Bleaching

1. 1
Textile Polymers and
Textile Polymers and
Requirement of
Requirement of
Pretreatment on Them
Pretreatment on Them
Prepared by
Prepared by
ROHIT SINGH
ROHIT SINGH
nitragzb20152019@gmail.com
nitragzb20152019@gmail.com
+91 9450316927
+91 9450316927
NITRA TECHNICAL CAMPUS
NITRA TECHNICAL CAMPUS
GHAZIABAD
GHAZIABAD

2. TEXTILES
TEXTILES
 All the Textiles are Polymers
All the Textiles are Polymers
 Poly (many);
Poly (many);
Mer (single unit)
Mer (single unit)
 Example: Ethylene n(CH
Example: Ethylene n(CH2
2=CH
=CH2
2) [Monomer] is formed
) [Monomer] is formed
to Polyethylene –(CH
to Polyethylene –(CH2
2-CH
-CH2
2)
)n
n-
-
 Functionality of polymer should be normally two
Functionality of polymer should be normally two
[unsaturation or functional groups such as
[unsaturation or functional groups such as
-OH, -COOH, etc]
-OH, -COOH, etc]
 The arrangement of polymers is normally linear or
The arrangement of polymers is normally linear or
branched not cross-linked
branched not cross-linked
 Textiles requirements are met by the polymers through
Textiles requirements are met by the polymers through
molecular chain length and molecular weight.
molecular chain length and molecular weight.

3. Classification of Textiles
Classification of Textiles
 Textiles are basically classified through natural and
Textiles are basically classified through natural and
synthetic means
synthetic means
 Sometimes it would be classified as organic or inorganic
Sometimes it would be classified as organic or inorganic
(silica, germanium, etc)
(silica, germanium, etc)
 Natural fibres are by plant, animal and also by insect
Natural fibres are by plant, animal and also by insect
origin
origin
 Synthetic fibres are from chemicals [monomers to
Synthetic fibres are from chemicals [monomers to
polymers through the process polymerization]
polymers through the process polymerization]
 Regenerated and/or modified fibres are from both
Regenerated and/or modified fibres are from both
natural and synthetic means
natural and synthetic means

4. Important Textile Fibres
Important Textile Fibres
 Natural textiles are classified as Cellulosic and Non
Natural textiles are classified as Cellulosic and Non
cellulosics
cellulosics
 Cotton, linen, jute, sisal, banana fibres are important
Cotton, linen, jute, sisal, banana fibres are important
natural cellulosic textile fibres
natural cellulosic textile fibres
 Silk, wool, and some special hairs are some of the
Silk, wool, and some special hairs are some of the
important non cellulosic (protein) fibres.
important non cellulosic (protein) fibres.
 Polyester, Acrylic, Nylon, Lycra, Polypropylene, etc are
Polyester, Acrylic, Nylon, Lycra, Polypropylene, etc are
some of the important synthetic fibres.
some of the important synthetic fibres.
 Lyocell / Viscose, cuprammonium rayon, and cellulose
Lyocell / Viscose, cuprammonium rayon, and cellulose
acetate are some of the regenerated and/or modified
acetate are some of the regenerated and/or modified
textile fibres.
textile fibres.

5. Requirement for Pretreatment
Requirement for Pretreatment
 All the natural textile fibres have impurities in
All the natural textile fibres have impurities in
different extent due to various reasons
different extent due to various reasons
 Pretreatment(s) remove the impurities, both
Pretreatment(s) remove the impurities, both
natural and added, from the textile polymers
natural and added, from the textile polymers
 Pretreatment(s) facilitate the textiles to carry out
Pretreatment(s) facilitate the textiles to carry out
the main processing in a efficient way
the main processing in a efficient way
 Pretreatment(s) mostly decide the quality of the
Pretreatment(s) mostly decide the quality of the
end use products
end use products

6. Scouring on Cotton fibres
Scouring on Cotton fibres
 Scouring is an alkali treatment on cotton fibre using
Scouring is an alkali treatment on cotton fibre using
sodium hydroxide and/or sodium carbonate
sodium hydroxide and/or sodium carbonate
 During scouring, the alkali reacts with the natural
During scouring, the alkali reacts with the natural
impurities (oil/fat – insoluble) and converts them into
impurities (oil/fat – insoluble) and converts them into
soluble soap
soluble soap
 For scouring, sodium hydroxide is used in the
For scouring, sodium hydroxide is used in the
concentration of 3%(owm), 3 hours, at boil
concentration of 3%(owm), 3 hours, at boil
 Scouring removes the hydrophobicity and reveals
Scouring removes the hydrophobicity and reveals
hydrophilicity and promotes absorbency
hydrophilicity and promotes absorbency

7. Bleaching of Cotton Fibre
Bleaching of Cotton Fibre
 Bleaching is another important pretreatment
Bleaching is another important pretreatment
next to scouring, performed on cotton fibres
next to scouring, performed on cotton fibres
 Bleaching removes the unwanted natural
Bleaching removes the unwanted natural
colouring pigments.
colouring pigments.
 Bleaching could be performed by two types of
Bleaching could be performed by two types of
techniques; reductive and oxidative
techniques; reductive and oxidative
 Reductive technique is not followed nowadays
Reductive technique is not followed nowadays
due to its inefficient performance on cotton
due to its inefficient performance on cotton

8. Oxidative Bleaching on Cotton
Oxidative Bleaching on Cotton
 Normally oxidative bleaching action is performed in the
Normally oxidative bleaching action is performed in the
industries on cotton fibre substrates
industries on cotton fibre substrates
 Though number of bleaching agents are available in the
Though number of bleaching agents are available in the
chemical market, few bleaching agents are being used
chemical market, few bleaching agents are being used
extensively
extensively
 Calcium hypochlorite, Sodium hypochlorite and
Calcium hypochlorite, Sodium hypochlorite and
Hydrogen peroxide are the most frequent used
Hydrogen peroxide are the most frequent used
bleaching agents in the conventional cotton processing
bleaching agents in the conventional cotton processing
units
units

9. Pretreatment on Silk
Pretreatment on Silk
 Silk is a natural fine filament material
Silk is a natural fine filament material
 Original silk filament contains two protein
Original silk filament contains two protein
substrates; one is fibrous protein called Fibroin,
substrates; one is fibrous protein called Fibroin,
another one is gummy protein called Sericin
another one is gummy protein called Sericin
 Fibroin is responsible for the fibre polymer
Fibroin is responsible for the fibre polymer
composed of sixteen amino acids.
composed of sixteen amino acids.
 Sericin is a gum considered impurity and to be
Sericin is a gum considered impurity and to be
removed from the material based on the
removed from the material based on the
considerations.
considerations.

10. …
…continued
continued
 Silk pretreatment requires mainly the removal
Silk pretreatment requires mainly the removal
of gummy substance (sericin) which if
of gummy substance (sericin) which if
performed fully makes the silk pure of fibre
performed fully makes the silk pure of fibre
protein and pure white
protein and pure white
 The removal of sericin from silk filament is
The removal of sericin from silk filament is
called degumming which is performed by
called degumming which is performed by
applying 2%owm soap, 1%owm sodium
applying 2%owm soap, 1%owm sodium
carbonate at 95
carbonate at 95o
o
C for 2 hours
C for 2 hours

11. …
…continued
continued
 If required only hydrogen peroxide bleaching is
If required only hydrogen peroxide bleaching is
performed on degummed silk, since alkaline pH
performed on degummed silk, since alkaline pH
damages protein textiles, but hydrogen
damages protein textiles, but hydrogen
peroxide’s pH could be altered by situations
peroxide’s pH could be altered by situations
 Degumming is performed in different ways; ¼
Degumming is performed in different ways; ¼th
th
removal, ½ removal, ¾th removal and full
removal, ½ removal, ¾th removal and full
(100%) removal, depending on the market /
(100%) removal, depending on the market /
commercial / end use product’s considerations
commercial / end use product’s considerations

12. Pretreatment on Wool
Pretreatment on Wool
 Wool is another protein polymer (Keratin) composed
Wool is another protein polymer (Keratin) composed
of 20 different amino acids with some similarities and
of 20 different amino acids with some similarities and
differences with silk
differences with silk
 Unlike cotton and silk, wool contains differed
Unlike cotton and silk, wool contains differed
impurities on the basis of species, country, place, etc of
impurities on the basis of species, country, place, etc of
the animal
the animal
 Fats (grease) and vegetable matters are the major
Fats (grease) and vegetable matters are the major
impurities in wool to be considered
impurities in wool to be considered
 The removal of wool fats (grease) is called as degreasing
The removal of wool fats (grease) is called as degreasing
 The removal of vegetable matters is performed
The removal of vegetable matters is performed
generally by carbonization
generally by carbonization

13. …
…continued
continued
 Nowadays degreasing is mostly done by 2 ways; one is
Nowadays degreasing is mostly done by 2 ways; one is
by controlled mild alkaline scouring method and the
by controlled mild alkaline scouring method and the
other is by solvent extraction method
other is by solvent extraction method
 In the commercial point of view alkaline method is
In the commercial point of view alkaline method is
cheap and preferred, whereas quality point of view
cheap and preferred, whereas quality point of view
solvent extraction method (solvents are costly) is
solvent extraction method (solvents are costly) is
preferred. Alkalies are highly sensitive on wool and
preferred. Alkalies are highly sensitive on wool and
possibility of damage is also high, but by solvent
possibility of damage is also high, but by solvent
extraction method the damage on wool is nil.
extraction method the damage on wool is nil.

14. …
…continued
continued
 Carbonization is applied on original wool fibres
Carbonization is applied on original wool fibres
to remove the vegetable matters by treating with
to remove the vegetable matters by treating with
dilute sulphuric acid followed by drying. By this
dilute sulphuric acid followed by drying. By this
the vegetable matters are converted to carbon
the vegetable matters are converted to carbon
contents and charred to ash which is washed
contents and charred to ash which is washed
away. This process is called carbonization.
away. This process is called carbonization.
 Degreasing and carbonization removes almost
Degreasing and carbonization removes almost
all the natural impurities present in the wool
all the natural impurities present in the wool
fibre substrates
fibre substrates

15. …
….continued
.continued
 Other possible pretreatments on wool fibre
Other possible pretreatments on wool fibre
substrates are Non-felting, Decatizing, Potting ,
substrates are Non-felting, Decatizing, Potting ,
etc
etc
 Non felting is the process carried out on wool
Non felting is the process carried out on wool
fibres to give partial scale removal so that
fibres to give partial scale removal so that
chemicals entry in the wool polymer is easy
chemicals entry in the wool polymer is easy
 Decatizing and potting are similar treatments in
Decatizing and potting are similar treatments in
acidic medium to improve the characters of
acidic medium to improve the characters of
wool for some special applications
wool for some special applications

16. T
H
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K
Y
O
U
!
T
H
A
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Y
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!