1. Polymer Fibers

2. Polymer Processing
Shaping Polymers
Extrusion
Molding
Fibers
Coatings

4. Product Shaping / Secondary Operations
EXTRUSION
Final Product (pipe, profile)
Secondary operation
Fiber spinning (fibers)
Cast film (overhead transparencies,
Blown film (grocery bags)
Shaping through die
Preform for other molding processes
Blow molding (bottles),
Thermoforming (appliance liners)
Compression molding (seals)

5. Fibers
A Fiber is a long, thin thing!
Aspect ratio >100
At diameters > 75 , the fiber is a rod
Long means:
> 1 kilometer
At a density of 1.4 and a denier of 5, 1 kilometer weighs less than 5 grams
> 1 kilogram
1.5 kilograms at 5 dpf is 20,000 miles
Few commercial fibers are produced at a scale of less than 500 tons
The length at 5 dpf is ~ .01 lightyear
Typical melt spinning speeds are in excess of 100 miles/hour
To be viable, polymer to fiber conversions must be ~ 90%
Minimum property CVs are < 10%
Real fibers are hard to make!!

6. Griffith’s experiments with glass fibers (1921)
MACROSCALE vs MICROSCALE
Griffith’s experiments with glass fibers (1921)
FIBER DIAMETER (micron)
Strength of bulk glass: 170 MPa
Extrapolates to
11 GPa 1 2 3
TENSILE STRENGTH (GPa) 20 40 60 80
100
120

7. Griffith’s equation for the strength of materials
a = length of defect
g = surface energy
Thus, going from the macroscale to the atomic scale (via the nanoscale), defects progressively become smaller and/or are eliminated, which is why the strength increases (see equation).
Note that the Griffith model predicts that defects have no effect on the modulus, only on strength
But note: the model also predicts that defects of zero length lead to infinitely strong materials, an obvious impossibility!

8. Fibers 1000 X longer than diameter Often uniaxial strength
Kevlar-strongest organic fiber
Melt spinning technology can be applied to polyamide (Nylon), polyesters, polyurethanes and polyolefins such as PP and HDPE.
The drawing and cooling processes determine the morphology and mechanical properties of the final fiber. For example ultra high molecular weight HDPE fibers with high degrees of orientation in the axial direction have extremely high stiffness !!
Of major concern during fiber spinning are the instabilities that arise during drawing, such as brittle fracture and draw resonance. Draw resonance manifests itself as periodic fluctuations that result in diameter oscillation.

9. TABLE 4.2. Fiber Propertiesa
Fiber Type
Natural
Cotton
Wool
Synthetic
Polyester
Nylon
Aromatic polyamide
(aramid)c
Polybenzimidazole
Polypropylene
Polyethylene (high strength)
Inorganicc
Glass
Steel
Tenacityb
(N/tex)
0.27
2.65d
0.31
Specific
Gravity
1.50
1.30
1.38
1.14
1.44
1.43
0.90
0.95
2.56
7.7
aUnless otherwise noted, data taken form L. Rebenfeld, in Encyclopedia of Polymer Science and Engineering (H. f. Mark,
N. M. Bikales, C. G. Overberger, G. Menges, and J. I. Kroschwitz, Eds.), Vol. 6, Wiley-Interscience, New York, 1986, pp
bTo convert newtons per tex to grams per denier, multiply by 11.3.
cKevlar (see Chap. 3, structure 58.)
dFrom Chem. Eng. New, 63(8), 7 (1985).
eFrom V. L. Erlich, in Encyclopedia of Polymer Science and Technology (H.F. Mark, N. G. Gaylord, and N. M. Bikales,
Eds.), Vol. 9, Wiley-Interscience, New Uork, 1968, p. 422.

10. Polymer fibers Nylon PP, PE Normal spinning Melt spinning Super
stretching
HMW PE
Wet
spinning
UHMW PE
Flexible
molecules Dy
spinning
Cellulose
Acetate
Organic
polymers
Melt
spinning
Aromatic
polyesters
Stiff
molecules
Wet
spinning
Aramides

11. Fibers Dry Spinning: From solution Melt Spinning: From Melt
Wet Spinning: From solution into solution
Kevlar, rayon, acrylics, Aramids, spandex
Cellulose Acetate
Nylon 6,6 & PETE

12. Fiber Spinning: Melt
Bobbin
Extruded Fiber Cools
and Solidifies Here
Metered Extrusion
(controlled flow)
Melting Zone
Polymer Chips/Beads
Pump
Filter and Spinneret
Air Diffuser
Heating Grid
Pool
Lubrication by oil disk and trough
Packaging
Bobbin drive
Yarn driver
Feed rolls
Moisture Conditioning
Steam
Chamber
Fiber spinning is used to manufacture synthetic fibers. A filament is continuously extruded through an orifice and stretched to diameters of 100 mm and smaller. The molten polymer is first extruded through a filter or “screen pack”, to eliminate small contaminants. It is then extruded through a “spinneret”, a die composed of multiple orifices (it can have 1-10,000 holes). The fibers are then drawn to their final diameter, solidified (in a water bath or by forced convection) and wound-up.
Nylon 6,6 & PETE

13. Cellulose Acetate
Dry Spinning of Fibers
from a Solution

14. Wet Spinning (e.g. Kevlar)
take-up
godet
feed
line
drawing
elements
spinneret
filaments
Kevlar, rayon, acrylics
Aramids, spandex
coagulation bath
plastisizing bath

16. Melt spinning

17. Acrylic Fibers 85% acrylonitrile Wet spun Acrylic's benefits are:
･Superior moisture management or wickability･
Quick drying time (75% faster than cotton)･
Easy care, shape retention･
Excellent light fastness, sun light resistance･
Takes color easily, bright vibrant colors･
Odor and mildew resistant

19. Nanotube effecting crystallization of PP
Sandler et al, J MacroMol Science B, B42(3&4), pp ,2003

20. Why are strong fibers strong?
The source of strength: van der Waals forces
Flexible molecules,
normally spun
Flexible molecules
ultra stretched
Rigid molecules
liquid crystallinity

21. Kevlar Fiber orientation High Tensile Strength at Low Weight
Low Elongation to Break High Modulus (Structural Rigidity)
Low Electrical Conductivity
High Chemical Resistance
Low Thermal Shrinkage
High Toughness (Work-To-Break)
Excellent Dimensional Stability
High Cut Resistance
Flame Resistant, Self-Extinguishing

22. Kevlar or Twaron High Tensile Strength at Low Weight
Low Elongation to Break High Modulus (Structural Rigidity)
Low Electrical Conductivity
High Chemical Resistance
Low Thermal Shrinkage
High Toughness (Work-To-Break)
Excellent Dimensional Stability
High Cut Resistance
Flame Resistant, Self-Extinguishing

23. Polypropylene elastomers

25. Aramide fibers the complete spinning line
H2SO4
80 wt%
ice
machine
Long washing traject
(initially difficult to control)
Sometimes post-strech of 1%
to enhance orientation
H2SO4 ice
PPD-T
20 wt%
mixer
extruder
air gap
H2O
spinneret
Washing
csulf.ac. < 0.5 %
neutralising
winding
drying
2000C
H2SO4 + H2O

26. Strong fibers from flexible chains
Super-stretched polyethylene:
Mw = 105 (just spinnable)
conventional melt spinning
additional stretching of 30 to 50 times
below the melting point
Wet (gel) spinning of polyethylene
Mw = 106 (to high elasticity for melt spinning)
decalin or parafin as solvent
formation of thick (weak) fibers without stretching
removal of the solvent
stretching of 50 to 100 times close to melting point

27. POLYETHYLENE (LDPE) Molecular Weights: 20,000-100,000; MWD = 3-20
density = g/cm3
Highly branched structure—both long and short chain branches
Tm ~ 105 C, X’linity ~ 40%
15-30 Methyl groups/1000 C atoms
Applications: Packaging Film, wire and cable coating, toys, flexible bottles, housewares, coatings

28. Polyethylene (HDPE) Essentially linear structure
Few long chain branches, methyl groups/ 1000 C atoms
Molecular Weights: 50, ,000 for molding compounds
250,000-1,500,000 for pipe compounds
>1,500,000 super abrasion resistance—medical implants
MWD = 3-20
density = g/cm3
Tm ~ C, X’linity ~ 80%
Generally opaque
Applications: Bottles, drums, pipe, conduit, sheet, film

29. UHMWPE fibers: Dyneema or Spectra
Gel spinning process
Dyneema(r), the worldﾕs strongest fiberDSM Dyneema is the inventor and manufacturer of Dyneemaｨ, the world's strongest fiber. Dyneemaｨ is a superstrong polyethylene fiber that offers maximum strength combined with minimum weight. It is up to 15 times stronger than quality steel and up to 40% stronger than aramid fibers, both on weight for weight basis. Dyneemaｨ floats on water and is extremely durable and resistant to moisture, UV light and chemicals. The applications are therefore more or less unlimited. Dyneemaｨ is an important component in ropes, cables and nets in the fishing, shipping and offshore industries. Dyneemaｨ is also used in safety gloves for the metalworking industry and in fine yarns for applications in sporting goods and the medical sector. In addition, Dyneemaｨ is also used in bullet resistant armor and clothing for police and military personnel.
Structure of UHMWPE,
with n = 100, ,000

30. Comparison of mechanical properties
Strength Modulus stretch
(Gpa) (Gpa) (%)
Classical fibres
nylon
glass
steel
Strong fibres
superstretched PE
wet spun PE (Dyneema)
melt spun PE (Vectran)
wet spun aramide
idem with post-stretch
Relative Flexlife: Dyneema 100, Vectran 55, ﾊAramid 8.

31. Aramide fibers the spinning mechanism
polymer in
pure sulfuric acid
at 850C
Specific points:
solvent: pure H2SO4
polymer concentration 20%
general orientation
in the capillary
extra orientation in
the air gap
coagulation in cooled
diluted sulfuric acid
platinum
capillary 65
air gap 10 mm with
elongational stretch (6x)
coagulation
bath at 100C
removal of
sulfuric acid

32. Vectran
Vectran fiber is thermotropic, it is melt-spun, and it flows at a high temperature under pressure

39. Carbon Fibers: Pyrolyzing Polyacrylonitrile Fibers
Young’s Modulus 325 Gpa
Tensile Strength 3-6 GPa

41. Electrospinning of Fibers
5-30 kV
Driving force is charge dissipation, opposed by surface tension
Forces are low
Level of charge density is limited by breakdown voltage – Taylor cone formation
Fiber diameter  [Voltage]-1
“Inexpensive” and easy to form nanofibers from a solution of practically any polymer (Formhals 1934)
Only small amount of material required

44. Electrospun polymers
Human hair (.06mm)

46. Fibers 1000 X longer than diameter Often uniaxial strength
Kevlar-strongest organic fiber
tensile strength 60GPa
Young’s modulus 1TPa)

47. Making Carbon Nanotubes

49. Carbon Nanotube Fibers
1cm
Nature 423, 703 (12 June 2003); doi: /423703a

51. Fig. 4. Scanning electron micrograph of a dry ribbon deposited on a glass substrate. The black arrow indicates the main axis of the ribbons, which corresponds to the direction of the initial fluid velocity. Despite the presence of a significant amount of carbon spherical impurities, SWNTs bundles are preferentially oriented along the main axis. Scale BAR=667 nm

52. SWNT Fiber after drawing
25 mm

53. Fibers • Large aspect ratio (length/diameter) & strong (fewer defects)
• Common fibers: cellulose acetate, viscous cellulose, polyethylene, polypropylene, acrylics (acrylonitrile copolymers), nylon’s, polyester (PETE), PMMA (optics), urethane (Spandex).
• High performance fibers: polyaramides (Kevlar), Uniaxially oriented gels (UHMWPE), Liquid crystals (Vectran)
• Carbon fibers (Black Orlon or pitch based), carbon nanotubes
• Methods for preparing:
-Dry spinning -Wet spinning
-Melt spinning
-Gel spinning
-electrospinning
-growing (self-assembly)

54. Polymides (PI) - Vespel®, Aurum®, P84®, and more.
Polybenzimidazole (PBI) - Celazole®
Polyamide-imide (PAI) - Torlon®
Polyetheretherketone (PEEK) - Victrex®, Kadel®, and more.
Polytetrafluoroethylene (PTFE) - Teflon®, Hostaflon®
Polyphenylene Sulfide (PPS) - Ryton®, Fortron®, Thermocomp®, Supec® and more.
Polyetherimide (PEI) - Ultem®
Polypthalamide (PPA) - Amodel®, BGU®, and more.
Aromatic Polyamides - Reny®, Zytel HTN®, Stanyl®
Liquid Crystal Polymer (LCP) - Xydar®, Vectra®, Zenite®, and more.
Other Polymers - Nylon, Polyacetal, Polycarbonate, Polypropylene, Ultra High Molecular Weight Polyethylene, ABS, PBT, and mor