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Melt Spinning of Textile Fibers
Bengt Hagstrm
Swerea IVF
+46 31 706 63 00
E-mail: [email protected]
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Global fiber production 2009(Mtons)
Synthetic fibers 43.6
Polyester 32.0
PP (Polypropylene) 5.8
Polyamide (Nylon) 3.3
Acrylics (PAN) 1.95
Others (elastane, aramids, PVC, PTFE) 0.64
Cellulosic (Viscose, CA) 3.5
Lyocell (cellulosic) 0.2
Cotton 22
Wool 1.17
Silk 0.14
Total 70.5
Melt spun
fibers
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Structure of polymers (long
molecules)ex. PVC
Repeating unit in PVC
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Manufacturing of polymers
(polymerisation)
Poly addition: A+A = A-A, A-A+A = A-A-A ...
H
C
HH
H
C +
Polyethylene
H
C
HH
H
C
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Low pressure process for polymerisation of ethylene gas
into polyethylene (HDPE, LLDPE), similar for PP but
propylene is monomer.
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Manufacturing of polymers
(polymerisation)
Poly condensation: A+B+A+B+A+B = C-C-C + 3H2O
Example: PET, PC, PA
Sensitive fr hydrolysis = depolymerisation
Raw material must by dry before processing
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JJ
Macromolecules
A polymer molecule is like avery long and thin chain
consisting of many links
(repeating units)
Example: In polyethylene the
link is ethylene. The
number of links can be
10.000-100.000 and the
chain length 1-10 m
(thickness of plastic bag 30
m)
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(Semi) crystalline polymers
If the chain structure is regular and fairly
symetrical crystallisation is possible when the
temperature is lowered. In the crystalline region
the chains are closely packed in a regular why.
The crystallites are surrounded and connectedby amorphous chains. That is, crystalline
polymers are never 100 % crystalline. The
crystalline blocks are hard and regide. The
surrounding amophous layers are soft (melt)
when the temperature is higher than Tg for the
amophous phase. A single polymer chain mayparticipate in several blocks and then ties the
crystalline blocks toghether.
Cooling from melt
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Crystalline lamellae structure
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Stacked lamellae
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Spherulites and cylindrites(Superstructures)
From quiescent
(non-oriented)melt
From deformed(oriented) melt
Fiber
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E-modulus/hardness
Temperature
Tg Tm
Crystalline
polymer
brittle tough
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Change of volume during cooling or
heating
Crystalline polymer
Temperature
cm3/g
TcTg Tm
Some polymers
hardly crystallise at
all during fast
cooling (PET)
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Bond strength within and between
polymer chains
Very strong
Weak (but
increase with chainlength)
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High strength fibres
C
PE: Dyneema, Spectra
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High strength fibres
Polymer Tensile strength (Mpa)
oriented fibre
PPTA (Kevlar) 3000
PA6 600
PEEK 700
PPS 500
PE 500 (3000)
Tensile strength (Mpa)
injection moulded item
-
65
115
70
30
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Deformation of crystalline polymer
a
c d
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Process SchematicOverview
Melt spinning is the preferred method of
manufacture for polymeric fibers. The
polymer is melted and pumped through a
spinneret (die) with numerous holes (one to
thousands). The molten fibers are cooled,
solidified, and collected on a take-up wheel.Stretching of the fibers in both the molten and
solid states provides for orientation of the
polymer chains along the fiber axis. Polymers
such as poly(ethylene terephthalate) and
nylon 6,6 are melt spun in high volumes.
An excellent general reference on fiber spinning is:
A. Ziabicki, Fundamentals of Fiber Formation, Wiley, New
York (1976). ISBN 0471982202.
A classic article which emphasizes structure development
during melt spinning is:
J.R. Dees and J.E. Spruiell, J. Appl. Polym. Sci., 18, pp. 1053-
1078 (1974).
Spinning fibers from a polymer melt
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Different fiber cross sections are possibleExamples
Hollow Tri-lobal Bi-component
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Principle of melt spinning
Gear pump
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The extruder
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Gear pump for stable volumetric flow rate
Extruder Spinneret
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Spinneret
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Melt spinning facility at Swerea IVF
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Top rollers
Middle rollers (heated)
Bottom rollers (heated)
Take off roller
Spinneret
Melt draw
Solid state draw
Melt spinning facility at Swerea IVF
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Drawing (stretching) in melt and solid states
V0
V2
V1
Melt Drawing (T>Tm)
MDR = V1 / V0
Solid State Drawing (Tm>T>Tg)
SSDR = V2 / V1
Extruder gear pump spinneret
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Task
V0
V1
Given:
PP is fed from extruder at 230C. Gear pump
speed is 10 rpm and its specific output is 2.4
cm3/revolution. Spinneret has 48 holes withexit diameter of 0.6 mm. Winding speed is
370 m/minute.
Questions:
What is the filament linear density in units of
dtex (=g/10000m)? What is the fiberdiameter? What is the melt draw ratio?
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Melt spinning of PET yarnsdifferent processes
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High speed spinning of PET
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Stress-strain curves for PET
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Tenacity and elongation at break vs. winding speed
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Structure formation during high speed spinning
of PET
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Heat shrinkage and dyeability of PET fibers
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Classical way to make a yarn
Cutting to
staples (2-5cm)
Stuffer box crimping Spinning into a yarn
Carding into a sliver
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Texturing of filament yarns
Air texturing
Loops and a hairy morphology
Softer and comfortable feel
(hand)
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Loops and a hairy morphology
Softer and comfortable feel (hand)
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False twist texturing
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Melt spun multi-component fibers
Sheath-core Sheath-sheath-core
Bi component fiber extrusion
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40
Sheathpolymer
Core polymer
Bi-component fiber extrusion
technology
V0
V2
V1
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Melt spun multi-component fibers
Islands-in-the-sea (micro / nano fibers)
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Melt spun multi-component fibers
Sea polymer is dissolved producing submicron fibers
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Melt spun multi-component fibers
Segmented pie Mechanical agitation is freeing microfibers
D l f f i l fib
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Development of functional fibers
at Swerea IVF
2012-09-11 44
Techniques used for producing fibers are:
Melt spinning
Solvent spinning (wet spinning) Electrospinning
The fibers act as building blocks in refined textile
materials, e.g. in clothing, technical textiles and medicalapplications, where they increase the technically added
value.
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Laboratory scale fiber production
2012-09-11 45
Melt spinning: 1-3 kg/h
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Laboratory scale fiber production
2012-09-11 46
Wet spinning (with/without air gap): 0.2 kg/h
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Laboratory scale fiber production
2012-09-11 47
Electrospinning of nanofibers: 0.1 kg/h
Swedish patent 0700403-9
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Active fiber developments
2012-09-11 48
Melt spinning
Temperature regulating fibers
Conductive fibers
Piezoelectric fibers
Electro spinning of nanofibers
Technical textiles (filter media)
Biomedical applications (wound care, TE)
Solution spinning
Biopolymers (cellulose)
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High latent heat upon phase change(melting / crystallization)
49
Heat energy Q
Solid
Liquid
Temperature T
Examples: Water: 333 J/g, Tm=0C
Paraffin: 150-250 J/g, Tm = -3C80C
Tm
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PCM in clothsHow it is supposed to work
50
Ski booth with PCM Hard work, PCM
melts, energy is
absorbed as latent heat
Cooling effect
At rest, PCM
solidifies, heat is
given off
Heating effect
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Bi-component PCM-fibers
2012-09-11 51
Sheathpolymer
PCM/Polymer
alloy
WO/2009/031946
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PCM-fibers in contact with the skin
52
25 30 35 C
Heat release (exo, warming)
Heat absorption (endo, cooling)
Comfortable skin
temperature
Melting
Solidifi-
cation
H
H
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PCM-fibers in intermediate layers (works as a thin insulation)
53
100
80
60
40
20
0
-20
-40
Fireman
Cold-storage work
Skin contact
Heat flow ~ dT/dx
Effect of washing on thermal
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Effect of washing on thermal
efficiency
2012-09-11 54
5 dtex fibers with PET and PA6 sheaths (60J/g at 32 C)
Continous filaments 38 mm staples
Heat flow from a body at 34 C into
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0
20
40
60
80
100
120
140
160
0 1000 2000 3000 4000 5000
Time, s
Heatflow,
W/m2
Heat flow from a body at 34 C into
a PCM fiber wading
55
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Electrically conductive fibres
2012-09-11 56
Bi-component fibers with conductive material in the core
Conductive material: Carbon black
Carbon nanotubes
Graphene
Scientific issues: Dispersion and percolation
Source: R. B. Rosner, Compliance Engineering Magazine, (2001).
100 nm
% Conductive filler
Conductivity (log scale)
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Conductivity of CPCs
2012-09-11 57
N-MWNT/PE ()
CB/PP ()
CB/PE (o)
H-MWNT/PE ( )
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Conductivity vs. melt drawing, CB
2012-09-11 58
6% CB/PP ()
6% CB/PE ()
4% CB/PP ()
4% CB/PE ()
6% H-MWNT/PE ()
Conductivity vs melt drawing
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Conductivity vs. melt drawing,
MWNT
2012-09-11 59
4% N-MWNT/PE ()
2% N-MWNT/PE ()
6% H-MWNT/PE ()
1.5% N-MWNT/PE ()
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Piezoelectric effect
2012-09-11 60
Use:
Sensors
Actuators
Energy harvesting
G33 (V/m/Pa)
G31 (V/m/Pa)
1
3
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-crystalline PVDF is piezoelectric
2012-09-11 61
-
+ + + +
-- -
Melt spinning and cold drawing
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Melt spinning and cold drawing
produce -crystalline PVDF fibers
2012-09-11 62
D l t t t i f i l t i t til
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2012-09-11 63
Development strategies for piezoelectric textile
fibers
Conductive sheath/core
PVDF
V
Bi-component fibers
embedded in conductive
matrix/coating
3-component fibers or
coated bi-component fibers
phase PVDF bi co fibers with
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-phase PVDF bi-co fibers with
conductive core
2012-09-11 64
Poling in radial direction
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Poling in radial direction
(orientation of crystallite dipoles)
2012-09-11 65
+
Silver paint or
conductive polymer
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Response in tension
2012-09-11 66
Measured characteristics:
3000 Volts per unit of tensile strain
g31 0.3 V/m/Pa (field strength in
radial direction as result of axial
stress)
Commercial films: g31=0.2 V/m/Pa
66
Bi-component yarn (100-200 filaments)
Woven heart beat sensor from
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Woven heart beat sensor from
piezoelectric PVDF yarn