1. CHEMICAL FINISHING OF TEXTILES
BY :TESFAY GEBREKIROS TSEGAY
DEPARTMENT OF TEXTILE ENGINEERING
Chemical Finishing refers to the use of chemicals to
achieve a desired end-use property.
Processes that change the chemical composition of
the fibers OR improve the surface characteristics
Can be applied in yarn, fabric, and garment stages
Can be durable or on durable based on resistance to laundering
Chemical finish is solution or emulsion of active chemical in
3. METHOD OF APPLICATION
PAD-DRY-CURE --- Most widely used
Chemicals that have strong affinities for fiber
surfaces can be applied in batch/discontinuous
processes by exhaustion
Chemicals that have low/no affinity for fibers are applied by
continuous processes that involve padding with chemical
solution, squeezing, drying and curing for fixation
By passing fabric through chemical finish
solution by ‘wet on dry’ process.
Factors affecting wet pick up:
Fiber, yarn and fabric characteristics
Machine settings [e.g. Squeeze pressure]
Solution properties [Viscosity, surface tension]
PAD APPLICATION OF CHEMICALS
Removal of large amount of water during drying
Migration leading to uneven finish distribution
For consistent chemical application:
Nip pressure should be uniform across the fabric width
Solution level & temperature in pad should be constant
Fabric speed should not vary throughout the application
7. Wet pickup’ (wpu): amount of finishing solution applied
Add on: amount of supplied chemical added to the fabric
gpl to weight percent concentration
IMPORTANT CONCENTRATION RELATIONS
8. Feed rate to maintain constant liquor level in the pad
A cotton fabric is to be treated with 5.0 % on weight of fabric (owf)
with a chemical finish in a wet on dry padding process. If the wet
pickup is 90 %, what concentration of chemical is needed?
9. If the solution density is 1.05 g ml–1 ,what is the required
concentration in g l–1?
If the fabric with linear density of 0.250 kg m–1 has a speed of 80
m min–1, what is the flow rate of solution necessary to maintain a
constant level in the pad?
10. The same fabric is to be treated with 5 % owf of same
chemical finish in wet on wet pad application with entry
wet pickup of 75 %, exit wet pickup of 90 % and
interchange factor of 0.7. What is the effective wet
WET ON WET
wpu0 is percentage wet pickup of fabric exiting the pad
wpui is percentage wet pickup of fabric entering the pad
f is the interchange factor, a measure of interaction between
incoming water and the pad solution (0-1)
12. Two main types of low wet pickup applicators.
With the first type fabric is completely saturated
with the finish liquor and then the excess liquor is
With the second type, a precise amount of finish
liquor is uniformly applied to the fabric
TOPICAL APPLICATIONHowever, too low a wet pickup can be equally problematic and also
lead to uneven finish distribution if the liquid phase is discontinuous.
15. KISS ROLL
The kiss roll picks up the chemical finish and
transfers it by direct contact to the fabric.
16. Triatex MA (minimum application) system
Measurement of mass per unit area based on
the intensity of electrons that pass through the
fabric. The kiss roll rotational speed is automatically
adjusted relative to the fabric speed to maintain the desired
17. LOOP TRANSFER SYSTEM
LOOP OF FABRIC IS IMMERSED IN FINISH
LIQUOR, AND SQUEEZED WITH FABRIC TO BE
TREATED BETWEEN SQUEEZE ROLLERS.
Engraved roll transfer precise amount of chemical finish to fabrics;
a doctor blade for removal of excess liquid from the roll surface
ENGRAVED ROLL APPLICATOR
MULTIPLE ROLLSFOR FABRICSWITH DIFFERENT WET PICK-UP
20. FOAM FINISHING
By replacing part of water in chemical formulation with
air, amount of water added to fabric can be reduced.
Surfactants are included in formulation to be foamed.
Foam densities 0.1 g cm–3 are routinely used
One side and two side foam applicators
22. The one side applicators apply foam to only one side of the
fabric, leaving open the possibility of two different finishes
on different sides of the same fabric.
Two slots to apply the foam to the fabric. Two distinctly different finishes can be applied to
24. DRYING WET
Water in a wet textile resides in three different areas.
Looselyboundwateris on fabricsurface /interstices.
Much of this water is taken out by mechanical means
such as squeezing, centrifugation or vacuum extraction.
Remaining water, water held in the yarn capillaries and
water absorbed internally by the fiber, must be removed
through vaporization by thermal means.