This document presents on dry-jet wet spinning. It discusses that dry-jet wet spinning is a modification of wet spinning where the spinning solution is extruded into air and drawn before being submerged in a coagulation bath. This allows benefits of both dry and wet spinning processes. Key aspects of dry-jet wet spinning covered include the extrusion through an air gap, its use for specific polymers like lyocell, and how post-spinning drawing and heating processes can further improve fiber properties. Factors that influence fiber morphology and properties through this process are also summarized.

1. PRESENTATION ON DRY-JET WET SPINNING
SUBMITTED BY :-
AMIT SINGH
AMIT SHUKLA
ABHISHEK GUPTA
SUBMITTED TO :-
Prof. S CHAKARBORTY SIR
UPTTI, KANPUR

2. Introduction
The key properties of polymer influencing fibre formation are :
(a)Chemical structure and properties
(b) Mol. Wt. and distribution
(c) Defects in linear chain structure
(d) Impurities or side reaction product
(e) Thermal stability

3. Various method of spinning
 Melt spinning
 Dry spinning
 Wet spinning
 Dry jet wet spinning
 Gel spinning
 Electro spinning

4. Dry jet wet spinning
• It is modification in wet spinning technique
• Spinneret is kept just outside the surface of coagulation bath
• Air gap between spinneret and coagulation bath varies with type
of polymer and technique used.
• It has benefit of both dry as well as wet spinning
• In acrylic spinning this gap may be small but in lyocell it may be
up to several centimeters
• High performance fibres ,Industrial grade fibres are mainly
manufactured by dry jet wet ,gel spinning.

6. Method of dry jet wet spinning
 A variant of wet spinning is dry jet wet spinning where the
solution is extruded into air and drawn and then submerged
into liquid bath
 This method is used in lyocell spinning of dissolved cellulose
 In this method the polymer is dissolved in appropriate solvent
to make the fibre solution this solution is then extruded under
heat and pressure into an air gap before it enters a coagulation
bath

7.  The produced fibre is the washed and dried before it is heat
treated and drawn
 This is an alternative method to wet spinning and is required
as spinning directive into the bath for some fibres create
micro void that negatively affect the fibre properties this is
due to solvent being drawn out of the liquid too quickly
 An inert atmosphere may be required to prevent oxidation in
some polymer if so fibres are extruded into an nitrogen
atmosphere

8. Benefits of dry jet wet spnning
 High sped of spinning
 High concentration of dope
 High degree of jet stretch ratio
 Control of coagulation kinetics by monitoring coagulation
bath parameters

9. Effect of post spinning operations
 In case of thermo plastic fiber such as PAN copolymers
the fibers are drawn subsequently in boiling water bath to
impart better morphology higher orientation and better
mechanical properties
 Drawing speed has great influence on the orientation and
properties of fiber the orientation increases with
increasing speed of drawing
 The properties such as tenacity and stability to repeated
deformation achieve a maximum at some optimum
velocity (drawing speed)

10.  The fiber spun using dry jet
wet spinning system are often
subjected to high draw ratio
such as glycerol at 170 C
 The fibers are also collapsed by
subjecting them to dry or
steam heat treatment in the
range of 150-170 C , this allows
collapse of remaining voids
inside the fibers and a kind of
transparency is obtained in the
collapsed fiber

11. Diffusion coefficient of solvent and non solvent
 Diffusion coefficient for both solvent and non solvent in dry
jet wet spinning are smaller than the immersion jet wet
spinning .
 This is possible because of the formation of more dense
structure of the entire proto fibre or the formation of cuticle
on the surface of proto fibre as it passes through the air gap
in dry jet wet spinning

13.  Diffusion coefficient for both solvent and non solvent in dry jet wet
spinning are smaller than the immersion jet wet spinning .
 This is possible because of the formation of more dense structure
of the entire proto fibre or the formation of cuticle on the surface of
proto fibre as it passes through the air gap in dry jet wet spinning
 Jet stretch ratio has a significant effect on diffusion coefficient.
 The diffusion coefficient of solvent increases and of water(non
solvent) decreases with increases jet stretch ratio.
 However they both increase abruptly after a certain critical jet
stretch ratio in the immersion jet wet spinning possibly due to the
formation of voids or crevice openings on the fibre surface.

14. Table 3.2 Effect of coagulation parameters on morphology of
wet spun fibres.
Coagulation
parameters
Cross-section of
proto fibre
(Dry jet and
immersion jet)
Void formation
(immersion jet)
Void formation
(dry jet)
Properties
(dry jet)
Increasing bath
temperature
goes towards
symmetric circular
shape
towards more voids no voids
tenacity modulus
lower and elongation
increases
Decreasing bath
concentration
goes towards
asymmetric
shape
towards more voids no voids no significant effect
Increasing jet stretch small effect
towards more
peripheral voids
no influence
tenacity, modulus
increases,
elongation
decreases
Increasing dope
concentration
no change more number of voids No influence no significant effect

15. THANK YOU