Processing of High-Strength Polymer Fibers

Donggang Yao, Professor

School of Materials Science & Engineering

Georgia Institute of Technology

Atlanta, GA 30332

Email: yao@gatech.edu

Phone: 404-894-9076

http://www.prism.gatech.edu/~dy30

Bicomponent melt spinning line

Single-component melt spinning

Mixing and formulation

Flow & deformation

Fiber Spinning Research in Our Group

� Solution spinning

� Wet spinning

- Amides

- Protein

- Polyacrylonitrile

- Cellulose and its derivatives

� Gel spinning

- Fast solvent removal

- High-strength PE fibers

- New high-strength POM fibers

- New high-strength PEO fibers

- Gel spinning of polyketone

� Melt spinning

� Blends spinning

� Elastomeric fibers

� Special drawing and heat-setting techniques

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Processing of High-Strength Polymer Fibers

Our research in fiber spinning focuses on development of new processes to

improve fiber strength and fiber spinning economics. We have a great interest in

solving grand challenges from the polymer/fiber industry. The approaches we take

involve both chemical and mechanical processing to address various aspects in

new fiber products development. The engineering component of our work is

supported by deep materials science, advanced characterization, theoretical

analysis and modeling. In the past 10 years, our work has primarily focused on

1) Formulate new spin dopes suitable for gel spinning

2) Improve the economics of the gel spinning process

3) Improve strength of wet-spun fibers

4) Heat setting of natural and regenerated fibers

Our fiber research has been funded by federal agencies (including NSF and

National Textile Center), the Georgia State, as well as by various industrial

supports.

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Recent Accomplishments in Wet/Gel Spinning

� Oligomer-polymer spinning

� Spinning of molecular or physical blends (rather than classical

solution) with controllable phase miscibility and separation

- A compatible or miscible blend or solution above the polymer Tm

- A largely phase-separated blend below the polymer Tc

� Mechanical removal of solvents

� 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

� Gel spun high-strength fibers for several new polymers

including PEO, POM and other more polar polymers

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Twist Gel Spinning (TGS) ProcessI: MixingII: Gel extrusion & twistingIII: Extraction (optional)IV: Hot drawinga: Gel fiberb: Undrawn fiberc: Drawn fiberA: Solution or blendB: Quenching bathC: Extraction bathD: Heated bath

II III

IV

a

b c

B

C

D

A

I

Twisting

Wyatt, Deng and Yao, Polym. Eng. Sci., 55 (4): 745-752 (2015)

Wyatt, Fang and Yao, Polym. Eng. Sci., 55(6): 1389-1395 (2015) 5

Example UHMWPE Fiber Properties

0

10

20

30

40

50

60

0

1

2

3

4

5

0 0.02 0.04 0.06 0.08

Str

ess (

g/d

en

ier)

Str

ess (

GP

a)

Strain (mm/mm)

GA Tech FiberSpectra 2000Dyneema SK90

SampleStrength

(GPa) / (g/denier)Error

Modulus (GPa)

Error Elongation Error

GA Tech Fiber 4.68 / 53 3.4% 181.09 4.4% 4.8% 2%

Dyneema SK90 yarn 3.69 / 42 3.7% 101.04 2.3% 6.7% 3%

Spectra S2000 fiber 3.56 / 40 6.1% 140.65 6.7% 4% 5%

• Ga Tech fibers are ~ 30%

stronger and stiffer than the

top-notch commercial fibers.

• Ga Tech fibers are available

at large fiber diameter up to

100 µm while commercial

fibers have diameter typically

smaller than 25 µm.

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New High-Modulus, High-Strength POM Fibers

• Strebgth ~ 2 GPa

• Modulus ~ 50 GPa

• High resistance to creeping, fatigure, solvent and salt.

Comparing：：：：

Nylon fibers：Strength < 0.9 Gpa；Modulus < 5 GPa

PPPPolyoxymethylene (POM)

7Ph.D. Thesis by Xudong Fang, April 2016

New High-Strength PEO Fibers

Wyatt, Chien, Kumar and Yao, Polym. Eng. Sci., 54 (12): 2839-2847(2014) 8

PEO fibers nearly 10 times stronger than traditional melt-spun ones were produced.

Strengthening of Natural Silk Fibers

Developed a special hot drawing process for strengthening of silk by rapid heating

and localized drawing. Increase in fiber strength of ~40% was achieved.

Natural silk yarn

PEG bath

Feed roller

Heated roller

Collection

roller

9X. Fang, T. Wyatt, and D. Yao, Fibers and Polymer, 16(12): 2609-2616 (2015)

80 100 120 140 160 180 200 220 240380

400

420

440

460

480

500

520

540 dr=1.067

dr=1.13

Avera

ged

str

en

gth

(M

Pa)

Temperature (°C)

Melt Spinning Example:High-Strength Fiber from Low MW PP

10

110

040 130

131/041

022

10 15 20 25 30 35

Inte

nsi

ty

2θ [degrees]

second stage

first stage

precursor

0

100

200

300

400

500

600

700

0 0.02 0.04 0.06 0.08

Str

ess

[MP

a]

Strain

frist stage

second stage

PP with high MFI or low MW, although desired in melt spinning for enhanced productivity, is difficult to be spun into high-strength fiber using the standard process where extensive jet stretching is applied. In this work, a processing route involving minimal jet stretch and a two-stage hot drawing procedure in the solid state was able to produce fibers with tensile strength and Young’s modulus of ~ 600 MPa and 12 GPa, respectively.

Q. Mao, T.P. Wyatt, J. Chen, and D. Yao, Polym. Eng. Sci., 56(2): 233-239 (2016).

New Spin Dope Formulation Example: Binary/Ternary or multi-component Spin Dopes

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Single phase blend/solution

Phase separated

Gelling

Spinning

Control and optimization of miscibility, compatibility, phase separation, transport, and sequence of extraction through thermodynamic and kinetical calculations.

Design of Pilot Fiber Spinning Lines for Industry

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