Melt Spinning New

7/30/2019 Melt Spinning New

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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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Sheathpolymer

Core polymer

Bi-component fiber extrusion

technology

V0

V2

V1


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Islands-in-the-sea (micro / nano fibers)


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Sea polymer is dissolved producing submicron fibers


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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

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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

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Melt spinning: 1-3 kg/h


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Wet spinning (with/without air gap): 0.2 kg/h


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Electrospinning of nanofibers: 0.1 kg/h

Swedish patent 0700403-9


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Active fiber developments

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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)

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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

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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

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Sheathpolymer

PCM/Polymer

alloy

WO/2009/031946


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PCM-fibers in contact with the skin

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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)

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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

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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

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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

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N-MWNT/PE ()

CB/PP ()

CB/PE (o)

H-MWNT/PE ( )


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Conductivity vs. melt drawing, CB

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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

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4% N-MWNT/PE ()

2% N-MWNT/PE ()

6% H-MWNT/PE ()

1.5% N-MWNT/PE ()


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Piezoelectric effect

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Use:

Sensors

Actuators

Energy harvesting

G33 (V/m/Pa)

G31 (V/m/Pa)

1

3


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-crystalline PVDF is piezoelectric

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-

+ + + +

-- -

Melt spinning and cold drawing


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Melt spinning and cold drawing

produce -crystalline PVDF fibers

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D l t t t i f i l t i t til


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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

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Poling in radial direction


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Poling in radial direction

(orientation of crystallite dipoles)

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+

Silver paint or

conductive polymer


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Response in tension

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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

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Bi-component yarn (100-200 filaments)

Woven heart beat sensor from


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Woven heart beat sensor from

piezoelectric PVDF yarn

Documents

Melt Spinning New