Post on 18-Apr-2018
Cost-Effective Production of Super-Strong Polymer FibersXudong Fang, Tom Wyatt and Donggang Yao; email: yao@gatech.edu
School of Materials Science & Engineering
Georgia Institute of Technology
Research Focuses: 1. Developing cost-effective methods for gel spinning of super-strong
polymer fibers.
Twist-Gel Spinning Process:• A majority of solvent is removed by twisting rather than by evaporation or coagulation as
used in conventional gel spinning.
• Thermal behavior of gels
Gel-Fiber before extractionTPmm 0.5TPmm 2 70%
80%90%
100%
%)polymer fibers.
2. Making super-strong polymer fibers from polar polymers, including polyoxymethylene and nylon 6.
3. Making high-strength polymer fibers from biopolymers, including protein, cellulose and polyhydroxybutyrate.
I: MixingII: Gel extrusion & twistingIII: Extraction (optional)IV: Hot drawingA: Solution or blendB: Quenching bathC: Extraction bathD Heated bath
II III
C
I
Novel twist-gel spinning process
• Reducing emission for volatile solvents and reduce production of solvent waste or coagulation byproducts for non-volatile solvents, leading to an environmentally more friendly and economically more viable solvent removal process for gel spinning.
• Improving the recyclability of solvent.• Reducing the time of solvent extraction, particularly useful for large-diameter fibers.
100 110 120 130 140 150
Hea
t Flo
w
Temperature (C)
TPmm 2TPmm 4TPmm 8Conventional extraction in hexane
DSC melting endotherms of mechanically extracted PE/paraffin gel-fibers; gel-fibers before extraction and conventionally extracted are included for reference.
0%10%20%30%40%50%60%
0 60 120 180
Wei
ght L
oss
(%
Time (min)
Conventional Extraction TPmm 4Neat Paraffin Oil
TGA weight loss curves of PE/paraffin gel-fiber and drawn fibers as a function of time. Fibers heated to 300C in N2 atmosphere for 180 min.
• X-ray diffraction of gel and drawn fibers
Methods for gel twisting
V1 V2
N2N1
Mono-filament twisting Continuous twisting with a rotating roving frame
Gel-fiber feed in, V1
N1
Significant Achievements:• A novel twist-gel spinning (TGS) process.
D: Heated bath
IV
B D
A
Twisting
W
22 ' WL
Twist drying mechanism
TPmm=4 ConventionalTPmm=0 TPmm=0.5 TPmm=2
WAXD 2-D patterns of mechanically extracted PE/paraffin gel-fibers with TPmm 0, 0.5, 2, and 4 as noted and conventional fiber extracted in hexane.
110
Conventional
Twisted
Conventional Twisted
Rotating disk
Rotating axis
Gel-fiber feed outGel-fiber feed in
False twisting by a spinning disk
Twist-drying region
Frame drive
Bobbin drive
Frame
Bobbin
To remove solvent mechanically rather than by evaporation/extraction To produce more drawable fiber precursors. To allow direct drawing in a continuous setup. To enable a process similar to melt spinning.
• New oligomer/polymer spinning dopes, allowing spinning of molecular blends with controllable miscibility and separation.
• New polymers for gel spinning: PEO, POM, and other polar polymers. Gel spun PEO and POM fibers 5-10 times stronger than melt spun fibers.
• Production of large-diameter super-strong polymer fibers for ropes, nets and armors.
Existing fibers have diameter smaller than 35 m
L W’
x
L’
222
222
22
2
2
2
414'1
RR
xLx
WW
22' xLL 22
'xL
WLW
100%
Selected Results:• Solvent removal by mechanical twisting
PE/decalin gel-fiber100%
PE/paraffin oil gel-fiber
0 30 60 90 120 150 180
0 30 60 90 120 150 180
200
Conventional
Twisted
WAXD of hot-drawn fibers. LEFT: azimuthal integrations of the [110] and [200] diffractions of the conventional and twisted fibers – offset by 1 for clarity; RIGHT: 2-D patterns of the conventional fiber and twisted fiber.
• Mechanical properties
40
50
60
3
4
5
deni
er)
GPa
) 40
50
60
3
4
5
enie
r)
GPa
)
30
40
50
60
3
4
5
deni
er)
GPa
)
• Existing fibers have diameter smaller than 35 m.• The TGS process can make fibers with diameter ~ 100 m.
Gel Spinning and Limitations:
Comparison between twist-gel spun polyethylene fibers and top-notch commercial fibers
Sample Strength(GPa) / (g/denier) Modulus (GPa) Elongation
Twist gel spun fiber 4.68 / 53 181.09 4.8%
Dyneema SK90 yarn 3.69 / 42 101.04 6.7%
Spectra S2000 fiber 3.56 / 40 140.65 4%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
0 2 4 6 8 10
Perc
enta
ge o
f Sol
vent
Rem
oved
Applied Twist per mm (TPmm)
ExperimentalTheoretical
0%
10%20%
30%
40%50%
60%
70%80%
90%
0 2 4 6 8 10
Perc
enta
ge S
olve
nt R
emov
ed
Applied Twist per mm (TPmm)
• Twisted gel filament and drawn fiber appearance
0
10
20
30
0
1
2
0 0.01 0.02 0.03 0.04 0.05 0.06
Stre
ss (g
/d
Stre
ss (G
Strain (mm/mm)
GA Tech single filament 0
10
20
30
0
1
2
0 0.01 0.02 0.03 0.04 0.05 0.06
Stre
ss (g
/de
Stre
ss (G
Strain (mm/mm)
Spectra S2000 filament0
10
20
30
0
1
2
0 0.02 0.04 0.06 0.08
Stre
ss (g
/d
Stre
ss (G
Strain (mm/mm)
Dyneema 5-fiber bundle
Tensile properties of PE fibers: GaTech (left); Spectra S2000 (middle); Dyneema SK91 yarns.
Undrawn gel-fiber 10X drawn – before extraction
110
120032
20060X
10X
• Oligomer/polymer spinning (PEO and POM)
Acknowledgements
Gel Spinning and Limitations:
Limitations of gel spinning
• High cost, 10 times more expensive than nylon fibers and polyester fibers.
• High processing cost due to slow production and complex solvent recovery steps.
• Solvent concentration > 80% is typical for commercial gel-spun UHMWPE fiber production, making the process inherently inefficient in that for 1 kg of high strength fiber produced 4 kg spin
Coagulation or evaporation
Stretch
Melt spinning Gel spinning vs.
TPmm=1 TPmm=2 TPmm=4
TPmm=0 TPmm=0.25 TPmm=0.5
TPmm=2 TPmm=0
A B C D
Fibers prepared from PE/ paraffin oil spin dope: precursor fibers (left); drawn fibers at a draw ratio of 120 (right).
A
C
B
D
10X drawn – after extraction 60X drawn fiber
12 17 22 272 theta (degrees)
0X
120 azimuthal peak
0X10X20X
PEO and POM fibers, 5-10 times stronger than traditional melt-spun ones, were produced.
School of Materials Science and Engineering
• Resin supplied by Ticona, Mitsui and DSM.• X-ray diffraction from Prof. Satish Kumar’s group at Georgia Tech.• Related research funding from KDH Defense and Ticona.
Acknowledgementshigh strength fiber produced, 4 kg spin-solvent byproduct is created and another 400 kg solvent for extraction.
• Only applicable to very few polymers Polyethylene, PVA, PAN.
Low orientationHigh entanglementLow strength
Hot drawing
Highly extendedHigh crystallinityHigh strength
100 µm 100 µm 100 µm 100 µm
SEM of PE/decalin gel-fibers mechanically extracted using different level of twisting: A) TPmm=0; B) TPmm=2; C) TPmm=4; D) TPmm=8.