About cotton and knit.

2. What is a fiber?
• A "fiber" is defined as any product capable
of being woven or otherwise made into a
fabric. It may be thought of as the smallest
visible unit of textile production 'or' a fiber
can be defined as a pliable hair like strand
that is very small in diameter in relation to
its length. Fibers are the fundamental units
or the building blocks used in the making of
textile yarns and fabrics.

3. Properties of Fiber-Forming
Polymers
• Properties of Fiber
making polymer:
• Hydrophilic (water loving)
• Chemically resistant
• Linear
• Long in length
• Capable of being
orientated to create
crystalline regions
• Able to form high-
melting-point polymer
systems.
• Textile fiber
determined by their;
• Chemical structure
• DP
• Crosslinking between
individual molecules

4. 4
Cotton Fiber
•
• DP of cotton is around 1000-14000.

5. 5
Fine structure of cotton fiber
• Cotton is basically a crystalline (about 70%)
fiber but small portion of amorophus region also
present in the fiber.

6. 6
Some physical properties of cotton
fiber
 Tenacity
Cotton is about 70% crystalline fiber which attribute good strength (about 27-44 g/tex). It is
one of the few fiber which gains strength when wet about 5% because improve alignment in
amorophus region and hydrogen bond.
 Elastic and plastic nature
The cotton is relatively inelastic because of its crystalline polymer system, and for this reason
cotton textiles wrinkle and crease readily.
 Hygroscopic properties
The cotton fiber is very absorbent, owing to the countless polar –OH groups in its polymers;
these attracts water molecules, which are also polar. However, the later can only enter the
polymer system in its amorophus regions, as the inter-polymer spaces in the crystalline region
are too small for the water molecule. Moisture regain at 65% RH is 7.0-8.5%.
Thermal properties
Cotton is not a thermoplastic fiber. In excessive heat energy cause to burn without prior melting
point.

7. 7
Microscopic appearance of
cotton
 Under microscope, the cotton
look like a twisted ribbon or a
collapsed and twisted tube. This
twisted properties of cotton is
called convolutions.
 The convolutions give cotton an
uneven surface, which increase
inter-fiber friction and enables
fine cotton yarns of adequate
strength to be spun.

8. Cotton structure

9. Composition of Typical Cotton
Contents Whole Fiber
(%)
Cuticle (%) Primary wall
(%)
Cellulose 88 - 96 52
Pectic substance 0.7 – 1.9 19.6 12
Ash 0.7 – 1.6 6.5 3
Wax and fat 0.4 – 1.0 17.4 7
Proteins 1.1 – 1.9 36.4 12
Pigments Trace Trace Trace
Others 2.0 – 3.4 3.3 14
Source : The cotton fiber chemistry & Technology by Philips Walkelyn

11. Pectic substance
These are polygalacturonic acid, and its salts (Mg, Ca, Fe
etc), methylester, xylose. It is covalently linked with cellulose
and attached to calcium ions by coulombic interaction.
Pectic substances react with caustic soda and make water
soluble salt, thus can be removed by caustic scouring process.

12. Ash
• The mineral matter
consists of mostly
chlorides, carbonate
and phosphates of
Potassium, calcium
and Magnesium.
• Generally remain in
salt form with
pectin substances.

13. Ash content
Proportion
Content %
Sodium Carbonate 44.8
Potassium Chloride 9.9
Potassium Sulphate 9.3
Calcium salts 10.6
Magnesium salts 8.4
Ferric oxide 3
Alluminium oxide 5
How much inside the fiber
Place Ca PPM Mg PPM Fe PPM
Sendhwa India 1000 600 125
Bailhongal India 1030 845 115
Jetpur India 580 585 84
Pendurana India 980 790 475
Izmir Turkey 905 890 22
Hatay Turkey 725 640 24
Urfa Turkey 985 620 29
Paranah Brazil 2711 1119 313
Sao Paulo Brazil 944 863 72
Peru 700 440 13
Texas USA 810 365 75
California USA 600 540 40
Russia 1320 567 112
Standard for pretreated goods
Ca & Mg 100 – 300 PPM
Fe 4 – 8 PPM

14. Chemical character of Ash
• Complexion of earth
alkali salt (Ca and Mg)
is possible in the acid
and heavy metals (Fe
and Mn) is possible in
alkaline medium.

15. Chemical character of Ash

16. Disadvantage of Ash substances
• Insoluble carbonates, hydroxides, phophates formed in
alkali.
• Build-up deposits on machines.
• Peroxide stabilizers blocked by excess calcium-megnesium
ions – poor peroxide stability.
• Insoluble yellowish-green salts formed with FBA’s.
• Emulsion of oils and greases are splits by Ca and Mg.
• Solubility of dyes impaired.
• Form spot and stains of dyes.
• Cause change of shade and reduced fastness.
• Create pin hole during bleaching.

17. Fat & Wax
• The wax is a mixture of high molecular weight,
primarily long chain saturated fatty acids and
alchohols (C28 to C34), resins, saturated and
unsaturated hydrocarbons, sterols and sterol
glucosides.
• A portion of fat and wax can be removed by
saponifiaction, treating with caustic soda.

18. Detectable wax acids and alcohols in cotton
Chemical formula Systematic name Melting point in oC
C15H31COOH Hexadecanoic acid 64
C17H35COOH Octadecanoic acid 69
C19H39COOH Eicosanoic acid 76
C21H43COOH Docosanoic acid 81
C23H47COOH Tetracosanic acid 81
C25H51COOH Hexacosanic acid 88
C27H55COOH Octacosanic acid 91 - 93
C29H59COOH Triacosanic acid 92
C24H49OH Tetracosanol 75-77
C26H53OH Hexacosanol 79-81
C28H57OH Octacosanol 83
C30H61OH Triacontanol 90
C32H69OH Dotriacontanol 92

19. Fat and Wax
Elements Value
Melting point 76 – 85oC
Specific gravity 0.97 – 0.99
Saponification Number 50 – 76
Saponifiable matter 36 – 50%
Non-saponifable matter 50 -63%
Inert 3%
Caster oil 180
Coconut oil 260
Olive oil 190

20. Emulsification

21. Proteins
Variety of protein are found in all layers of
the cotton cell but they are more abundant
in the primary wall layers.
They are readily converted into soluble
compounds and removed from the fiber by
boiling with alkalis.

22. Cellulose

23. 23
Cellulose swelling
Cellulose is hydrophilic and swells in
present of water.
Cellulose also swell with an aqueous
solution of Sodium Hydroxide (NaOH)
which is utilized in mercerization.

24. Degradation of cellulose
 Acids
 Alkalis
 Oxidizing agent
 Enzymes
 Heat
 Radiation

25. Acid hydrolysis

26. Effect of oxidizing agent

27. 27
Degradation by Enzymes
 The degradation of cellulose is caused by
enzymes, known as cellulase. Cellulase are
produced by microorganism (bacteria and fungi).
The primary reaction in the enzymatic degradation
of cellulose is hydrolysis and degradation is a
function available surface area and crystallinity of
the cellulose.
 If damp cotton is exposed to air, mildew may
gradually develop on it, accompanied by staining
that is difficult or impossible to remove. Prolong
exposure also cause serious loss of tensile
strength.

28. 28
Degradation by Heat
Cellulose can be heated for many hours up
to 120oC without any serious deleterious
effect.
When cotton are heated above 140oC,
tensile strength and viscosity decrease and
carbonyl and carboxyl contents increase.
Distinct discoloration of the fiber is seen
first a yellowing, then a deepening to brown
as thermal degradation escalates. In air
oxidation of the cotton occurs at these

29. 29
Degradation by radiation
The most important type of photochemical
degradation that can affect cellulose is that
caused by visible and near-u.v radiation.
Pure cellulose scarcely affected by daylight.
However degradation occurs in the presence
of oxygen and a photosensitiser and this
enhanced by the presence of moisture.