Wet spinning is the oldest of the five processes. This process is used for polymers that need to be dissolved in a solvent to be spun. The spinneret is submerged in a chemical bath that causes the fiber to precipitate, and then solidify, as it emerges. The process gets its name from this "wet" bath.
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BAHIR DAR UNIVERSITY
Ethiopian Institute of Textile and Fashion Technology
“Manmade fiber Technology”
Title: Wet spinning of Acrylic fiber
Prepared By:-Berihun Gashu (MSc in TC)
Submitted to:- Mr. Adane H. (Assoc. Prof.)
June 2021 G.C.
2. Contents
2
o Introduction
o Theoretical background
o Wet spinning of Acrylic fiber
o Working principle
o Parameters of wet spinning of acrylic fiber
o summery
o References
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Introduction
Oldest spinning mothed from other processes.
Non- volatile solvent for preparation,
Non-solvents for coagulation,
Submerged in a coagulation bath
Acrylic, rayon, aramid, modacrylic, and spandex.
Acrylonitrile
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Conti…
volatile solvent
non-volatile solvent
Coagulation medium.
Warm Air
Spinneret in
coagulation bath
Wet spinning Dry spinning
Comparison of Solution Spinning
No phase separation
No non-solvent
No coagulation
No voids
Existence of voids
non-solvent involves
Phase separation
5. 5
Theoretical background of acrylic fiber
Nylon, polyester, PP, and polyacrylonitrile.
Stability in the molten stage,
Polyacrylonitrile would not melt without decomposition, degradation of polymer,
Low cost , plastics and rubber nature intensive research to find a solvent for polyacrylonitrile
was initiated by a number of American and German companies in the 1940s.
extrusion
Organic solvents Wet and dry-spinning
melt-spinning technology
8. 20 000–100 000 holes with diameters of 0.05–0.25 mm.
T°C spinning dope & coagulation bath,25–125°C and 0–50°C, respectively.
The spinneret is immersed in the coagulation bath =solidified
8
Conti….
The solidification speed is affected by :-
o The concentration of the spinning dope,
o The ratio of solvent/non-solvent and
o The temperature of the coagulation bath.
Easy flow of fluid vs Cohesiveness
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solid polymer dissolved
1
solution heated in the heat exchanger
2
solution is passed/extruded to spinneret
3
The filament wound on the bobbin
5
Wended filament is then drawn
6
washed & dried wound on a suitable package
7
Delivery
8
filament of solid form
4
Spinning process
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B. Coagulation
Spinning dope form gel fibers due to phase separation of the dope in solvent/water mixture.
The initial fiber formation performed at exits the spinnerets capillaries.
Counter-diffusion of the solvent from the dope and counter-diffusion of the non-solvent from
the coagulation bath,
But it may occur at different rates, which depend on
20,000 to 100,000 capillaries
Mass transfer
The coagulation bath composition and temperature
protofibers
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The Effect of Coagulation Variables
on Initial Fiber Structure
1. The effect of dope composition,
2. The effect of coagulation bath composition,
3. The effect of coagulant temperature, and
4. The Effect of Jet stretch
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1. The Effect of Dope Solids
Raising dope solids, improves the homogeneity of the fiber structure by reducing voids.
No simultaneous change in the cross-sectional shape of the fiber occurs, and
Solvent/polymer
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2. Effect of spin bath composition
Effect of spin bath composition on protofibre structure at 55°C bath temperature
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3. The Effect of coagulation temperature
Dwell time
Retardation
Solidification speed
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4. The Effect of Jet stretch
It is the ratio of taken out of the coagulation bath to dope is pumped
through the spinneret holes.
At a given set of bath conditions, increasing jet stretch is accompanied
by decreasing density, decreasing surface area, and decrease the
number of voids.
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C. Diffusion
Spinning solution contact with a coagulation bath diffusional interchange occurs.
Due to concentration differences extruded dope and coagulation proceeds at the exit of the
capillary.
Solvent leaves, while non-solvent enters,
After a sufficient length of time no more exchange takes place,
Mass Transfer
mixture of solvent and non-solvent
state of equilibrium
polymer phase
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Conti…
Diffusion process influenced by,
o Spin rate,
o Dope concentration and
o Temperature of dope.
increase in temperature increases
the diffusion of solvent and nonsolvent
Increased polymer concentrations less solvent,
high rate of diffusion due to increase solvent out
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D. Phase Separation
Polymer solution to a solid phase or porous gel
network.
A polymer rich phase and solvent/non-solvent
phase.
The voids are due to solvent/non-solvent phase
separation and diffusion processes.
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E. Structure
It is result of the counter-diffusion of solvent and non-solvent and the phase separation.
Gel network of interconnected polymer fibrils separated by void.
The void size is determined by the rate of diffusion and phase separation.
Fiber cross section can be altered by changing the coagulation conditions.
The void size increases as the rates of diffusion and phase separation increase.
size and number of voids dry, collapse, and relax
VS
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1. Washing
Fiber washing with the help of temperature and wash liquid concentration.
Water use a wash temperature limited to the boiling point of the water.
Conducted mainly preceding, or concurrent with, stretching.
A small amount of residual solvent is usually purposefully left in fiber to optimize
processing behavior.
The fibrillar network remains a porous structure at this point in the process and gel state.
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Fibers oriented the molecular chains, which resulted in an improvement in tenacity.
Diameter of fibers decreased, and their surfaces became smoother
The porosity decreased and became more compact,
The crystalline orientation of PAN fibers increased with increasing draw ratio.
2. Drawing
due to the draw ratio increases
improvement in the mechanical properties
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3. Finish
A chemical treatment is applied to the fiber.
The chemical or "finish" is normally an aqueous solution or
emulsion and
It has both lubricants and antistatic components that facilitate
fiber processing in the subsequent collapse/drying steps and
transforming the fiber into yarns and fabrics.
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4. Drying, Collapsing, Relaxing
A drying/collapsing process passing the fiber over heated zones and/or hot rolls.
While drying the fiber, collapsing is also occurring as the water is driven from the internal
fibrillar network.
The fiber collapse is the closure of the oriented open pore structure,
The relaxation process is the final step in changing fiber morphology and significantly alters
the fiber stress-strain behavior.
A hot, wet environment; both batch and continuous relaxation systems are utilized.
External and internal fiber water
27. The conversion of polyacrylonitrile to fiber was more difficult as the polymer would not melt
without decomposition wet spinning technology for such fiber production.
Wet spinning basically used for polymers that need to be dissolved in a solvent to be spun.
The spinneret is submerged in a chemical bath that causes the fiber to precipitate, and then
solidify, as it emerges.
The only different from other spinning solidification due to coagulation bath that makes
precipitated filament.
27
Summery
28. Reference
Dong, R., Zhao, J., Zhang, Y. and Pan, D., 2009. Morphology control of polyacrylonitrile (PAN) fibers by phase separation technique. Journal of Polymer Science
Part B: Polymer Physics, 47(3), pp.261-275.
Han, C. D., & Segal, L. (1970). A study of fiber extrusion in wet spinning. II. Effects of spinning conditions on fiber formation. Journal of Applied Polymer Science,
14(12), 2999–3019.
Knudsen, J.P., 1963. The influence of coagulation variables on the structure and physical properties of an acrylic fiber. Textile Research Journal, 33(1), pp.13-20.
Paul, D.R., 1968. Diffusion during the coagulation step of wet‐spinning. Journal of Applied Polymer Science, 12(3), pp.383-402.
Masson, J. ed., 1995. Acrylic fiber technology and applications. CRC Press.
Paul, D.R., 1968. A study of spinnability in the wet‐spinning of acrylic fibers. Journal of Applied Polymer Science, 12(10), pp.2273-2298.
Zhou, P., Lu, C., Shi, J., Li, K., He, F., Zhang, S. and Li, Y., 2011. Effect of bath concentration on coagulation kinetics at the early stage during wet spinning of PAN
copolymer nascent fibers. Journal of Macromolecular Science, Part B, 50(6), pp.1215-1225.
Peng, G.Q., Wen, Y.F., Yang, Y.G., Liu, L. and Wang, W., 2009. Effect of dope extrusion rate on the formation and characterization of polyacrylonitrile nascent fibers
during wet-spinning. Polymer bulletin, 62(5), pp.657-666.
Arbab, S., Noorpanah, P., Mohammadi, N. and Zeinolebadi, A., 2011. Exploring the effects of non-solvent concentration, jet-stretching and hot-drawing on
microstructure formation of poly (acrylonitrile) fibers during wet-spinning. Journal of Polymer Research, 18(6), pp.1343-1351.
Han, C.D. and Segal, L., 1970. A study of fiber extrusion in wet spinning. II. Effects of spinning conditions on fiber formation. Journal of Applied Polymer Science,
14(12), pp.2999-3019.
Knudsen, J.P., 1963. The influence of coagulation variables on the structure and physical properties of an acrylic fiber. Textile Research Journal, 33(1), pp.13-20.
Wang, Y.-X., Wang, C.-G., Bai, Y.-J., & Bo, Z. (2007). Effect of the drawing process on the wet spinning of polyacrylonitrile fibers in a system of dimethyl sulfoxide
and water. Journal of Applied Polymer Science, 104(2), 1026–1037.
