produce 0.1
micron fibres. This has already achieved
0.2 microns in the lab and 0.4 microns on the pilot line.
·
“Nanoseparator” brings together Hengst GmbH, Junker GmbH,
Nano-X, LFG Erlangen and ITV (all Germany) to produce nanofibres by centrifugal
spinning. In one application the finest
PP is performing best and for this melt-blow technology is now used.
·
“Nanofatex” is a collaboration between Freudenberg Household
Products, Polman GmbH, TransMit, and the Research Centres at the University of
Marberg and ITV to develop nanofibres for use in cleaning towels.
Spunlaced Spunlaid Composites
Dr Ralf
Taubner of the Saxony Textile Research Institute (STFI - Germany)
introduced Hycospun®, their registered name for hydroentangled nonwovens
containing fine-fibre meltblown webs.
These were part of a project aimed at developing functional multilayer
structures for technical applications.
Hydroentanglement
was now the most important nonwoven bonding technology for staple fibre
webs. Their 1m wide pilot line used an
Adritz-Küsters hydroentanglement unit fed by a Reicofil 4 SMS with bico
capability and a Küsters thermal bonding calendar was ideally suited to this
sort of experimentation. (It also had in-line Dilo needlepunching and a
Fleissner through-air bonder-drier before the Celli winder.)
Numerous data tables provided the properties
of many laminates and illustrated Dr Taubner’s main point: using
hydroentanglement to laminate a wide range of nonwovens together offered
excellent possibilities for manufacturing high performance nonwoven composites.
Has
STFI tried laminating spunbonds made of crimped bico-fibres to get more
volume? Yes.
Acoustic Nonwovens
Dr
Francois Rault, Associate Professor – ENSAIT (France) defined
noise as unpleasant, undesirable and unwanted sound which has adverse health
effects such as deafness, sleep deprivation, auditory tiredness, stress and
increased risk of accident. He reviewed
sound absorbtion theory and recent work on the Normal- incidence sound
Absorbtion Coefficient (NAC) of fibrous absorbents concluding that:
·
Finer fibres absorb more sound (higher NAC)
·
Irregular fibres absorb more sound than round fibres, so
natural fibres are generally better absorbers than man-made.
·
The 4DG “deep-grooved” polyester absorbs as much sound at
6.7 dtex as round fibre does at 1.7 dtex.
·
Flax fibres give the best NAC
·
Multilayer structures absorb more sound than the equivalent
thickness and weight of a monolayer.
For
the multilayer structures, needlepunching and hydroentangled materials were
used, and the best performance was with hydroentanglement when the sound
approached from the hydroentangled side.
Furthermore, alternating layers of HE and NP fabrics in a 4-ply
structure absorbed more sound that the same fabrics arranged in pairs.
Simulated Needlepunching
Dr Simone
Gramisch of the Fraunhofer Institute for Industrial Mathematics (Germany) showed
how the needle-hole pattern in a needlepunched nonwoven could be
computer-derived from the needle layout and knowledge of the web properties,
its feed rate, and the drafting forces applied.
If this pattern looked unacceptably non-random it was possible to
calculate which needles to move to which free holes in the needle-board to
correct the problem, without ever making any nonwoven fabric. An intriguing spin-off of the technique was
the potential to set up a needleboard with an apparently nonsensical
arrangement of needles which in production, after multiple punches and
drafting, produced a nonwoven with holes in the form of whatever letters or
logo had been pre-programmed into the board set-up. However in practise, a 1% change in the
theoretically required feed rate would result in the logo being unacceptably
blurred.
Modelling Thermal Bonds
Dr Amit
Rawal, Associate Professor of Textile Technology, Indian Institute of
Technology, (India) used the theory of fibre contacts to model the mechanical
properties of thermally bonded nonwovens.
The mathematical approach proved inscrutable, but the following
conclusions were gleaned:
·
Tensile failure occurs due to fibre pull-out from the bonds.
·
A simple 2D micromechanical model can predict the behaviour
in compression.
·
Classic Freeston and Platt modelling overestimates bending
rigidity, but Dr Rawal’s modification of the procedure gets nearer the truth.
Work
continues on the modelling of nonwovens hydraulics, shear, tear, permeability,
wetting and wicking using the same theory of fibre contacts.
Automotive Biocomposites
Dr
Philippe Vroman, Associate Professor, ENSAIT (France) focussed
on the potential of long vegetable fibres as substitutes for glass in
composites. Of the vegetable fibres
considered, flax, hemp, ramie, jute, kenaf, coir, sisal and cotton, flax showed
the greatest potential especially when specific (i.e. corrected for fibre
density) tensiles and elastic modulii
were considered. However, the
incorporation of natural fibres into polymer matrices is fraught with problems:
·
Lack of adhesion to the polymer. Compatibilisers or coupling agents need to be
added to the fibre surface.
·
Poor thermal stability can cause not only a deterioration of
mechanical properties but also odours, fogging, dust and colour changes. Fibres need to be coated or grafted with
monomers to improve stability.
·
Moisture sensitivity can lead to dimensional
instability. Again grafting with
monomers helps.
·
Biodegradability and photodegradability need correcting and
here again; monomer grafting could be the solution.
·
Variation in fibre properties with harvest, region grown etc
leads to variation in composite properties.
In
trials to date, the best results have been obtained using a 70/30 flax/PP
needled nonwoven faced with lightweight webs of the same blend hydroentangled
onto each surface. This laminate, with a
1650 gsm basis weight was thermo-compressed at 200oC to make a 2mm
thick bar for testing.
Testing Automotive Nonwovens
Mohit Raina, Head of Spinning Technology, RWTH Aachen
(Germany) has
been working on new methods for non-destructive characterisation of the
structure of nonwovens.
·
Fibre orientation was assessed by scanning an A3 size sheet
and using image analysis to quantify the fibre directions. The resulting fibre orientation vectors could
be overlaid onto the original image to give a visualisation of the variations
in orientation.
·
The capacitance and hence the permittivity coefficient of
the web was measured over a wide range of frequencies (1000 to 600,00 Hz). Results from this dielectric analysis have
been correlated with basis weight, and fibre blend ratio. However the results are not absolute and
relative humidity must be tightly controlled.
·
A micro CT scanner has been used to visualise the 3D
structure of a porous nonwoven. Fibre
positioning and the resulting pore size and volume can be analysed.
Multi-Jet Electrospinning
Christoph
Hacker of the Institute for Technical Textiles at RWTH Aachen, (Germany)
described the RWTH development of multi-jet electrospinning of commodity
polymer melts to make fibres of less than 0.5 micron diameter under conditions
which could be operated on an industrial scale. The procedure involves:
·
Using a reduced melt viscosity (PP with 190,000 molecular
weight was mentioned).
·
Blending it with a “slipping agent”.
·
Spinning it from a charged 64-nozzle spinneret block fed
from a piston pump at a throughput of 0.2ml/hr/nozzle.
·
The conveyor collected filaments with 552 ± 260nm diameter.
·
18 m2/hr of 0.5 gsm “nonwoven” results.
This
nano-nonwoven is very fragile and must be bonded to the surface of a
substrate. Early trials with
calendering, needling or hydroentanglement of webs spun from a single nozzle
destroyed the nano-nonwoven. Spray
bonding looks possible but has the disadvantage of reducing the porosity and
thickening the filaments. Applications
in filtration and tissue engineering are anticipated.
Penetration-Proof Nonwovens
Kay
Grinneback, Senior Scientist, SWEREA (Sweden) is developing carded/bonded nonwovens
which are highly resistant to penetration by nails, high pressure water jet
cutters, or knife-stabs. This market is
currently dominated by wovens made from para-aramids or ultra high molecular weight
polyethylene yarns where the force taken to prise apart the warp and weft
accounts for much of the penetration resistance. SWEREA is concentrating on developing
nonwovens for two specific applications, one being a shoe liner to prevent nail
penetration through the sole and the other being protection from the water jets
used in hydro-demolition and rust removal.
Water
jets at the highest pressure used in industry can penetrate the woven
protection and cause serious injuries.
The energy released in 0.1 second
hit from a 3000 bar water jet at a distance of 7mm is equivalent to a direct
hit from a hunting rifle. The new
nonwovens made by carding Dyneema fibres (UHMWPE from DSM) and bonding with a
special polymer can now offer protection against these jets.
FR Meltblown
Ina
Sigmund of STFI (Germany) has been using the new extrudable melamine resins from
Borealis Agrolinz in an innovative lab-scale meltblown process to make 35 to
350 gsm self-bonded nonwovens containing fibres from 1 to 12 microns in diameter. These are inherently flame retardant
(LOI=32), don’t melt or shrink in a flame and also offer high thermal and
acoustic insulation. They have high
filtration efficiency and are resistant to alkalis and organic chemicals. Acid resistance is only fair however. Applications in hot gas filtration and
protective clothing are envisaged.
Nonwovens and Nanotech
Thomas
Broch Nielsen of Fibertex (Denmark) has developed super-hydrophobic, self
cleaning nonwovens by coating with isotactic PP nanospheres and here the
repellency arose from the so-called “lotus effect”. He now has a permanently hydrophilic coat for
topsheet which can be applied from a kiss roll and this has been shown to give
a constant strikethrough time of 2 seconds over 20 insults where the normal
hydrophilic finishes fail after 6 insults.
For
geotextiles production, a modification of the polymer with UV absorbing
nano-particles improved their stability according to EN12224 from 14 days to 4
months, and this material is now commercially available.
Fibertex
also have an Elmarco Nanospider 0.5m electrospinning pilot line and are using
this to coat various substrates with various polymers in the form of fibres
below 1 micron diameter. They see the resulting
products as filling the gap in the purification market between traditional
nonwoven filters and membranes.
Nanosilk
Dr Gunter
Scharfenberger, Manager, Fibres and Finishing, Freudenberg R&D
Services(Germany) reviewed the progress on the government funded project to
make “bio-inspired nonwovens on the base of recombinant silk proteins.” Here, Freudenberg (nonwoven production) along
with BASF (raw materials), and Lohmann & Rauscher (converting and retail),
are collaborating with the University of Bayreuth and RWTH Aachen on the
development of wound dressings and anti-allergenic surfaces. The recombinant protein being electrospun is
composed of well-known sequences of spider silk and resilin insect protein and
is produced by “white biotechnology” and expressed by bacteria. 10% aqueous solutions of the protein
stabilised with polymeric detergents and electrospun yield webs with too-many
beads, but at 20% the yield of nanofibres increased dramatically. Further improvements followed from the use of
polyethylene oxide additives at up to 1.5%.
The
process is now being scaled up and the laboratory samples are being subjected
to medical tests to evaluate performance.
Calvin
Woodings
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