Transcript Cellulose Regeneration

Cellulose Regeneration
Puu-0.4100 Advanced Biomaterial Chemistry and
Technology
Herbert Sixta
30-09-2014
Learning outcomes
§  Overview on relevant cellulose solvents
§  Basic knowledge on the mechanisms of cellulose
dissolution and regeneration (what are solvent
parameters?)
§  Regenerated cellulose products (fibers) based on
–  Commercial process techniques
–  Non-commercial processing
§  Basics in wet and dry-wet spinning processes
Cellulose solvents
Dissolution and regeneration
mechanisms
Regenerated cellulose products
Cellulose solvents
1.  Derivatizing solvents
2.  Aqueous solvents
– 
– 
– 
Complexing agents
Aqueous alkali containing solvent: NaOH, NaOH/urea..
Aqueous salt containing solvent: e.g. ZnCl2, LiClO4
3.  Non-aqueous, non-derivatizing solvents
– 
– 
– 
NMMO.H2O
Ionic liquids
Polar, aprotic organic liquids/salts
§ 
§ 
LiCl/DMAc
DMSO/TBAF.3H2O
Liebert, T. et al.: ACS Symposium Series, 2010
Derivatizing Solvents
Cellulose nitrate
Cellulose xanthate
Cellulose acetate
Cellulose formate
Cellulose carbamate
Aqueous complexing agents
§  Cuoxam: polyolato-complex with vicinal OH groups of
cellulose with [Cu(NH3)4](OH)2
§  Cuoxen: bi-dentate diolato-ligand
§  Ni(tren)(OH)2 [tren=tris(2-aminoethyl)amine]*
*Burger, J., Kettenbach, G. and Klüfers, P. (1995) Macromol. Symp. 99, 113–126.
Aqueous alkali containing solvents
Phase diagram of ternary system cellulose / NaOH / water
”Q” denotes the
area where cellulose
dissolves
§  NaOH/Poly(ethylene glycol): max solubility 13 wt% of
cellulose with DP 800
§  NaOH/urea (thiourea): in precooled mixture at -12°C
Sobue, H.; Kiessig, H.; Hess,K.Z. Phys. Chem. 1939, 43, 309
Aqueous salt containing solvents
§  Li, Ca and Zn as cations, SCN-, J-, [HgJ4]2-, [ZnCl4]2- as anions:
capable of dissolving cellulose up to a DP of 50
§  Criterion is a strongly polarizing cation with a voluminous, weakly
hydrated and easy polarizable anion
Rhodanid anions act as a spacer between the cellulose molecules
N-methylmorpholine-N-oxide: NMMO
O
+
N
O
_
Ionic Liquids
§  Compound which consists only
of ions.
§  Melting point below 100°C.
§  Anhydrous
§  Sometimes supercooled melts.
Salt melts
(> 100°C)
100°
Ionic Liquids
(< 100°C)
25°
Room temperature
ionic liquids
(RTIL)
Charge distribution of
1-butyl-3-methylimidazolium
hexafluorophosphate
Most common ions
Adopted from M. Hummel (2012)
Cellulose Aggregate Solution
0.2-0.3 wt% Pulp dissolved in NMMO.MH
aggregate number*
250
*MW/162 DP
200
600
150
400
100
200
50
0
no
wat2e0r % NaO Hammoni a
li qui d
pre-treatment
0
Rg, radius of gyration, nm
800
Molecules laterally aligned,
core surrounded by
disordered regions;
aggregate size not affected
Interpenetrated network
solution
Static light scattering measurements (Guinier-Zimm)
T. Röder, B. Morgenstern, Polymer 40 (1999) 4143 - 4147
12
N,N-dimethylacetamide (DMAc)/LiCl
§  LiCl/DMAc und LiCl/NMP as cellulose solvents (Patent,
1979 by Rayonier).
§  Ion dipole:
§  Li+ reveals a strong interaction with cellulose (7Li NMR
shift with increasing cellulose concentration: Ligand-exchange
mechanism
Morgenstern, B.; Kammer, H.-W. Trends in Polymer Science (1996), 4(3), 87-92.
Cellulose solvents
Dissolution and regeneration
mechanisms
Regenerated cellulose products
Cellulose dissolution
§  Cellulose is amphiphilic (structural anisotropy): contains polar
in equatorial and nonpolar groups in axial directions
>electrostatic repulsion between charged backbones prevents re-association (Zn[OH]42-]
§  Thermodynamic aspects: hydrophobic interactions, 2.0 kcal/
mol/residue, H-bonding, effect of charges
§  Kinetic aspects: removal of primary cell wall structure facilitates
the penetration of the solvent molecules into internal cellulose
structure->ballooning phenomena avoided
• 
• 
• 
• 
Martin Kihlman et al. Braz. Chem. Soc., Vol. 24, No. 2, 295-303, 2013
Medronoh, B.; A. Romano; M.G. Miguel; L. Stigsson; B. Lindman. Cellulose (2012), 19, 581-587
Bergenstråhle,M.; J.Wohlert, ME Himmel, JW Brady. Carbohydr Res (2010), 14, 2060-2066
Le Moigne, N.; Navard, P. ACS Symposium Series (2010), 1033 (Cellulose Solvents), 137-148.
Dissolution of Cellulose in ILs
+
+
−
−
O3-H-O5 intrachain
O2-H-O6 intrachain
O6-H-O3 interchain
Intersheet bonds
O3-H-O5 intrachain
O2-H-O6 intrachain
O6-H-O3 interchain
intersheet H-bond
Solvation of nonpolar cellulose surface by
the +cation −
O3-H-O5 intrachain
O2-H-O6 intrachain
O6-H-O3 interchain
intersheet H-bond
Cho, H.M.; Gross, A; Chu J.-W. J. Am. Chem. Soc. 2011, doi 10.1021/ja2046155.
Regeneration of cellulose
Re-formation of intersheet and intrachain
+
HO
−
bonds
2
O3-H-O5 intrachain
O2-H-O6 intrachain
intersheet H-bond
Liu, H.; Sale, K.L.; Simmons, B.A.; Singh, S. Phys. Chem. B 2011, 115, 10251–10258.
150
Wood pulp
600
dissolved
Torque, Nm
Temperature, C
Cellulose dissolution in a vertical kneader
100
400
50
200
0
0
30
60
Time, min
90
120
0
IL / H2O
Final dope has to be filtrated and degassed
20
Cellulose solvents
Dissolution and regeneration
mechanisms
Regenerated cellulose products
Textile Fibers Overview
FIBERS
Natural fibers
Man-made fibers
From natural
polymers
Synthetic Inorganic
polymers compounds
Protein- Cellulose Cellulose
Protein- Polyester
based
based
based
based Polyamide
(MMC)
Carbon
Elastan
Wool
Silk
Angora
Cashmere
others
Cotton
Flax
Jute
Hemp
Others
Viscose
Modal
Lyocell
Cupro
Acetate
Casein
Collagen
Ardein
Zein
Eichinger, Lenzing AG, 2012
PP
PU
Acryl
PET
Ceramics
Glass
Metal
Global Production of Textiles
Global Fiber Production, Mio t
Global textile market
80
-  Cotton stagnant: 26-28 Mio
t/a
-  High cotton prices
-  33-37% minimum share of
cellulosics in textiles
-  GAP of 15 Mio t/a of
cellulosic fibers in 2030
60
Synthetics
40
Natural
20
10
8
6
4
2
0
Man-made cellulosics
1970
1980
1990
2000
predicted
2010
Man-made cellulosics : CV, CLY, ACETATE
Natural fibers : CO, Wool, Flax, Hemp, Silk, etc.
Synthetic fibers: PE, PP, PA, PAC
2020
Growth rates
- 
- 
- 
- 
Viscose, Lyocell > 9%/a
Acetate 1.5%/a
Ethers 3.5%/a
Others 0-5%/a
The Fiber Year 2013 - World Survey on Textiles & Nonwovens
Short History
o  1857
E. Schweizer used copper oxide and
ammonia to dissolve cotton
o  1865
M.P. Schützenberger produces cellulose
acetate for the first time.
o  1892
C.F. Cross, E.J. Bevan und C. Beadle
discover the viscose process.
o  >1950 development of the high-performance
viscose fibres POLYNOSIC-and MODAL.
Short History
o  1939
Patent to dissolve cellulose in amine oxide.
o  1992
Full scale production Tencel® plant in
Mobile, USA.
o  1997
Lenzing starts a production plant in
Heiligenkreuz, Austria.
o  2014
daily
Lenzing starts the 4th Lyocell mill with a
production of 70 t in spring and 180 t by end
of the year.
Wet spinning
Dry-wet spinning
Wet spinning
§  Viscose
–  Viscose, CV
–  Modal, CMD
§  Cupro, CUP
Viscose Process
Cellulose is converted to a xanthate which is then
dissolved in diluted caustic.
o  CV:
Regular Viscose
o  CMD: Modal Fibres are high wet modulus
fibres produced by a modified viscose
process: Bisfa wet modulus > 5 cN/tex/5%ε
Cupro Process
Dissolution by complexing cellulose:
Cuoxam completely dissolves cellulose by
deprotonating and coordinative binding the C2- and
C3-OHs positions of the AHG.
Cupro Process
Cupro Process
§  Only producer is ASAHI Chemical Industries Co
(NoBeoka, Japan) Bemberg™
§  Bemberg™ cupro regenerated cellulose fiber from cotton
linter. Made by Asahi Kasei Fibers since 1931,
Bemberg™ is used in applications ranging from linings to
outerwear, innerwear, sportswear, and beddings.
§  Recovery of copper improved from 70% in 1930 to
99.9% in the 1980 (ion exchange resin)
Cuprofiber products
§ 
§ 
§ 
§ 
§ 
Filament and staple fiber
Nonwovens
Hollow fiber membrane: UF, haemodialysis
Artificial kidney
Virus removal filter: mean pore diameter 15±2 nm
Textile Chain
Yarn Spinning
Ring: 20 m/min
Compact: 20 m/min
Weaving
Knitting
OE: 150 m/min
Dyeing
Air jet: 450 m/min
woven
knitted
Lenzing AG
Cotton Lyocell
Viscose Process
PULP
Deaeration
Caustic Soda
Dissolving Lye
Solving Water
Carbon Disulfide
Steeping
Lye
Removal
Cooling
Shredding
Ageing
Xanthogenation
Filtration
Dissolving
Ripening
Cutting
Stretching
Spinning
Aftertreatment
Drying
and
Opening
Baling Press
VISCOSE
FIBRES
Viscose Spinning Process
Viscose Spinning Process
Spinning
Stretching
Cutting
Washing
Drying
Viscose Spinning Process
o  Each spinning position has up to 200.000 holes for
staple fibres.
o  The diameter of the typically round shaped holes is
between 40 and 90 mm.
o  Spinning velocity is slow in wet spinning, only 12 to
20 m/min.
o  The viscose is pumped through the spinnerets into
the spinbath where it coagulates.
Viscose Spinning Process
H2SO4:
Na2SO4:
ZnSO4:
Temperature:
~ 2 mol/L
~ 2.5 - 2.7 mol/L
~ 0.1 - 0.2 mol/L
~ 50°C
Spinneret:
1053 holes
50 µm
Viscose Spinning Process
NaHSO4, CS2, H2S
Spin bath
solid
Regeneration of Viscose
Prim. Structure Formation
-  Coagulation
Second. Structure Formation
liquid
H2SO4
Gel
-  Dehydratation, densification
-  Regeneration
-  Orientation, crystallization
Skin Core Structure
Skin plastic
Core not yet
coagulated
§  Skin show higher
orientation; smaller sized
crystallites
§  Core less oriented
§  Skin thickness can be
increased by additives
which retard coagulation
Stretching of Viscose Fibers
Stretching zone
Davenport
T thermostat
P pump
T
T
P
P
T
[
]
⎛
⎞
final take − up, m ⋅ min−1
⎟⎟ ⋅ 100
stretch ratio ,% = ⎜⎜
−
1
−1
⎝ take − up after 1. godet m ⋅ min
⎠
[
]
Stretching of Viscose Fibers
o  Elongational flow in monoaxial direction of the
solidified threads at infinte relaxation time.
o  The molecules are aligned along the fibre axis.
Cutting
Injector draws the cable into a
chute where rotating knifes cut
the filaments to staple:
Staple Length: 38 - 40 mm
Fibre Aftertreatment
Cutting
machine
CS2 condensation
pressing
Wet opener
CS2
Expel tray
Acid
water
EBA Desulfurization
EBB bleaching EBC Soft finish
Wet spinning
Dry-wet spinning
Lyocell
Generic name for a fiber process in which the
cellulose is regenerated from a direct solvent
1.  Lyocell-NMMO: Commercial process of Lenzing AG,
brand Tencel®, with a production of 125 kt/a in 2012
2.  Lyocell-Ionic liquids: in development by several
research group. AALTO has recently launched a fiber
process using a novel ionic liquid.
Tencel® Process
-  Lyocell dope is extruded and spun through an air
gap into a spin bath containing diluted NMMO
solution.
-  The pressure in the metering pump is up to 30 bar.
Lyocell Process
NMMO,
Stabilizer
Lyocell-Fiber
Pulp
(Cellulose)
Dissolution
Water
Filtration
Spinning
Regeneration
NMMO recycling
Washing
Bleaching
Finishing
Drying
Waste Water
Lyocell Dope Preparation
Long vertical vessel with steam
heating in jackets around the vessel.
A shaft down the centre of the vessel
with blades attached to its circumference is rotated to smear the
material around the heated surface to
promote the evaporation process.
Buss Filmtruder
Dope rheology
o  G’, storage modulus, characterizes the elastic
properties of the fluid, while G’’, the loss modulus,
characterizes the viscous properties.
o  Beyond the cross-over point, G’=G’’, the elastic
properties dominate.
o  With increasing MW and polymer concentration,
the crossover point shifts to lower shear rates.
Higher tan δ (loss tangent) indicates
lower polydispersity
G ''
tan δ = '
G
G', G'' / Pa ; |η*| / Pa.s
Viscose vs. Lyocell Viscosity
10
5
10
4
10
3
10
2
10
1
Lyocell, 90°C
Viscose, 0° C
10 0
10
-1
10
-2
0,01
Viscose:
Lyocell;
G'
G'
0,1
G''
G''
1
η
η
10
100
1000
Angular frequency, s
-1
Air Gap Spinning
Filtering and
spinning
Air gap treatment
Take-up velocity
Irregular
molecules
arrangement
L
§  Extrusion through orifices: shear stress
§  Extrusion through air-gap: extensional stress
§  Draw through spin bath: spinodal decomposition,
solidification, structure formation
53
Rheological aspects of Air-Gap Spinning
1. Cellulose-IL solution
Extrusion
2. Shear stress
3. Extensional stress
4. Diffusion controlled
regeneration of cellulose
Fourné, Synthetic Fibers; Carl Hanser Verlag,
Munich 1999.
54
Andrzej Ziabicki, Fundamentals of fiber spinning, John Wiley & Sons Ltd, (ISBN: 0-471-98220-2).
Shear stress
Number of holes:
Diameter of holes:
Extrusion velocity:
​" ↓% =(​4'/)∗​
%↑3 )
n
d
v_0
[]
[µm]
[mL/min]
1000
85
25
​" ↓% =(​4∙25∙​10↑−6 /)∙60∙1000∙​(42.5∙​10↑−6 )
↑3 )=6911 ​,↑−1 Valid only for a Newtonan fluid.
No wall effects considered
Strain hardening and shear thinning
Spinning, Precipitation
Spinneret, airgap: chain orientation
Coagulation bath: desolvation, re-formation of
hydrogen bonds -> highly swollen gel in fibrillar form
-> fibrillar cellulose II crystal structure
Structure Formation:
Build-up of a fibrillar network.
Phase separation time < relaxation time
H.A. Coulsey, S.B. Smith. LenzBer, 75, 51-61 (1996)
57
Phase Changes during Coagulation
1.  At interface quick exchange
of water and NMMO
2. Inside gel, NMMO
diffusion impeded
2
D, m /s
1E-9
H2O
1E-10
3. Later, rapid desolvation,1E-11
NMMO
phase separationinside 1E-12
0 10 20 30 40 50
the biphasic region,
NMMO in Spinbath, %
where spinodal
decomposition occurs:
formation of mutually interconnected polymer chains and pores.
P.R. Laity et al. Polymer
43, 5827-5837 (2002)
58
O. Biganska, P. Navard. Biomacromolecules, 6, 1948-1953 (2005)
Effect of Draw ratio on Fibre
Diameter
DR = 3.0
40
Diameter (µm)
19.5µm
DR = 0.7
37.7µm
-0.49
d = 33 (DR)
30
20
10
0
2
4
6
Draw ratio
8
10
-  Fibre diameter is strongly related with draw
ratio
-  The relationship of fibre diameter and draw
ratio indicating that lyocell process is mass
conversation
Mortimer, S. A and Péguy, A. A. (1996), Cell. Chem. Technol, 30, 117
S. J. Eichhorn, K. Kong. 229th ACS National meeting March 13 – 17, 2005
59
Adjustment of Linear Density (Titer)
Number of holes:
Diameter of holes:
Dope density:
Cellulose content:
Draw ratio:
Extrusion velocity:
n
d
ρ
C
DR
v_0
v_ex
Takeup velocity:
v_tu [m/min]
35.2
T
[dtex]
Titer
​-↓./ =​-↓0 / (0∙​(​1∕2 ∙​10↑−4 )↑2 )) ∙​10↑−2
[]
[µm]
[kg/mL]
[wt%]
[]
[mL/min]
[m/min]
1000
85
1.2
12
8
25
4.4
1.0
The measured titer is higher than the
calculated one due to contraction.
However, a clear relationship allows
the adjustment of the actual titer by
an empirical factor
measured titer (dtex)
3=(​((​1∕2 )∙​1%↑−0.5 ∙​10↑−6 )↑2 ∙))∙4∙5∙​10↑8 20
15
8
7
6
5
4
3
2
1
0
10
5
0
0
5
0
10
1
2
3
4
15
5
6
7
8
20
calculated titer (dtex)
Tendency of Fibrillation
Crosslinking
Mechanically treated
Lyocell
Triacrylamido-trihydrotriazin
(Lenzing, A100).
Lyocell LF
2,4-Dichloro-6-hydroxy-1,3,5-triazin
(Lenzing, Lyocell LF).
61
Crimp
The crimp of a fibre increases the covering power
(capacity to cohere) and is the prerequisite for the further
processing to yarn and fabric.
Viscose Stapel fibres receive a spontaneous crimp due to
the skin-core structure
Textile Chain
Textile Chain
Yarn Spinning
Ring: 20 m/min
Compact: 20 m/min
Weaving
Knitting
OE: 150 m/min
Dyeing
Air jet: 450 m/min
woven
knitted
Lenzing AG
Cotton Lyocell
IONCELL FIBERS*
1,0
σ, GPa
0,8
ION CELL- F
Tirecord
IONCELL-F
800
NMMO
Modal, CMD
Viscose, CV
Cupro
600
400
200
0
0
Fl ax
0,6
5
10
15
CM D
CV
0,2
0
10
20
30
Young's m odulus [GP a]
*Birch Prehydrolysis-Kraft Pulp from Stora
Enso as raw material
20
Elongationcond [%]
NM MO
0,4
0,0
1000
Tenacity cond [MPa]
IONCELL fiber shows
superior strength properties
as compared to commercial
man-made cellulosic fibers
(MMCF).
Dry-jet wet spinning
process
40
Filament
Staple Fibre
25
Demonstration runs
Men’s
accessories
9/14
SCARF: 11/13
Marimekko®
DRESS: 3/14
Knitted fabric
Woven fabric
Knitted fabric
designed by Tuula Pöyhönen
Physical Properties of MMCFs
Initital Modulus
Specific strain
Initital modulus = tan a
a
Strain
Yield Point
§  Yield point as occuring at the
stress given by the
intersection of the tangent at
the origin with the tangent
having the least slope.
§  At the yield point, elastic
recovery becomes less
complete for higher strains.
§  Point at which permanent
deformation starts
1000
800
Stage I:
stress-strain curve:
IONCELL
15 wt% Euca-PHK IONCELL
Internal energy elasticity: Extension
of fibrillar&molecular structure without
disrupting H-bonds between fibrils.
Plastic deformation due to disruption
of interfibrillar H-bonds close to PL
III
600
PL
400
dry
Tensile strength, MPa
Tensile deformation of dry cellulose fibres
II
Stage II:
Orientation of fibrils unhindered by
interconnecting H-bonds. Slower buildup of stress
200
0
I
0
5
10
Elongation, %
15
Stage III:
Chain slippage and chain rupture
Terms and Definitions
Linear Density (fiber fineness)
Mass per unit length (= titre)
1 dtex = g fibre / 10000 m
Circular cross section
Area A is related to diameter D:
Linear density c:
c... tex
D...mm
ρ....g/cm3
Diameter of a 1.3 dtex fibre?
9=​)​1↑2 /4 :=94= ​)4​1↑2 /4 1=2∙√⁠​:/)∙4 ​(​0.13 6/1000 7 ∙​1/) ∙​10↑−6 /1.53 6 )↑0.5 ∙2=10.5∙​10↑−6 7=10.5 87
1 [87]=11.3√⁠​:↓>?./ /4 Tensile properties
​:@/?./ =​10↑−2 ∙A6∙7∙​,↑2 ​∙10↑3 ∙7/​,↑2 ∙A6∙7∙9.81∙​10↑−3 ≈​10↑3 7
​%↓7 =​:@/?./ ∙4∙6=​10↑3 7∙​1500 A6∙9.81∙​7∙, ↑−2 /​,↑2 ∙A6∙7∙9.81∙​10↑−3 ≈​1.5∙​10↑7 @/​7↑2 =15 BCD=0.015 ECD
Stress-strain curves of Regenerated
Cellulose Fibers
1200
CMD
CV
Cupro
Tenacitycond [MPa]
1000
IONCELL
NMMO
BOCELL
800
600
400
200
0
0
5
10
15
20
Elongationcond [%]
25
Structural vs. Mechanical Properties
§  Mechanical properties such as fibre tenacity, FFc,
are determined by
-  the DPn in relation to the size of
-  the elementary crystallites DPnL
-  the degree of lateral order, Xc, and
-  the degree of orientation, fc and ftot.
§  Krässig has shown a linear relationship between
FFc and (​2∕​FG↓HI −​2∕​FG↓H )∙JKL∙​M↓K ↑3 ∙​24↑5 valid for cellulose fibres including fortisan,
polynosic and HWM.
Hans Krässig: Cellulose (1993), p161
Tenacity (cN/tex)
Effect of molecular an structural characteristics
on the conditioned tensile strength
70
60
50
40
30
20
10
0
0
5
10
15
Hans Krässig: Cellulose (1993), p161
Short-chain molecules, DP < 100
Working Strength[cN/tex*%]
VISCOSE FIBRES
Maximum strength
550
properties (tensile strength
times elongation) of regular
visose fibres dependend on
500
the amount of DP<100
fraction.
450
commercial dissolving pulps
0
3
6
9
DP < 100 weight fraction in pulp [wt%]
Continuous chain model
-  Chains are oriented parallel to the
symmetry axis and the orientation
angle of this axis N with the fiber axis
shows a distribution O(N)
-  Elastic tensile deformation is due to
the chain elongation and the shear
deformation.
CELL I
Chain modulus =
140 GPa
CELL II
Chain modulus =
90 GPa
-  Chain modulus, eC, purely elastic,
shear deformation, g, is determined
by intermolecular H-bonding (time
dependent) and denotes the shear
between adjacent chains.
​1/P =​1/​.↓: +​⟨​,R0↑2 S⟩↓P /26 ⟨​,R0↑2 S⟩
P, ​.↓: , 6 U
tensile stress
orientation parameter
elastic, chain, shear moduli
Structure and Mechanical Properties
Fiber
Mechanical properties
σC
GPa
Fw
εC
Structural properties
DPv
%
Xc
fC
ftot
%
CV
0.38
20
0.50
430
28
0.62
0.41
CMD
0.51
13
0.57
650
29
0.66
0.47
CLY-NMMO
0.60
15
0.90
900
41
0.85
0.59
CLY-IL
0.85
10
0.92
900
0.96*
0.81*
Bocell
1.30
7
0.85
650
Fw
xc
fc
ftot
*
59
ratio wet-to-dry strength
WAXS degree of crystallinity
crystalline orientation parameter (Hermans, 1946)
total orientation parameter
different method
​V↓D =​V↓? −(​/↓5 ∙​V↓5 )/(1−​
/↓5 )∙0.91 *T. Röder, P. Zipper (2003), Lenzing AG
**H-P Fink (2014)
Fiber Cross-Sections, Cryo Fractures
CV
CMD
CLY
Magn.
10 µm
*1070
1 µm
* 6000
1 µm
*20 000
100
2,2
chain modulus
Tensile stress (GPa)
Dynamic modulus, GPa
Ultimate strength of cellulose fibers
80
EHM
60
Fortisan
40
20
0
0
1
2
3
4
Extension, %
5
max CELL II
2,0
1,8
DuPont
1,5
Bocell
1,2
Fortisan
Hemp
0,9
TC
0,6
0,3
0,0
Dynamic modulus depends only on the
extension: E as a f (ε) for welloriented regenerated cellulose fibers:
second loading cycle.
Northolt, M.G. Lenzinger Berichte, (1985), 59, 71-79. De Vries. Appl. Sci. Res. A3, 111 (1952).
CV CMD
0
IC-F
CLY
20
40
60 80100
Young's modulus (GPa)
Emax:
σmax:
~ 60 GPa (IC-F: 35)
~ 1.8 GPa (IC-F: 0.9)
Absorbed Water in Cellulose Fibers
CO
Cotton absorbs only little water
CLY
Tencel shows uniform water absorption
over the whole fiber cross section
CMD
Visualization of water:
Solvent exchange procedure followed by
isoprene polymerization and OsO4 staining in
aqueous solution:
81
M. Abu-Rous et al. Cellulose, 13, 411-419 (2006)
Crystalline skin of Modal
contains less water than the
core
CV
Uneven
water
distribution in
viscose
Water Retention
Cotton
Lyocell Fiber – NanoMultifilament
-  Nonswelling hydrophilic crystalline microfibrils
-  Swelling amorphous regions and interfibril capillaries
1 µm
Skin, app. 100 nm dry, can
swell widely in H2O
Fibre, diameter
8 - 30 µm
Macro-fibril (0,5 - 1µm), made
up of micro-fibrils (10 - 100 nm)
Microfibrils (D & A),
non swelling
H. Firgo et al., Dornbirn 2003
83
Water Vapour Sorption
1800
Absorption capacity of
equivalent beds at 100 % RH
g H2O
1500
Lyocell beds helps to make a
comfortable sleeping climate.
1200
900
600
300
0
Lyocell Wool Cotton PES
Water absorption takes place in
the capillaires between the
fibrils only
84
*Total textile material = 4.24 kg.
H. Firgo et al., Dornbirn 2003
ANNEX
Continuous Chain Model
Continuous chain model
§  Serial arrangment of small domains.
§  Elastic tensile deformation is due to the elongation of the polymer
chain and the shear deformation of the chain segment.
§  The shear deformation induces a rotation of the direction of the chain
segment towards the fiber axis
Fibers > Fibrils > Crystallites-> orientation distribution relative
to fiber
​ /P =​1/​.↓: +​⟨​,R0↑2 S⟩↓P /
1
26 axis: ⟨​,R0↑2 S⟩ orientation parameter
P, ​.↓: , 6 elastic, chain, shear moduli
U
tensile stress
For small strains:
W=​U/​.↓: +​⟨​,R0↑2 S⟩/2 (1−P/X(−​U/6 ))
• 
• 
​Δ0/Δ​0↓7D/ =1−​3/2 ⟨​,R0↑2 S⟩
elastic extension of the polymer chains
Elastic shearing of the crystallites (row of book
when falling over)
Birefringence vs chain orientation in a fiber: Hermans,
Elsevier, 1949
Δ0=​Δ0↓7D/ (1+​36/​.↓: )−​36Δ​0↓7D/ /P From (1) and (3): Δnmax is the value for perfectly
oriented fibers for which E = ec
shear between adjacent chains
Northolt, M.G. et al. Polymer (2001), 42, 8249-8264; Northolt, M.G. Lenzinger Berichte, (1985), 59, 71-79
Birefringence vs Compliance
Δ0=​Δ0↓7D/ (1+​36/​.↓: )−​36Δ​0↓7D/ /P 0,07
Birefringence, Δn
0,06
Fiber B
Cordenka EHM
Fortisan
0,05
Ioncell, E>20 GPa
Ioncell, E<20 GPa
NMMO, E>20 GPa (lit)
NMMO, E<20 GPa (lit)
0,04
Viscose
0,03
0,01
0,00
0,00 0,02 0,04 0,06 0,08 0,10 0,12 0,14
Compliance (1/GPa)
P, ​.↓: , 6 shear moduli
elastic, chain,
​,YZX./R0?.[:.X? =​36/1+
6/​.↓: aGb
`​3 =3.>? @​H↓cbd =4.4AB
g = 2.5 GPa, dnmax = 0.0621
g = 3.6 Gpa, dnmax = 0.0812
0,02
1/eC
Linear part:
highly oriented fibers ​.↓: =90 ECD (\\)
Non-linear part:
Medium and low oriented fibers
(viscose): g is likely to be a
function of the orientation:
6=1.3​ln⁠(P) −0.81 ]^K _=24, `=3.3 aGb
Northolt,
M.G.−et​.al.
P=​3.↓: ∙6∙∆​0↓7D/ /​.↓: ∙​∆0↓7D/ +​3612∙∆
0↓7D/ ↓: Polymer,
∙∆0 (2001), 42, 8249
Kong, K.; Eichhorn, S.J. Polymer (2005), 46, 6380-6390