Textile Chemical Processing for the
Fibres (Preparatory Operations)
• The fabric collected from various weaving setups,
can not be used directly for manufacturing
various textile products.
• There are number of impurities present in the
fabric such as dust, dirt, oil stains, oil and waxes,
starches or other sizing materials, seed particles,
and natural coloring materials.
These impurities can be classified as.
I. Natural Impurities &
II. Added Impurities
The main objectives of preparatory treatments
of textile materials are,
1. To remove all the impurities, both naturals
and those added during production that may
interfere in subsequent dyeing or finishing
2. Improve the ability of the fibers to absorb
water, dyes solutions and chemicals.
3. Impart proper brightness or whiteness to
fabrics according to need, especially when
brilliant or pastel shades are desired.
Important Preparatory Steps for Cotton Fabric
• Singeing is a process of burning off protruding
fibers from the surface of the yarn of the fabric
in order to improve the lustre and
Smoothness of the material.
Types of singeing:
• Hot plate singeing machine
• Roller singeing machine
• Gas-singeing machine
• The removal of added size material in process of
sizing is known as desizing.
Methods Of Desizing
Hydrolic Oxidative Novel
Rot steep Chlorine Solvent
Enzymatic Chlorite Desizing 2000
Acid steep Bromite LT plasma
• The oils and fatty acids of inorganic compounds
form a layer on fabric which are hydrophobic and
affect the absorbency of cloth. the process by
which the water resistant layer is removed is
known as Scouring.
• Scouring Processes for cotton:-
1.The lime soda process
3.Treatment with soap and soda ash
• Bleaching is a process by which the natural
colouring matter and any other colouring
matter is removed from natural fibers or
process discoloration from man-made
• Classification of Bleaching Agents:
1. Oxidizing bleaching agents
Cl₂, H₂O₂, Na₂O₂, K₂S₂O₈, HOCl, KMnO₄, O₃
2. Reducing bleaching agents
So₂, Na₂SO₃, Na₂S₂O₄, H₂SO₃, NaHSO₃
• Mercerization process was invented by John Mercer.
• In the Mercerization process, cotton fabric or yarn is
treated with a cold concentrated solution of sodium
hydroxide for one minute or less. In this process
cotton fibers swell, untwist and their bean shaped
cross section changes into a round form
Mercerization improves the following properties of the
1. Strength would be increased to 15-25%.
2. Enhanced luster.
3. Greater affinity to water, dyes and other chemical
4. Shrinkage control in both the direction of the fabric.
• Dyeing is by far the most widely used
means of applying color to textiles.
• Dyes, by definition, are soluble in the
medium in which they are applied, and the
medium is almost always water.
Immerse Textile in
Apply Heat, Time,
Chemicals to Drive
Dye into Textiles
Rinse to Remove
All Dye is in Bath
Most of the Dye
Now on Textiles
Dyeing Can Be Done at Different Stages:
• Fiber Stage • Yarn Stage • Fabric Stage • Garment Stage
• General Principles and Terms Met in Dyeing
1) Dye Exhaustion – This describes how much of the total dye
applied resides on the fiber rather than in the dye liquor.
2) Equilibrium – This is when the final or equilibrium degree of
exhaustion has been reached. If the dyeing is allowed to proceed
under the same conditions for a longer time, the shade of the
dyed goods will remain the same.
3) Levelness and Leveling Power - levelness depends on:
» Liquor ratio – The leveling power increase as the LR increases as
there is more dye in the bath
» Substantivity – Low substantivity favors leveling
» Temperature – Higher temperature give more level dyeing
» Time – Longer times give more level dyeing
(or beck) Dyeing
• Fabric pieces are sewn end to end and this
rope-like form is dyed in a relaxed state.
• It is most widely used on knitted, woolen
and worsted fabrics.
Piece Jig Dyeing
• Fabric is treated in open width and is
passed through the dye bath rather than
immersed in to a dye bath and this is
• There is a degree of
tension on the fabric and
is therefore used on woven
fabrics and not knits.
Piece Pad Dyeing
• The dye solution is applied by
means of a padder and the
fabric in open form is run
through an open vat.
• The fabric is subject to tension, so
only selected fabrics can be dyed.
• Advantages: System can handle
thousands of yards and dye can be
added automatically to provide
consistency of dye color
The reactive dyes are water-soluble anionic dyes,
which react with hydroxyl groups of cellulose to
become covalently bonded to the fiber.
• The chemical reaction between a reactive dye and a
cellulose fiber takes place in the presence of a base
and can be summarized as follows
• Offers bright colors with very good colorfastness,
(particularly good washfastness and excellent light
• Susceptible to damage from chlorine bleaches
The Vat dyes are insoluble organic compounds that are
not substantive to cellulose. The following steps are
involved in dyeing:
1) Reduction (Vatting): Prior to dyeing they are converted
to their soluble form (leuco soluble vat dye) by means
of reduction in the presence of a strong base.
2) Dyeing: In this soluble form, they are substantive to
cellulosic fibers, and can be applied to them.
3) Oxidation: Once inside the fibers, uniformly
distributed, the Vat dyes are then oxidized and
converted back to their original insoluble form.
4) Soaping: to achieve a stable shade.
• The soft water throughout the dyeing stage
is a must with Vat dyes, since the soluble
Leuco salts form insoluble salts with Calcium
or Magnesium ions as well as with transition
• A wide choice of colors with good to
excellent colorfastness is available, although
their lightfastness may be somewhat
• Direct dyes are soluble anionic dyes.
• The Direct dyes are so called because they were the first dyes to
dye cellulosic fibers directly without the need for a pre-
treatment of the fibers with a mordant.
• The mechanisms by which direct dyes become attached to
cellulose is assumed to be through the formation of a large
number of weak attractions between the dye and the fiber.
• Direct dyes exhibit relatively good colorfastness to sunlight, and
some are considered to have excellent lightfastness. However
colorfastness to washing is poor and therefore not appropriate
for frequently washed apparel.
• The problem of poor washfastness can be improved to some
degree by formaldehyde after treatment.
• A reduction in the length or width of a fibre, yarn or fabric is
known as shrinkage. Growth occurs when a fabric increases
in dimension. It is essential to know the shrinkage of the
fabrics in both the directions ( Warp wise and weft wise) to
determine construction and design of garment
• Causes of Shrinkage
• Intermolecular structure of fibres
• Yarn twist
• Fabric construction (Yarns / inch)
• Weave / knit structure
• In Compressive Shrinkage process, the fabric is
dampened and is placed on a machine
equipped with a continuous thick woolen felt
blanket. The blanket travels around a smaller
roller carrying the
• fabric with it as it
• stretches around
• the curve of the roller.
It is a process design for treating the industrial waste water for its reuse
or safe disposal to the environment.
• Influent: Untreated industrial waste water.
• Effluent: Treated industrial waste water.
• Sludge: Solid part separated from waste water by ETP.
4. Tertiary (or advanced)
• Treatment mechanisms:
• I learnt all the techniques and process of
• This Internship help in knowing the various
machine used for processing.
• Due to secrecy act, all the data on recipe,
method & activities has not been supplied &
hence the data given regarding to this do not
resemblance to the actual data.
• The whole process is not possible to bind in
such a small frame as this report, hence our
effort spenton summarizing, not describing
• Textile chemical processing, Students Handbook Central Board Of
Secondary Education Shiksha Kendra, 2, Community Centre, Preet
• Wet Processing Technology-Internship Report
Technology-Internship-Report-pdf accessed on 28th, Jan 2018
• Textile Internship Report - arvind denim division
• Internship report on dyeing
on-dyeing.html Accessed on 29th, Jan 2018
• Srini Venkatraman, 2006 Bureau Veritas
100504132149-phpapp01.pdf Accessed on 30/01/2018
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