Chemical composition and properties of cotton

 Chemical composition of cotton:

Cellulose ---------------------------------------------- 85.5%
Oil and wax -------------------------------------------- 0.5%
Proteins, Pectoses andColoring matters------------------- 5%
Mineral matters------------------------------------------ 1%
Moisture------------------------------------------------ 8.5%


Cotton is a crystalline fibre. Its polmer system is about 65 to70 percent crystalline and correspondingly about 35-30 percet amorphous. The cotton fibre is made up of a cuticle, primary wall, secondary wall and lumen.

Physical properties of cotton:

a.    Specific gravity—1.5-1.55
b.    Strength-Dry- 3.5 gm/den wet-Dry*1.11
c.    Elasticity- Low
d.    Breaking extension – 5-7%
e.    Stiffness – 57-60 gm/den
f.    Resilency – Low
g.    Abrasion resistance –Medium.

Chemical properties of cotton:

a.    Inorganic acids have no effect on cotton but organic acids can decompose or hydrolyze cotton.
b.    Cotton has a lot resistance to alkali. Cotton treated with alkali become oval form kidney shape and         more lustrous.
c.    Cotton can be bleached with all types of bleaching agents. Among them per hydroxide is less harmful.
d.    It has resistance to organic solvent.
e.    It has good heat conductivity.   
f.    It can be dyed by Azoic. Direct, Reactive, Sulphur and Vat dyes.

Cellulose and cellulosic fibres

Cellulose: 

   Cotton, viscose rayon and cuprammonium rayon are composed of an important fibre substance called cellulose. The cotton polymer consist of about 10000 cellubiose units.

Cellulose has an empirical formula (C6H10O5)n. Pure cellulose is a white substance that burns freely in air with luminous smokeless flame. It is insoluble in water in ammonical copper hydroxide and in concentrated solution of certain salt like such as zimc chloride and calcium thiocyanate.

                  Cellulose fibres can bedivided into two groups:

1.     Natural cellulose fibres: Natural cellulose fibres include cotton, flax jute, hemp etc.

2.     Regeuerated cellulosic fibres: Man made cellulose fibres include cuprammonium rayon, viccose rayon polynosic, Lyocell, Acetate, Triacetate etc.

    Some common properties of cellulose fibres are given below:

a.     Cellulose fibers have a good absorbency so it is comfortable for summer wear.

b.     Cellulose fabrics feel heavier due to its high density.

c.      Cellulose is a good conductor of heat so it used for sheer fabric.

d.     High count yarn can be made from cellulose as it packs well into compact yarn.    

e.      Cellulose fabrics can be boiled and no precipitation is needed for ironing as it can withstand high temperature.

f.      Cellulose fabrics are harmed by mineral acids but little effected by organic acids. Resistant to alkali but has a swelling effect. It has a resistance to moth.