This document discusses chemical finishing of textiles. It begins with an introduction that defines chemical finishing as using chemicals to impart desired end-use properties by changing the chemical composition or surface characteristics of fibers. There are two main methods of application: exhaust and pad-dry-cure. Pad-dry-cure, the most widely used method, involves padding fabric with a chemical solution, squeezing excess liquid, drying, and curing for fixation. Factors like fiber properties, machine settings, and solution viscosity affect the amount of solution absorbed in wet pickup. The document also covers various pad application techniques and drying methods used in chemical finishing.

1. CHEMICAL FINISHING OF TEXTILES
BY :TESFAY GEBREKIROS TSEGAY
AKSUM UNIVERSITY
DEPARTMENT OF TEXTILE ENGINEERING
2008 E.C

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INTRODUCTION
 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
water
Wet Finishing

3. METHOD OF APPLICATION
EXHAUST 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

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 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

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PAD-DRY-CURE
HIGH WET PICKUPS [70–100 %] IN PADDING
TECHNIQUES

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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
pickup?
WET ON WET
APPLICATION
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)

11. ECONOMICALAND ENVIRONMENTAL IMPACT
REDUCTION OF APPLIED WATER
LOW WET PICKUP METHODS
PAD APPLICATION?

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
removed
SATURATION REMOVAL
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.

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VACUUM EXTRACTION
PULLING A VACUUM THROUGH THE WET FABRIC

14. MACHNOZZLE SYSTEM
HIGH PRESSURE STEAM TO PUSHOUT EXCESS LIQUID

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.

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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

19. SPRAY APPLICATOR
Avoid overlapping spray patterns that could lead
to an unacceptable uneven finish distribution

20. FOAM FINISHING
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 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.
Theratioofliquidtoairinafoamisreferredtoasthe‘blow
ratio’.
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.

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Two slots to apply the foam to the fabric. Two distinctly different finishes can be applied to
differentsidesof thesamefabric

24. DRYING WET
TEXTILES
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.

25. STEAM HEATED CYLINDER DRYER
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26. HOT AIR STENTER
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27. CURING CHEMICAL FINISHES
Fixation of chemical finish for the desired final
property
Thermal treatments are used
Using the same heating equipment in drying of textiles